/**
* @file
*/
/*
* Copyright (c) 2012 Chris Johns (chrisj@rtems.org)
* Copyright (c) 2017 Gedare Bloom (gedare@rtems.org)
* Copyright (c) 2017 Kevin kirspel (kirspkt@gmail.com)
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#include "rtems/libio_.h"
#include <rtems/posix/mmanimpl.h>
#include <rtems/posix/shmimpl.h>
/**
* mmap chain of mappings.
*/
CHAIN_DEFINE_EMPTY( mmap_mappings );
void *mmap(
void *addr, size_t len, int prot, int flags, int fildes, off_t off
)
{
struct stat sb;
mmap_mapping *mapping;
mmap_mapping *current_mapping;
ssize_t r;
rtems_libio_t *iop;
bool map_fixed;
bool map_anonymous;
bool map_shared;
bool map_private;
bool is_shared_shm;
int err;
map_fixed = (flags & MAP_FIXED) == MAP_FIXED;
map_anonymous = (flags & MAP_ANON) == MAP_ANON;
map_shared = (flags & MAP_SHARED) == MAP_SHARED;
map_private = (flags & MAP_PRIVATE) == MAP_PRIVATE;
/* Clear errno. */
errno = 0;
iop = NULL;
if ( len == 0 ) {
errno = EINVAL;
return MAP_FAILED;
}
/*
* We can provide read, write and execute because the memory in RTEMS does
* not normally have protections but we cannot hide access to memory.
*/
if ( prot == PROT_NONE ) {
errno = ENOTSUP;
return MAP_FAILED;
}
/*
* We can not normally provide restriction of write access. Reject any
* attempt to map without write permission, since we are not able to
* prevent a write from succeeding.
*/
if ( PROT_WRITE != (prot & PROT_WRITE) ) {
errno = ENOTSUP;
return MAP_FAILED;
}
/*
* Anonymous mappings must have file descriptor set to -1 and the offset
* set to 0. Shared mappings are not supported with Anonymous mappings at
* this time
*/
if ( map_anonymous && (fildes != -1 || off != 0 || map_shared) ) {
errno = EINVAL;
return MAP_FAILED;
}
/*
* If MAP_ANON is declared without MAP_PRIVATE or MAP_SHARED,
* force MAP_PRIVATE
*/
if ( map_anonymous && !map_private && !map_shared ) {
flags |= MAP_PRIVATE;
map_private = true;
}
/* Check for supported flags */
if ((flags & ~(MAP_SHARED | MAP_PRIVATE | MAP_FIXED | MAP_ANON)) != 0) {
errno = EINVAL;
return MAP_FAILED;
}
/* Either MAP_SHARED or MAP_PRIVATE must be defined, but not both */
if ( map_shared ) {
if ( map_private ) {
errno = EINVAL;
return MAP_FAILED;
}
} else if ( !map_private ) {
errno = EINVAL;
return MAP_FAILED;
}
/* Check for illegal addresses. Watch out for address wrap. */
if ( map_fixed ) {
if ((uintptr_t)addr & PAGE_MASK) {
errno = EINVAL;
return MAP_FAILED;
}
if ( addr == NULL ) {
errno = EINVAL;
return MAP_FAILED;
}
if (addr + len < addr) {
errno = EINVAL;
return MAP_FAILED;
}
}
if ( !map_anonymous ) {
/*
* Get a stat of the file to get the dev + inode number and to make sure the
* fd is ok. The normal libio calls cannot be used because we need to return
* MAP_FAILED on error and they return -1 directly without coming back to
* here.
