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diff --git a/filesystem/filesystem_old_reference_only.rst b/filesystem/filesystem_old_reference_only.rst deleted file mode 100644 index f8c1746..0000000 --- a/filesystem/filesystem_old_reference_only.rst +++ /dev/null @@ -1,4602 +0,0 @@ -.. comment SPDX-License-Identifier: CC-BY-SA-4.0 - -:orphan: - - - -.. COMMENT: %**end of header - -.. COMMENT: COPYRIGHT (c) 1989-2013. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -.. COMMENT: Master file for the Filesystem Design Guide - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -.. COMMENT: The following determines which set of the tables and figures we will use. - -.. COMMENT: We default to ASCII but if available TeX or HTML versions will - -.. COMMENT: be used instead. - -.. COMMENT: @clear use-html - -.. COMMENT: @clear use-tex - -.. COMMENT: The following variable says to use texinfo or html for the two column - -.. COMMENT: texinfo tables. For somethings the format does not look good in html. - -.. COMMENT: With our adjustment to the left column in TeX, it nearly always looks - -.. COMMENT: good printed. - -.. COMMENT: Custom whitespace adjustments. We could fiddle a bit more. - -.. COMMENT: Title Page Stuff - -.. COMMENT: I don't really like having a short title page. -joel - -.. COMMENT: @shorttitlepage RTEMS Filesystem Design Guide - -============================= -RTEMS Filesystem Design Guide -============================= - -.. COMMENT: COPYRIGHT (c) 1988-2015. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -.. COMMENT: The following puts a space somewhere on an otherwise empty page so we - -.. COMMENT: can force the copyright description onto a left hand page. - -COPYRIGHT © 1988 - 2015. - -On-Line Applications Research Corporation (OAR). - -The authors have used their best efforts in preparing -this material. These efforts include the development, research, -and testing of the theories and programs to determine their -effectiveness. No warranty of any kind, expressed or implied, -with regard to the software or the material contained in this -document is provided. No liability arising out of the -application or use of any product described in this document is -assumed. The authors reserve the right to revise this material -and to make changes from time to time in the content hereof -without obligation to notify anyone of such revision or changes. - -The RTEMS Project is hosted at http://www.rtems.org. Any -inquiries concerning RTEMS, its related support components, or its -documentation should be directed to the Community Project hosted athttp://www.rtems.org. - -Any inquiries for commercial services including training, support, custom -development, application development assistance should be directed tohttp://www.rtems.com. - -.. COMMENT: This prevents a black box from being printed on "overflow" lines. - -.. COMMENT: The alternative is to rework a sentence to avoid this problem. - -RTEMS Filesystem Design Guide -############################# - -.. COMMENT: COPYRIGHT (c) 1989-2011. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Preface -####### - -This document describes the implementation of the RTEMS filesystem -infrastructure. This infrastructure supports the following -capabilities: - -- Mountable file systems - -- Hierarchical file system directory structure - -- POSIX compliant set of routines for the manipulation of files and directories - -- Individual file and directory support for the following: - # Permissions for read, write and execute - # User ID - # Group ID - # Access time - # Modification time - # Creation time - -- Hard links to files and directories - -- Symbolic links to files and directories - -This has been implemented to provide the framework for a UNIX-like -file system support. POSIX file and directory functions have been -implemented that allow a standard method of accessing file, device and -directory information within file systems. The file system concept that -has been implemented allows for expansion and adaptation of the file -system to a variety of existing and future data storage devices. To this -end, file system mount and unmount capabilities have been included in this -RTEMS framework. - -This framework slightly alters the manner in which devices are handled -under RTEMS from that of public release 4.0.0 and earlier. Devices that -are defined under a given RTEMS configuration will now be registered as -files in a mounted file system. Access to these device drivers and their -associated devices may now be performed through the traditional file system -open(), read(), write(), lseek(), fstat() and ioctl() functions in addition -to the interface provided by the IO Manager in the RTEMS Classic API. - -An In-Memory File System (IMFS) is included which provides full POSIX -filesystem functionality yet is RAM based. The IMFS maintains a -node structure for each file, device, and directory in each mounted -instantiation of its file system. The node structure is used to -manage ownership, access rights, access time, modification time, -and creation time. A union of structures within the IMFS nodal -structure provide for manipulation of file data, device selection, -or directory content as required by the nodal type. Manipulation of -these properties is accomplished through the POSIX set of file and -directory functions. In addition to being useful in its own right, -the IMFS serves as a full featured example filesystem. - -The intended audience for this document is those persons implementing -their own filesystem. Users of the filesystem may find information -on the implementation useful. But the user interface to the filesystem -is through the ISO/ANSI C Library and POSIX 1003.1b file and directory -APIs. - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Pathname Evaluation -################### - -This chapter describes the pathname evaluation process for the -RTEMS Filesystem Infrastructure. -.. code:: c - - XXX Include graphic of the path evaluation process - -Pathname Evaluation Handlers -============================ - -There are two pathname evaluation routines. The handler patheval() -is called to find, verify privlages on and return information on a node -that exists. The handler evalformake() is called to find, verify -permissions, and return information on a node that is to become a parent. -Additionally, evalformake() returns a pointer to the start of the name of -the new node to be created. - -Pathname evaluation is specific to a filesystem. -Each filesystem is required to provide both a patheval() and an evalformake() -routine. Both of these routines gets a name to evaluate and a node indicating -where to start the evaluation. - -Crossing a Mount Point During Path Evaluation -============================================= - -If the filesystem supports the mount command, the evaluate routines -must handle crossing the mountpoint. The evaluate routine should evaluate -the name upto the first directory node where the new filesystem is mounted. -The filesystem may process terminator characters prior to calling the -evaluate routine for the new filesystem. A pointer to the portion of the -name which has not been evaluated along with the root node of the new -file system ( gotten from the mount table entry ) is passed to the correct -mounted filesystem evaluate routine. - -The rtems_filesystem_location_info_t Structure -============================================== - -The ``rtems_filesystem_location_info_t`` structure contains all information -necessary for identification of a node. - -The generic rtems filesystem code defines two global -rtems_filesystem_location_info_t structures, the``rtems_filesystem_root`` and the ``rtems_filesystem_current``. -Both are initially defined to be the root node of the base filesystem. -Once the chdir command is correctly used the ``rtems_filesystem_current`` -is set to the location specified by the command. - -The filesystem generic code peeks at the first character in the name to be -evaluated. If this character is a valid seperator, the``rtems_filesystem_root`` is used as the node to start the evaluation -with. Otherwise, the ``rtems_filesystem_current`` node is used as the -node to start evaluating with. Therefore, a valid -rtems_filesystem_location_info_t is given to the evaluate routine to start -evaluation with. The evaluate routines are then responsible for making -any changes necessary to this structure to correspond to the name being -parsed. -.. code:: c - - struct rtems_filesystem_location_info_tt { - void \*node_access; - rtems_filesystem_file_handlers_r \*handlers; - rtems_filesystem_operations_table \*ops; - rtems_filesystem_mount_table_entry_t \*mt_entry; - }; - -*node_access* - This element is filesystem specific. A filesystem can define and store - any information necessary to identify a node at this location. This element - is normally filled in by the filesystem’s evaluate routine. For the - filesystem’s root node, the filesystem’s initilization routine should - fill this in, and it should remain valid until the instance of the - filesystem is unmounted. - -*handlers* - This element is defined as a set of routines that may change within a - given filesystem based upon node type. For example a directory and a - memory file may have to completely different read routines. This element - is set to an initialization state defined by the mount table, and may - be set to the desired state by the evaluation routines. - -*ops* - This element is defined as a set of routines that remain static for the - filesystem. This element identifies entry points into the filesystem - to the generic code. - -*mt_entry* - This element identifies the mount table entry for this instance of the - filesystem. - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -System Initialization -##################### - -After the RTEMS initialization is performed, the application’s -initialization will be performed. Part of initialization is a call to -rtems_filesystem_initialize(). This routine will mount the ‘In Memory File -System’ as the base filesystem. Mounting the base filesystem consists -of the following: - -- Initialization of mount table chain control structure - -- Allocation of a ``jnode`` structure that will server as the root node - of the ‘In Memory Filesystem’ - -- Initialization of the allocated ``jnode`` with the appropriate OPS, - directory handlers and pathconf limits and options. - -- Allocation of a memory region for filesystem specific global - management variables - -- Creation of first mount table entry for the base filesystem - -- Initialization of the first mount table chain entry to indicate that - the mount point is NULL and the mounted filesystem is the base file - system - -After the base filesystem has been mounted, the following operations are -performed under its directory structure: - -- Creation of the /dev directory - -- Registration of devices under /dev directory - -Base Filesystem -=============== - -RTEMS initially mounts a RAM based file system known as the base file system. -The root directory of this file system tree serves as the logical root of the -directory hierarchy (Figure 3). Under the root directory a ‘/dev’ directory -is created under which all I/O device directories and files are registered as -part of the file system hierarchy. -.. code:: c - - Figure of the tree structure goes here. - -A RAM based file system draws its management resources from memory. File and -directory nodes are simply allocated blocks of memory. Data associated with -regular files is stored in collections of memory blocks. When the system is -turned off or restarted all memory-based components of the file system are -lost. - -The base file system serves as a starting point for the mounting of file -systems that are resident on semi-permanent storage media. Examples of such -media include non- volatile memory, flash memory and IDE hard disk drives -(Figure 3). File systems of other types will be mounted onto mount points -within the base file system or other file systems that are subordinate to the -base file system. The framework set up under the base file system will allow -for these new file system types and the unique data and functionality that is -required to manage the future file systems. - -Base Filesystem Mounting ------------------------- - -At present, the first file system to be mounted is the ‘In Memory File -System’. It is mounted using a standard MOUNT() command in which the mount -point is NULL. This flags the mount as the first file system to be -registered under the operating system and appropriate initialization of file -system management information is performed (See figures 4 and 5). If a -different file system type is desired as the base file system, alterations -must be made to base_fs.c. This routine handles the mount of the base file -system. - -.. code:: c - - Figure of the mount table chain goes here. - -Once the root of the base file system has been established and it has been -recorded as the mount point of the base file system, devices are integrated -into the base file system. For every device that is configured into the -system (See ioman.c) a device registration process is