githubmirror/glibc

malloc/malloc-debug.c
677 строк20 KB
William Hunt
malloc: replace instances of __builtin_expect with __glibc_unlikely
26 июн 2025, 18:07
26 июн 2025, 18:079a5a761
/* Malloc debug DSO.
   Copyright (C) 2021-2025 Free Software Foundation, Inc.
   Copyright The GNU Toolchain Authors.
   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; see the file COPYING.LIB.  If
   not, see <https://www.gnu.org/licenses/>.  */

#include <atomic.h>
#include <libc-symbols.h>
#include <shlib-compat.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>

/* Support only the glibc allocators.  */
extern void *__libc_malloc (size_t);
extern void __libc_free (void *);
extern void *__libc_realloc (void *, size_t);
extern void *__libc_memalign (size_t, size_t);
extern void *__libc_valloc (size_t);
extern void *__libc_pvalloc (size_t);
extern void *__libc_calloc (size_t, size_t);

#define DEBUG_FN(fn) \
  static __typeof (__libc_ ## fn) __debug_ ## fn

DEBUG_FN(malloc);
DEBUG_FN(free);
DEBUG_FN(realloc);
DEBUG_FN(memalign);
DEBUG_FN(valloc);
DEBUG_FN(pvalloc);
DEBUG_FN(calloc);

static int debug_initialized = -1;

enum malloc_debug_hooks
{
  MALLOC_NONE_HOOK = 0,
  MALLOC_MCHECK_HOOK = 1 << 0, /* mcheck()  */
  MALLOC_MTRACE_HOOK = 1 << 1, /* mtrace()  */
  MALLOC_CHECK_HOOK = 1 << 2,  /* MALLOC_CHECK_ or glibc.malloc.check.  */
};
static unsigned __malloc_debugging_hooks;

static __always_inline bool
__is_malloc_debug_enabled (enum malloc_debug_hooks flag)
{
  return __malloc_debugging_hooks & flag;
}

static __always_inline void
__malloc_debug_enable (enum malloc_debug_hooks flag)
{
  __malloc_debugging_hooks |= flag;
}

static __always_inline void
__malloc_debug_disable (enum malloc_debug_hooks flag)
{
  __malloc_debugging_hooks &= ~flag;
}

#include "mcheck.c"
#include "mtrace.c"
#include "malloc-check.c"

#if SHLIB_COMPAT (libc_malloc_debug, GLIBC_2_0, GLIBC_2_24)
extern void (*__malloc_initialize_hook) (void);
compat_symbol_reference (libc, __malloc_initialize_hook,
			 __malloc_initialize_hook, GLIBC_2_0);
#endif

static void *malloc_hook_ini (size_t, const void *) __THROW;
static void *realloc_hook_ini (void *, size_t, const void *) __THROW;
static void *memalign_hook_ini (size_t, size_t, const void *) __THROW;

void (*__free_hook) (void *, const void *) = NULL;
void *(*__malloc_hook) (size_t, const void *) = malloc_hook_ini;
void *(*__realloc_hook) (void *, size_t, const void *) = realloc_hook_ini;
void *(*__memalign_hook) (size_t, size_t, const void *) = memalign_hook_ini;

/* Hooks for debugging versions.  The initial hooks just call the
   initialization routine, then do the normal work. */

/* These hooks will get executed only through the interposed allocator
   functions in libc_malloc_debug.so.  This means that the calls to malloc,
   realloc, etc. will lead back into the interposed functions, which is what we
   want.

   These initial hooks are assumed to be called in a single-threaded context,
   so it is safe to reset all hooks at once upon initialization.  */

static void
generic_hook_ini (void)
{
  debug_initialized = 0;
  __malloc_hook = NULL;
  __realloc_hook = NULL;
  __memalign_hook = NULL;

  /* malloc check does not quite co-exist with libc malloc, so initialize
     either on or the other.  */
  if (!initialize_malloc_check ())
    /* The compiler does not know that these functions are allocators, so it
       will not try to optimize it away.  */
    __libc_free (__libc_malloc (0));

#if SHLIB_COMPAT (libc_malloc_debug, GLIBC_2_0, GLIBC_2_24)
  void (*hook) (void) = __malloc_initialize_hook;
  if (hook != NULL)
    (*hook)();
#endif

  debug_initialized = 1;
}

static void *
malloc_hook_ini (size_t sz, const void *caller)
{
  generic_hook_ini ();
  return __debug_malloc (sz);
}

static void *
realloc_hook_ini (void *ptr, size_t sz, const void *caller)
{
  generic_hook_ini ();
  return __debug_realloc (ptr, sz);
}

static void *
memalign_hook_ini (size_t alignment, size_t sz, const void *caller)
{
  generic_hook_ini ();
  return __debug_memalign (alignment, sz);
}

static size_t pagesize;