*/
if ( fstat( fildes, &sb ) < 0 ) {
errno = EBADF;
return MAP_FAILED;
}
/* fstat ensures we have a good file descriptor. Hold on to iop. */
iop = rtems_libio_iop( fildes );
/* Check the type of file we have and make sure it is supported. */
if ( S_ISDIR( sb.st_mode ) || S_ISLNK( sb.st_mode )) {
errno = ENODEV;
return MAP_FAILED;
}
/* Check to see if the mapping is valid for a regular file. */
if ( S_ISREG( sb.st_mode )
/* FIXME: Should this be using strict inequality (>) comparisons? It would
* be valid to map a region exactly equal to the st_size, e.g. see below. */
&& (( off >= sb.st_size ) || (( off + len ) >= sb.st_size ))) {
errno = EOVERFLOW;
return MAP_FAILED;
}
/* Check to see if the mapping is valid for other file/object types. */
if ( !S_ISCHR( sb.st_mode ) && sb.st_size < off + len ) {
errno = ENXIO;
return MAP_FAILED;
}
/* Do not seek on character devices, pipes, sockets, or memory objects. */
if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) ) {
if ( lseek( fildes, off, SEEK_SET ) < 0 ) {
return MAP_FAILED;
}
}
/* cdevs do not provide private mappings of any kind. */
if ( S_ISCHR( sb.st_mode ) && map_private ) {
errno = EINVAL;
return MAP_FAILED;
}
}
/* Create the mapping */
mapping = malloc( sizeof( mmap_mapping ));
if ( !mapping ) {
errno = ENOMEM;
return MAP_FAILED;
}
memset( mapping, 0, sizeof( mmap_mapping ));
mapping->len = len;
mapping->flags = flags;
if ( !map_anonymous ) {
/*
* HACK: We should have a better generic way to distinguish between
* shm objects and other mmap'd files. We need to know at munmap time
* if the mapping is to a shared memory object in order to refcnt shms.
* We could do this by providing mmap in the file operations if needed.
*/
if ( S_ISREG( sb.st_mode ) || S_ISBLK( sb.st_mode ) ||
S_ISCHR( sb.st_mode ) || S_ISFIFO( sb.st_mode ) ||
S_ISSOCK( sb.st_mode ) ) {
is_shared_shm = false;
} else {
is_shared_shm = true;
}
} else {
is_shared_shm = false;
}
if ( map_fixed ) {
mapping->addr = addr;
} else if ( map_private ) {
/* private mappings of shared memory do not need special treatment. */
is_shared_shm = false;
err = posix_memalign( &mapping->addr, PAGE_SIZE, len );
if ( err != 0 ) {
free( mapping );
errno = ENOMEM;
return MAP_FAILED;
}
}
/* MAP_FIXED is not supported for shared memory objects with MAP_SHARED. */
if ( map_fixed && is_shared_shm ) {
free( mapping );
errno = ENOTSUP;
return MAP_FAILED;
}
mmap_mappings_lock_obtain();
if ( map_fixed ) {
rtems_chain_node* node = rtems_chain_first (&mmap_mappings);
while ( !rtems_chain_is_tail( &mmap_mappings, node )) {
/*
* If the map is fixed see if this address is already mapped. At this
* point in time if there is an overlap in the mappings we return an
* error. POSIX allows us to also return successfully by unmapping
* the overlapping prior mappings.
*/
current_mapping = (mmap_mapping*) node;
if ( ( addr >= current_mapping->addr ) &&
( addr < ( current_mapping->addr + current_mapping->len )) ) {
free( mapping );
mmap_mappings_lock_release( );
errno = ENXIO;
return MAP_FAILED;
}
node = rtems_chain_next( node );
}
}
/* Populate the data */
if ( map_private ) {
if ( !map_anonymous ) {
/*
* Use read() for private mappings. This updates atime as needed.
* Changes to the underlying object will NOT be reflected in the mapping.
* The underlying object can be removed while the mapping exists.
*/
r = read( fildes, mapping->addr, len );
if ( r != len ) {
mmap_mappings_lock_release( );
if ( !map_fixed ) {
free( mapping->addr );
}
free( mapping );
errno = ENXIO;
return MAP_FAILED;
}
} else if ( !map_fixed ) {
memset( mapping->addr, 0, len );
}
} else if ( map_shared ) {
if ( is_shared_shm ) {
/* FIXME: This use of implementation details is a hack. */
mapping->shm = iop_to_shm( iop );
}
err = (*iop->pathinfo.handlers->mmap_h)(
iop, &mapping->addr, len, prot, off );
if ( err != 0 ) {
mmap_mappings_lock_release( );
free( mapping );
return MAP_FAILED;
}
}
rtems_chain_append_unprotected( &mmap_mappings, &mapping->node );
mmap_mappings_lock_release( );
return mapping->addr;
}