performed. Device -registration produces a unique dev_t handle that consists of a major and -minor device number. In addition, the configuration information for each -device contains a text string that represents the fully qualified pathname to -that device’s place in the base file system’s hierarchy. A file system node -is created for the device along the specified registration path. - -.. code:: c - - Figure of the Mount Table Processing goes here. - -Note: Other file systems can be mounted but they are mounted onto points -(directory mount points) in the base file system. - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Mounting and Unmounting Filesystems -################################### - -Mount Points -============ - -The following is the list of the characteristics of a mount point: - -- The mount point must be a directory. It may have files and other - directories under it. These files and directories will be hidden when the - filesystem is mounted. - -- The task must have read/write/execute permissions to the mount point - or the mount attempt will be rejected. - -- Only one filesystem can be mounted to a single mount point. - -- The Root of the mountable filesystem will be referenced by the name - of the mount point after the mount is complete. - -Mount Table Chain -================= - -The mount table chain is a dynamic list of structures that describe -mounted filesystems a specific points in the filesystem hierarchy. It is -initialized to an empty state during the base filesystem initialization. -The mount operation will add entries to the mount table chain. The -un-mount operation will remove entries from the mount table chain. - -Each entry in the mount table chain is of the following type: -.. code:: c - - struct rtems_filesystem_mount_table_entry_tt - { - Chain_Node Node; - rtems_filesystem_location_info_t mt_point_node; - rtems_filesystem_location_info_t mt_fs_root; - int options; - void \*fs_info; - rtems_filesystem_limits_and_options_t pathconf_limits_and_options; - /* - * When someone adds a mounted filesystem on a real device, - * this will need to be used. - * - * The best option long term for this is probably an - * open file descriptor. - \*/ - char \*dev; - }; - -*Node* - The Node is used to produce a linked list of mount table entry nodes. - -*mt_point_node* - The mt_point_node contains all information necessary to access the - directory where a filesystem is mounted onto. This element may contain - memory that is allocated during a path evaluation of the filesystem - containing the mountpoint directory. The generic code allows this - memory to be returned by unmount when the filesystem identified by - mt_fs_root is unmounted. - -*mt_fs_root* - The mt_fs_root contains all information necessary to identify the root - of the mounted filesystem. The user is never allowed access to this - node by the generic code, but it is used to identify to the mounted - filesystem where to start evaluation of pathnames at. - -*options* - XXX - -*fs_info* - The fs_info element is a location available for use by the mounted file - system to identify unique things applicable to this instance of the file - system. For example the IMFS uses this space to provide node - identification that is unique for each instance (mounting) of the filesystem. - -*pathconf_limits_and_options* - XXX - -*dev* - This character string represents the device where the filesystem will reside. - -Adding entries to the chain during mount -======================================== - -When a filesystem is mounted, its presence and location in the file -system hierarchy is recorded in a dynamic list structure known as a chain. -A unique rtems_filesystem_mount_table_entry_tt structure is logged for -each filesystem that is mounted. This includes the base filesystem. - -Removing entries from the chain during unmount -============================================== - -When a filesystem is dismounted its entry in the mount table chain is -extracted and the memory for this entry is freed. - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -System Call Development Notes -############################# - -This set of routines represents the application’s interface to files and directories -under the RTEMS filesystem. All routines are compliant with POSIX standards if a -specific interface has been established. The list below represents the routines that have -been included as part of the application’s interface. - -# access() - -# chdir() - -# chmod() - -# chown() - -# close() - -# closedir() - -# dup() - -# dup2() - -# fchmod() - -# fcntl() - -# fdatasync() - -# fpathconf() - -# fstat() - -# ioctl() - -# link() - -# lseek() - -# mkdir() - -# mkfifo() - -# mknod() - -# mount() - -# open() - -# opendir() - -# pathconf() - -# read() - -# readdir() - -# unmount() - -The sections that follow provide developmental information concerning each -of these functions. - -.. COMMENT: @page - -access -====== - -**File:** - -access.c - -**Processing:** - -This routine is layered on the stat() function. It acquires the current -status information for the specified file and then determines if the -caller has the ability to access the file for read, write or execute -according to the mode argument to this function. - -**Development Comments:** - -This routine is layered on top of the stat() function. As long as the -st_mode element in the returned structure follow the standard UNIX -conventions, this function should support other filesystems without -alteration. - -.. COMMENT: @page - -chdir -===== - -**File:** - -chdir.c - -**Processing:** - -This routine will determine if the pathname that we are attempting to make -that current directory exists and is in fact a directory. If these -conditions are met the global indication of the current directory -(rtems_filesystem_current) is set to the rtems_filesystem_location_info_t -structure that is returned by the rtems_filesystem_evaluate_path() -routine. - -**Development Comments:** - -This routine is layered on the rtems_filesystem_evaluate_path() routine -and the filesystem specific OP table function node_type(). - -The routine node_type() must be a routine provided for each filesystem -since it must access the filesystems node information to determine which -of the following types the node is: - -- RTEMS_FILESYSTEM_DIRECTORY - -- RTEMS_FILESYSTEM_DEVICE - -- RTEMS_FILESYSTEM_HARD_LINK - -- RTEMS_FILESYSTEM_MEMORY_FILE - -This acknowledges that the form of the node management information can -vary from one filesystem implementation to another. - -RTEMS has a special global structure that maintains the current directory -location. This global variable is of type rtems_filesystem_location_info_t -and is called rtems_filesystem_current. This structure is not always -valid. In order to determine if the structure is valid, you must first -test the node_access element of this structure. If the pointer is NULL, -then the structure does not contain a valid indication of what the current -directory is. - -.. COMMENT: @page - -chmod -===== - -**File:** - -chmod.c - -**Processing:** - -This routine is layered on the open(), fchmod() and close() functions. As -long as the standard interpretation of the mode_t value is maintained, -this routine should not need modification to support other filesystems. - -**Development Comments:** - -The routine first determines if the selected file can be open with -read/write access. This is required to allow modification of the mode -associated with the selected path. - -The fchmod() function is used to actually change the mode of the path -using the integer file descriptor returned by the open() function. - -After mode modification, the open file descriptor is closed. - -.. COMMENT: @page - -chown -===== - -**File:** - -chown.c - -**Processing:** - -This routine is layered on the rtems_filesystem_evaluate_path() and the -file system specific chown() routine that is specified in the OPS table -for the file system. - -**Development Comments:** - -rtems_filesystem_evaluate_path() is used to determine if the path -specified actually exists. If it does a rtems_filesystem_location_info_t -structure will be obtained that allows the shell function to locate the -OPS table that is to be used for this filesystem. - -It is possible that the chown() function that should be in the OPS table -is not defined. A test for a non-NULL OPS table chown() entry is performed -before the function is called. - -If the chown() function is defined in the indicated OPS table, the -function is called with the rtems_filesystem_location_info_t structure -returned from the path evaluation routine, the desired owner, and group -information. - -.. COMMENT: @page - -close -===== - -**File:** - -close.c - -**Processing:** - -This routine will allow for the closing of both network connections and -file system devices. If the file descriptor is associated with a network -device, the appropriate network function handler will be selected from a -table of previously registered network functions (rtems_libio_handlers) -and that function will be invoked. - -If the file descriptor refers to an entry in the filesystem, the -appropriate handler will be selected using information that has been -placed in the file control block for the device (rtems_libio_t structure). - -**Development Comments:** - -rtems_file_descriptor_type examines some of the upper bits of the file -descriptor index. If it finds that the upper bits are set in the file -descriptor index, the device referenced is a network device. - -Network device handlers are obtained from a special registration table -(rtems_libio_handlers) that is set up during network initialization. The -network handler invoked and the status of the network handler will be -returned to the calling process. - -If none of the upper bits are set in the file descriptor index, the file -descriptor refers to an element of the RTEMS filesystem. - -The following sequence will be performed for any filesystem file -descriptor: - -# Use the rtems_libio_iop() function to obtain the rtems_libio_t - structure for the file descriptor - -# Range check the file descriptor using rtems_libio_check_fd() - -# Determine if there is actually a function in the selected handler - table that processes the close() operation for the filesystem and node - type selected. This is generally done to avoid execution attempts on - functions that have not been implemented. - -# If the function has been defined it is invoked with the file control - block pointer as its argument. - -# The file control block that was associated with the open file - descriptor is marked as free using rtems_libio_free(). - -# The return code from the close handler is then passed back to the - calling program. - -.. COMMENT: @page - -closedir -======== - -**File:** - -closedir.c - -**Processing:** - -The code was obtained from the BSD group. This routine must clean up the -memory resources that are required to track an open directory. The code is -layered on the close() function and standard memory free() functions. It -should not require alterations to support other filesystems. - -**Development Comments:** - -The routine alters the file descriptor and the index into the DIR -structure to make it an invalid file descriptor. Apparently the memory -that is about to be freed may still be referenced before it is -reallocated. - -The dd_buf structure’s memory is reallocated before the control structure -that contains the pointer to the dd_buf region. - -DIR control memory is reallocated. - -The close() function is used to free the file descriptor index. - -.. COMMENT: @page - -dup() Unimplemented -======================== - -**File:** - -dup.c - -**Processing:** - -**Development Comments:** - -.. COMMENT: @page - -dup2() Unimplemented -========================= - -**File:** - -dup2.c - -**Processing:** - -**Development Comments:** - -.. COMMENT: @page - -fchmod -====== - -**File:** - -fchmod.c - -**Processing:** - -This routine will alter the permissions of a node in a filesystem. It is -layered on the following functions and macros: - -- rtems_file_descriptor_type() - -- rtems_libio_iop() - -- rtems_libio_check_fd() - -- rtems_libio_check_permissions() - -- fchmod() function that is referenced by the handler table in the - file control block associated with this file descriptor - -**Development Comments:** - -The routine will test to see if the file descriptor index is associated -with a network connection. If it is, an error is returned from this -routine. - -The file descriptor index is used to obtain the associated file control -block. - -The file descriptor value is range checked. - -The file control block is examined to determine if it has write -permissions to allow us to alter the mode of the file. - -A test is made to determine if the handler table that is referenced in the -file control block contains an entry for the fchmod() handler function. If -it does not, an error is returned to the calling routine. - -If the fchmod() handler function exists, it is called with the file -control block and the desired mode as parameters. - -.. COMMENT: @page - -fcntl() -======= - -**File:** - -fcntl.c - -**Processing:** - -This routine currently only