malloc/tst-interpose-aux.c

   1 /* Minimal malloc implementation for interposition tests.
   2    Copyright (C) 2016-2018 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 License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    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; see the file COPYING.LIB.  If
  17    not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include "tst-interpose-aux.h"
  20
  21 #include <errno.h>
  22 #include <stdarg.h>
  23 #include <stddef.h>
  24 #include <stdint.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <sys/mman.h>
  29 #include <sys/uio.h>
  30 #include <unistd.h>
  31
  32 #if INTERPOSE_THREADS
  33 #include <pthread.h>
  34 #endif
  35
  36 /* Print the error message and terminate the process with status 1.  */
  37 __attribute__ ((noreturn))
  38 __attribute__ ((format (printf, 1, 2)))
  39 static void *
  40 fail (const char *format, ...)
  41 {
  42   /* This assumes that vsnprintf will not call malloc.  It does not do
  43      so for the format strings we use.  */
  44   char message[4096];
  45   va_list ap;
  46   va_start (ap, format);
  47   vsnprintf (message, sizeof (message), format, ap);
  48   va_end (ap);
  49
  50   enum { count = 3 };
  51   struct iovec iov[count];
  52
  53   iov[0].iov_base = (char *) "error: ";
  54   iov[1].iov_base = (char *) message;
  55   iov[2].iov_base = (char *) "\n";
  56
  57   for (int i = 0; i < count; ++i)
  58     iov[i].iov_len = strlen (iov[i].iov_base);
  59
  60   int unused __attribute__ ((unused));
  61   unused = writev (STDOUT_FILENO, iov, count);
  62   _exit (1);
  63 }
  64
  65 #if INTERPOSE_THREADS
  66 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  67 #endif
  68
  69 static void
  70 lock (void)
  71 {
  72 #if INTERPOSE_THREADS
  73   int ret = pthread_mutex_lock (&mutex);
  74   if (ret != 0)
  75     {
  76       errno = ret;
  77       fail ("pthread_mutex_lock: %m");
  78     }
  79 #endif
  80 }
  81
  82 static void
  83 unlock (void)
  84 {
  85 #if INTERPOSE_THREADS
  86   int ret = pthread_mutex_unlock (&mutex);
  87   if (ret != 0)
  88     {
  89       errno = ret;
  90       fail ("pthread_mutex_unlock: %m");
  91     }
  92 #endif
  93 }
  94
  95 struct __attribute__ ((aligned (__alignof__ (max_align_t)))) allocation_header
  96 {
  97   size_t allocation_index;
  98   size_t allocation_size;
  99 };
 100
 101 /* Array of known allocations, to track invalid frees.  */
 102 enum { max_allocations = 65536 };
 103 static struct allocation_header *allocations[max_allocations];
 104 static size_t allocation_index;
 105 static size_t deallocation_count;
 106
 107 /* Sanity check for successful malloc interposition.  */
 108 __attribute__ ((destructor))
 109 static void
 110 check_for_allocations (void)
 111 {
 112   if (allocation_index == 0)
 113     {
 114       /* Make sure that malloc is called at least once from libc.  */
 115       void *volatile ptr = strdup ("ptr");
 116       /* Compiler barrier.  The strdup function calls malloc, which
 117          updates allocation_index, but strdup is marked __THROW, so
 118          the compiler could optimize away the reload.  */
 119       __asm__ volatile ("" ::: "memory");
 120       free (ptr);
 121       /* If the allocation count is still zero, it means we did not
 122          interpose malloc successfully.  */
 123       if (allocation_index == 0)
 124         fail ("malloc does not seem to have been interposed");
 125     }
 126 }
 127
 128 static struct allocation_header *get_header (const char *op, void *ptr)
 129 {
 130   struct allocation_header *header = ((struct allocation_header *) ptr) - 1;
 131   if (header->allocation_index >= allocation_index)
