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diff --git a/ada_user/stack_bounds_checker.rst b/ada_user/stack_bounds_checker.rst deleted file mode 100644 index 44bf03f..0000000 --- a/ada_user/stack_bounds_checker.rst +++ /dev/null @@ -1,198 +0,0 @@ -Stack Bounds Checker -#################### - -Introduction -============ - -The stack bounds checker is an RTEMS support component that determines -if a task has overrun its run-time stack. The routines provided -by the stack bounds checker manager are: - -- ``rtems.stack_checker_is_blown`` - Has the Current Task Blown its Stack - -- ``rtems.stack_checker_report_usage`` - Report Task Stack Usage - -Background -========== - -Task Stack ----------- - -Each task in a system has a fixed size stack associated with it. This -stack is allocated when the task is created. As the task executes, the -stack is used to contain parameters, return addresses, saved registers, -and local variables. The amount of stack space required by a task -is dependent on the exact set of routines used. The peak stack usage -reflects the worst case of subroutine pushing information on the stack. -For example, if a subroutine allocates a local buffer of 1024 bytes, then -this data must be accounted for in the stack of every task that invokes that -routine. - -Recursive routines make calculating peak stack usage difficult, if not -impossible. Each call to the recursive routine consumes *n* bytes -of stack space. If the routine recursives 1000 times, then ``1000 * *n*`` bytes of stack space are required. - -Execution ---------- - -The stack bounds checker operates as a set of task extensions. At -task creation time, the task’s stack is filled with a pattern to -indicate the stack is unused. As the task executes, it will overwrite -this pattern in memory. At each task switch, the stack bounds checker’s -task switch extension is executed. This extension checks that: - -- the last ``n`` bytes of the task’s stack have - not been overwritten. If this pattern has been damaged, it - indicates that at some point since this task was context - switch to the CPU, it has used too much stack space. - -- the current stack pointer of the task is not within - the address range allocated for use as the task’s stack. - -If either of these conditions is detected, then a blown stack -error is reported using the ``printk`` routine. - -The number of bytes checked for an overwrite is processor family dependent. -The minimum stack frame per subroutine call varies widely between processor -families. On CISC families like the Motorola MC68xxx and Intel ix86, all -that is needed is a return address. On more complex RISC processors, -the minimum stack frame per subroutine call may include space to save -a significant number of registers. - -Another processor dependent feature that must be taken into account by -the stack bounds checker is the direction that the stack grows. On some -processor families, the stack grows up or to higher addresses as the -task executes. On other families, it grows down to lower addresses. The -stack bounds checker implementation uses the stack description definitions -provided by every RTEMS port to get for this information. - -Operations -========== - -Initializing the Stack Bounds Checker -------------------------------------- - -The stack checker is initialized automatically when its task -create extension runs for the first time. - -The application must include the stack bounds checker extension set -in its set of Initial Extensions. This set of extensions is -defined as ``STACK_CHECKER_EXTENSION``. If using ``<rtems/confdefs.h>`` -for Configuration Table generation, then all that is necessary is -to define the macro ``CONFIGURE_STACK_CHECKER_ENABLED`` before including``<rtems/confdefs.h>`` as shown below: -.. code:: c - - #define CONFIGURE_STACK_CHECKER_ENABLED - ... - #include <rtems/confdefs.h> - -Checking for Blown Task Stack ------------------------------ - -The application may check whether the stack pointer of currently -executing task is within proper bounds at any time by calling -the ``rtems.stack_checker_is_blown`` method. This -method return ``FALSE`` if the task is operating within its -stack bounds and has not damaged its pattern area. - -Reporting Task Stack Usage --------------------------- - -The application may dynamically report the stack usage for every task -in the system by calling the``rtems.stack_checker_report_usage`` routine. -This routine prints a table with the peak usage and stack size of -every task in the system. The following is an example of the -report generated: -.. code:: c - - ID NAME LOW HIGH AVAILABLE USED - 0x04010001 IDLE 0x003e8a60 0x003e9667 2952 200 - 0x08010002 TA1 0x003e5750 0x003e7b57 9096 1168 - 0x08010003 TA2 0x003e31c8 0x003e55cf 9096 1168 - 0x08010004 TA3 0x003e0c40 0x003e3047 9096 1104 - 0xffffffff INTR 0x003ecfc0 0x003effbf 12160 128 - -Notice the last time. The task id is 0xffffffff and its name is "INTR". -This is not actually a task, it is the interrupt stack. - -When a Task Overflows the Stack -------------------------------- - -When the stack bounds checker determines that a stack overflow has occurred, -it will attempt to print a message using ``printk`` identifying the -task and then shut the system down. If the stack overflow has caused -corruption, then it is possible that the message cannot be printed. - -The following is an example of the output generated: -.. code:: c - - BLOWN STACK!!! Offending task(0x3eb360): id=0x08010002; name=0x54413120 - stack covers range 0x003e5750 - 0x003e7b57 (9224 bytes) - Damaged pattern begins at 0x003e5758 and is 128 bytes long - -The above includes the task id and a pointer to the task control block as -well as enough information so one can look at the task’s stack and -see what was happening. - -Routines -======== - -This section details the stack bounds checker’s routines. -A subsection is dedicated to each of routines -and describes the calling sequence, related constants, usage, -and status codes. - -.. COMMENT: rtems_stack_checker_is_blown - -STACK_CHECKER_IS_BLOWN - Has Current Task Blown Its Stack ---------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. code:: c - - function Stack_Checker_Is_Blown return RTEMS.Boolean; - -**STATUS CODES:** - -``TRUE`` - Stack is operating within its stack limits -``FALSE`` - Current stack pointer is outside allocated area - -**DESCRIPTION:** - -This method is used to determine if the current stack pointer -of the currently executing task is within bounds. - -**NOTES:** - -This method checks the current stack pointer against -the high and low addresses of the stack memory allocated when -the task was created and it looks for damage to the high water -mark pattern for the worst case usage of the task being called. - -STACK_CHECKER_REPORT_USAGE - Report Task Stack Usage ----------------------------------------------------- - -**CALLING SEQUENCE:** - -.. code:: c - - procedure Stack_Checker_Report_Usage; - -**STATUS CODES: NONE** - -**DESCRIPTION:** - -This routine prints a table with the peak stack usage and stack space -allocation of every task in the system. - -**NOTES:** - -NONE - -.. COMMENT: COPYRIGHT (c) 1988-2007. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - |