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/**
* \file mmap_anon.c
* \brief Provide a compatible anonymous space mapping function
*/
#include "config.h"
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.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, 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 */
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);
close(fd);
#endif /* MAP_ANONYMOUS */
return result;
}
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