glibc/malloc/tst-interpose-aux.c

271 lines
6.6 KiB
C

/* Minimal malloc implementation for interposition tests.
Copyright (C) 2016-2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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; see the file COPYING.LIB. If
not, see <http://www.gnu.org/licenses/>. */
#include "tst-interpose-aux.h"
#include <errno.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/uio.h>
#include <unistd.h>
#if INTERPOSE_THREADS
#include <pthread.h>
#endif
/* Print the error message and terminate the process with status 1. */
__attribute__ ((noreturn))
__attribute__ ((format (printf, 1, 2)))
static void *
fail (const char *format, ...)
{
/* This assumes that vsnprintf will not call malloc. It does not do
so for the format strings we use. */
char message[4096];
va_list ap;
va_start (ap, format);
vsnprintf (message, sizeof (message), format, ap);
va_end (ap);
enum { count = 3 };
struct iovec iov[count];
iov[0].iov_base = (char *) "error: ";
iov[1].iov_base = (char *) message;
iov[2].iov_base = (char *) "\n";
for (int i = 0; i < count; ++i)
iov[i].iov_len = strlen (iov[i].iov_base);
int unused __attribute__ ((unused));
unused = writev (STDOUT_FILENO, iov, count);
_exit (1);
}
#if INTERPOSE_THREADS
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
#endif
static void
lock (void)
{
#if INTERPOSE_THREADS
int ret = pthread_mutex_lock (&mutex);
if (ret != 0)
{
errno = ret;
fail ("pthread_mutex_lock: %m");
}
#endif
}
static void
unlock (void)
{
#if INTERPOSE_THREADS
int ret = pthread_mutex_unlock (&mutex);
if (ret != 0)
{
errno = ret;
fail ("pthread_mutex_unlock: %m");
}
#endif
}
struct __attribute__ ((aligned (__alignof__ (max_align_t)))) allocation_header
{
size_t allocation_index;
size_t allocation_size;
};
/* Array of known allocations, to track invalid frees. */
enum { max_allocations = 65536 };
static struct allocation_header *allocations[max_allocations];
static size_t allocation_index;
static size_t deallocation_count;
/* Sanity check for successful malloc interposition. */
__attribute__ ((destructor))
static void
check_for_allocations (void)
{
if (allocation_index == 0)
{
/* Make sure that malloc is called at least once from libc. */
void *volatile ptr = strdup ("ptr");
free (ptr);
/* Compiler barrier. The strdup function calls malloc, which
updates allocation_index, but strdup is marked __THROW, so
the compiler could optimize away the reload. */
__asm__ volatile ("" ::: "memory");
/* If the allocation count is still zero, it means we did not
interpose malloc successfully. */
if (allocation_index == 0)
fail ("malloc does not seem to have been interposed");
}
}
static struct allocation_header *get_header (const char *op, void *ptr)
{
struct allocation_header *header = ((struct allocation_header *) ptr) - 1;
if (header->allocation_index >= allocation_index)
fail ("%s: %p: invalid allocation index: %zu (not less than %zu)",
op, ptr, header->allocation_index, allocation_index);
if (allocations[header->allocation_index] != header)
fail ("%s: %p: allocation pointer does not point to header, but %p",
op, ptr, allocations[header->allocation_index]);
return header;
}
/* Internal helper functions. Those must be called while the lock is
acquired. */
static void *
malloc_internal (size_t size)
{
if (allocation_index == max_allocations)
{
errno = ENOMEM;
return NULL;
}
size_t allocation_size = size + sizeof (struct allocation_header);
if (allocation_size < size)
{
errno = ENOMEM;
return NULL;
}
size_t index = allocation_index++;
void *result = mmap (NULL, allocation_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (result == MAP_FAILED)
return NULL;
allocations[index] = result;
*allocations[index] = (struct allocation_header)
{
.allocation_index = index,
.allocation_size = allocation_size
};
return allocations[index] + 1;
}
static void
free_internal (const char *op, struct allocation_header *header)
{
size_t index = header->allocation_index;
int result = mprotect (header, header->allocation_size, PROT_NONE);
if (result != 0)
fail ("%s: mprotect (%p, %zu): %m", op, header, header->allocation_size);
/* Catch double-free issues. */
allocations[index] = NULL;
++deallocation_count;
}
static void *
realloc_internal (void *ptr, size_t new_size)
{
struct allocation_header *header = get_header ("realloc", ptr);
size_t old_size = header->allocation_size - sizeof (struct allocation_header);
if (old_size >= new_size)
return ptr;
void *newptr = malloc_internal (new_size);
if (newptr == NULL)
return NULL;
memcpy (newptr, ptr, old_size);
free_internal ("realloc", header);
return newptr;
}
/* Public interfaces. These functions must perform locking. */
size_t
malloc_allocation_count (void)
{
lock ();
size_t count = allocation_index;
unlock ();
return count;
}
size_t
malloc_deallocation_count (void)
{
lock ();
size_t count = deallocation_count;
unlock ();
return count;
}
void *
malloc (size_t size)
{
lock ();
void *result = malloc_internal (size);
unlock ();
return result;
}
void
free (void *ptr)
{
if (ptr == NULL)
return;
lock ();
struct allocation_header *header = get_header ("free", ptr);
free_internal ("free", header);
unlock ();
}
void *
calloc (size_t a, size_t b)
{
if (b > 0 && a > SIZE_MAX / b)
{
errno = ENOMEM;
return NULL;
}
lock ();
/* malloc_internal uses mmap, so the memory is zeroed. */
void *result = malloc_internal (a * b);
unlock ();
return result;
}
void *
realloc (void *ptr, size_t n)
{
if (n ==0)
{
free (ptr);
return NULL;
}
else if (ptr == NULL)
return malloc (n);
else
{
lock ();
void *result = realloc_internal (ptr, n);
unlock ();
return result;
}
}