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