glibc/malloc/mtrace.c

/* More debugging hooks for `malloc'.
   Copyright (C) 1991-2012 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
		 Written April 2, 1991 by John Gilmore of Cygnus Support.
		 Based on mcheck.c by Mike Haertel.

   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
   <http://www.gnu.org/licenses/>.  */

#ifndef	_MALLOC_INTERNAL
#define	_MALLOC_INTERNAL
#include <malloc.h>
#include <mcheck.h>
#include <bits/libc-lock.h>
#endif

#include <dlfcn.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include <_itoa.h>

#include <libc-internal.h>

#include <libio/iolibio.h>
#define setvbuf(s, b, f, l) _IO_setvbuf (s, b, f, l)
#define fwrite(buf, size, count, fp) _IO_fwrite (buf, size, count, fp)

#include <kernel-features.h>

#ifndef attribute_hidden
# define attribute_hidden
#endif

#define TRACE_BUFFER_SIZE 512

static FILE *mallstream;
static const char mallenv[]= "MALLOC_TRACE";
static char *malloc_trace_buffer;

__libc_lock_define_initialized (static, lock);

/* Address to breakpoint on accesses to... */
__ptr_t mallwatch;

/* Old hook values.  */
static void (*tr_old_free_hook) (__ptr_t ptr, const __ptr_t);
static __ptr_t (*tr_old_malloc_hook) (__malloc_size_t size, const __ptr_t);
static __ptr_t (*tr_old_realloc_hook) (__ptr_t ptr, __malloc_size_t size,
				       const __ptr_t);
static __ptr_t (*tr_old_memalign_hook) (__malloc_size_t __alignment,
					__malloc_size_t __size,
					const __ptr_t);

/* This function is called when the block being alloc'd, realloc'd, or
   freed has an address matching the variable "mallwatch".  In a debugger,
   set "mallwatch" to the address of interest, then put a breakpoint on
   tr_break.  */

extern void tr_break (void) __THROW;
libc_hidden_proto (tr_break)
void
tr_break ()
{
}
libc_hidden_def (tr_break)

static void tr_where (const __ptr_t, Dl_info *) __THROW internal_function;
static void
internal_function
tr_where (caller, info)
     const __ptr_t 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 *));

	      buf[0] = '(';
	      __stpcpy (_fitoa (caller >= (const __ptr_t) info->dli_saddr
				? caller - (const __ptr_t) info->dli_saddr
				: (const __ptr_t) info->dli_saddr - caller,
				__stpcpy (__mempcpy (buf + 1, info->dli_sname,
						     len),
					  caller >= (__ptr_t) info->dli_saddr
					  ? "+0x" : "-0x"),
				16, 0),
			")");
	    }

	  fprintf (mallstream, "@ %s%s%s[%p] ",
		   info->dli_fname ?: "", info->dli_fname ? ":" : "",
		   buf, caller);
	}
      else
	fprintf (mallstream, "@ [%p] ", caller);
    }
}


static Dl_info *
lock_and_info (const __ptr_t caller, Dl_info *mem)
{
  if (caller == NULL)
    return NULL;

  Dl_info *res = _dl_addr (caller, mem, NULL, NULL) ? mem : NULL;

  __libc_lock_lock (lock);

  return res;
}


static void tr_freehook (__ptr_t, const __ptr_t) __THROW;
static void
tr_freehook (ptr, caller)
     __ptr_t ptr;
     const __ptr_t 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);
  if (ptr == mallwatch)
    {
      __libc_lock_unlock (lock);
      tr_break ();
      __libc_lock_lock (lock);
    }
  __free_hook = tr_old_free_hook;
  if (tr_old_free_hook != NULL)
    (*tr_old_free_hook) (ptr, caller);
  else
    free (ptr);
  __free_hook = tr_freehook;
  __libc_lock_unlock (lock);
}

static __ptr_t tr_mallochook (__malloc_size_t, const __ptr_t) __THROW;
static __ptr_t
tr_mallochook (size, caller)
     __malloc_size_t size;
     const __ptr_t caller;
{
  __ptr_t hdr;

  Dl_info mem;
  Dl_info *info = lock_and_info (caller, &mem);

  __malloc_hook = tr_old_malloc_hook;
  if (tr_old_malloc_hook != NULL)
    hdr = (__ptr_t) (*tr_old_malloc_hook) (size, caller);
  else
    hdr = (__ptr_t) malloc (size);
  __malloc_hook = tr_mallochook;

  tr_where (caller, info);
  /* We could be printing a NULL here; that's OK.  */
  fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);

  __libc_lock_unlock (lock);

  if (hdr == mallwatch)
    tr_break ();

  return hdr;
}

static __ptr_t tr_reallochook (__ptr_t, __malloc_size_t, const __ptr_t)
     __THROW;
static __ptr_t
tr_reallochook (ptr, size, caller)
     __ptr_t ptr;
     __malloc_size_t size;
     const __ptr_t caller;
{
  __ptr_t hdr;

  if (ptr == mallwatch)
    tr_break ();