 132     fail ("%s: %p: invalid allocation index: %zu (not less than %zu)",
 133           op, ptr, header->allocation_index, allocation_index);
 134   if (allocations[header->allocation_index] != header)
 135     fail ("%s: %p: allocation pointer does not point to header, but %p",
 136           op, ptr, allocations[header->allocation_index]);
 137   return header;
 138 }
 139
 140 /* Internal helper functions.  Those must be called while the lock is
 141    acquired.  */
 142
 143 static void *
 144 malloc_internal (size_t size)
 145 {
 146   if (allocation_index == max_allocations)
 147     {
 148       errno = ENOMEM;
 149       return NULL;
 150     }
 151   size_t allocation_size = size + sizeof (struct allocation_header);
 152   if (allocation_size < size)
 153     {
 154       errno = ENOMEM;
 155       return NULL;
 156     }
 157
 158   size_t index = allocation_index++;
 159   void *result = mmap (NULL, allocation_size, PROT_READ | PROT_WRITE,
 160                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 161   if (result == MAP_FAILED)
 162     return NULL;
 163   allocations[index] = result;
 164   *allocations[index] = (struct allocation_header)
 165     {
 166       .allocation_index = index,
 167       .allocation_size = allocation_size
 168     };
 169   return allocations[index] + 1;
 170 }
 171
 172 static void
 173 free_internal (const char *op, struct allocation_header *header)
 174 {
 175   size_t index = header->allocation_index;
 176   int result = mprotect (header, header->allocation_size, PROT_NONE);
 177   if (result != 0)
 178     fail ("%s: mprotect (%p, %zu): %m", op, header, header->allocation_size);
 179   /* Catch double-free issues.  */
 180   allocations[index] = NULL;
 181   ++deallocation_count;
 182 }
 183
 184 static void *
 185 realloc_internal (void *ptr, size_t new_size)
 186 {
 187   struct allocation_header *header = get_header ("realloc", ptr);
 188   size_t old_size = header->allocation_size - sizeof (struct allocation_header);
 189   if (old_size >= new_size)
 190     return ptr;
 191
 192   void *newptr = malloc_internal (new_size);
 193   if (newptr == NULL)
 194     return NULL;
 195   memcpy (newptr, ptr, old_size);
 196   free_internal ("realloc", header);
 197   return newptr;
 198 }
 199
 200 /* Public interfaces.  These functions must perform locking.  */
 201
 202 size_t
 203 malloc_allocation_count (void)
 204 {
 205   lock ();
 206   size_t count = allocation_index;
 207   unlock ();
 208   return count;
 209 }
 210
 211 size_t
 212 malloc_deallocation_count (void)
 213 {
 214   lock ();
 215   size_t count = deallocation_count;
 216   unlock ();
 217   return count;
 218 }
 219 void *
 220 malloc (size_t size)
 221 {
 222   lock ();
 223   void *result = malloc_internal (size);
 224   unlock ();
 225   return result;
 226 }
 227
 228 void
 229 free (void *ptr)
 230 {
 231   if (ptr == NULL)
 232     return;
 233   lock ();
 234   struct allocation_header *header = get_header ("free", ptr);
 235   free_internal ("free", header);
 236   unlock ();
 237 }
 238
 239 void *
 240 calloc (size_t a, size_t b)
 241 {
 242   if (b > 0 && a > SIZE_MAX / b)
 243     {
 244       errno = ENOMEM;
 245       return NULL;
 246     }
 247   lock ();
 248   /* malloc_internal uses mmap, so the memory is zeroed.  */
 249   void *result = malloc_internal (a * b);
 250   unlock ();
 251   return result;
 252 }
 253
 254 void *
 255 realloc (void *ptr, size_t n)
 256 {
 257   if (n ==0)
 258     {
 259       free (ptr);
 260       return NULL;
 261     }
 262   else if (ptr == NULL)
 263     return malloc (n);
 264   else
 265     {
 266       lock ();
 267       void *result = realloc_internal (ptr, n);
 268       unlock ();
 269       return result;
 270     }
 271 }