malloc/mtrace.c

   1 /* More debugging hooks for `malloc'.
   2    Copyright (C) 1991-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4                  Written April 2, 1991 by John Gilmore of Cygnus Support.
   5                  Based on mcheck.c by Mike Haertel.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #ifndef _MALLOC_INTERNAL
  22 # define _MALLOC_INTERNAL
  23 # include <malloc.h>
  24 # include <mcheck.h>
  25 # include <libc-lock.h>
  26 #endif
  27
  28 #include <dlfcn.h>
  29 #include <fcntl.h>
  30 #include <stdio.h>
  31 #include <string.h>
  32 #include <stdlib.h>
  33
  34 #include <_itoa.h>
  35
  36 #include <libc-internal.h>
  37
  38 #include <libio/iolibio.h>
  39 #define setvbuf(s, b, f, l) _IO_setvbuf (s, b, f, l)
  40 #define fwrite(buf, size, count, fp) _IO_fwrite (buf, size, count, fp)
  41
  42 #include <kernel-features.h>
  43
  44 #define TRACE_BUFFER_SIZE 512
  45
  46 static FILE *mallstream;
  47 static const char mallenv[] = "MALLOC_TRACE";
  48 static char *malloc_trace_buffer;
  49
  50 __libc_lock_define_initialized (static, lock);
  51
  52 /* Address to breakpoint on accesses to... */
  53 __ptr_t mallwatch;
  54
  55 /* Old hook values.  */
  56 static void (*tr_old_free_hook) (__ptr_t ptr, const __ptr_t);
  57 static __ptr_t (*tr_old_malloc_hook) (size_t size, const __ptr_t);
  58 static __ptr_t (*tr_old_realloc_hook) (__ptr_t ptr, size_t size,
  59                                        const __ptr_t);
  60 static __ptr_t (*tr_old_memalign_hook) (size_t __alignment, size_t __size,
  61                                         const __ptr_t);
  62
  63 /* This function is called when the block being alloc'd, realloc'd, or
  64    freed has an address matching the variable "mallwatch".  In a debugger,
  65    set "mallwatch" to the address of interest, then put a breakpoint on
  66    tr_break.  */
  67
  68 extern void tr_break (void) __THROW;
  69 libc_hidden_proto (tr_break)
  70 void
  71 tr_break (void)
  72 {
  73 }
  74 libc_hidden_def (tr_break)
  75
  76 static void internal_function
  77 tr_where (const __ptr_t caller, Dl_info *info)
  78 {
  79   if (caller != NULL)
  80     {
  81       if (info != NULL)
  82         {
  83           char *buf = (char *) "";
  84           if (info->dli_sname != NULL)
  85             {
  86               size_t len = strlen (info->dli_sname);
  87               buf = alloca (len + 6 + 2 * sizeof (void *));
  88
  89               buf[0] = '(';
  90               __stpcpy (_fitoa (caller >= (const __ptr_t) info->dli_saddr
  91                                 ? caller - (const __ptr_t) info->dli_saddr
  92                                 : (const __ptr_t) info->dli_saddr - caller,
  93                                 __stpcpy (__mempcpy (buf + 1, info->dli_sname,
  94                                                      len),
  95                                           caller >= (__ptr_t) info->dli_saddr
  96                                           ? "+0x" : "-0x"),
  97                                 16, 0),
  98                         ")");
  99             }
 100
 101           fprintf (mallstream, "@ %s%s%s[%p] ",
 102                    info->dli_fname ? : "", info->dli_fname ? ":" : "",
 103                    buf, caller);
 104         }
 105       else
 106         fprintf (mallstream, "@ [%p] ", caller);
 107     }
 108 }
 109
 110 static Dl_info *
 111 lock_and_info (const __ptr_t caller, Dl_info *mem)
 112 {
 113   if (caller == NULL)
 114     return NULL;
 115
 116   Dl_info *res = _dl_addr (caller, mem, NULL, NULL) ? mem : NULL;
 117
