path: root/malloc/malloc-debug.c

/* Malloc debug DSO.
   Copyright (C) 2021 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; 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()  */
};
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"

extern void (*__malloc_initialize_hook) (void);
compat_symbol_reference (libc, __malloc_initialize_hook,
			 __malloc_initialize_hook, GLIBC_2_0);

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;
  /* The compiler does not know that these functions are allocators, so it will
     not try to optimize it away.  */
  __libc_free (__libc_malloc (0));

  void (*hook) (void) = __malloc_initialize_hook;
  if (hook != NULL)
    (*hook)();
  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;

/* The allocator functions.  */

static void *
__debug_malloc (size_t bytes)
{
  void *(*hook) (size_t, const void *) = atomic_forced_read (__malloc_hook);
  if (__builtin_expect (hook != NULL, 0))
    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 = __libc_malloc (bytes);
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = malloc_mcheck_after (victim, orig_bytes);

  return victim;
}
strong_alias (__debug_malloc, malloc)

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

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

  __libc_free (mem);
}
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 (__builtin_expect (hook != NULL, 0))
    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))
    {
      victim = __libc_realloc (oldmem, bytes);
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = realloc_mcheck_after (victim, oldmem, orig_bytes,
				   oldsize);

  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 (__builtin_expect (hook != NULL, 0))
    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 = __libc_memalign (alignment, bytes);
    }
  if (__is_malloc_debug_enabled (MALLOC_MCHECK_HOOK) && victim != NULL)
    victim = memalign_mcheck_after (victim, alignment, orig_bytes);

  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)
strong_alias (__debug_memalign, 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 (__builtin_expect (hook != NULL, 0))
    {
      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 = __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);
    }
  return victim;
}
strong_alias (__debug_calloc, calloc)