glibc/malloc/hooks.c

/* Malloc implementation for multiple threads without lock contention.
   Copyright (C) 2001,02 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Wolfram Gloger <wg@malloc.de>, 2001.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

/* $Id$ */

#ifndef weak_variable
#ifndef _LIBC
#define weak_variable /**/
#else
/* In GNU libc we want the hook variables to be weak definitions to
   avoid a problem with Emacs.  */
#define weak_variable weak_function
#endif
#endif

#ifndef DEFAULT_CHECK_ACTION
#define DEFAULT_CHECK_ACTION 1
#endif

/* What to do if the standard debugging hooks are in place and a
   corrupt pointer is detected: do nothing (0), print an error message
   (1), or call abort() (2). */

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

static Void_t*
#if __STD_C
malloc_hook_ini(size_t sz, const __malloc_ptr_t caller)
#else
malloc_hook_ini(sz, caller)
     size_t sz; const __malloc_ptr_t caller;
#endif
{
  __malloc_hook = NULL;
  ptmalloc_init();
  return public_mALLOc(sz);
}

static Void_t*
#if __STD_C
realloc_hook_ini(Void_t* ptr, size_t sz, const __malloc_ptr_t caller)
#else
realloc_hook_ini(ptr, sz, caller)
     Void_t* ptr; size_t sz; const __malloc_ptr_t caller;
#endif
{
  __malloc_hook = NULL;
  __realloc_hook = NULL;
  ptmalloc_init();
  return public_rEALLOc(ptr, sz);
}

static Void_t*
#if __STD_C
memalign_hook_ini(size_t alignment, size_t sz, const __malloc_ptr_t caller)
#else
memalign_hook_ini(alignment, sz, caller)
     size_t alignment; size_t sz; const __malloc_ptr_t caller;
#endif
{
  __memalign_hook = NULL;
  ptmalloc_init();
  return public_mEMALIGn(alignment, sz);
}

void weak_variable (*__malloc_initialize_hook) __MALLOC_P ((void)) = NULL;
void weak_variable (*__free_hook) __MALLOC_P ((__malloc_ptr_t __ptr,
					       const __malloc_ptr_t)) = NULL;
__malloc_ptr_t weak_variable (*__malloc_hook)
 __MALLOC_P ((size_t __size, const __malloc_ptr_t)) = malloc_hook_ini;
__malloc_ptr_t weak_variable (*__realloc_hook)
 __MALLOC_P ((__malloc_ptr_t __ptr, size_t __size, const __malloc_ptr_t))
     = realloc_hook_ini;
__malloc_ptr_t weak_variable (*__memalign_hook)
 __MALLOC_P ((size_t __alignment, size_t __size, const __malloc_ptr_t))
     = memalign_hook_ini;
void weak_variable (*__after_morecore_hook) __MALLOC_P ((void)) = NULL;


static int check_action = DEFAULT_CHECK_ACTION;

/* Whether we are using malloc checking.  */
static int using_malloc_checking;

/* A flag that is set by malloc_set_state, to signal that malloc checking
   must not be enabled on the request from the user (via the MALLOC_CHECK_
   environment variable).  It is reset by __malloc_check_init to tell
   malloc_set_state that the user has requested malloc checking.

   The purpose of this flag is to make sure that malloc checking is not
   enabled when the heap to be restored was constructed without malloc
   checking, and thus does not contain the required magic bytes.
   Otherwise the heap would be corrupted by calls to free and realloc.  If
   it turns out that the heap was created with malloc checking and the
   user has requested it malloc_set_state just calls __malloc_check_init
   again to enable it.  On the other hand, reusing such a heap without
   further malloc checking is safe.  */
static int disallow_malloc_check;

/* Activate a standard set of debugging hooks. */
void
__malloc_check_init()
{
  if (disallow_malloc_check) {
    disallow_malloc_check = 0;
    return;
  }
  using_malloc_checking = 1;
  __malloc_hook = malloc_check;
  __free_hook = free_check;
  __realloc_hook = realloc_check;
  __memalign_hook = memalign_check;
  if(check_action & 1)
    fprintf(stderr, "malloc: using debugging hooks\n");
}

/* A simple, standard set of debugging hooks.  Overhead is `only' one
   byte per chunk; still this will catch most cases of double frees or
   overruns.  The goal here is to avoid obscure crashes due to invalid
   usage, unlike in the MALLOC_DEBUG code. */

#define MAGICBYTE(p) ( ( ((size_t)p >> 3) ^ ((size_t)p >> 11)) & 0xFF )