/* These variables are used for undumping support.  Chunked are marked
   as using mmap, but we leave them alone if they fall into this
   range.  NB: The chunk size for these chunks only includes the
   initial size field (of SIZE_SZ bytes), there is no trailing size
   field (unlike with regular mmapped chunks).  */
static mchunkptr dumped_main_arena_start; /* Inclusive.  */
static mchunkptr dumped_main_arena_end;   /* Exclusive.  */

/* True if the pointer falls into the dumped arena.  Use this after
   chunk_is_mmapped indicates a chunk is mmapped.  */
#define DUMPED_MAIN_ARENA_CHUNK(p) \
  ((p) >= dumped_main_arena_start && (p) < dumped_main_arena_end)

/* The allocator functions.  */

static void *
__debug_malloc (size_t bytes)
{
  void *(*hook) (size_t, const void *) = atomic_forced_read (__malloc_hook);
  if (__glibc_unlikely (hook != NULL))
    return (*hook)(bytes, RETURN_ADDRESS (0));

  void *victim = NULL;
  size_t orig_bytes = bytes;
  if ((!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK)
       || !malloc_mcheck_before (&bytes, &victim)))
    {
      victim = (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK)
		? malloc_check (bytes) : __libc_malloc (bytes));
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = malloc_mcheck_after (victim, orig_bytes);
  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
    malloc_mtrace_after (victim, orig_bytes, RETURN_ADDRESS (0));

  return victim;
}
strong_alias (__debug_malloc, malloc)

static void
__debug_free (void *mem)
{
  void (*hook) (void *, const void *) = atomic_forced_read (__free_hook);
  if (__glibc_unlikely (hook != NULL))
    {
      (*hook)(mem, RETURN_ADDRESS (0));
      return;
    }

  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
    mem = free_mcheck (mem);

  if (DUMPED_MAIN_ARENA_CHUNK (mem2chunk (mem)))
    /* Do nothing.  */;
  else if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    free_check (mem);
  else
    __libc_free (mem);
  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
    free_mtrace (mem, RETURN_ADDRESS (0));
}
strong_alias (__debug_free, free)

static void *
__debug_realloc (void *oldmem, size_t bytes)
{
  void *(*hook) (void *, size_t, const void *) =
    atomic_forced_read (__realloc_hook);
  if (__glibc_unlikely (hook != NULL))
    return (*hook)(oldmem, bytes, RETURN_ADDRESS (0));

  size_t orig_bytes = bytes, oldsize = 0;
  void *victim = NULL;

  if ((!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK)
       || !realloc_mcheck_before (&oldmem, &bytes, &oldsize, &victim)))
    {
      mchunkptr oldp = mem2chunk (oldmem);

      /* If this is a faked mmapped chunk from the dumped main arena,
	 always make a copy (and do not free the old chunk).  */
      if (DUMPED_MAIN_ARENA_CHUNK (oldp))
	{
	  if (bytes == 0 && oldmem != NULL)
	    victim = NULL;
	  else
	    {
	      const INTERNAL_SIZE_T osize = chunksize (oldp);
	      /* Must alloc, copy, free. */
	      victim = __debug_malloc (bytes);
	      /* Copy as many bytes as are available from the old chunk
		 and fit into the new size.  NB: The overhead for faked
		 mmapped chunks is only SIZE_SZ, not CHUNK_HDR_SZ as for
		 regular mmapped chunks.  */
	      if (victim != NULL)
		{
		  if (bytes > osize - SIZE_SZ)
		    bytes = osize - SIZE_SZ;
		  memcpy (victim, oldmem, bytes);
		}
	    }
	}
      else if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
	victim =  realloc_check (oldmem, bytes);
      else
	victim = __libc_realloc (oldmem, bytes);
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = realloc_mcheck_after (victim, oldmem, orig_bytes,
				   oldsize);
  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
    realloc_mtrace_after (victim, oldmem, orig_bytes, RETURN_ADDRESS (0));

  return victim;
}
strong_alias (__debug_realloc, realloc)

static void *
_debug_mid_memalign (size_t alignment, size_t bytes, const void *address)
{
  void *(*hook) (size_t, size_t, const void *) =
    atomic_forced_read (__memalign_hook);
  if (__glibc_unlikely (hook != NULL))
    return (*hook)(alignment, bytes, address);