  Dl_info mem;
  Dl_info *info = lock_and_info (caller, &mem);

  __free_hook = tr_old_free_hook;
  __malloc_hook = tr_old_malloc_hook;
  __realloc_hook = tr_old_realloc_hook;
  if (tr_old_realloc_hook != NULL)
    hdr = (__ptr_t) (*tr_old_realloc_hook) (ptr, size, caller);
  else
    hdr = (__ptr_t) realloc (ptr, size);
  __free_hook = tr_freehook;
  __malloc_hook = tr_mallochook;
  __realloc_hook = tr_reallochook;

  tr_where (caller, info);
  if (hdr == NULL)
    /* Failed realloc.  */
    fprintf (mallstream, "! %p %#lx\n", ptr, (unsigned long int) size);
  else if (ptr == NULL)
    fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
  else
    {
      fprintf (mallstream, "< %p\n", ptr);
      tr_where (caller, info);
      fprintf (mallstream, "> %p %#lx\n", hdr, (unsigned long int) size);
    }

  __libc_lock_unlock (lock);

  if (hdr == mallwatch)
    tr_break ();

  return hdr;
}

static __ptr_t tr_memalignhook (__malloc_size_t, __malloc_size_t,
				const __ptr_t) __THROW;
static __ptr_t
tr_memalignhook (alignment, size, caller)
     __malloc_size_t alignment, size;
     const __ptr_t caller;
{
  __ptr_t hdr;

  Dl_info mem;
  Dl_info *info = lock_and_info (caller, &mem);

  __memalign_hook = tr_old_memalign_hook;
  __malloc_hook = tr_old_malloc_hook;
  if (tr_old_memalign_hook != NULL)
    hdr = (__ptr_t) (*tr_old_memalign_hook) (alignment, size, caller);
  else
    hdr = (__ptr_t) memalign (alignment, size);
  __memalign_hook = tr_memalignhook;
  __malloc_hook = tr_mallochook;

  tr_where (caller, info);
  /* We could be printing a NULL here; that's OK.  */
  fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);

  __libc_lock_unlock (lock);

  if (hdr == mallwatch)
    tr_break ();

  return hdr;
}



#ifdef _LIBC

/* 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 __libc_freeres_fn_section
release_libc_mem (void)
{
  /* Only call the free function if we still are running in mtrace mode.  */
  if (mallstream != NULL)
    __libc_freeres ();
}
#endif


/* We enable tracing if either the environment variable MALLOC_TRACE
   is set, or if the variable mallwatch has been patched to an address
   that the debugging user wants us to stop on.  When patching mallwatch,
   don't forget to set a breakpoint on tr_break!  */

void
mtrace ()
{
#ifdef _LIBC
  static int added_atexit_handler;
#endif
  char *mallfile;

  /* Don't panic if we're called more than once.  */
  if (mallstream != NULL)
    return;

#ifdef _LIBC
  /* When compiling the GNU libc we use the secure getenv function
     which prevents the misuse in case of SUID or SGID enabled
     programs.  */
  mallfile = __libc_secure_getenv (mallenv);
#else
  mallfile = getenv (mallenv);
#endif
  if (mallfile != NULL || mallwatch != NULL)
    {
      char *mtb = malloc (TRACE_BUFFER_SIZE);
      if (mtb == NULL)
	return;

      mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
      if (mallstream != NULL)
	{
#ifndef __ASSUME_O_CLOEXEC
	  /* Make sure we close the file descriptor on exec.  */
	  int flags = __fcntl (fileno (mallstream), F_GETFD, 0);
	  if (flags >= 0)
	    {
	      flags |= FD_CLOEXEC;
	      __fcntl (fileno (mallstream), F_SETFD, flags);
	    }
#endif
	  /* Be sure it doesn't malloc its buffer!  */
	  malloc_trace_buffer = mtb;
	  setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE);
	  fprintf (mallstream, "= Start\n");
	  tr_old_free_hook = __free_hook;
	  __free_hook = tr_freehook;
	  tr_old_malloc_hook = __malloc_hook;
	  __malloc_hook = tr_mallochook;
	  tr_old_realloc_hook = __realloc_hook;
	  __realloc_hook = tr_reallochook;
	  tr_old_memalign_hook = __memalign_hook;
	  __memalign_hook = tr_memalignhook;
#ifdef _LIBC
	  if (!added_atexit_handler)
	    {
	      extern void *__dso_handle __attribute__ ((__weak__));
	      added_atexit_handler = 1;
	      __cxa_atexit ((void (*) (void *)) release_libc_mem, NULL,
			     &__dso_handle ? __dso_handle : NULL);
	    }
#endif
	}
      else
	free (mtb);
    }
}

void
muntrace ()
{
  if (mallstream == NULL)
    return;

  fprintf (mallstream, "= End\n");
  fclose (mallstream);
  mallstream = NULL;
  __free_hook = tr_old_free_hook;
  __malloc_hook = tr_old_malloc_hook;
  __realloc_hook = tr_old_realloc_hook;
  __memalign_hook = tr_old_memalign_hook;
}