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mtrace.c

/* More debugging hooks for `malloc'.
   Copyright (C) 1991-1994,1996-2001,2002 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, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#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 <stdio-common/_itoa.h>

#ifdef _LIBC
# include <libc-internal.h>

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

#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;

#ifdef USE_MTRACE_FILE
/* File name and line number information, for callers that had
   the foresight to call through a macro.  */
char *_mtrace_file;
int _mtrace_line;
#endif

/* Old hook values.  */
static void (*tr_old_free_hook) __P ((__ptr_t ptr, const __ptr_t));
static __ptr_t (*tr_old_malloc_hook) __P ((__malloc_size_t size,
                                 const __ptr_t));
static __ptr_t (*tr_old_realloc_hook) __P ((__ptr_t ptr,
                                  __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 __P ((void));
libc_hidden_proto (tr_break)
void
tr_break ()
{
}
libc_hidden_def (tr_break)

static void tr_where __P ((const __ptr_t)) internal_function;
static void
internal_function
tr_where (caller)
     const __ptr_t caller;
{
#ifdef USE_MTRACE_FILE
  if (_mtrace_file)
    {
      fprintf (mallstream, "@ %s:%d ", _mtrace_file, _mtrace_line);
      _mtrace_file = NULL;
    }
  else
#endif
    if (caller != NULL)
    {
#ifdef HAVE_ELF
      Dl_info info;
      if (_dl_addr (caller, &info))
      {
        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
#endif
      fprintf (mallstream, "@ [%p] ", caller);
    }
}

static void tr_freehook __P ((__ptr_t, const __ptr_t));
static void
tr_freehook (ptr, caller)
     __ptr_t ptr;
     const __ptr_t caller;
{
  if (ptr == NULL)
    return;
  __libc_lock_lock (lock);
  tr_where (caller);
  /* Be sure to print it first.  */
  fprintf (mallstream, "- %p\n", ptr);
  __libc_lock_unlock (lock);
  if (ptr == mallwatch)
    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 __P ((__malloc_size_t, const __ptr_t));
static __ptr_t
tr_mallochook (size, caller)
     __malloc_size_t size;
     const __ptr_t caller;
{
  __ptr_t hdr;

  __libc_lock_lock (lock);

  __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);
  /* 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 __P ((__ptr_t, __malloc_size_t, const __ptr_t));
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 ();

  __libc_lock_lock (lock);

  __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);
  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);
      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 = __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", "w");
      if (mallstream != NULL)
      {
        /* 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);
          }
        /* 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;
#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;
}

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