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fa53723cdb
Refactor the support_next_to_fault and add the support_next_to_fault_before method returns a buffer with a protected page before it, to be able to test buffer underflow accesses. Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@redhat.com>
77 lines
2.6 KiB
C
77 lines
2.6 KiB
C
/* Memory allocation either before or after an unmapped page.
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Copyright (C) 2017-2025 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <stdbool.h>
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#include <support/check.h>
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#include <support/next_to_fault.h>
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#include <support/xunistd.h>
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#include <sys/mman.h>
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#include <sys/param.h>
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static struct support_next_to_fault
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support_next_to_fault_allocate_any (size_t size, bool fault_after_alloc)
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{
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long page_size = sysconf (_SC_PAGE_SIZE);
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long protect_offset = 0;
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long buffer_offset = page_size;
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TEST_VERIFY_EXIT (page_size > 0);
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struct support_next_to_fault result;
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result.region_size = roundup (size, page_size) + page_size;
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if (size + page_size <= size || result.region_size <= size)
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FAIL_EXIT1 ("%s (%zu): overflow", __func__, size);
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result.region_start
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= xmmap (NULL, result.region_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS, -1);
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if (fault_after_alloc)
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{
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protect_offset = result.region_size - page_size;
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buffer_offset = protect_offset - size;
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}
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/* Unmap the page before or after the allocation. */
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xmprotect (result.region_start + protect_offset, page_size, PROT_NONE);
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/* Align the allocation within the region so that it starts after or ends
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just before the PROT_NONE page. */
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result.buffer = result.region_start + buffer_offset;
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result.length = size;
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return result;
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}
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/* Unmapped a page after the buffer */
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struct support_next_to_fault
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support_next_to_fault_allocate (size_t size)
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{
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return support_next_to_fault_allocate_any (size, true);
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}
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/* Unmapped a page before the buffer */
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struct support_next_to_fault
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support_next_to_fault_allocate_before (size_t size)
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{
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return support_next_to_fault_allocate_any (size, false);
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}
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void
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support_next_to_fault_free (struct support_next_to_fault *ntf)
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{
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xmunmap (ntf->region_start, ntf->region_size);
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*ntf = (struct support_next_to_fault) { NULL, };
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}
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