/* Instrument a chunk with overrun detector byte(s) and convert it
   into a user pointer with requested size sz. */

static Void_t*
internal_function
#if __STD_C
mem2mem_check(Void_t *ptr, size_t sz)
#else
mem2mem_check(ptr, sz) Void_t *ptr; size_t sz;
#endif
{
  mchunkptr p;
  unsigned char* m_ptr = (unsigned char*)BOUNDED_N(ptr, sz);
  size_t i;

  if (!ptr)
    return ptr;
  p = mem2chunk(ptr);
  for(i = chunksize(p) - (chunk_is_mmapped(p) ? 2*SIZE_SZ+1 : SIZE_SZ+1);
      i > sz;
      i -= 0xFF) {
    if(i-sz < 0x100) {
      m_ptr[i] = (unsigned char)(i-sz);
      break;
    }
    m_ptr[i] = 0xFF;
  }
  m_ptr[sz] = MAGICBYTE(p);
  return (Void_t*)m_ptr;
}

/* Convert a pointer to be free()d or realloc()ed to a valid chunk
   pointer.  If the provided pointer is not valid, return NULL. */

static mchunkptr
internal_function
#if __STD_C
mem2chunk_check(Void_t* mem)
#else
mem2chunk_check(mem) Void_t* mem;
#endif
{
  mchunkptr p;
  INTERNAL_SIZE_T sz, c;
  unsigned char magic;

  p = mem2chunk(mem);
  if(!aligned_OK(p)) return NULL;
  if( (char*)p>=mp_.sbrk_base &&
      (char*)p<(mp_.sbrk_base+main_arena.system_mem) ) {
    /* Must be a chunk in conventional heap memory. */
    if(chunk_is_mmapped(p) ||
       ( (sz = chunksize(p)),
	 ((char*)p + sz)>=(mp_.sbrk_base+main_arena.system_mem) ) ||
       sz<MINSIZE || sz&MALLOC_ALIGN_MASK || !inuse(p) ||
       ( !prev_inuse(p) && (p->prev_size&MALLOC_ALIGN_MASK ||
                            (long)prev_chunk(p)<(long)mp_.sbrk_base ||
                            next_chunk(prev_chunk(p))!=p) ))
      return NULL;
    magic = MAGICBYTE(p);
    for(sz += SIZE_SZ-1; (c = ((unsigned char*)p)[sz]) != magic; sz -= c) {
      if(c<=0 || sz<(c+2*SIZE_SZ)) return NULL;
    }
    ((unsigned char*)p)[sz] ^= 0xFF;
  } else {
    unsigned long offset, page_mask = malloc_getpagesize-1;

    /* mmap()ed chunks have MALLOC_ALIGNMENT or higher power-of-two
       alignment relative to the beginning of a page.  Check this
       first. */
    offset = (unsigned long)mem & page_mask;
    if((offset!=MALLOC_ALIGNMENT && offset!=0 && offset!=0x10 &&
        offset!=0x20 && offset!=0x40 && offset!=0x80 && offset!=0x100 &&
        offset!=0x200 && offset!=0x400 && offset!=0x800 && offset!=0x1000 &&
        offset<0x2000) ||
       !chunk_is_mmapped(p) || (p->size & PREV_INUSE) ||
       ( (((unsigned long)p - p->prev_size) & page_mask) != 0 ) ||
       ( (sz = chunksize(p)), ((p->prev_size + sz) & page_mask) != 0 ) )
      return NULL;
    magic = MAGICBYTE(p);
    for(sz -= 1; (c = ((unsigned char*)p)[sz]) != magic; sz -= c) {
      if(c<=0 || sz<(c+2*SIZE_SZ)) return NULL;
    }
    ((unsigned char*)p)[sz] ^= 0xFF;
  }
  return p;
}

/* Check for corruption of the top chunk, and try to recover if
   necessary. */

static int
internal_function
#if __STD_C
top_check(void)
#else
top_check()
#endif
{
  mchunkptr t = top(&main_arena);
  char* brk, * new_brk;
  INTERNAL_SIZE_T front_misalign, sbrk_size;
  unsigned long pagesz = malloc_getpagesize;

  if((char*)t + chunksize(t) == mp_.sbrk_base + main_arena.system_mem ||
     t == initial_top(&main_arena)) return 0;

  if(check_action & 1)
    fprintf(stderr, "malloc: top chunk is corrupt\n");
  if(check_action & 2)
    abort();

