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Diffstat (limited to 'gnulib-tests/test-free.c')
| -rw-r--r-- | gnulib-tests/test-free.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/gnulib-tests/test-free.c b/gnulib-tests/test-free.c new file mode 100644 index 0000000..c530e86 --- /dev/null +++ b/gnulib-tests/test-free.c @@ -0,0 +1,175 @@ +/* Test of free() function. + Copyright (C) 2020-2023 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2020. */ + +#include <config.h> + +/* Specification. */ +#include <stdlib.h> + +#include <errno.h> +#include <string.h> +#include <unistd.h> +#if defined __linux__ +# include <fcntl.h> +# include <stdint.h> +# include <string.h> +# include <sys/mman.h> +#endif + +#include "macros.h" + +/* The indirection through a volatile function pointer is necessary to prevent + a GCC optimization. Without it, when optimizing, GCC would "know" that errno + is unchanged by calling free(ptr), when ptr was the result of a malloc(...) + call in the same function. */ +static int +get_errno (void) +{ + volatile int err = errno; + return err; +} + +static int (* volatile get_errno_func) (void) = get_errno; + +int +main () +{ + /* Check that free() preserves errno. */ + { + errno = 1789; /* Liberté, égalité, fraternité. */ + free (NULL); + ASSERT_NO_STDIO (get_errno_func () == 1789); + } + { /* Small memory allocations. */ + #define N 10000 + void * volatile ptrs[N]; + size_t i; + for (i = 0; i < N; i++) + ptrs[i] = malloc (15); + for (i = 0; i < N; i++) + { + errno = 1789; + free (ptrs[i]); + ASSERT_NO_STDIO (get_errno_func () == 1789); + } + #undef N + } + { /* Medium memory allocations. */ + #define N 1000 + void * volatile ptrs[N]; + size_t i; + for (i = 0; i < N; i++) + ptrs[i] = malloc (729); + for (i = 0; i < N; i++) + { + errno = 1789; + free (ptrs[i]); + ASSERT_NO_STDIO (get_errno_func () == 1789); + } + #undef N + } + { /* Large memory allocations. */ + #define N 10 + void * volatile ptrs[N]; + size_t i; + for (i = 0; i < N; i++) + ptrs[i] = malloc (5318153); + for (i = 0; i < N; i++) + { + errno = 1789; + free (ptrs[i]); + ASSERT_NO_STDIO (get_errno_func () == 1789); + } + #undef N + } + + /* Test a less common code path. + When malloc() is based on mmap(), free() can sometimes call munmap(). + munmap() usually succeeds, but fails in a particular situation: when + - it has to unmap the middle part of a VMA, and + - the number of VMAs of a process is limited and the limit is + already reached. + The latter condition is fulfilled on Linux, when the file + /proc/sys/vm/max_map_count exists. This file contains the limit + - for Linux >= 2.4.19: 65536 (DEFAULT_MAX_MAP_COUNT in linux/include/linux/sched.h) + - for Linux >= 2.6.31: 65530 (DEFAULT_MAX_MAP_COUNT in linux/include/linux/mm.h). + But do not test it with glibc < 2.15, since that triggers a glibc internal + abort: "malloc.c:3551: munmap_chunk: Assertion `ret == 0' failed." + */ + #if defined __linux__ && !(__GLIBC__ == 2 && __GLIBC_MINOR__ < 15) + if (open ("/proc/sys/vm/max_map_count", O_RDONLY) >= 0) + { + /* Preparations. */ + size_t pagesize = getpagesize (); + void *firstpage_backup = malloc (pagesize); + void *lastpage_backup = malloc (pagesize); + /* Allocate a large memory area, as a bumper, so that the MAP_FIXED + allocation later will not overwrite parts of the memory areas + allocated to ld.so or libc.so. */ + void *bumper_region = + mmap (NULL, 0x1000000, PROT_READ, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); + /* A file descriptor pointing to a regular file. */ + int fd = open ("test-free", O_RDONLY); + + if (firstpage_backup != NULL && lastpage_backup != NULL + && bumper_region != (void *)(-1) + && fd >= 0) + { + /* Do a large memory allocation. */ + size_t big_size = 0x1000000; + void * volatile ptr = malloc (big_size - 0x100); + char *ptr_aligned = (char *) ((uintptr_t) ptr & ~(pagesize - 1)); + /* This large memory allocation allocated a memory area + from ptr_aligned to ptr_aligned + big_size. + Enlarge this memory area by adding a page before and a page + after it. */ + memcpy (firstpage_backup, ptr_aligned, pagesize); + memcpy (lastpage_backup, ptr_aligned + big_size - pagesize, pagesize); + if (mmap (ptr_aligned - pagesize, pagesize + big_size + pagesize, + PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0) + != (void *)(-1)) + { + memcpy (ptr_aligned, firstpage_backup, pagesize); + memcpy (ptr_aligned + big_size - pagesize, lastpage_backup, pagesize); + + /* Now add as many mappings as we can. + Stop at 65536, in order not to crash the machine (in case the + limit has been increased by the system administrator). */ + size_t i; + for (i = 0; i < 65536; i++) + if (mmap (NULL, pagesize, PROT_READ, MAP_FILE | MAP_PRIVATE, fd, 0) + == (void *)(-1)) + break; + /* Now the number of VMAs of this process has hopefully attained + its limit. */ + + errno = 1789; + /* This call to free() is supposed to call + munmap (ptr_aligned, big_size); + which increases the number of VMAs by 1, which is supposed + to fail. */ + free (ptr); + ASSERT_NO_STDIO (get_errno_func () == 1789); + } + } + } + #endif + + return 0; +} |