  void *victim = NULL;
  size_t orig_bytes = bytes;

  if ((!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK)
       || !memalign_mcheck_before (alignment, &bytes, &victim)))
    {
      victim = (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK)
		? memalign_check (alignment, bytes)
		: __libc_memalign (alignment, bytes));
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = memalign_mcheck_after (victim, alignment, orig_bytes);
  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
    memalign_mtrace_after (victim, orig_bytes, address);

  return victim;
}

static void *
__debug_memalign (size_t alignment, size_t bytes)
{
  return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_memalign, memalign)
static void *
__debug_aligned_alloc (size_t alignment, size_t bytes)
{
  if (!powerof2 (alignment) || alignment == 0)
    return NULL;
  return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_aligned_alloc, aligned_alloc)

static void *
__debug_pvalloc (size_t bytes)
{
  size_t rounded_bytes;

  if (!pagesize)
    pagesize = sysconf (_SC_PAGESIZE);

  /* ALIGN_UP with overflow check.  */
  if (__glibc_unlikely (__builtin_add_overflow (bytes,
						pagesize - 1,
						&rounded_bytes)))
    {
      errno = ENOMEM;
      return NULL;
    }
  rounded_bytes = rounded_bytes & -(pagesize - 1);

  return _debug_mid_memalign (pagesize, rounded_bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_pvalloc, pvalloc)

static void *
__debug_valloc (size_t bytes)
{
  if (!pagesize)
    pagesize = sysconf (_SC_PAGESIZE);

  return _debug_mid_memalign (pagesize, bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_valloc, valloc)

static int
__debug_posix_memalign (void **memptr, size_t alignment, size_t bytes)
{
  /* Test whether the SIZE argument is valid.  It must be a power of
     two multiple of sizeof (void *).  */
  if (alignment % sizeof (void *) != 0
      || !powerof2 (alignment / sizeof (void *))
      || alignment == 0)
    return EINVAL;

  *memptr = _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));

  if (*memptr == NULL)
    return ENOMEM;

  return 0;
}
strong_alias (__debug_posix_memalign, posix_memalign)

static void *
__debug_calloc (size_t nmemb, size_t size)
{
  size_t bytes;

  if (__glibc_unlikely (__builtin_mul_overflow (nmemb, size, &bytes)))
    {
      errno = ENOMEM;
      return NULL;
    }

  void *(*hook) (size_t, const void *) = atomic_forced_read (__malloc_hook);
  if (__glibc_unlikely (hook != NULL))
    {
      void *mem = (*hook)(bytes, RETURN_ADDRESS (0));

      if (mem != NULL)
	memset (mem, 0, bytes);

      return mem;
    }

  size_t orig_bytes = bytes;
  void *victim = NULL;

  if ((!__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK)
       || !malloc_mcheck_before (&bytes, &victim)))
    {
      victim = (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK)
		? malloc_check (bytes) : __libc_malloc (bytes));
    }
  if (victim != NULL)
    {
      if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
	victim = malloc_mcheck_after (victim, orig_bytes);
      memset (victim, 0, orig_bytes);
    }
  if (__is_malloc_debug_enabled (MALLOC_MTRACE_HOOK))
    malloc_mtrace_after (victim, orig_bytes, RETURN_ADDRESS (0));

  return victim;
}
strong_alias (__debug_calloc, calloc)

size_t
malloc_usable_size (void *mem)
{
  if (mem == NULL)
    return 0;

  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK))
    return mcheck_usable_size (mem);
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return malloc_check_get_size (mem);

  mchunkptr p = mem2chunk (mem);
  if (DUMPED_MAIN_ARENA_CHUNK (p))
    return chunksize (p) - SIZE_SZ;

  return musable (mem);
}

#define LIBC_SYMBOL(sym) libc_ ## sym
#define SYMHANDLE(sym) sym ## _handle

#define LOAD_SYM(sym) ({ \
  static void *SYMHANDLE (sym);						      \
  if (SYMHANDLE (sym) == NULL)						      \
    SYMHANDLE (sym) = dlsym (RTLD_NEXT, #sym);				      \
  SYMHANDLE (sym);							      \
})

int
malloc_info (int options, FILE *fp)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __malloc_info (options, fp);

  int (*LIBC_SYMBOL (malloc_info)) (int, FILE *) = LOAD_SYM (malloc_info);
  if (LIBC_SYMBOL (malloc_info) == NULL)
    return -1;

  return LIBC_SYMBOL (malloc_info) (options, fp);
}

int
mallopt (int param_number, int value)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __libc_mallopt (param_number, value);

  int (*LIBC_SYMBOL (mallopt)) (int, int) = LOAD_SYM (mallopt);
  if (LIBC_SYMBOL (mallopt) == NULL)
    return 0;

  return LIBC_SYMBOL (mallopt) (param_number, value);
}

void
malloc_stats (void)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __malloc_stats ();

  void (*LIBC_SYMBOL (malloc_stats)) (void) = LOAD_SYM (malloc_stats);
  if (LIBC_SYMBOL (malloc_stats) == NULL)
    return;

