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The new Linux 5.17 feature PR_SET_VMA_ANON_NAME can give names to anonymous private memory, see: https://lwn.net/Articles/867818/ It can be useful while debugging, to identify which portion of the process's memory belongs to which subsystem. This is how /proc/PID/maps can look like: 555ccd400000-555ccdc00000 r-xp 00000000 00:00 0 [anon:huge_code_pages] 7f6ec6600000-7f6ec6800000 rw-p 00000000 00:00 0 [anon:zend_alloc] The first mapping is the PHP executable copied to anonymous memory by option "opcache.huge_code_pages". The second one is a memory area for the "zend_alloc.h" memory allocator library. Unfortunately, it is not possible to give names to shared memory (MAP_SHARED), because Linux MAP_SHARED really maps /dev/zero (see shmem_zero_setup()), which makes madvise_vma_anon_name() believe this is a file mapping, failing the prctl() with EBADF.
45 lines
1.5 KiB
C
45 lines
1.5 KiB
C
/*
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+----------------------------------------------------------------------+
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| This source file is subject to version 2.00 of the Zend license, |
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| that is bundled with this package in the file LICENSE, and is |
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| available through the world-wide-web at the following url: |
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| http://www.zend.com/license/2_00.txt. |
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| If you did not receive a copy of the Zend license and are unable to |
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| obtain it through the world-wide-web, please send a note to |
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| license@zend.com so we can mail you a copy immediately. |
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+----------------------------------------------------------------------+
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| Authors: Max Kellermann <max.kellermann@ionos.com> |
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+----------------------------------------------------------------------+
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*/
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#ifndef ZEND_MMAP_H
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#define ZEND_MMAP_H
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#include "zend_portability.h"
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#ifdef __linux__
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# include <sys/prctl.h>
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/* fallback definitions if our libc is older than the kernel */
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# ifndef PR_SET_VMA
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# define PR_SET_VMA 0x53564d41
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# endif
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# ifndef PR_SET_VMA_ANON_NAME
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# define PR_SET_VMA_ANON_NAME 0
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# endif
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#endif // __linux__
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/**
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* Set a name for the specified memory area.
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*
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* This feature requires Linux 5.17.
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*/
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static zend_always_inline void zend_mmap_set_name(const void *start, size_t len, const char *name)
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{
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#ifdef __linux__
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prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, (unsigned long)start, len, (unsigned long)name);
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#endif
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}
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#endif /* ZEND_MMAP_H */
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