malloc/mtrace-impl.c

   1 /* mtrace implementation for `malloc'.
   2    Copyright (C) 1991-2021 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    <https://www.gnu.org/licenses/>.  */
  20
  21
  22 #include <malloc.h>
  23 #include <mcheck.h>
  24
  25 #include <dlfcn.h>
  26 #include <fcntl.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <stdlib.h>
  30 #include <inttypes.h>
  31
  32 #include <libc-internal.h>
  33 #include <dso_handle.h>
  34
  35 #include <kernel-features.h>
  36
  37 #define TRACE_BUFFER_SIZE 512
  38
  39 static FILE *mallstream;
  40 static const char mallenv[] = "MALLOC_TRACE";
  41 static char *malloc_trace_buffer;
  42
  43 static void
  44 tr_where (const void *caller, Dl_info *info)
  45 {
  46   if (caller != NULL)
  47     {
  48       if (info != NULL)
  49         {
  50           char *buf = (char *) "";
  51           if (info->dli_sname != NULL)
  52             {
  53               size_t len = strlen (info->dli_sname);
  54               buf = alloca (len + 6 + 2 * sizeof (void *));
  55               char sign;
  56               ptrdiff_t offset =
  57                 (ptrdiff_t) info->dli_saddr - (ptrdiff_t) caller;
  58
  59               if (caller >= (const void *) info->dli_saddr)
  60                 {
  61                   sign = '+';
  62                   offset = -offset;
  63                 }
  64               else
  65                   sign = '-';
  66
  67               sprintf (buf, "(%s%c%" PRIxPTR ")", info->dli_sname, sign,
  68                        offset);
  69             }
  70
  71           fprintf (mallstream, "@ %s%s%s[%p] ", info->dli_fname ? : "",
  72                    info->dli_fname ? ":" : "",
  73                    buf, caller);
  74         }
  75       else
  76         fprintf (mallstream, "@ [%p] ", caller);
  77     }
  78 }
  79
  80 static Dl_info *
  81 lock_and_info (const void *caller, Dl_info *mem)
  82 {
  83   if (caller == NULL)
  84     return NULL;
  85
  86   Dl_info *res = dladdr (caller, mem) ? mem : NULL;
  87
  88   flockfile (mallstream);
  89
  90   return res;
  91 }
  92
  93 static void
  94 free_mtrace (void *ptr, const void *caller)
  95 {
  96   if (ptr == NULL)
  97     return;
  98
  99   Dl_info mem;
 100   Dl_info *info = lock_and_info (caller, &mem);
 101   tr_where (caller, info);
 102   /* Be sure to print it first.  */
 103   fprintf (mallstream, "- %p\n", ptr);
 104   funlockfile (mallstream);
 105 }
 106
 107 static void
 108 malloc_mtrace_after (void *block, size_t size, const void *caller)
 109 {
 110   Dl_info mem;
 111   Dl_info *info = lock_and_info (caller, &mem);
 112
 113   tr_where (caller, info);
 114   /* We could be printing a NULL here; that's OK.  */
 115   fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 116
 117   funlockfile (mallstream);
 118 }
 119
 120 static void
 121 realloc_mtrace_after (void *block, const void *oldptr, size_t size,
 122                       const void *caller)
 123 {
 124   Dl_info mem;
 125   Dl_info *info = lock_and_info (caller, &mem);
 126
 127   tr_where (caller, info);
 128   if (block == NULL)
 129     {
 130       if (size != 0)
 131         /* Failed realloc.  */
 132         fprintf (mallstream, "! %p %#lx\n", oldptr, (unsigned long int) size);
 133       else
 134         fprintf (mallstream, "- %p\n", oldptr);
 135     }
 136   else if (oldptr == NULL)
 137     fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 138   else
 139     {
 140       fprintf (mallstream, "< %p\n", oldptr);
 141       tr_where (caller, info);
 142       fprintf (mallstream, "> %p %#lx\n", block, (unsigned long int) size);
 143     }
 144
 145   funlockfile (mallstream);
 146 }
 147
 148 static void
 149 memalign_mtrace_after (void *block, size_t size, const void *caller)
 150 {
 151   Dl_info mem;
 152   Dl_info *info = lock_and_info (caller, &mem);
 153
 154   tr_where (caller, info);
 155   /* We could be printing a NULL here; that's OK.  */
 156   fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 157
 158   funlockfile (mallstream);
 159 }
 160
 161 /* This function gets called to make sure all memory the library
 162    allocates get freed and so does not irritate the user when studying
 163    the mtrace output.  */
 164 static void
 165 release_libc_mem (void)
 166 {
 167   /* Only call the free function if we still are running in mtrace mode.  */
 168   if (mallstream != NULL)
 169     __libc_freeres ();
 170 }
 171
 172 /* We enable tracing if the environment variable MALLOC_TRACE is set.  */
 173
 174 static void
 175 do_mtrace (void)
 176 {
 177   static int added_atexit_handler;
 178   char *mallfile;
 179
 180   /* Don't panic if we're called more than once.  */
 181   if (mallstream != NULL)
 182     return;
 183
 184   mallfile = secure_getenv (mallenv);
 185   if (mallfile != NULL)
 186     {
 187       char *mtb = malloc (TRACE_BUFFER_SIZE);
 188       if (mtb == NULL)
 189         return;
 190
 191       mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
 192       if (mallstream != NULL)
 193         {
 194           /* Be sure it doesn't malloc its buffer!  */
 195           malloc_trace_buffer = mtb;
 196           setvbuf (mallstream, malloc_trace_buffer, _IOFBF, TRACE_BUFFER_SIZE);
 197           fprintf (mallstream, "= Start\n");
 198           if (!added_atexit_handler)
 199             {
 200               added_atexit_handler = 1;
 201               __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
 202                             __dso_handle);
 203             }
 204           __malloc_debug_enable (MALLOC_MTRACE_HOOK);
 205         }
 206       else
 207         free (mtb);
 208     }
 209 }
 210
 211 static void
 212 do_muntrace (void)
 213 {
 214   __malloc_debug_disable (MALLOC_MTRACE_HOOK);
 215   if (mallstream == NULL)
 216     return;
 217
 218   /* Do the reverse of what done in mtrace: first reset the hooks and
 219      MALLSTREAM, and only after that write the trailer and close the
 220      file.  */
 221   FILE *f = mallstream;
 222   mallstream = NULL;
 223
 224   fprintf (f, "= End\n");
 225   fclose (f);
 226 }