  /* Try to set up a new top chunk. */
  brk = MORECORE(0);
  front_misalign = (unsigned long)chunk2mem(brk) & MALLOC_ALIGN_MASK;
  if (front_misalign > 0)
    front_misalign = MALLOC_ALIGNMENT - front_misalign;
  sbrk_size = front_misalign + mp_.top_pad + MINSIZE;
  sbrk_size += pagesz - ((unsigned long)(brk + sbrk_size) & (pagesz - 1));
  new_brk = (char*)(MORECORE (sbrk_size));
  if (new_brk == (char*)(MORECORE_FAILURE)) return -1;
  /* Call the `morecore' hook if necessary.  */
  if (__after_morecore_hook)
    (*__after_morecore_hook) ();
  main_arena.system_mem = (new_brk - mp_.sbrk_base) + sbrk_size;

  top(&main_arena) = (mchunkptr)(brk + front_misalign);
  set_head(top(&main_arena), (sbrk_size - front_misalign) | PREV_INUSE);

  return 0;
}

static Void_t*
#if __STD_C
malloc_check(size_t sz, const Void_t *caller)
#else
malloc_check(sz, caller) size_t sz; const Void_t *caller;
#endif
{
  Void_t *victim;

  (void)mutex_lock(&main_arena.mutex);
  victim = (top_check() >= 0) ? _int_malloc(&main_arena, sz+1) : NULL;
  (void)mutex_unlock(&main_arena.mutex);
  return mem2mem_check(victim, sz);
}

static void
#if __STD_C
free_check(Void_t* mem, const Void_t *caller)
#else
free_check(mem, caller) Void_t* mem; const Void_t *caller;
#endif
{
  mchunkptr p;

  if(!mem) return;
  (void)mutex_lock(&main_arena.mutex);
  p = mem2chunk_check(mem);
  if(!p) {
    (void)mutex_unlock(&main_arena.mutex);
    if(check_action & 1)
      fprintf(stderr, "free(): invalid pointer %p!\n", mem);
    if(check_action & 2)
      abort();
    return;
  }
#if HAVE_MMAP
  if (chunk_is_mmapped(p)) {
    (void)mutex_unlock(&main_arena.mutex);
    munmap_chunk(p);
    return;
  }
#endif
#if 0 /* Erase freed memory. */
  memset(mem, 0, chunksize(p) - (SIZE_SZ+1));
#endif
  _int_free(&main_arena, mem);
  (void)mutex_unlock(&main_arena.mutex);
}

static Void_t*
#if __STD_C
realloc_check(Void_t* oldmem, size_t bytes, const Void_t *caller)
#else
realloc_check(oldmem, bytes, caller)
     Void_t* oldmem; size_t bytes; const Void_t *caller;
#endif
{
  mchunkptr oldp;
  INTERNAL_SIZE_T nb, oldsize;
  Void_t* newmem = 0;

  if (oldmem == 0) return malloc_check(bytes, NULL);
  (void)mutex_lock(&main_arena.mutex);
  oldp = mem2chunk_check(oldmem);
  (void)mutex_unlock(&main_arena.mutex);
  if(!oldp) {
    if(check_action & 1)
      fprintf(stderr, "realloc(): invalid pointer %p!\n", oldmem);
    if(check_action & 2)
      abort();
    return malloc_check(bytes, NULL);
  }
  oldsize = chunksize(oldp);

  checked_request2size(bytes+1, nb);
  (void)mutex_lock(&main_arena.mutex);

#if HAVE_MMAP
  if (chunk_is_mmapped(oldp)) {
#if HAVE_MREMAP
    mchunkptr newp = mremap_chunk(oldp, nb);
    if(!newp) {
#endif
      /* Note the extra SIZE_SZ overhead. */
      if(oldsize - SIZE_SZ >= nb)
	newmem = oldmem; /* do nothing */
      else {
        /* Must alloc, copy, free. */
        if (top_check() >= 0)
	  newmem = _int_malloc(&main_arena, bytes+1);
        if (newmem) {
          MALLOC_COPY(BOUNDED_N(newmem, bytes+1), oldmem, oldsize - 2*SIZE_SZ);
          munmap_chunk(oldp);
        }
      }
#if HAVE_MREMAP
    }
#endif
  } else {
#endif /* HAVE_MMAP */
    if (top_check() >= 0)
      newmem = _int_realloc(&main_arena, oldmem, bytes+1);
#if 0 /* Erase freed memory. */
    if(newmem)
      newp = mem2chunk(newmem);
    nb = chunksize(newp);
    if(oldp<newp || oldp>=chunk_at_offset(newp, nb)) {
      memset((char*)oldmem + 2*sizeof(mbinptr), 0,
             oldsize - (2*sizeof(mbinptr)+2*SIZE_SZ+1));
    } else if(nb > oldsize+SIZE_SZ) {
      memset((char*)BOUNDED_N(chunk2mem(newp), bytes) + oldsize,
	     0, nb - (oldsize+SIZE_SZ));
    }
#endif
#if HAVE_MMAP
  }
#endif
  (void)mutex_unlock(&main_arena.mutex);