 118   __libc_lock_lock (lock);
 119
 120   return res;
 121 }
 122
 123 static void
 124 tr_freehook (__ptr_t ptr, const __ptr_t caller)
 125 {
 126   if (ptr == NULL)
 127     return;
 128
 129   Dl_info mem;
 130   Dl_info *info = lock_and_info (caller, &mem);
 131   tr_where (caller, info);
 132   /* Be sure to print it first.  */
 133   fprintf (mallstream, "- %p\n", ptr);
 134   if (ptr == mallwatch)
 135     {
 136       __libc_lock_unlock (lock);
 137       tr_break ();
 138       __libc_lock_lock (lock);
 139     }
 140   __free_hook = tr_old_free_hook;
 141   if (tr_old_free_hook != NULL)
 142     (*tr_old_free_hook)(ptr, caller);
 143   else
 144     free (ptr);
 145   __free_hook = tr_freehook;
 146   __libc_lock_unlock (lock);
 147 }
 148
 149 static __ptr_t
 150 tr_mallochook (size_t size, const __ptr_t caller)
 151 {
 152   __ptr_t hdr;
 153
 154   Dl_info mem;
 155   Dl_info *info = lock_and_info (caller, &mem);
 156
 157   __malloc_hook = tr_old_malloc_hook;
 158   if (tr_old_malloc_hook != NULL)
 159     hdr = (__ptr_t) (*tr_old_malloc_hook)(size, caller);
 160   else
 161     hdr = (__ptr_t) malloc (size);
 162   __malloc_hook = tr_mallochook;
 163
 164   tr_where (caller, info);
 165   /* We could be printing a NULL here; that's OK.  */
 166   fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
 167
 168   __libc_lock_unlock (lock);
 169
 170   if (hdr == mallwatch)
 171     tr_break ();
 172
 173   return hdr;
 174 }
 175
 176 static __ptr_t
 177 tr_reallochook (__ptr_t ptr, size_t size, const __ptr_t caller)
 178 {
 179   __ptr_t hdr;
 180
 181   if (ptr == mallwatch)
 182     tr_break ();
 183
 184   Dl_info mem;
 185   Dl_info *info = lock_and_info (caller, &mem);
 186
 187   __free_hook = tr_old_free_hook;
 188   __malloc_hook = tr_old_malloc_hook;
 189   __realloc_hook = tr_old_realloc_hook;
 190   if (tr_old_realloc_hook != NULL)
 191     hdr = (__ptr_t) (*tr_old_realloc_hook)(ptr, size, caller);
 192   else
 193     hdr = (__ptr_t) realloc (ptr, size);
 194   __free_hook = tr_freehook;
 195   __malloc_hook = tr_mallochook;
 196   __realloc_hook = tr_reallochook;
 197
 198   tr_where (caller, info);
 199   if (hdr == NULL)
 200     {
 201       if (size != 0)
 202         /* Failed realloc.  */
 203         fprintf (mallstream, "! %p %#lx\n", ptr, (unsigned long int) size);
 204       else
 205         fprintf (mallstream, "- %p\n", ptr);
 206     }
 207   else if (ptr == NULL)
 208     fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
 209   else
 210     {
 211       fprintf (mallstream, "< %p\n", ptr);
 212       tr_where (caller, info);
 213       fprintf (mallstream, "> %p %#lx\n", hdr, (unsigned long int) size);
 214     }
 215
 216   __libc_lock_unlock (lock);
 217
 218   if (hdr == mallwatch)
 219     tr_break ();
 220
 221   return hdr;
 222 }
 223
 224 static __ptr_t
 225 tr_memalignhook (size_t alignment, size_t size, const __ptr_t caller)
 226 {
 227   __ptr_t hdr;
 228
 229   Dl_info mem;
 230   Dl_info *info = lock_and_info (caller, &mem);
 231
 232   __memalign_hook = tr_old_memalign_hook;
 233   __malloc_hook = tr_old_malloc_hook;
 234   if (tr_old_memalign_hook != NULL)
 235     hdr = (__ptr_t) (*tr_old_memalign_hook)(alignment, size, caller);
 236   else
 237     hdr = (__ptr_t) memalign (alignment, size);
 238   __memalign_hook = tr_memalignhook;
 239   __malloc_hook = tr_mallochook;
 240
 241   tr_where (caller, info);
 242   /* We could be printing a NULL here; that's OK.  */
 243   fprintf (mallstream, "+ %p %#lx\n", hdr, (unsigned long int) size);
 244
 245   __libc_lock_unlock (lock);
 246
