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/* mtrace implementation for `malloc'.
Copyright (C) 1991-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <malloc.h>
#include <mcheck.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>
#include <libc-internal.h>
#include <dso_handle.h>
#include <kernel-features.h>
static FILE *mallstream;
static const char mallenv[] = "MALLOC_TRACE";
static void
tr_where (const void *caller, Dl_info *info)
{
if (caller != NULL)
{
if (info != NULL)
{
char *buf = (char *) "";
if (info->dli_sname != NULL)
{
size_t len = strlen (info->dli_sname);
buf = alloca (len + 6 + 2 * sizeof (void *));
char sign;
ptrdiff_t offset =
(ptrdiff_t) info->dli_saddr - (ptrdiff_t) caller;
if (caller >= (const void *) info->dli_saddr)
{
sign = '+';
offset = -offset;
}
else
sign = '-';
sprintf (buf, "(%s%c%" PRIxPTR ")", info->dli_sname, sign,
offset);
}
fprintf (mallstream, "@ %s%s%s[0x%" PRIxPTR "] ",
info->dli_fname ? : "", info->dli_fname ? ":" : "", buf,
caller - info->dli_fbase);
}
else
fprintf (mallstream, "@ [%p] ", caller);
}
}
static Dl_info *
lock_and_info (const void *caller, Dl_info *mem)
{
if (caller == NULL)
return NULL;
Dl_info *res = dladdr (caller, mem) ? mem : NULL;
flockfile (mallstream);
return res;
}
static void
free_mtrace (void *ptr, const void *caller)
{
if (ptr == NULL)
return;
Dl_info mem;
Dl_info *info = lock_and_info (caller, &mem);
tr_where (caller, info);
/* Be sure to print it first. */
fprintf (mallstream, "- %p\n", ptr);
funlockfile (mallstream);
}
static void
malloc_mtrace_after (void *block, size_t size, const void *caller)
{
Dl_info mem;
Dl_info *info = lock_and_info (caller, &mem);
tr_where (caller, info);
/* We could be printing a NULL here; that's OK. */
fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
funlockfile (mallstream);
}
static void
realloc_mtrace_after (void *block, const void *oldptr, size_t size,
const void *caller)
{
Dl_info mem;
Dl_info *info = lock_and_info (caller, &mem);
tr_where (caller, info);
if (block == NULL)
{
if (size != 0)
/* Failed realloc. */
fprintf (mallstream, "! %p %#lx\n", oldptr, (unsigned long int) size);
else
fprintf (mallstream, "- %p\n", oldptr);
}
else if (oldptr == NULL)
fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
else
{
fprintf (mallstream, "< %p\n", oldptr);
tr_where (caller, info);
fprintf (mallstream, "> %p %#lx\n", block, (unsigned long int) size);
}
funlockfile (mallstream);
}
static void
memalign_mtrace_after (void *block, size_t size, const void *caller)
{
Dl_info mem;
Dl_info *info = lock_and_info (caller, &mem);
tr_where (caller, info);
/* We could be printing a NULL here; that's OK. */
fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
funlockfile (mallstream);
}
/* This function gets called to make sure all memory the library
allocates get freed and so does not irritate the user when studying
the mtrace output. */
static void
release_libc_mem (void)
{
/* Only call the free function if we still are running in mtrace mode. */
if (mallstream != NULL)
__libc_freeres ();
}
/* We enable tracing if the environment variable MALLOC_TRACE is set. */
static void
do_mtrace (void)
{
static int added_atexit_handler;
char *mallfile;
/* Don't panic if we're called more than once. */
if (mallstream != NULL)
return;
mallfile = secure_getenv (mallenv);
if (mallfile != NULL)
{
mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
if (mallstream != NULL)
{
/* Be sure it doesn't malloc its buffer! */
static char tracebuf [512];
setvbuf (mallstream, tracebuf, _IOFBF, sizeof (tracebuf));
fprintf (mallstream, "= Start\n");
if (!added_atexit_handler)
{
added_atexit_handler = 1;
__cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
__dso_handle);
}
__malloc_debug_enable (MALLOC_MTRACE_HOOK);
}
}
}
static void
do_muntrace (void)
{
__malloc_debug_disable (MALLOC_MTRACE_HOOK);
if (mallstream == NULL)
return;
/* Do the reverse of what done in mtrace: first reset the hooks and
MALLSTREAM, and only after that write the trailer and close the
file. */
FILE *f = mallstream;
mallstream = NULL;
fprintf (f, "= End\n");
fclose (f);
}
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