interacts with the file control block. If the -structure of the file control block and the associated meanings do not -change, the partial implementation of fcntl() should remain unaltered for -other filesystem implementations. - -**Development Comments:** - -The only commands that have been implemented are the F_GETFD and F_SETFD. -The commands manipulate the LIBIO_FLAGS_CLOSE_ON_EXEC bit in the``flags`` element of the file control block associated with the file -descriptor index. - -The current implementation of the function performs the sequence of -operations below: - -# Test to see if we are trying to operate on a file descriptor - associated with a network connection - -# Obtain the file control block that is associated with the file - descriptor index - -# Perform a range check on the file descriptor index. - -.. COMMENT: @page - -fdatasync -========= - -**File:** - -fdatasync.c - -**Processing:** - -This routine is a template in the in memory filesystem that will route us to the -appropriate handler function to carry out the fdatasync() processing. In the in -memory filesystem this function is not necessary. Its function in a disk based file -system that employs a memory cache is to flush all memory based data buffers to -disk. It is layered on the following functions and macros: - -- rtems_file_descriptor_type() - -- rtems_libio_iop() - -- rtems_libio_check_fd() - -- rtems_libio_check_permissions() - -- fdatasync() function that is referenced by the handler table in the - file control block associated with this file descriptor - -**Development Comments:** - -The routine will test to see if the file descriptor index is associated -with a network connection. If it is, an error is returned from this -routine. - -The file descriptor index is used to obtain the associated file control -block. - -The file descriptor value is range checked. - -The file control block is examined to determine if it has write -permissions to the file. - -A test is made to determine if the handler table that is referenced in the -file control block contains an entry for the fdatasync() handler function. -If it does not an error is returned to the calling routine. - -If the fdatasync() handler function exists, it is called with the file -control block as its parameter. - -.. COMMENT: @page - -fpathconf -========= - -**File:** - -fpathconf.c - -**Processing:** - -This routine is layered on the following functions and macros: - -- rtems_file_descriptor_type() - -- rtems_libio_iop() - -- rtems_libio_check_fd() - -- rtems_libio_check_permissions() - -When a filesystem is mounted, a set of constants is specified for the -filesystem. These constants are stored with the mount table entry for the -filesystem. These constants appear in the POSIX standard and are listed -below. - -- PCLINKMAX - -- PCMAXCANON - -- PCMAXINPUT - -- PCNAMEMAX - -- PCPATHMAX - -- PCPIPEBUF - -- PCCHOWNRESTRICTED - -- PCNOTRUNC - -- PCVDISABLE - -- PCASYNCIO - -- PCPRIOIO - -- PCSYNCIO - -This routine will find the mount table information associated the file -control block for the specified file descriptor parameter. The mount table -entry structure contains a set of filesystem specific constants that can -be accessed by individual identifiers. - -**Development Comments:** - -The routine will test to see if the file descriptor index is associated -with a network connection. If it is, an error is returned from this -routine. - -The file descriptor index is used to obtain the associated file control -block. - -The file descriptor value is range checked. - -The file control block is examined to determine if it has read permissions -to the file. - -Pathinfo in the file control block is used to locate the mount table entry -for the filesystem associated with the file descriptor. - -The mount table entry contains the pathconf_limits_and_options element. -This element is a table of constants that is associated with the -filesystem. - -The name argument is used to reference the desired constant from the -pathconf_limits_and_options table. - -.. COMMENT: @page - -fstat -===== - -**File:** - -fstat.c - -**Processing:** - -This routine will return information concerning a file or network -connection. If the file descriptor is associated with a network -connection, the current implementation of ``fstat()`` will return a -mode set to ``S_IFSOCK``. In a later version, this routine will map the -status of a network connection to an external handler routine. - -If the file descriptor is associated with a node under a filesystem, the -fstat() routine will map to the fstat() function taken from the node -handler table. - -**Development Comments:** - -This routine validates that the struct stat pointer is not NULL so that -the return location is valid. - -The struct stat is then initialized to all zeros. - -rtems_file_descriptor_type() is then used to determine if the file -descriptor is associated with a network connection. If it is, network -status processing is performed. In the current implementation, the file -descriptor type processing needs to be improved. It currently just drops -into the normal processing for file system nodes. - -If the file descriptor is associated with a node under a filesystem, the -following steps are performed: - -# Obtain the file control block that is associated with the file descriptor - index. - -# Range check the file descriptor index. - -# Test to see if there is a non-NULL function pointer in the handler - table for the fstat() function. If there is, invoke the function with the - file control block and the pointer to the stat structure. - -.. COMMENT: @page - -ioctl -===== - -**File:** - -ioctl.c - -**Processing:** - -Not defined in the POSIX 1003.1b standard but commonly supported in most -UNIX and POSIX system. Ioctl() is a catchall for I/O operations. Routine -is layered on external network handlers and filesystem specific handlers. -The development of new filesystems should not alter the basic processing -performed by this routine. - -**Development Comments:** - -The file descriptor is examined to determine if it is associated with a -network device. If it is processing is mapped to an external network -handler. The value returned by this handler is then returned to the -calling program. - -File descriptors that are associated with a filesystem undergo the -following processing: - -# The file descriptor index is used to obtain the associated file - control block. - -# The file descriptor value is range checked. - -# A test is made to determine if the handler table that is referenced - in the file control block contains an entry for the ioctl() handler - function. If it does not, an error is returned to the calling routine. - -# If the ioctl() handler function exists, it is called with the file - control block, the command and buffer as its parameters. - -# The return code from this function is then sent to the calling - routine. - -.. COMMENT: @page - -link -==== - -**File:** - -link.c - -**Processing:** - -This routine will establish a hard link to a file, directory or a device. -The target of the hard link must be in the same filesystem as the new link -being created. A link to an existing link is also permitted but the -existing link is evaluated before the new link is made. This implies that -links to links are reduced to links to files, directories or devices -before they are made. - -**Development Comments:** - -Calling parameters: -const char \*existing -const char \*new - -link() will determine if the target of the link actually exists using -rtems_filesystem_evaluate_path() - -rtems_filesystem_get_start_loc() is used to determine where to start the -path evaluation of the new name. This macro examines the first characters -of the name to see if the name of the new link starts with a -rtems_filesystem_is_separator. If it does the search starts from the root -of the RTEMS filesystem; otherwise the search will start from the current -directory. - -The OPS table evalformake() function for the parent’s filesystem is used -to locate the node that will be the parent of the new link. It will also -locate the start of the new path’s name. This name will be used to define -a child under the parent directory. - -If the parent is found, the routine will determine if the hard link that -we are trying to create will cross a filesystem boundary. This is not -permitted for hard-links. - -If the hard-link does not cross a filesystem boundary, a check is -performed to determine if the OPS table contains an entry for the link() -function. - -If a link() function is defined, the OPS table link() function will be -called to establish the actual link within the filesystem. - -The return code from the OPS table link() function is returned to the -calling program. - -.. COMMENT: @page - -lseek -===== - -**File:** - -lseek.c - -**Processing:** - -This routine is layered on both external handlers and filesystem / node -type specific handlers. This routine should allow for the support of new -filesystems without modification. - -**Development Comments:** - -This routine will determine if the file descriptor is associated with a -network device. If it is lseek will map to an external network handler. -The handler will be called with the file descriptor, offset and whence as -its calling parameters. The return code from the external handler will be -returned to the calling routine. - -If the file descriptor is not associated with a network connection, it is -associated with a node in a filesystem. The following steps will be -performed for filesystem nodes: - -# The file descriptor is used to obtain the file control block for the - node. - -# The file descriptor is range checked. - -# The offset element of the file control block is altered as indicated - by the offset and whence calling parameters - -# The handler table in the file control block is examined to determine - if it contains an entry for the lseek() function. If it does not an error - is returned to the calling program. - -# The lseek() function from the designated handler table is called - with the file control block, offset and whence as calling arguments - -# The return code from the lseek() handler function is returned to the - calling program - -.. COMMENT: @page - -mkdir -===== - -**File:** - -mkdir.c - -**Processing:** - -This routine attempts to create a directory node under the filesystem. The -routine is layered the mknod() function. - -**Development Comments:** - -See mknod() for developmental comments. - -.. COMMENT: @page - -mkfifo -====== - -**File:** - -mkfifo.c - -**Processing:** - -This routine attempts to create a FIFO node under the filesystem. The -routine is layered the mknod() function. - -**Development Comments:** - -See mknod() for developmental comments - -.. COMMENT: @page - -mknod -===== - -**File:** - -mknod.c - -**Processing:** - -This function will allow for the creation of the following types of nodes -under the filesystem: - -- directories - -- regular files - -- character devices - -- block devices - -- fifos - -At the present time, an attempt to create a FIFO will result in an ENOTSUP -error to the calling function. This routine is layered the filesystem -specific routines evalformake and mknod. The introduction of a new -filesystem must include its own evalformake and mknod function to support -the generic mknod() function. Under this condition the generic mknod() -function should accommodate other filesystem types without alteration. - -**Development Comments:** - -Test for nodal types - I thought that this test should look like the -following code: -.. code:: c - - if ( (mode & S_IFDIR) = = S_IFDIR) \|| - (mode & S_IFREG) = = S_IFREG) \|| - (mode & S_IFCHR) = = S_IFCHR) \|| - (mode & S_IFBLK) = = S_IFBLK) \|| - (mode & S_IFIFO) = = S_IFIFO)) - Set_errno_and_return_minus_one (EINVAL); - -Where: - -- S_IFREG (0100000) - Creation of a regular file - -- S_IFCHR (0020000) - Creation of a character device - -- S_IFBLK (0060000) - Creation of a block device - -- S_IFIFO (0010000) - Creation of a FIFO - -Determine if the pathname that we are trying to create starts at the root -directory or is relative to the current directory using the -rtems_filesystem_get_start_loc() function. - -Determine if the pathname leads to a valid directory that can be accessed -for the creation of a node. - -If the pathname is a valid location to create a node, verify that a -filesystem specific mknod() function exists. - -If the mknod() function exists, call the filesystem specific mknod() -function. Pass the name, mode, device type and the location information -associated with the directory under which the node will be created. - -.. COMMENT: @page - -mount -===== - -**File:** - -mount.c - -Arguments (Not a standard POSIX call): - -rtems_filesystem_mount_table_entry_t \**mt_entry, - -If the mount operation is successful, this pointer to a pointer will be -set to reference the mount table chain entry that has been allocated for -this file system mount. - -rtems_filesystem_operations_table \*fs_ops, - -This is a pointer to a table of functions that are associated with the -file system that we are about to mount. This is the mechanism to selected -file system type without keeping a dynamic