 247   if (hdr == mallwatch)
 248     tr_break ();
 249
 250   return hdr;
 251 }
 252
 253
 254 #ifdef _LIBC
 255
 256 /* This function gets called to make sure all memory the library
 257    allocates get freed and so does not irritate the user when studying
 258    the mtrace output.  */
 259 static void __libc_freeres_fn_section
 260 release_libc_mem (void)
 261 {
 262   /* Only call the free function if we still are running in mtrace mode.  */
 263   if (mallstream != NULL)
 264     __libc_freeres ();
 265 }
 266 #endif
 267
 268
 269 /* We enable tracing if either the environment variable MALLOC_TRACE
 270    is set, or if the variable mallwatch has been patched to an address
 271    that the debugging user wants us to stop on.  When patching mallwatch,
 272    don't forget to set a breakpoint on tr_break!  */
 273
 274 void
 275 mtrace (void)
 276 {
 277 #ifdef _LIBC
 278   static int added_atexit_handler;
 279 #endif
 280   char *mallfile;
 281
 282   /* Don't panic if we're called more than once.  */
 283   if (mallstream != NULL)
 284     return;
 285
 286 #ifdef _LIBC
 287   /* When compiling the GNU libc we use the secure getenv function
 288      which prevents the misuse in case of SUID or SGID enabled
 289      programs.  */
 290   mallfile = __libc_secure_getenv (mallenv);
 291 #else
 292   mallfile = getenv (mallenv);
 293 #endif
 294   if (mallfile != NULL || mallwatch != NULL)
 295     {
 296       char *mtb = malloc (TRACE_BUFFER_SIZE);
 297       if (mtb == NULL)
 298         return;
 299
 300       mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
 301       if (mallstream != NULL)
 302         {
 303 #ifndef __ASSUME_O_CLOEXEC
 304           /* Make sure we close the file descriptor on exec.  */
 305           int flags = __fcntl (fileno (mallstream), F_GETFD, 0);
 306           if (flags >= 0)
 307             {
 308               flags |= FD_CLOEXEC;
 309               __fcntl (fileno (mallstream), F_SETFD, flags);
 310             }
 311 #endif
 312           /* Be sure it doesn't malloc its buffer!  */
 313           malloc_trace_buffer = mtb;
 314           setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE);
 315           fprintf (mallstream, "= Start\n");
 316           tr_old_free_hook = __free_hook;
 317           __free_hook = tr_freehook;
 318           tr_old_malloc_hook = __malloc_hook;
 319           __malloc_hook = tr_mallochook;
 320           tr_old_realloc_hook = __realloc_hook;
 321           __realloc_hook = tr_reallochook;
 322           tr_old_memalign_hook = __memalign_hook;
 323           __memalign_hook = tr_memalignhook;
 324 #ifdef _LIBC
 325           if (!added_atexit_handler)
 326             {
 327               extern void *__dso_handle __attribute__ ((__weak__));
 328               added_atexit_handler = 1;
 329               __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
 330                             &__dso_handle ? __dso_handle : NULL);
 331             }
 332 #endif
 333         }
 334       else
 335         free (mtb);
 336     }
 337 }
 338
 339 void
 340 muntrace (void)
 341 {
 342   if (mallstream == NULL)
 343     return;
 344
 345   /* Do the reverse of what done in mtrace: first reset the hooks and
 346      MALLSTREAM, and only after that write the trailer and close the
 347      file.  */
 348   FILE *f = mallstream;
 349   mallstream = NULL;
 350   __free_hook = tr_old_free_hook;
 351   __malloc_hook = tr_old_malloc_hook;
 352   __realloc_hook = tr_old_realloc_hook;
 353   __memalign_hook = tr_old_memalign_hook;
 354
 355   fprintf (f, "= End\n");
 356   fclose (f);
 357 }