  return mem2mem_check(newmem, bytes);
}

static Void_t*
#if __STD_C
memalign_check(size_t alignment, size_t bytes, const Void_t *caller)
#else
memalign_check(alignment, bytes, caller)
     size_t alignment; size_t bytes; const Void_t *caller;
#endif
{
  INTERNAL_SIZE_T nb;
  Void_t* mem;

  if (alignment <= MALLOC_ALIGNMENT) return malloc_check(bytes, NULL);
  if (alignment <  MINSIZE) alignment = MINSIZE;

  checked_request2size(bytes+1, nb);
  (void)mutex_lock(&main_arena.mutex);
  mem = (top_check() >= 0) ? _int_memalign(&main_arena, alignment, bytes+1) :
    NULL;
  (void)mutex_unlock(&main_arena.mutex);
  return mem2mem_check(mem, bytes);
}

#ifndef NO_THREADS

/* The following hooks are used when the global initialization in
   ptmalloc_init() hasn't completed yet. */

static Void_t*
#if __STD_C
malloc_starter(size_t sz, const Void_t *caller)
#else
malloc_starter(sz, caller) size_t sz; const Void_t *caller;
#endif
{
  Void_t* victim;

  victim = _int_malloc(&main_arena, sz);

  return victim ? BOUNDED_N(victim, sz) : 0;
}

static void
#if __STD_C
free_starter(Void_t* mem, const Void_t *caller)
#else
free_starter(mem, caller) Void_t* mem; const Void_t *caller;
#endif
{
  mchunkptr p;

  if(!mem) return;
  p = mem2chunk(mem);
#if HAVE_MMAP
  if (chunk_is_mmapped(p)) {
    munmap_chunk(p);
    return;
  }
#endif
  _int_free(&main_arena, mem);
}

#endif /* NO_THREADS */


/* Get/set state: malloc_get_state() records the current state of all
   malloc variables (_except_ for the actual heap contents and `hook'
   function pointers) in a system dependent, opaque data structure.
   This data structure is dynamically allocated and can be free()d
   after use.  malloc_set_state() restores the state of all malloc
   variables to the previously obtained state.  This is especially
   useful when using this malloc as part of a shared library, and when
   the heap contents are saved/restored via some other method.  The
   primary example for this is GNU Emacs with its `dumping' procedure.
   `Hook' function pointers are never saved or restored by these
   functions, with two exceptions: If malloc checking was in use when
   malloc_get_state() was called, then malloc_set_state() calls
   __malloc_check_init() if possible; if malloc checking was not in
   use in the recorded state but the user requested malloc checking,
   then the hooks are reset to 0.  */

#define MALLOC_STATE_MAGIC   0x444c4541l
#define MALLOC_STATE_VERSION (0*0x100l + 2l) /* 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;
  unsigned int  n_mmaps;
  unsigned int  max_n_mmaps;
  unsigned long mmapped_mem;
  unsigned long max_mmapped_mem;
  int           using_malloc_checking;
};

Void_t*
public_gET_STATe(void)
{
  struct malloc_save_state* ms;
  int i;
  mbinptr b;

