mirror of https://github.com/mpv-player/mpv
68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
|
/**
|
||
|
|
* \file mmap_anon.c
|
||
|
|
* \brief Provide a compatible anonymous space mapping function
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <sys/mman.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <unistd.h>
|
||
|
|
#include <fcntl.h>
|
||
|
|
|
||
|
|
#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
|
||
|
|
#define MAP_ANONYMOUS MAP_ANON
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/*
|
||
|
|
* mmap() anonymous space, depending on the system's mmap() style. On systems
|
||
|
|
* that use the /dev/zero mapping idiom, zerofd will be set to the file descriptor
|
||
|
|
* of the opened /dev/zero.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief mmap() anonymous space, depending on the system's mmap() style. On systems
|
||
|
|
* that use the /dev/zero mapping idiom, zerofd will be set to the file descriptor
|
||
|
|
* of the opened /dev/zero.
|
||
|
|
*
|
||
|
|
* \param addr address to map at.
|
||
|
|
* \param len number of bytes from addr to be mapped.
|
||
|
|
* \param prot protections (region accessibility).
|
||
|
|
* \param flags specifies the type of the mapped object.
|
||
|
|
* \param offset start mapping at byte offset.
|
||
|
|
* \param zerofd
|
||
|
|
* \return a pointer to the mapped region upon successful completion, -1 otherwise.
|
||
|
|
*/
|
||
|
|
void *mmap_anon(void *addr, size_t len, int prot, int flags, int *zerofd, off_t offset)
|
||
|
|
{
|
||
|
|
int fd;
|
||
|
|
void *result;
|
||
|
|
|
||
|
|
/* From loader/ext.c:
|
||
|
|
* "Linux EINVAL's on us if we don't pass MAP_PRIVATE to an anon mmap"
|
||
|
|
* Therefore we preserve the same behavior on all platforms, ie. no
|
||
|
|
* shared mappings of anon space (if the concepts are supported). */
|
||
|
|
#if defined(MAP_SHARED) && defined(MAP_PRIVATE)
|
||
|
|
flags = (flags & ~MAP_SHARED) | MAP_PRIVATE;
|
||
|
|
#endif /* defined(MAP_SHARED) && defined(MAP_PRIVATE) */
|
||
|
|
|
||
|
|
#ifdef MAP_ANONYMOUS
|
||
|
|
/* BSD-style anonymous mapping */
|
||
|
|
fd = -1;
|
||
|
|
result = mmap(addr, len, prot, flags | MAP_ANONYMOUS, -1, offset);
|
||
|
|
#else
|
||
|
|
/* SysV-style anonymous mapping */
|
||
|
|
fd = open("/dev/zero", O_RDWR);
|
||
|
|
if(fd < 0){
|
||
|
|
perror( "Cannot open /dev/zero for READ+WRITE. Check permissions! error: ");
|
||
|
|
return NULL;
|
||
|
|
}
|
||
|
|
|
||
|
|
result = mmap(addr, len, prot, flags, fd, offset);
|
||
|
|
#endif /* MAP_ANONYMOUS */
|
||
|
|
|
||
|
|
if (zerofd)
|
||
|
|
*zerofd = fd;
|
||
|
|
|
||
|
|
return result;
|
||
|
|
}
|
||
|
|
|