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mcheck: Wean away from malloc hooks [BZ #23489]
Split the mcheck implementation into the debugging hooks and API so that the API can be replicated in libc and libc_malloc_debug.so. The libc APIs always result in failure. The mcheck implementation has also been moved entirely into libc_malloc_debug.so and with it, all of the hook initialization code can now be moved into the debug library. Now the initialization can be done independently of libc internals. With this patch, libc_malloc_debug.so can no longer be used with older libcs, which is not its goal anyway. tst-vfork3 breaks due to this since it spawns shell scripts, which in turn execute using the system glibc. Move the test to tests-container so that only the built glibc is used. This move also fixes bugs in the mcheck version of memalign and realloc, thus allowing removal of the tests from tests-mcheck exclusion list. Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Siddhesh Poyarekar
406
malloc/mcheck-impl.c
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406
malloc/mcheck-impl.c
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@@ -0,0 +1,406 @@
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/* mcheck debugging hooks for malloc.
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Copyright (C) 1990-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Written May 1989 by Mike Haertel.
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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 <malloc-internal.h>
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#include <mcheck.h>
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#include <libintl.h>
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#include <stdint.h>
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#include <stdio.h>
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/* Arbitrary magical numbers. */
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#define MAGICWORD 0xfedabeeb
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#define MAGICFREE 0xd8675309
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#define MAGICBYTE ((char) 0xd7)
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#define MALLOCFLOOD ((char) 0x93)
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#define FREEFLOOD ((char) 0x95)
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/* Function to call when something awful happens. */
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static void (*abortfunc) (enum mcheck_status);
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struct hdr
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{
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size_t size; /* Exact size requested by user. */
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unsigned long int magic; /* Magic number to check header integrity. */
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struct hdr *prev;
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struct hdr *next;
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void *block; /* Real block allocated, for memalign. */
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unsigned long int magic2; /* Extra, keeps us doubleword aligned. */
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} __attribute__ ((aligned (MALLOC_ALIGNMENT)));
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/* This is the beginning of the list of all memory blocks allocated.
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It is only constructed if the pedantic testing is requested. */
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static struct hdr *root;
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/* Nonzero if pedentic checking of all blocks is requested. */
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static bool pedantic;
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#if defined _LIBC || defined STDC_HEADERS || defined USG
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# include <string.h>
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# define flood memset
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#else
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static void flood (void *, int, size_t);
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static void
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flood (void *ptr, int val, size_t size)
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{
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char *cp = ptr;
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while (size--)
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*cp++ = val;
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}
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#endif
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static enum mcheck_status
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checkhdr (const struct hdr *hdr)
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{
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enum mcheck_status status;
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bool mcheck_used = __is_malloc_debug_enabled (MALLOC_MCHECK_HOOK);
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if (!mcheck_used)
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/* Maybe the mcheck used is disabled? This happens when we find
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an error and report it. */
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return MCHECK_OK;
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switch (hdr->magic ^ ((uintptr_t) hdr->prev + (uintptr_t) hdr->next))
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{
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default:
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status = MCHECK_HEAD;
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break;
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case MAGICFREE:
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status = MCHECK_FREE;
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break;
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case MAGICWORD:
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if (((char *) &hdr[1])[hdr->size] != MAGICBYTE)
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status = MCHECK_TAIL;
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else if ((hdr->magic2 ^ (uintptr_t) hdr->block) != MAGICWORD)
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status = MCHECK_HEAD;
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else
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status = MCHECK_OK;
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break;
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}
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if (status != MCHECK_OK)
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{
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mcheck_used = 0;
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(*abortfunc) (status);
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mcheck_used = 1;
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}
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return status;
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}
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static enum mcheck_status
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__mcheck_checkptr (const void *ptr)
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{
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if (!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
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return MCHECK_DISABLED;
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if (ptr != NULL)
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return checkhdr (((struct hdr *) ptr) - 1);
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/* Walk through all the active blocks and test whether they were tampered
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with. */
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struct hdr *runp = root;
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/* Temporarily turn off the checks. */
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pedantic = false;
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while (runp != NULL)
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{
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(void) checkhdr (runp);
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runp = runp->next;
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}
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/* Turn checks on again. */
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pedantic = true;