  LIBC_SYMBOL (malloc_stats) ();
}

struct mallinfo2
mallinfo2 (void)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __libc_mallinfo2 ();

  struct mallinfo2 (*LIBC_SYMBOL (mallinfo2)) (void) = LOAD_SYM (mallinfo2);
  if (LIBC_SYMBOL (mallinfo2) == NULL)
    {
      struct mallinfo2 ret = {0};
      return ret;
    }

  return LIBC_SYMBOL (mallinfo2) ();
}

struct mallinfo
mallinfo (void)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __libc_mallinfo ();

  struct mallinfo (*LIBC_SYMBOL (mallinfo)) (void) = LOAD_SYM (mallinfo);
  if (LIBC_SYMBOL (mallinfo) == NULL)
    {
      struct mallinfo ret = {0};
      return ret;
    }

  return LIBC_SYMBOL (mallinfo) ();
}

int
malloc_trim (size_t s)
{
  if (__is_malloc_debug_enabled (MALLOC_CHECK_HOOK))
    return __malloc_trim (s);

  int (*LIBC_SYMBOL (malloc_trim)) (size_t) = LOAD_SYM (malloc_trim);
  if (LIBC_SYMBOL (malloc_trim) == NULL)
    return 0;

  return LIBC_SYMBOL (malloc_trim) (s);
}

#if SHLIB_COMPAT (libc_malloc_debug, GLIBC_2_0, GLIBC_2_25)

/* Support for restoring dumped heaps contained in historic Emacs
   executables.  The heap saving feature (malloc_get_state) is no
   longer implemented in this version of glibc, but we have a heap
   rewriter in malloc_set_state which transforms the heap into a
   version compatible with current malloc.  */

#define MALLOC_STATE_MAGIC   0x444c4541l
#define MALLOC_STATE_VERSION (0 * 0x100l + 5l) /* major*0x100 + minor */

struct malloc_save_state
{
  long magic;
  long version;
  mbinptr av[NBINS * 2 + 2];
  char *sbrk_base;
  int sbrked_mem_bytes;
  unsigned long trim_threshold;
  unsigned long top_pad;
  unsigned int n_mmaps_max;
  unsigned long mmap_threshold;
  int check_action;
  unsigned long max_sbrked_mem;
  unsigned long max_total_mem;	/* Always 0, for backwards compatibility.  */
  unsigned int n_mmaps;
  unsigned int max_n_mmaps;
  unsigned long mmapped_mem;
  unsigned long max_mmapped_mem;
  int using_malloc_checking;
  unsigned long max_fast;
  unsigned long arena_test;
  unsigned long arena_max;
  unsigned long narenas;
};

/* Dummy implementation which always fails.  We need to provide this
   symbol so that existing Emacs binaries continue to work with
   BIND_NOW.  */
void *
malloc_get_state (void)
{
  __set_errno (ENOSYS);
  return NULL;
}
compat_symbol (libc_malloc_debug, malloc_get_state, malloc_get_state,
	       GLIBC_2_0);

int
malloc_set_state (void *msptr)
{
  struct malloc_save_state *ms = (struct malloc_save_state *) msptr;

  if (ms->magic != MALLOC_STATE_MAGIC)
    return -1;

  /* Must fail if the major version is too high. */
  if ((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl))
    return -2;

  if (debug_initialized == 1)
    return -1;

  bool check_was_enabled = __is_malloc_debug_enabled (MALLOC_CHECK_HOOK);

  /* It's not too late, so disable MALLOC_CHECK_ and all of the hooks.  */
  __malloc_hook = NULL;
  __realloc_hook = NULL;
  __free_hook = NULL;
  __memalign_hook = NULL;
  __malloc_debug_disable (MALLOC_CHECK_HOOK);