database of all possible file -system types that are valid for the mount operation. Using this method, it -is only necessary to configure the filesystems that we wish to use into -the RTEMS build. Unused filesystems types will not be drawn into the -build. - -char \*fsoptions, - -This argument points to a string that selects mounting for read only -access or read/write access. Valid states are "RO" and "RW" - -char \*device, - -This argument is reserved for the name of a device that will be used to -access the filesystem information. Current filesystem implementations are -memory based and do not require a device to access filesystem information. - -char \*mount_point - -This is a pathname to a directory in a currently mounted filesystem that -allows read, write and execute permissions. If successful, the node found -by evaluating this name, is stored in the mt_entry. - -**Processing:** - -This routine will handle the mounting of a filesystem on a mount point. If -the operation is successful, a pointer to the mount table chain entry -associated with the mounted filesystem will be returned to the calling -function. The specifics about the processing required at the mount point -and within the filesystem being mounted is isolated in the filesystem -specific mount() and fsmount_me() functions. This allows the generic -mount() function to remain unaltered even if new filesystem types are -introduced. - -**Development Comments:** - -This routine will use get_file_system_options() to determine if the mount -options are valid ("RO" or "RW"). - -It confirms that a filesystem ops-table has been selected. - -Space is allocated for a mount table entry and selective elements of the -temporary mount table entry are initialized. - -If a mount point is specified: The mount point is examined to determine -that it is a directory and also has the appropriate permissions to allow a -filesystem to be mounted. - -The current mount table chain is searched to determine that there is not -another filesystem mounted at the mount point we are trying to mount onto. - -If a mount function is defined in the ops table for the filesystem -containing the mount point, it is called at this time. - -If no mount point is specified: Processing if performed to set up the -mount table chain entry as the base filesystem. - -If the fsmount_me() function is specified for ops-table of the filesystem -being mounted, that function is called to initialize for the new -filesystem. - -On successful completion, the temporary mount table entry will be placed -on the mount table chain to record the presence of the mounted filesystem. - -.. COMMENT: @page - -open -==== - -**File:** - -open.c - -**Processing:** - -This routine is layered on both RTEMS calls and filesystem specific -implementations of the open() function. These functional interfaces should -not change for new filesystems and therefore this code should be stable as -new file systems are introduced. - -**Development Comments:** - -This routine will allocate a file control block for the file or device -that we are about to open. - -It will then test to see if the pathname exists. If it does a -rtems_filesystem_location_info_t data structure will be filled out. This -structure contains information that associates node information, -filesystem specific functions and mount table chain information with the -pathname. - -If the create option has been it will attempt to create a node for a -regular file along the specified path. If a file already exists along this -path, an error will be generated; otherwise, a node will be allocated for -the file under the filesystem that contains the pathname. When a new node -is created, it is also evaluated so that an appropriate -rtems_filesystem_location_info_t data structure can be filled out for the -newly created node. - -If the file exists or the new file was created successfully, the file -control block structure will be initialized with handler table -information, node information and the rtems_filesystem_location_info_t -data structure that describes the node and filesystem data in detail. - -If an open() function exists in the filesystem specific handlers table for -the node that we are trying to open, it will be called at this time. - -If any error is detected in the process, cleanup is performed. It consists -of freeing the file control block structure that was allocated at the -beginning of the generic open() routine. - -On a successful open(), the index into the file descriptor table will be -calculated and returned to the calling routine. - -.. COMMENT: @page - -opendir -======= - -**File:** - -opendir.c - -**Processing:** - -This routine will attempt to open a directory for read access. It will -setup a DIR control structure that will be used to access directory -information. This routine is layered on the generic open() routine and -filesystem specific directory processing routines. - -**Development Comments:** - -The BSD group provided this routine. - -.. COMMENT: @page - -pathconf -======== - -**File:** - -pathconf.c - -**Processing:** - -This routine will obtain the value of one of the path configuration -parameters and return it to the calling routine. It is layered on the -generic open() and fpathconf() functions. These interfaces should not -change with the addition of new filesystem types. - -**Development Comments:** - -This routine will try to open the file indicated by path. - -If successful, the file descriptor will be used to access the pathconf -value specified by ``name`` using the fpathconf() function. - -The file that was accessed is then closed. - -.. COMMENT: @page - -read -==== - -**File:** - -deviceio.c - -**Processing:** - -This routine is layered on a set of RTEMS calls and filesystem specific -read operations. The functions are layered in such a way as to isolate -them from change as new filesystems are introduced. - -**Development Comments:** - -This routine will examine the type of file descriptor it is sent. - -If the file descriptor is associated with a network device, the read -function will be mapped to a special network handler. The return code from -the network handler will then be sent as the return code from generic -read() function. - -For file descriptors that are associated with the filesystem the following -sequence will be performed: - -# Obtain the file control block associated with the file descriptor - -# Range check the file descriptor - -# Determine that the buffer pointer is not invalid - -# Check that the count is not zero - -# Check the file control block to see if we have permissions to read - -# If there is a read function in the handler table, invoke the handler - table read() function - -# Use the return code from the handler table read function(number of - bytes read) to increment the offset element of the file control block - -# Return the number of bytes read to the calling program - -.. COMMENT: @page - -readdir -======= - -**File:** - -readdir.c - -**Processing:** - -This routine was acquired from the BSD group. It has not been altered from -its original form. - -**Development Comments:** - -The routine calls a customized getdents() function that is provided by the -user. This routine provides the filesystem specific aspects of reading a -directory. - -It is layered on the read() function in the directory handler table. This -function has been mapped to the Imfs_dir_read() function. - -.. COMMENT: @page - -unmount -======= - -**File:** - -unmount.c - -**Processing:** - -This routine will attempt to dismount a mounted filesystem and then free -all resources that were allocated for the management of that filesystem. - -**Development Comments:** - -- This routine will determine if there are any filesystems currently - mounted under the filesystem that we are trying to dismount. This would - prevent the dismount of the filesystem. - -- It will test to see if the current directory is in the filesystem - that we are attempting to dismount. This would prevent the dismount of the - filesystem. - -- It will scan all the currently open file descriptors to determine is - there is an open file descriptor to a file in the filesystem that we are - attempting to unmount(). - -If the above preconditions are met then the following sequence is -performed: - -# Call the filesystem specific unmount() function for the filesystem - that contains the mount point. This routine should indicate that the mount - point no longer has a filesystem mounted below it. - -# Call the filesystem specific fsunmount_me() function for the mounted - filesystem that we are trying to unmount(). This routine should clean up - any resources that are no longer needed for the management of the file - system being un-mounted. - -# Extract the mount table entry for the filesystem that was just - dismounted from the mount table chain. - -# Free the memory associated with the extracted mount table entry. - -.. COMMENT: @page - -eval -==== - -**File:** - -XXX - -**Processing:** - -XXX - -**Development Comments:** - -XXX - -.. COMMENT: @page - -getdentsc -========= - -**File:** - -XXX - -**Processing:** - -XXX - -**Development Comments:** - -XXX - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Filesystem Implementation Requirements -###################################### - -This chapter details the behavioral requirements that all filesystem -implementations must adhere to. - -General -======= - -The RTEMS filesystem framework was intended to be compliant with the -POSIX Files and Directories interface standard. The following filesystem -characteristics resulted in a functional switching layer. -.. code:: c - - Figure of the Filesystem Functional Layering goes here. - This figure includes networking and disk caching layering. - -# Application programs are presented with a standard set of POSIX - compliant functions that allow them to interface with the files, devices - and directories in the filesystem. The interfaces to these routines do - not reflect the type of subordinate filesystem implementation in which - the file will be found. - -# The filesystem framework developed under RTEMS allows for mounting - filesystem of different types under the base filesystem. - -# The mechanics of locating file information may be quite different - between filesystem types. - -# The process of locating a file may require crossing filesystem - boundaries. - -# The transitions between filesystem and the processing required to - access information in different filesystem is not visible at the level - of the POSIX function call. - -# The POSIX interface standard provides file access by character - pathname to the file in some functions and through an integer file - descriptor in other functions. - -# The nature of the integer file descriptor and its associated - processing is operating system and filesystem specific. - -# Directory and device information must be processed with some of the - same routines that apply to files. - -# The form and content of directory and device information differs - greatly from that of a regular file. - -# Files, directories and devices represent elements (nodes) of a tree - hierarchy. - -# The rules for processing each of the node types that exist under the - filesystem are node specific but are still not reflected in the POSIX - interface routines. - -.. code:: c - - Figure of the Filesystem Functional Layering goes here. - This figure focuses on the Base Filesystem and IMFS. - -.. code:: c - - Figure of the IMFS Memfile control blocks - - -File and Directory Removal Constraints -====================================== - -The following POSIX constraints must be honored by all filesystems. - -- If a node is a directory with children it cannot be removed. - -- The root node of any filesystem, whether the base filesystem or a - mounted filesystem, cannot be removed. - -- A node that is a directory that is acting as the mount point of a file - system cannot be removed. - -- On filesystems supporting hard links, a link count is maintained. - Prior to node removal, the node’s link count is decremented by one. The - link count must be less than one to allow for removal of the node. - -API Layering -============ - -Mapping of Generic System Calls to Filesystem Specific Functions ----------------------------------------------------------------- - -The list of generic system calls includes the routines open(), read(), -write(), close(), etc.. - -The Files and Directories section of the POSIX Application Programs -Interface specifies a set of functions with calling arguments that are -used to gain access to the information in a filesystem. To the -application program, these functions allow access to information in any -mounted filesystem without explicit knowledge of the filesystem type or -the filesystem mount configuration. The following are functions that are -provided to the application: - -# access() - -# chdir() - -# chmod() - -# chown() - -# close() - -# closedir() - -# fchmod() - -# fcntl() - -# fdatasync() - -# fpathconf() - -# fstat() - -# fsync() - -# ftruncate() - -# link() - -# lseek() - -# mkdir() - -# mknod() - -# mount() - -# open() - -# opendir() - -# pathconf() - -# read() - -# readdir() - -# rewinddir() - -# rmdir() - -# rmnod() - -# scandir() - -# seekdir() - -# stat() - -# telldir() - -# umask() - -# unlink() - -# unmount() - -# utime() - -# write() - -The