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return MCHECK_OK;
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}
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static void
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unlink_blk (struct hdr *ptr)
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{
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if (ptr->next != NULL)
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{
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ptr->next->prev = ptr->prev;
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ptr->next->magic = MAGICWORD ^ ((uintptr_t) ptr->next->prev
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+ (uintptr_t) ptr->next->next);
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}
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if (ptr->prev != NULL)
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{
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ptr->prev->next = ptr->next;
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ptr->prev->magic = MAGICWORD ^ ((uintptr_t) ptr->prev->prev
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+ (uintptr_t) ptr->prev->next);
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}
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else
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root = ptr->next;
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}
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static void
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link_blk (struct hdr *hdr)
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{
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hdr->prev = NULL;
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hdr->next = root;
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root = hdr;
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hdr->magic = MAGICWORD ^ (uintptr_t) hdr->next;
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/* And the next block. */
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if (hdr->next != NULL)
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{
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hdr->next->prev = hdr;
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hdr->next->magic = MAGICWORD ^ ((uintptr_t) hdr
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+ (uintptr_t) hdr->next->next);
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}
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}
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static void *
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free_mcheck (void *ptr)
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{
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if (pedantic)
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__mcheck_checkptr (NULL);
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if (ptr)
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{
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struct hdr *hdr = ((struct hdr *) ptr) - 1;
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checkhdr (hdr);
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hdr->magic = MAGICFREE;
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hdr->magic2 = MAGICFREE;
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unlink_blk (hdr);
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hdr->prev = hdr->next = NULL;
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flood (ptr, FREEFLOOD, hdr->size);
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ptr = hdr->block;
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}
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return ptr;
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}
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static bool
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malloc_mcheck_before (size_t *sizep, void **victimp)
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{
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size_t size = *sizep;
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if (pedantic)
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__mcheck_checkptr (NULL);
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if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
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{
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__set_errno (ENOMEM);
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*victimp = NULL;
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return true;
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}
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*sizep = sizeof (struct hdr) + size + 1;
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return false;
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}
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static void *
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malloc_mcheck_after (void *mem, size_t size)
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{
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struct hdr *hdr = mem;
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if (hdr == NULL)
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return NULL;
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hdr->size = size;
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link_blk (hdr);
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hdr->block = hdr;
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hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
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((char *) &hdr[1])[size] = MAGICBYTE;
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flood ((void *) (hdr + 1), MALLOCFLOOD, size);
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return (void *) (hdr + 1);
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}
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static bool
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memalign_mcheck_before (size_t alignment, size_t *sizep, void **victimp)
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{
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struct hdr *hdr;
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size_t slop, size = *sizep;
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/* Punt to malloc to avoid double headers. */
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if (alignment <= MALLOC_ALIGNMENT)
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{
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*victimp = __debug_malloc (size);
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return true;
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}
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if (pedantic)
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__mcheck_checkptr (NULL);
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slop = (sizeof *hdr + alignment - 1) & - alignment;
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if (size > ~((size_t) 0) - (slop + 1))
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{
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__set_errno (ENOMEM);
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*victimp = NULL;
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return true;
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}
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*sizep = slop + size + 1;
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return false;
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}
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static void *
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memalign_mcheck_after (void *block, size_t alignment, size_t size)
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{
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if (block == NULL)
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return NULL;
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/* This was served by __debug_malloc, so return as is. */
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if (alignment <= MALLOC_ALIGNMENT)
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return block;
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size_t slop = (sizeof (struct hdr) + alignment - 1) & - alignment;
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struct hdr *hdr = ((struct hdr *) (block + slop)) - 1;
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hdr->size = size;
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link_blk (hdr);
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hdr->block = (void *) block;
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hdr->magic2 = (uintptr_t) block ^ MAGICWORD;