  ms = (struct malloc_save_state*)public_mALLOc(sizeof(*ms));
  if (!ms)
    return 0;
  (void)mutex_lock(&main_arena.mutex);
  malloc_consolidate(&main_arena);
  ms->magic = MALLOC_STATE_MAGIC;
  ms->version = MALLOC_STATE_VERSION;
  ms->av[0] = 0;
  ms->av[1] = 0; /* used to be binblocks, now no longer used */
  ms->av[2] = top(&main_arena);
  ms->av[3] = 0; /* used to be undefined */
  for(i=1; i<NBINS; i++) {
    b = bin_at(&main_arena, i);
    if(first(b) == b)
      ms->av[2*i+2] = ms->av[2*i+3] = 0; /* empty bin */
    else {
      ms->av[2*i+2] = first(b);
      ms->av[2*i+3] = last(b);
    }
  }
  ms->sbrk_base = mp_.sbrk_base;
  ms->sbrked_mem_bytes = main_arena.system_mem;
  ms->trim_threshold = mp_.trim_threshold;
  ms->top_pad = mp_.top_pad;
  ms->n_mmaps_max = mp_.n_mmaps_max;
  ms->mmap_threshold = mp_.mmap_threshold;
  ms->check_action = check_action;
  ms->max_sbrked_mem = main_arena.max_system_mem;
#ifdef NO_THREADS
  ms->max_total_mem = max_total_mem;
#else
  ms->max_total_mem = 0;
#endif
  ms->n_mmaps = mp_.n_mmaps;
  ms->max_n_mmaps = mp_.max_n_mmaps;
  ms->mmapped_mem = mp_.mmapped_mem;
  ms->max_mmapped_mem = mp_.max_mmapped_mem;
  ms->using_malloc_checking = using_malloc_checking;
  (void)mutex_unlock(&main_arena.mutex);
  return (Void_t*)ms;
}

int
public_sET_STATe(Void_t* msptr)
{
  struct malloc_save_state* ms = (struct malloc_save_state*)msptr;
  int i;
  mbinptr b;

  disallow_malloc_check = 1;
  ptmalloc_init();
  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;
  (void)mutex_lock(&main_arena.mutex);
  /* There are no fastchunks.  */
  clear_fastchunks(&main_arena);
  set_max_fast(&main_arena, DEFAULT_MXFAST);
  for (i=0; i<NFASTBINS; ++i)
    main_arena.fastbins[i] = 0;
  for (i=0; i<BINMAPSIZE; ++i)
    main_arena.binmap[i] = 0;
  top(&main_arena) = ms->av[2];
  main_arena.last_remainder = 0;
  for(i=1; i<NBINS; i++) {
    b = bin_at(&main_arena, i);
    if(ms->av[2*i+2] == 0) {
      assert(ms->av[2*i+3] == 0);
      first(b) = last(b) = b;
    } else {
      if(i<NSMALLBINS || (largebin_index(chunksize(ms->av[2*i+2]))==i &&
			  largebin_index(chunksize(ms->av[2*i+3]))==i)) {
	first(b) = ms->av[2*i+2];
	last(b) = ms->av[2*i+3];
	/* Make sure the links to the bins within the heap are correct.  */
	first(b)->bk = b;
	last(b)->fd = b;
	/* Set bit in binblocks.  */
	mark_bin(&main_arena, i);
      } else {
	/* Oops, index computation from chunksize must have changed.
           Link the whole list into unsorted_chunks.  */
	first(b) = last(b) = b;
	b = unsorted_chunks(&main_arena);
	ms->av[2*i+2]->bk = b;
	ms->av[2*i+3]->fd = b->fd;
	b->fd->bk = ms->av[2*i+3];
	b->fd = ms->av[2*i+2];
      }
    }
  }
  mp_.sbrk_base = ms->sbrk_base;
  main_arena.system_mem = ms->sbrked_mem_bytes;
  mp_.trim_threshold = ms->trim_threshold;
  mp_.top_pad = ms->top_pad;
  mp_.n_mmaps_max = ms->n_mmaps_max;
  mp_.mmap_threshold = ms->mmap_threshold;
  check_action = ms->check_action;
  main_arena.max_system_mem = ms->max_sbrked_mem;
#ifdef NO_THREADS
  mp_.max_total_mem = ms->max_total_mem;
#endif
  mp_.n_mmaps = ms->n_mmaps;
  mp_.max_n_mmaps = ms->max_n_mmaps;
  mp_.mmapped_mem = ms->mmapped_mem;
  mp_.max_mmapped_mem = ms->max_mmapped_mem;
  /* add version-dependent code here */
  if (ms->version >= 1) {
    /* Check whether it is safe to enable malloc checking, or whether
       it is necessary to disable it.  */
    if (ms->using_malloc_checking && !using_malloc_checking &&
        !disallow_malloc_check)
      __malloc_check_init ();
    else if (!ms->using_malloc_checking && using_malloc_checking) {
      __malloc_hook = 0;
      __free_hook = 0;
      __realloc_hook = 0;
      __memalign_hook = 0;
      using_malloc_checking = 0;
    }
  }
  check_malloc_state(&main_arena);

  (void)mutex_unlock(&main_arena.mutex);
  return 0;
}

/*
 * Local variables:
 * c-basic-offset: 2
 * End:
 */