filesystem’s type as well as the node type within the filesystem -determine the nature of the processing that must be performed for each of -the functions above. The RTEMS filesystem provides a framework that -allows new filesystem to be developed and integrated without alteration -to the basic framework. - -To provide the functional switching that is required, each of the POSIX -file and directory functions have been implemented as a shell function. -The shell function adheres to the POSIX interface standard. Within this -functional shell, filesystem and node type information is accessed which -is then used to invoke the appropriate filesystem and node type specific -routine to process the POSIX function call. - -File/Device/Directory function access via file control block - rtems_libio_t structure --------------------------------------------------------------------------------------- - -The POSIX open() function returns an integer file descriptor that is used -as a reference to file control block information for a specific file. The -file control block contains information that is used to locate node, file -system, mount table and functional handler information. The diagram in -Figure 8 depicts the relationship between and among the following -components. - -# File Descriptor Table - This is an internal RTEMS structure that tracks all currently defined file - descriptors in the system. The index that is returned by the file open() - operation references a slot in this table. The slot contains a pointer to - the file descriptor table entry for this file. The rtems_libio_t structure - represents the file control block. - -# Allocation of entry in the File Descriptor Table - Access to the file descriptor table is controlled through a semaphore that - is implemented using the rtems_libio_allocate() function. This routine - will grab a semaphore and then scan the file control blocks to determine - which slot is free for use. The first free slot is marked as used and the - index to this slot is returned as the file descriptor for the open() - request. After the alterations have been made to the file control block - table, the semaphore is released to allow further operations on the table. - -# Maximum number of entries in the file descriptor table is - configurable through the src/exec/sapi/headers/confdefs.h file. If the - CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS constant is defined its value - will represent the maximum number of file descriptors that are allowed. - If CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS is not specified a default - value of 20 will be used as the maximum number of file descriptors - allowed. - -# File control block - rtems_libio_t structure - - .. code:: c - - struct rtems_libio_tt { - rtems_driver_name_t \*driver; - off_t size; - off_t offset; - unsigned32 flags; - rtems_filesystem_location_info_t pathinfo; - Objects_Id sem; - unsigned32 data0; - void data1; - void file_info; - rtems_filesystem_file_handlers_r handlers; - }; - - A file control block can exist for regular files, devices and directories. - The following fields are important for regular file and directory access: - - - Size - For a file this represents the number of bytes currently - stored in a file. For a directory this field is not filled in. - - - Offset - For a file this is the byte file position index relative to - the start of the file. For a directory this is the byte offset into a - sequence of dirent structures. - - - Pathinfo - This is a structure that provides a pointer to node - information, OPS table functions, Handler functions and the mount table - entry associated with this node. - - - file_info - A pointer to node information that is used by Handler - functions - - - handlers - A pointer to a table of handler functions that operate on - a file, device or directory through a file descriptor index - -File/Directory function access via rtems_filesystem_location_info_t structure ------------------------------------------------------------------------------ - -The rtems_filesystem_location_info_tt structure below provides sufficient -information to process nodes under a mounted filesystem. - -.. code:: c - - struct rtems_filesystem_location_info_tt { - void \*node_access; - rtems_filesystem_file_handlers_r \*handlers; - rtems_filesystem_operations_table \*ops; - rtems_filesystem_mount_table_entry_t \*mt_entry; - }; - -It contains a void pointer to filesystem specific nodal structure, -pointers to the OPS table for the filesystem that contains the node, the -node type specific handlers for the node and a reference pointer to the -mount table entry associated with the filesystem containing the node - -Operation Tables -================ - -Filesystem specific operations are invoked indirectly. The set of -routines that implement the filesystem are configured into two tables. -The Filesystem Handler Table has routines that are specific to a -filesystem but remain constant regardless of the actual file type. -The File Handler Table has routines that are both filesystem and file type -specific. - -Filesystem Handler Table Functions ----------------------------------- - -OPS table functions are defined in a ``rtems_filesystem_operations_table`` -structure. It defines functions that are specific to a given filesystem. -One table exists for each filesystem that is supported in the RTEMS -configuration. The structure definition appears below and is followed by -general developmental information on each of the functions contained in this -function management structure. - -.. code:: c - - typedef struct { - rtems_filesystem_evalpath_t evalpath; - rtems_filesystem_evalmake_t evalformake; - rtems_filesystem_link_t link; - rtems_filesystem_unlink_t unlink; - rtems_filesystem_node_type_t node_type; - rtems_filesystem_mknod_t mknod; - rtems_filesystem_rmnod_t rmnod; - rtems_filesystem_chown_t chown; - rtems_filesystem_freenode_t freenod; - rtems_filesystem_mount_t mount; - rtems_filesystem_fsmount_me_t fsmount_me; - rtems_filesystem_unmount_t unmount; - rtems_filesystem_fsunmount_me_t fsunmount_me; - rtems_filesystem_utime_t utime; - rtems_filesystem_evaluate_link_t eval_link; - rtems_filesystem_symlink_t symlink; - } rtems_filesystem_operations_table; - -.. COMMENT: @page - -evalpath Handler -~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -evalpath - -**Arguments:** - -.. code:: c - - const char \*pathname, /* IN \*/ - int flags, /* IN \*/ - rtems_filesystem_location_info_t \*pathloc /* IN/OUT \*/ - -**Description:** - -This routine is responsible for evaluating the pathname passed in -based upon the flags and the valid ``rthems_filesystem_location_info_t``. -Additionally, it must make any changes to pathloc necessary to identify -the pathname node. This should include calling the evalpath for a mounted -filesystem, if the given filesystem supports the mount command. - -This routine returns a 0 if the evaluation was successful. -Otherwise, it returns a -1 and sets errno to the correct error. - -This routine is required and should NOT be set to NULL. - -.. COMMENT: @page - -evalformake Handler -~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -evalformake - -**Arguments:** - -.. code:: c - - const char \*path, /* IN \*/ - rtems_filesystem_location_info_t \*pathloc, /* IN/OUT \*/ - const char \**name /* OUT \*/ - -**Description:** - -This method is given a path to evaluate and a valid start location. It -is responsible for finding the parent node for a requested make command, -setting pathloc information to identify the parent node, and setting -the name pointer to the first character of the name of the new node. -Additionally, if the filesystem supports the mount command, this method -should call the evalformake routine for the mounted filesystem. - -This routine returns a 0 if the evaluation was successful. Otherwise, it -returns a -1 and sets errno to the correct error. - -This routine is required and should NOT be set to NULL. However, if -the filesystem does not support user creation of a new node, it may -set errno to ENOSYS and return -1. - -.. COMMENT: @page - -link Handler -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -link - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*to_loc, /* IN \*/ - rtems_filesystem_location_info_t \*parent_loc, /* IN \*/ - const char \*token /* IN \*/ - -**Description:** - -This routine is used to create a hard-link. - -It will first examine the st_nlink count of the node that we are trying to. -If the link count exceeds LINK_MAX an error will be returned. - -The name of the link will be normalized to remove extraneous separators from -the end of the name. - -This routine is not required and may be set to NULL. - -.. COMMENT: @page - -unlink Handler -~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -node_type Handler -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -node_type() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - -**Description:** - -XXX - -.. COMMENT: @page - -mknod Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -mknod() - -**Arguments:** - -.. code:: c - - const char \*token, /* IN \*/ - mode_t mode, /* IN \*/ - dev_t dev, /* IN \*/ - rtems_filesystem_location_info_t \*pathloc /* IN/OUT \*/ - -**Description:** - -XXX - -.. COMMENT: @page - -rmnod Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -chown Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -chown() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - uid_t owner /* IN \*/ - gid_t group /* IN \*/ - -**Description:** - -XXX - -.. COMMENT: @page - -freenod Handler -~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -freenod() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - -**Description:** - -This routine is used by the generic code to allow memory to be allocated -during the evaluate routines, and set free when the generic code is finished -accessing a node. If the evaluate routines allocate memory to identify -a node this routine should be utilized to free that memory. - -This routine is not required and may be set to NULL. - -.. COMMENT: @page - -mount Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -mount() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**Description:** - -XXX - -.. COMMENT: @page - -fsmount_me Handler -~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**Description:** - -This function is provided with a filesystem to take care of the internal -filesystem management details associated with mounting that filesystem -under the RTEMS environment. - -It is not responsible for the mounting details associated the filesystem -containing the mount point. - -The rtems_filesystem_mount_table_entry_t structure contains the key elements -below: - -rtems_filesystem_location_info_t \*mt_point_node, - -This structure contains information about the mount point. This -allows us to find the ops-table and the handling functions -associated with the filesystem containing the mount point. - -rtems_filesystem_location_info_t \*fs_root_node, - -This structure contains information about the root node in the file -system to be mounted. It allows us to find the ops-table and the -handling functions associated with the filesystem to be mounted. - -rtems_filesystem_options_t options, - -Read only or read/write access - -void \*fs_info, - -This points to an allocated block of memory the will be used to -hold any filesystem specific information of a global nature. This -allocated region if important because it allows us to mount the -same filesystem type more than once under the RTEMS system. -Each instance of the mounted filesystem has its own set of global -management information that is separate from the global -management information associated with the other instances of the -mounted filesystem type. - -rtems_filesystem_limits_and_options_t pathconf_info, - -The table contains the following set of values associated with the -mounted filesystem: - -- link_max - -- max_canon - -- max_input - -- name_max - -- path_max - -- pipe_buf - -- posix_async_io - -- posix_chown_restrictions - -- posix_no_trunc - -- posix_prio_io - -- posix_sync_io - -- posix_vdisable - -These values are accessed with the pathconf() and the fpathconf () -functions. - -const char \*dev - -The is intended to contain a string that identifies the device that contains -the filesystem information. The filesystems that are currently implemented -are memory based and don’t require a device specification. - -If the mt_point_node.node_access is NULL then we are mounting the base file -system. - -The routine will create a directory node for the root of the IMFS file -system. - -The node will have read, write and execute permissions for owner, group and -others. - -The node’s name will be a null string. - -A filesystem information structure(fs_info) will be allocated and -initialized for the IMFS filesystem. The fs_info pointer in the mount table -entry will be set to point the filesystem information structure. - -The pathconf_info element of the mount table will be set to the appropriate -table of path configuration constants (LIMITS_AND_OPTIONS). - -The fs_root_node structure will be filled in with the following: - -- pointer to the allocated root node of the filesystem - -- directory handlers for a directory node under the IMFS filesystem - -- OPS table functions for the IMFS - -A 0 will be returned to the calling routine if the process succeeded, -otherwise a 1 will be returned. - -.. COMMENT: @page - -unmount Handler -~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -fsunmount_me Handler -~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_fsunmount_me() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**Description:** - -XXX - -.. COMMENT: @page - -utime Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -eval_link Handler -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -symlink Handler -~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -File Handler Table Functions ----------------------------- - -Handler table functions are defined in a ``rtems_filesystem_file_handlers_r`` -structure. It defines functions that are specific to a node type in a given -filesystem. One table exists for each of the filesystem’s node types. The -structure definition appears below. It is followed by general developmental -information on each of the functions associated with regular files contained -in this function management structure. -.. code:: c - - typedef struct { - rtems_filesystem_open_t open; - rtems_filesystem_close_t close; - rtems_filesystem_read_t read; - rtems_filesystem_write_t write; - rtems_filesystem_ioctl_t ioctl; - rtems_filesystem_lseek_t lseek; - rtems_filesystem_fstat_t fstat; - rtems_filesystem_fchmod_t fchmod; - rtems_filesystem_ftruncate_t ftruncate; - rtems_filesystem_fpathconf_t fpathconf; - rtems_filesystem_fsync_t fsync; - rtems_filesystem_fdatasync_t fdatasync; - rtems_filesystem_fcntl_t fcntl; - } rtems_filesystem_file_handlers_r; - -.. COMMENT: @page - -open Handler -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -open() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - const char \*pathname, - unsigned32 flag, - unsigned32 mode - -**Description:** - -XXX - -.. COMMENT: @page - -close Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -close() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -read Handler -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -read() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - void \*buffer, - unsigned32 count - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -write Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -ioctl Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - unsigned32 command, - void \*buffer - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -lseek Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -lseek() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - off_t offset, - int whence - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -fstat Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -fstat() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*loc, - struct stat \*buf - -**Description:** - -The following information is extracted from the filesystem -specific node and placed in the ``stat`` structure: - -- st_mode - -- st_nlink - -- st_ino - -- st_uid - -- st_gid - -- st_atime - -- st_mtime - -- st_ctime - -**NOTES:** - -Both the ``stat()`` and ``lstat()`` services are -implemented directly using the ``fstat()`` handler. The -difference in behavior is determined by how the path is evaluated -prior to this handler being called on a particular -file entity. - -The ``fstat()`` system call is implemented directly -on top of this filesystem handler. - -.. COMMENT: @page - -fchmod Handler -~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -fchmod() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - mode_t mode - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -ftruncate Handler -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -fpathconf Handler -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -fsync Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -fdatasync Handler -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: @page - -fcntl Handler -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**Description:** - -XXX - -**NOTES:** - -XXX - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -In-Memory Filesystem -#################### - -This chapter describes the In-Memory FileSystem (IMFS). The IMFS is a -full featured POSIX filesystem that keeps all information in memory. - -IMFS Per Node Data Structure -============================ - -Each regular file, device, hard link, and directory is represented by a data -structure called a ``jnode``. The ``jnode`` is formally represented by the -structure: -.. code:: c - - struct IMFS_jnode_tt { - Chain_Node Node; /* for chaining them together \*/ - IMFS_jnode_t \*Parent; /* Parent node \*/ - char name[NAME_MAX+1]; /* "basename" \*/ - mode_t st_mode; /* File mode \*/ - nlink_t st_nlink; /* Link count \*/ - ino_t st_ino; /* inode \*/ - uid_t st_uid; /* User ID of owner \*/ - gid_t st_gid; /* Group ID of owner \*/ - time_t st_atime; /* Time of last access \*/ - time_t st_mtime; /* Time of last modification \*/ - time_t st_ctime; /* Time of last status change \*/ - IMFS_jnode_types_t type; /* Type of this entry \*/ - IMFS_typs_union info; - }; - -The key elements of this structure are listed below together with a brief -explanation of their role in the filesystem. - -*Node* - exists to allow the entire ``jnode`` structure to be included in a chain. - -*Parent* - is a pointer to another ``jnode`` structure that is the logical parent of the - node in which it appears. This field may be NULL if the file associated with - this node is deleted but there are open file descriptors on this file or - there are still hard links to this node. - -*name* - is the name of this node within the filesystem hierarchical tree. Example: If - the fully qualified pathname to the ``jnode`` was ``/a/b/c``, the``jnode`` name field would contain the null terminated string ``"c"``. - -*st_mode* - is the standard Unix access permissions for the file or directory. - -*st_nlink* - is the number of hard links to this file. When a ``jnode`` is first created - its link count is set to 1. A ``jnode`` and its associated resources - cannot be deleted unless its link count is less than 1. - -*st_ino* - is a unique node identification number - -*st_uid* - is the user ID of the file’s owner - -*st_gid* - is the group ID of the file’s owner - -*st_atime* - is the time of the last access to this file - -*st_mtime* - is the time of the last modification of this file - -*st_ctime* - is the time of the last status change to the file - -*type* - is the indication of node type must be one of the following states: - - IMFS_DIRECTORY - - IMFS_MEMORY_FILE - - IMFS_HARD_LINK - - IMFS_SYM_LINK - - IMFS_DEVICE - -*info* - is this contains a structure that is unique to file type (See IMFS_typs_union - in imfs.h). - - - IMFS_DIRECTORY - - An IMFS directory contains a dynamic chain structure that - records all files and directories that are subordinate to the directory node. - - - IMFS_MEMORY_FILE - - Under the in memory filesystem regular files hold data. Data is dynamically - allocated to the file in 128 byte chunks of memory. The individual chunks of - memory are tracked by arrays of pointers that record the address of the - allocated chunk of memory. Single, double, and triple indirection pointers - are used to record the locations of all segments of the file. The - memory organization of an IMFS file are discussed elsewhere in this manual. - - - IMFS_HARD_LINK - - The IMFS filesystem supports the concept of hard links to other nodes in the - IMFS filesystem. These hard links are actual pointers to other nodes in the - same filesystem. This type of link cannot cross-filesystem boundaries. - - - IMFS_SYM_LINK - - The IMFS filesystem supports the concept of symbolic links to other nodes in - any filesystem. A symbolic link consists of a pointer to a character string - that represents the pathname to the target node. This type of link can - cross-filesystem boundaries. Just as with most versions of UNIX supporting - symbolic links, a symbolic link can point to a non-existent file. - - - IMFS_DEVICE - - All RTEMS devices now appear as files under the in memory filesystem. On - system initialization, all devices are registered as nodes under the file - system. - -Miscellaneous IMFS Information -============================== - -Memory associated with the IMFS -=============================== - -A memory based filesystem draws its resources for files and directories -from the memory resources of the system. When it is time to un-mount the -filesystem, the memory resources that supported filesystem are set free. -In order to free these resources, a recursive walk of the filesystems -tree structure will be performed. As the leaf nodes under the filesystem -are encountered their resources are freed. When directories are made empty -by this process, their resources are freed. - -Node removal constraints for the IMFS -------------------------------------- - -The IMFS conforms to the general filesystem requirements for node -removal. See `File and Directory Removal Constraints`_. - -IMFS General Housekeeping Notes -------------------------------- - -The following is a list of odd housekeeping notes for the IMFS. - -- If the global variable rtems_filesystem_current refers to the node that - we are trying to remove, the node_access element of this structure must be - set to NULL to invalidate it. - -- If the node was of IMFS_MEMORY_FILE type, free the memory associated - with the memory file before freeing the node. Use the IMFS_memfile_remove() - function. - -IMFS Operation Tables -===================== - -IMFS Filesystem Handler Table Functions ---------------------------------------- - -OPS table functions are defined in a rtems_filesystem_operations_table -structure. It defines functions that are specific to a given filesystem. -One table exists for each filesystem that is supported in the RTEMS -configuration. The structure definition appears below and is followed by -general developmental information on each of the functions contained in this -function management structure. -.. code:: c - - rtems_filesystem_operations_table IMFS_ops = { - IMFS_eval_path, - IMFS_evaluate_for_make, - IMFS_link, - IMFS_unlink, - IMFS_node_type, - IMFS_mknod, - IMFS_rmnod, - IMFS_chown, - IMFS_freenodinfo, - IMFS_mount, - IMFS_initialize, - IMFS_unmount, - IMFS_fsunmount, - IMFS_utime, - IMFS_evaluate_link, - IMFS_symlink, - IMFS_readlink - }; - -.. COMMENT: @page - -IMFS_evalpath() -~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_evalformake() -~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_link() -~~~~~~~~~~~ - -**Corresponding Structure Element:** - -link - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*to_loc, /* IN \*/ - rtems_filesystem_location_info_t \*parent_loc, /* IN \*/ - const char \*token /* IN \*/ - -**File:** - -imfs_link.c - -**Description:** - -This routine is used in the IMFS filesystem to create a hard-link. - -It will first examine the st_nlink count of the node that we are trying to. -If the link count exceeds LINK_MAX an error will be returned. - -The name of the link will be normalized to remove extraneous separators from -the end of the name. - -IMFS_create_node will be used to create a filesystem node that will have the -following characteristics: - -- parent that was determined in the link() function in file link.c - -- Type will be set to IMFS_HARD_LINK - -- name will be set to the normalized name - -- mode of the hard-link will be set to the mode of the target node - -If there was trouble allocating memory for the new node an error will be -returned. - -The st_nlink count of the target node will be incremented to reflect the new -link. - -The time fields of the link will be set to reflect the creation time of the -hard-link. - -.. COMMENT: @page - -IMFS_unlink() -~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_node_type() -~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_node_type() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - -**File:** - -imfs_ntype.c - -**Description:** - -This routine will locate the IMFS_jnode_t structure that holds ownership -information for the selected node in the filesystem. - -This structure is pointed to by pathloc->node_access. - -The IMFS_jnode_t type element indicates one of the node types listed below: - -- RTEMS_FILESYSTEM_DIRECTORY - -- RTEMS_FILESYSTEM_DEVICE - -- RTEMS_FILESYSTEM_HARD_LINK - -- RTEMS_FILESYSTEM_MEMORY_FILE - -.. COMMENT: @page - -IMFS_mknod() -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_mknod() - -**Arguments:** - -.. code:: c - - const char \*token, /* IN \*/ - mode_t mode, /* IN \*/ - dev_t dev, /* IN \*/ - rtems_filesystem_location_info_t \*pathloc /* IN/OUT \*/ - -**File:** - -imfs_mknod.c - -**Description:** - -This routine will examine the mode argument to determine is we are trying to -create a directory, regular file and a device node. The creation of other -node types is not permitted and will cause an assert. - -Memory space will be allocated for a ``jnode`` and the node will be set up -according to the nodal type that was specified. The IMFS_create_node() -function performs the allocation and setup of the node. - -The only problem that is currently reported is the lack of memory when we -attempt to allocate space for the ``jnode`` (ENOMEN). - -.. COMMENT: @page - -IMFS_rmnod() -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_chown() -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_chown() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - uid_t owner /* IN \*/ - gid_t group /* IN \*/ - -**File:** - -imfs_chown.c - -**Description:** - -This routine will locate the IMFS_jnode_t structure that holds ownership -information for the selected node in the filesystem. - -This structure is pointed to by pathloc->node_access. - -The st_uid and st_gid fields of the node are then modified. Since this is a -memory based filesystem, no further action is required to alter the -ownership of the IMFS_jnode_t structure. - -.. COMMENT: @page - -IMFS_freenod() -~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_freenod() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - -**File:** - -imfs_free.c - -**Description:** - -This method is a private function to the IMFS. It is called by IMFS routines -to free nodes that have been allocated. Examples of where this routine -may be called from are unlink and rmnod. - -Note: This routine should not be confused with the filesystem callback -freenod. The IMFS allocates memory until the node no longer exists. - -.. COMMENT: @page - -IMFS_freenodinfo() -~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_freenodinfo() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*pathloc /* IN \*/ - -**File:** - -imfs_free.c - -**Description:** - -The In-Memory File System does not need to allocate memory during the -evaluate routines. Therefore, this routine simply routines PASS. - -.. COMMENT: @page - -IMFS_mount() -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_mount() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**File:** - -imfs_mount.c - -**Description:** - -This routine provides the filesystem specific processing required to mount a -filesystem for the system that contains the mount point. It will determine -if the point that we are trying to mount onto is a node of IMFS_DIRECTORY -type. - -If it is the node’s info element is altered so that the info.directory.mt_fs -element points to the mount table chain entry that is associated with the -mounted filesystem at this point. The info.directory.mt_fs element can be -examined to determine if a filesystem is mounted at a directory. If it is -NULL, the directory does not serve as a mount point. A non-NULL entry -indicates that the directory does serve as a mount point and the value of -info.directory.mt_fs can be used to locate the mount table chain entry that -describes the filesystem mounted at this point. - -.. COMMENT: @page - -IMFS_fsmount_me() -~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_initialize() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**File:** - -imfs_init.c - -**Description:** - -This function is provided with a filesystem to take care of the internal -filesystem management details associated with mounting that filesystem -under the RTEMS environment. - -It is not responsible for the mounting details associated the filesystem -containing the mount point. - -The rtems_filesystem_mount_table_entry_t structure contains the key elements -below: - -rtems_filesystem_location_info_t \*mt_point_node, - -This structure contains information about the mount point. This -allows us to find the ops-table and the handling functions -associated with the filesystem containing the mount point. - -rtems_filesystem_location_info_t \*fs_root_node, - -This structure contains information about the root node in the file -system to be mounted. It allows us to find the ops-table and the -handling functions associated with the filesystem to be mounted. - -rtems_filesystem_options_t options, - -Read only or read/write access - -void \*fs_info, - -This points to an allocated block of memory the will be used to -hold any filesystem specific information of a global nature. This -allocated region if important because it allows us to mount the -same filesystem type more than once under the RTEMS system. -Each instance of the mounted filesystem has its own set of global -management information that is separate from the global -management information associated with the other instances of the -mounted filesystem type. - -rtems_filesystem_limits_and_options_t pathconf_info, - -The table contains the following set of values associated with the -mounted filesystem: - -- link_max - -- max_canon - -- max_input - -- name_max - -- path_max - -- pipe_buf - -- posix_async_io - -- posix_chown_restrictions - -- posix_no_trunc - -- posix_prio_io - -- posix_sync_io - -- posix_vdisable - -These values are accessed with the pathconf() and the fpathconf () -functions. - -const char \*dev - -The is intended to contain a string that identifies the device that contains -the filesystem information. The filesystems that are currently implemented -are memory based and don’t require a device specification. - -If the mt_point_node.node_access is NULL then we are mounting the base file -system. - -The routine will create a directory node for the root of the IMFS file -system. - -The node will have read, write and execute permissions for owner, group and -others. - -The node’s name will be a null string. - -A filesystem information structure(fs_info) will be allocated and -initialized for the IMFS filesystem. The fs_info pointer in the mount table -entry will be set to point the filesystem information structure. - -The pathconf_info element of the mount table will be set to the appropriate -table of path configuration constants ( IMFS_LIMITS_AND_OPTIONS ). - -The fs_root_node structure will be filled in with the following: - -- pointer to the allocated root node of the filesystem - -- directory handlers for a directory node under the IMFS filesystem - -- OPS table functions for the IMFS - -A 0 will be returned to the calling routine if the process succeeded, -otherwise a 1 will be returned. - -.. COMMENT: @page - -IMFS_unmount() -~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_unmount() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**File:** - -imfs_unmount.c - -**Description:** - -This routine allows the IMFS to unmount a filesystem that has been -mounted onto a IMFS directory. - -The mount entry mount point node access is verified to be a mounted -directory. It’s mt_fs is set to NULL. This identifies to future -calles into the IMFS that this directory node is no longer a mount -point. Additionally, it will allow any directories that were hidden -by the mounted system to again become visible. - -.. COMMENT: @page - -IMFS_fsunmount() -~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_fsunmount() - -**Arguments:** - -.. code:: c - - rtems_filesystem_mount_table_entry_t \*mt_entry - -**File:** - -imfs_init.c - -**Description:** - -This method unmounts this instance of the IMFS file system. It is the -counterpart to the IMFS_initialize routine. It is called by the generic -code under the fsunmount_me callback. - -All method loops finding the first encountered node with no children and -removing the node from the tree, thus returning allocated resources. This -is done until all allocated nodes are returned. - -.. COMMENT: @page - -IMFS_utime() -~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_eval_link() -~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -Regular File Handler Table Functions ------------------------------------- - -Handler table functions are defined in a rtems_filesystem_file_handlers_r -structure. It defines functions that are specific to a node type in a given -filesystem. One table exists for each of the filesystem’s node types. The -structure definition appears below. It is followed by general developmental -information on each of the functions associated with regular files contained -in this function management structure. -.. code:: c - - rtems_filesystem_file_handlers_r IMFS_memfile_handlers = { - memfile_open, - memfile_close, - memfile_read, - memfile_write, - memfile_ioctl, - memfile_lseek, - IMFS_stat, - IMFS_fchmod, - memfile_ftruncate, - NULL, /* fpathconf \*/ - NULL, /* fsync \*/ - IMFS_fdatasync, - IMFS_fcntl - }; - -.. COMMENT: @page - -memfile_open() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -memfile_open() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - const char \*pathname, - unsigned32 flag, - unsigned32 mode - -**File:** - -memfile.c - -**Description:** - -Currently this function is a shell. No meaningful processing is performed and -a success code is always returned. - -.. COMMENT: @page - -memfile_close() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -memfile_close() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - -**File:** - -memfile.c - -**Description:** - -This routine is a dummy for regular files under the base filesystem. It -performs a capture of the IMFS_jnode_t pointer from the file control block -and then immediately returns a success status. - -.. COMMENT: @page - -memfile_read() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -memfile_read() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - void \*buffer, - unsigned32 count - -**File:** - -memfile.c - -**Description:** - -This routine will determine the ``jnode`` that is associated with this file. - -It will then call IMFS_memfile_read() with the ``jnode``, file position index, -buffer and transfer count as arguments. - -IMFS_memfile_read() will do the following: - -- Verify that the ``jnode`` is associated with a memory file - -- Verify that the destination of the read is valid - -- Adjust the length of the read if it is too long - -- Acquire data from the memory blocks associated with the file - -- Update the access time for the data in the file - -.. COMMENT: @page - -memfile_write() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -memfile_ioctl() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - unsigned32 command, - void \*buffer - -**File:** - -memfile.c - -**Description:** - -The current code is a placeholder for future development. The routine returns -a successful completion status. - -.. COMMENT: @page - -memfile_lseek() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -Memfile_lseek() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - off_t offset, - int whence - -**File:** - -memfile.c - -**Description:** - -This routine make sure that the memory based file is sufficiently large to -allow for the new file position index. - -The IMFS_memfile_extend() function is used to evaluate the current size of -the memory file and allocate additional memory blocks if required by the new -file position index. A success code is always returned from this routine. - -.. COMMENT: @page - -IMFS_stat() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_stat() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*loc, - struct stat \*buf - -**File:** - -imfs_stat.c - -**Description:** - -This routine actually performs status processing for both devices and regular -files. - -The IMFS_jnode_t structure is referenced to determine the type of node under -the filesystem. - -If the node is associated with a device, node information is extracted and -transformed to set the st_dev element of the stat structure. - -If the node is a regular file, the size of the regular file is extracted from -the node. - -This routine rejects other node types. - -The following information is extracted from the node and placed in the stat -structure: - -- st_mode - -- st_nlink - -- st_ino - -- st_uid - -- st_gid - -- st_atime - -- st_mtime - -- st_ctime - -.. COMMENT: @page - -IMFS_fchmod() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_fchmod() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - mode_t mode - -**File:** - -imfs_fchmod.c - -**Description:** - -This routine will obtain the pointer to the IMFS_jnode_t structure from the -information currently in the file control block. - -Based on configuration the routine will acquire the user ID from a call to -getuid() or from the IMFS_jnode_t structure. - -It then checks to see if we have the ownership rights to alter the mode of -the file. If the caller does not, an error code is returned. - -An additional test is performed to verify that the caller is not trying to -alter the nature of the node. If the caller is attempting to alter more than -the permissions associated with user group and other, an error is returned. - -If all the preconditions are met, the user, group and other fields are set -based on the mode calling parameter. - -.. COMMENT: @page - -memfile_ftruncate() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -No pathconf() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -NULL - -**Arguments:** - -Not Implemented - -**File:** - -Not Implemented - -**Description:** - -Not Implemented - -.. COMMENT: @page - -No fsync() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_fdatasync() for Regular Files -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -Directory Handler Table Functions ---------------------------------- - -Handler table functions are defined in a rtems_filesystem_file_handlers_r -structure. It defines functions that are specific to a node type in a given -filesystem. One table exists for each of the filesystem’s node types. The -structure definition appears below. It is followed by general developmental -information on each of the functions associated with directories contained in -this function management structure. -.. code:: c - - rtems_filesystem_file_handlers_r IMFS_directory_handlers = { - IMFS_dir_open, - IMFS_dir_close, - IMFS_dir_read, - NULL, /* write \*/ - NULL, /* ioctl \*/ - IMFS_dir_lseek, - IMFS_dir_fstat, - IMFS_fchmod, - NULL, /* ftruncate \*/ - NULL, /* fpathconf \*/ - NULL, /* fsync \*/ - IMFS_fdatasync, - IMFS_fcntl - }; - -.. COMMENT: @page - -IMFS_dir_open() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_dir_open() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - const char \*pathname, - unsigned32 flag, - unsigned32 mode - -**File:** - -imfs_directory.c - -**Description:** - -This routine will look into the file control block to find the ``jnode`` that -is associated with the directory. - -The routine will verify that the node is a directory. If its not a directory -an error code will be returned. - -If it is a directory, the offset in the file control block will be set to 0. -This allows us to start reading at the beginning of the directory. - -.. COMMENT: @page - -IMFS_dir_close() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_dir_close() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - -**File:** - -imfs_directory.c - -**Description:** - -This routine is a dummy for directories under the base filesystem. It -immediately returns a success status. - -.. COMMENT: @page - -IMFS_dir_read() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_dir_read - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - void \*buffer, - unsigned32 count - -**File:** - -imfs_directory.c - -**Description:** - -This routine will read a fixed number of directory entries from the current -directory offset. The number of directory bytes read will be returned from -this routine. - -.. COMMENT: @page - -No write() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -No ioctl() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -ioctl - -**Arguments:** - -**File:** - -Not supported - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_dir_lseek() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_dir_lseek() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - off_t offset, - int whence - -**File:** - -imfs_directory.c - -**Description:** - -This routine alters the offset in the file control block. - -No test is performed on the number of children under the current open -directory. The imfs_dir_read() function protects against reads beyond the -current size to the directory by returning a 0 bytes transfered to the -calling programs whenever the file position index exceeds the last entry in -the open directory. - -.. COMMENT: @page - -IMFS_dir_fstat() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -imfs_dir_fstat() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*loc, - struct stat \*buf - -**File:** - -imfs_directory.c - -**Description:** - -The node access information in the rtems_filesystem_location_info_t structure -is used to locate the appropriate IMFS_jnode_t structure. The following -information is taken from the IMFS_jnode_t structure and placed in the stat -structure: - -- st_ino - -- st_mode - -- st_nlink - -- st_uid - -- st_gid - -- st_atime - -- st_mtime - -- st_ctime - -The st_size field is obtained by running through the chain of directory -entries and summing the sizes of the dirent structures associated with each -of the children of the directory. - -.. COMMENT: @page - -IMFS_fchmod() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_fchmod() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - mode_t mode - -**File:** - -imfs_fchmod.c - -**Description:** - -This routine will obtain the pointer to the IMFS_jnode_t structure from the -information currently in the file control block. - -Based on configuration the routine will acquire the user ID from a call to -getuid() or from the IMFS_jnode_t structure. - -It then checks to see if we have the ownership rights to alter the mode of -the file. If the caller does not, an error code is returned. - -An additional test is performed to verify that the caller is not trying to -alter the nature of the node. If the caller is attempting to alter more than -the permissions associated with user group and other, an error is returned. - -If all the preconditions are met, the user, group and other fields are set -based on the mode calling parameter. - -.. COMMENT: @page - -No ftruncate() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -No fpathconf() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -fpathconf - -**Arguments:** - -Not Implemented - -**File:** - -Not Implemented - -**Description:** - -Not Implemented - -.. COMMENT: @page - -No fsync() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -IMFS_fdatasync() for Directories -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -Device Handler Table Functions ------------------------------- - -Handler table functions are defined in a rtems_filesystem_file_handlers_r -structure. It defines functions that are specific to a node type in a given -filesystem. One table exists for each of the filesystem’s node types. The -structure definition appears below. It is followed by general developmental -information on each of the functions associated with devices contained in -this function management structure. -.. code:: c - - typedef struct { - rtems_filesystem_open_t open; - rtems_filesystem_close_t close; - rtems_filesystem_read_t read; - rtems_filesystem_write_t write; - rtems_filesystem_ioctl_t ioctl; - rtems_filesystem_lseek_t lseek; - rtems_filesystem_fstat_t fstat; - rtems_filesystem_fchmod_t fchmod; - rtems_filesystem_ftruncate_t ftruncate; - rtems_filesystem_fpathconf_t fpathconf; - rtems_filesystem_fsync_t fsync; - rtems_filesystem_fdatasync_t fdatasync; - } rtems_filesystem_file_handlers_r; - -.. COMMENT: @page - -device_open() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -device_open() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - const char \*pathname, - unsigned32 flag, - unsigned32 mode - -**File:** - -deviceio.c - -**Description:** - -This routine will use the file control block to locate the node structure for -the device. - -It will extract the major and minor device numbers from the ``jnode``. - -The major and minor device numbers will be used to make a rtems_io_open() -function call to open the device driver. An argument list is sent to the -driver that contains the file control block, flags and mode information. - -.. COMMENT: @page - -device_close() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -device_close() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - -**File:** - -deviceio.c - -**Description:** - -This routine extracts the major and minor device driver numbers from the -IMFS_jnode_t that is referenced in the file control block. - -It also forms an argument list that contains the file control block. - -A rtems_io_close() function call is made to close the device specified by the -major and minor device numbers. - -.. COMMENT: @page - -device_read() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -device_read() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - void \*buffer, - unsigned32 count - -**File:** - -deviceio.c - -**Description:** - -This routine will extract the major and minor numbers for the device from the - -jnode- associated with the file descriptor. - -A rtems_io_read() call will be made to the device driver associated with the file -descriptor. The major and minor device number will be sent as arguments as well -as an argument list consisting of: - -- file control block - -- file position index - -- buffer pointer where the data read is to be placed - -- count indicating the number of bytes that the program wishes to read - from the device - -- flags from the file control block - -On return from the rtems_io_read() the number of bytes that were actually -read will be returned to the calling program. - -.. COMMENT: @page - -device_write() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -device_ioctl() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -ioctl - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - unsigned32 command, - void \*buffer - -**File:** - -deviceio.c - -**Description:** - -This handler will obtain status information about a device. - -The form of status is device dependent. - -The rtems_io_control() function uses the major and minor number of the device -to obtain the status information. - -rtems_io_control() requires an rtems_libio_ioctl_args_t argument list which -contains the file control block, device specific command and a buffer pointer -to return the device status information. - -The device specific command should indicate the nature of the information -that is desired from the device. - -After the rtems_io_control() is processed, the buffer should contain the -requested device information. - -If the device information is not obtained properly a -1 will be returned to -the calling program, otherwise the ioctl_return value is returned. - -.. COMMENT: @page - -device_lseek() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -device_lseek() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop, - off_t offset, - int whence - -**File:** - -deviceio.c - -**Description:** - -At the present time this is a placeholder function. It always returns a -successful status. - -.. COMMENT: @page - -IMFS_stat() for Devices -~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_stat() - -**Arguments:** - -.. code:: c - - rtems_filesystem_location_info_t \*loc, - struct stat \*buf - -**File:** - -imfs_stat.c - -**Description:** - -This routine actually performs status processing for both devices and regular files. - -The IMFS_jnode_t structure is referenced to determine the type of node under the -filesystem. - -If the node is associated with a device, node information is extracted and -transformed to set the st_dev element of the stat structure. - -If the node is a regular file, the size of the regular file is extracted from the node. - -This routine rejects other node types. - -The following information is extracted from the node and placed in the stat -structure: - -- st_mode - -- st_nlink - -- st_ino - -- st_uid - -- st_gid - -- st_atime - -- st_mtime - -- st_ctime - -.. COMMENT: @page - -IMFS_fchmod() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -IMFS_fchmod() - -**Arguments:** - -.. code:: c - - rtems_libio_t \*iop - mode_t mode - -**File:** - -imfs_fchmod.c - -**Description:** - -This routine will obtain the pointer to the IMFS_jnode_t structure from the -information currently in the file control block. - -Based on configuration the routine will acquire the user ID from a call to -getuid() or from the IMFS_jnode_t structure. - -It then checks to see if we have the ownership rights to alter the mode of -the file. If the caller does not, an error code is returned. - -An additional test is performed to verify that the caller is not trying to -alter the nature of the node. If the caller is attempting to alter more than -the permissions associated with user group and other, an error is returned. - -If all the preconditions are met, the user, group and other fields are set -based on the mode calling parameter. - -.. COMMENT: @page - -No ftruncate() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -No fpathconf() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -fpathconf - -**Arguments:** - -Not Implemented - -**File:** - -Not Implemented - -**Description:** - -Not Implemented - -.. COMMENT: @page - -No fsync() for Devices -~~~~~~~~~~~~~~~~~~~~~~ - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: @page - -No fdatasync() for Devices -~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Not Implemented - -**Corresponding Structure Element:** - -XXX - -**Arguments:** - -XXX - -**File:** - -XXX - -**Description:** - -XXX - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Miniature In-Memory Filesystem -############################## - -This chapter describes the Miniature In-Memory FileSystem (miniIMFS). -The miniIMFS is a reduced feature version of the IMFS designed to -provide minimal functionality and have a low memory footprint. - -This chapter should be written after the IMFS chapter is completed -and describe the implementation of the mini-IMFS. - -.. COMMENT: COPYRIGHT (c) 1988-2002. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -Trivial FTP Client Filesystem -############################# - -This chapter describes the Trivial FTP (TFTP) Client Filesystem. - -This chapter should be written after the IMFS chapter is completed -and describe the implementation of the TFTP. - -Command and Variable Index -########################## - -There are currently no Command and Variable Index entries. - -.. COMMENT: @printindex fn - -Concept Index -############# - -There are currently no Concept Index entries. - -.. COMMENT: @printindex cp |