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((char *) &hdr[1])[size] = MAGICBYTE;
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flood ((void *) (hdr + 1), MALLOCFLOOD, size);
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return (void *) (hdr + 1);
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}
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static bool
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realloc_mcheck_before (void **ptrp, size_t *sizep, size_t *oldsize,
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void **victimp)
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{
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size_t size = *sizep;
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void *ptr = *ptrp;
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if (ptr == NULL)
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{
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*victimp = __debug_malloc (size);
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*oldsize = 0;
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return true;
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}
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if (size == 0)
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{
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__debug_free (ptr);
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*victimp = NULL;
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return true;
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}
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if (size > ~((size_t) 0) - (sizeof (struct hdr) + 1))
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{
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__set_errno (ENOMEM);
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*victimp = NULL;
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*oldsize = 0;
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return true;
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}
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if (pedantic)
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__mcheck_checkptr (NULL);
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struct hdr *hdr;
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size_t osize;
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/* Update the oldptr for glibc realloc. */
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*ptrp = hdr = ((struct hdr *) ptr) - 1;
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osize = hdr->size;
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checkhdr (hdr);
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unlink_blk (hdr);
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if (size < osize)
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flood ((char *) ptr + size, FREEFLOOD, osize - size);
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*oldsize = osize;
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*sizep = sizeof (struct hdr) + size + 1;
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return false;
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}
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static void *
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realloc_mcheck_after (void *ptr, void *oldptr, size_t size, size_t osize)
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{
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struct hdr *hdr = ptr;
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if (hdr == NULL)
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return NULL;
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/* Malloc already added the header so don't tamper with it. */
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if (oldptr == NULL)
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return ptr;
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hdr->size = size;
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link_blk (hdr);
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hdr->block = hdr;
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hdr->magic2 = (uintptr_t) hdr ^ MAGICWORD;
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((char *) &hdr[1])[size] = MAGICBYTE;
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if (size > osize)
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flood ((char *) (hdr + 1) + osize, MALLOCFLOOD, size - osize);
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return (void *) (hdr + 1);
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}
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__attribute__ ((noreturn))
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static void
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mabort (enum mcheck_status status)
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{
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const char *msg;
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switch (status)
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{
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case MCHECK_OK:
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msg = _ ("memory is consistent, library is buggy\n");
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break;
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case MCHECK_HEAD:
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msg = _ ("memory clobbered before allocated block\n");
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break;
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case MCHECK_TAIL:
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msg = _ ("memory clobbered past end of allocated block\n");
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break;
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case MCHECK_FREE:
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msg = _ ("block freed twice\n");
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break;
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default:
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msg = _ ("bogus mcheck_status, library is buggy\n");
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break;
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}
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#ifdef _LIBC
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__libc_fatal (msg);
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#else
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fprintf (stderr, "mcheck: %s", msg);
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fflush (stderr);
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abort ();
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#endif
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}
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/* Memory barrier so that GCC does not optimize out the argument. */
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#define malloc_opt_barrier(x) \
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({ __typeof (x) __x = x; __asm ("" : "+m" (__x)); __x; })
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static int
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__mcheck_initialize (void (*func) (enum mcheck_status), bool in_pedantic)
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{
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abortfunc = (func != NULL) ? func : &mabort;
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switch (debug_initialized)
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{
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case -1:
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/* Called before the first malloc was called. */
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__debug_free (__debug_malloc (0));
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/* FALLTHROUGH */
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case 0:
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/* Called through the initializer hook. */
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__malloc_debug_enable (MALLOC_MCHECK_HOOK);
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break;
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case 1:
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default:
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/* Malloc was already called. Fail. */
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return -1;
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}
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pedantic = in_pedantic;
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return 0;
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}
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