malloc/mtrace-impl.c

   1 /* mtrace implementation for `malloc'.
   2    Copyright (C) 1991-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19
  20 #include <malloc.h>
  21 #include <mcheck.h>
  22
  23 #include <dlfcn.h>
  24 #include <fcntl.h>
  25 #include <stdio.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28 #include <inttypes.h>
  29
  30 #include <libc-internal.h>
  31 #include <dso_handle.h>
  32
  33 #include <kernel-features.h>
  34
  35 static FILE *mallstream;
  36 static const char mallenv[] = "MALLOC_TRACE";
  37
  38 static void
  39 tr_where (const void *caller, Dl_info *info)
  40 {
  41   if (caller != NULL)
  42     {
  43       if (info != NULL)
  44         {
  45           char *buf = (char *) "";
  46           if (info->dli_sname != NULL)
  47             {
  48               size_t len = strlen (info->dli_sname);
  49               buf = alloca (len + 6 + 2 * sizeof (void *));
  50               char sign;
  51               ptrdiff_t offset =
  52                 (ptrdiff_t) info->dli_saddr - (ptrdiff_t) caller;
  53
  54               if (caller >= (const void *) info->dli_saddr)
  55                 {
  56                   sign = '+';
  57                   offset = -offset;
  58                 }
  59               else
  60                   sign = '-';
  61
  62               sprintf (buf, "(%s%c%" PRIxPTR ")", info->dli_sname, sign,
  63                        offset);
  64             }
  65
  66           fprintf (mallstream, "@ %s%s%s[0x%" PRIxPTR "] ",
  67                    info->dli_fname ? : "", info->dli_fname ? ":" : "", buf,
  68                    caller - info->dli_fbase);
  69         }
  70       else
  71         fprintf (mallstream, "@ [%p] ", caller);
  72     }
  73 }
  74
  75 static Dl_info *
  76 lock_and_info (const void *caller, Dl_info *mem)
  77 {
  78   if (caller == NULL)
  79     return NULL;
  80
  81   Dl_info *res = dladdr (caller, mem) ? mem : NULL;
  82
  83   flockfile (mallstream);
  84
  85   return res;
  86 }
  87
  88 static void
  89 free_mtrace (void *ptr, const void *caller)
  90 {
  91   if (ptr == NULL)
  92     return;
  93
  94   Dl_info mem;
  95   Dl_info *info = lock_and_info (caller, &mem);
  96   tr_where (caller, info);
  97   /* Be sure to print it first.  */
  98   fprintf (mallstream, "- %p\n", ptr);
  99   funlockfile (mallstream);
 100 }
 101
 102 static void
 103 malloc_mtrace_after (void *block, size_t size, const void *caller)
 104 {
 105   Dl_info mem;
 106   Dl_info *info = lock_and_info (caller, &mem);
 107
 108   tr_where (caller, info);
 109   /* We could be printing a NULL here; that's OK.  */
 110   fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 111
 112   funlockfile (mallstream);
 113 }
 114
 115 static void
 116 realloc_mtrace_after (void *block, const void *oldptr, size_t size,
 117                       const void *caller)
 118 {
 119   Dl_info mem;
 120   Dl_info *info = lock_and_info (caller, &mem);
 121
 122   tr_where (caller, info);
 123   if (block == NULL)
 124     {
 125       if (size != 0)
 126         /* Failed realloc.  */
 127         fprintf (mallstream, "! %p %#lx\n", oldptr, (unsigned long int) size);
 128       else
 129         fprintf (mallstream, "- %p\n", oldptr);
 130     }
 131   else if (oldptr == NULL)
 132     fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 133   else
 134     {
 135       fprintf (mallstream, "< %p\n", oldptr);
 136       tr_where (caller, info);
 137       fprintf (mallstream, "> %p %#lx\n", block, (unsigned long int) size);
 138     }
 139
 140   funlockfile (mallstream);
 141 }
 142
 143 static void
 144 memalign_mtrace_after (void *block, size_t size, const void *caller)
 145 {
 146   Dl_info mem;
 147   Dl_info *info = lock_and_info (caller, &mem);
 148
 149   tr_where (caller, info);
 150   /* We could be printing a NULL here; that's OK.  */
 151   fprintf (mallstream, "+ %p %#lx\n", block, (unsigned long int) size);
 152
 153   funlockfile (mallstream);
 154 }
 155
 156 /* This function gets called to make sure all memory the library
 157    allocates get freed and so does not irritate the user when studying
 158    the mtrace output.  */
 159 static void
 160 release_libc_mem (void)
 161 {
 162   /* Only call the free function if we still are running in mtrace mode.  */
 163   if (mallstream != NULL)
 164     __libc_freeres ();
 165 }
 166
 167 /* We enable tracing if the environment variable MALLOC_TRACE is set.  */
 168
 169 static void
 170 do_mtrace (void)
 171 {
 172   static int added_atexit_handler;
 173   char *mallfile;
 174
 175   /* Don't panic if we're called more than once.  */
 176   if (mallstream != NULL)
 177     return;
 178
 179   mallfile = secure_getenv (mallenv);
 180   if (mallfile != NULL)
 181     {
 182       mallstream = fopen (mallfile != NULL ? mallfile : "/dev/null", "wce");
 183       if (mallstream != NULL)
 184         {
 185           /* Be sure it doesn't malloc its buffer!  */
 186           static char tracebuf [512];
 187
 188           setvbuf (mallstream, tracebuf, _IOFBF, sizeof (tracebuf));
 189           fprintf (mallstream, "= Start\n");
 190           if (!added_atexit_handler)
 191             {
 192               added_atexit_handler = 1;
 193               __cxa_atexit ((void (*)(void *))release_libc_mem, NULL,
 194                             __dso_handle);
 195             }
 196           __malloc_debug_enable (MALLOC_MTRACE_HOOK);
 197         }
 198     }
 199 }
 200
 201 static void
 202 do_muntrace (void)
 203 {
 204   __malloc_debug_disable (MALLOC_MTRACE_HOOK);
 205   if (mallstream == NULL)
 206     return;
 207
 208   /* Do the reverse of what done in mtrace: first reset the hooks and
 209      MALLSTREAM, and only after that write the trailer and close the
 210      file.  */
 211   FILE *f = mallstream;
 212   mallstream = NULL;
 213
 214   fprintf (f, "= End\n");
 215   fclose (f);
 216 }