886dd92eee
From now, there are no auxiliary pointers stored in the free slab nodes. This led to strange debugging problems if use-after-free happened in slab-allocated structures, especially if the structure's first member is a next pointer. This also reduces the memory needed by 1 pointer per allocated object. OTOH, we now rely on pages being aligned to their size's multiple, which is quite common anyway.
81 lines
1.4 KiB
C
81 lines
1.4 KiB
C
/*
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* BIRD Internet Routing Daemon -- Raw allocation
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*
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* (c) 2020 Maria Matejka <mq@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#include "nest/bird.h"
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#include "lib/resource.h"
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#include <stdlib.h>
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#include <unistd.h>
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#ifdef HAVE_MMAP
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#include <sys/mman.h>
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#endif
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#ifdef HAVE_MMAP
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static u64 page_size = 0;
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static _Bool use_fake = 0;
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#else
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static const u64 page_size = 4096; /* Fake page size */
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#endif
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u64 get_page_size(void)
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{
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if (page_size)
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return page_size;
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#ifdef HAVE_MMAP
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if (page_size = sysconf(_SC_PAGESIZE))
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{
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if ((u64_popcount(page_size) > 1) || (page_size > 16384))
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{
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/* Too big or strange page, use the aligned allocator instead */
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page_size = 4096;
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use_fake = 1;
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}
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return page_size;
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}
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bug("Page size must be non-zero");
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#endif
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}
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void *
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alloc_page(void)
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{
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#ifdef HAVE_MMAP
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if (!use_fake)
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{
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void *ret = mmap(NULL, get_page_size(), PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (ret == MAP_FAILED)
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bug("mmap(%lu) failed: %m", page_size);
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return ret;
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}
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else
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#endif
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{
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void *ret = aligned_alloc(page_size, page_size);
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if (!ret)
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bug("aligned_alloc(%lu) failed", page_size);
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return ret;
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}
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}
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void
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free_page(void *ptr)
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{
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#ifdef HAVE_MMAP
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if (!use_fake)
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{
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if (munmap(ptr, get_page_size()) < 0)
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bug("munmap(%p) failed: %m", ptr);
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}
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else
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#endif
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free(ptr);
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}
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