  /* We do not need to perform locking here because malloc_set_state
     must be called before the first call into the malloc subsystem (usually via
     __malloc_initialize_hook).  pthread_create always calls calloc and thus
     must be called only afterwards, so there cannot be more than one thread
     when we reach this point.  Also handle initialization if either we ended
     up being called before the first malloc or through the hook when
     malloc-check was enabled.  */
  if (debug_initialized < 0)
    generic_hook_ini ();
  else if (check_was_enabled)
    __libc_free (__libc_malloc (0));

  /* Patch the dumped heap.  We no longer try to integrate into the
     existing heap.  Instead, we mark the existing chunks as mmapped.
     Together with the update to dumped_main_arena_start and
     dumped_main_arena_end, realloc and free will recognize these
     chunks as dumped fake mmapped chunks and never free them.  */

  /* Find the chunk with the lowest address with the heap.  */
  mchunkptr chunk = NULL;
  {
    size_t *candidate = (size_t *) ms->sbrk_base;
    size_t *end = (size_t *) (ms->sbrk_base + ms->sbrked_mem_bytes);
    while (candidate < end)
      if (*candidate != 0)
	{
	  chunk = mem2chunk ((void *) (candidate + 1));
	  break;
	}
      else
	++candidate;
  }
  if (chunk == NULL)
    return 0;

  /* Iterate over the dumped heap and patch the chunks so that they
     are treated as fake mmapped chunks.  */
  mchunkptr top = ms->av[2];
  while (chunk < top)
    {
      if (inuse (chunk))
	{
	  /* Mark chunk as mmapped, to trigger the fallback path.  */
	  size_t size = chunksize (chunk);
	  set_head (chunk, size | IS_MMAPPED);
	}
      chunk = next_chunk (chunk);
    }

  /* The dumped fake mmapped chunks all lie in this address range.  */
  dumped_main_arena_start = (mchunkptr) ms->sbrk_base;
  dumped_main_arena_end = top;

  return 0;
}
compat_symbol (libc_malloc_debug, malloc_set_state, malloc_set_state,
	       GLIBC_2_0);
#endif

/* Do not allow linking against the library.  */
compat_symbol (libc_malloc_debug, aligned_alloc, aligned_alloc, GLIBC_2_16);
compat_symbol (libc_malloc_debug, calloc, calloc, GLIBC_2_0);
compat_symbol (libc_malloc_debug, free, free, GLIBC_2_0);
compat_symbol (libc_malloc_debug, mallinfo2, mallinfo2, GLIBC_2_33);
compat_symbol (libc_malloc_debug, mallinfo, mallinfo, GLIBC_2_0);
compat_symbol (libc_malloc_debug, malloc_info, malloc_info, GLIBC_2_10);
compat_symbol (libc_malloc_debug, malloc, malloc, GLIBC_2_0);
compat_symbol (libc_malloc_debug, malloc_stats, malloc_stats, GLIBC_2_0);
compat_symbol (libc_malloc_debug, malloc_trim, malloc_trim, GLIBC_2_0);
compat_symbol (libc_malloc_debug, malloc_usable_size, malloc_usable_size,
	       GLIBC_2_0);
compat_symbol (libc_malloc_debug, mallopt, mallopt, GLIBC_2_0);
compat_symbol (libc_malloc_debug, mcheck_check_all, mcheck_check_all,
	       GLIBC_2_2);
compat_symbol (libc_malloc_debug, mcheck, mcheck, GLIBC_2_0);
compat_symbol (libc_malloc_debug, mcheck_pedantic, mcheck_pedantic, GLIBC_2_2);
compat_symbol (libc_malloc_debug, memalign, memalign, GLIBC_2_0);
compat_symbol (libc_malloc_debug, mprobe, mprobe, GLIBC_2_0);
compat_symbol (libc_malloc_debug, mtrace, mtrace, GLIBC_2_0);
compat_symbol (libc_malloc_debug, muntrace, muntrace, GLIBC_2_0);
compat_symbol (libc_malloc_debug, posix_memalign, posix_memalign, GLIBC_2_2);
compat_symbol (libc_malloc_debug, pvalloc, pvalloc, GLIBC_2_0);
compat_symbol (libc_malloc_debug, realloc, realloc, GLIBC_2_0);
compat_symbol (libc_malloc_debug, valloc, valloc, GLIBC_2_0);
compat_symbol (libc_malloc_debug, __free_hook, __free_hook, GLIBC_2_0);
compat_symbol (libc_malloc_debug, __malloc_hook, __malloc_hook, GLIBC_2_0);
compat_symbol (libc_malloc_debug, __realloc_hook, __realloc_hook, GLIBC_2_0);
compat_symbol (libc_malloc_debug, __memalign_hook, __memalign_hook, GLIBC_2_0);