glibc/support/blob_repeat.c

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/* Repeating a memory blob, with alias mapping optimization.
Copyright (C) 2018-2024 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; if not, see
Prefer https to http for gnu.org and fsf.org URLs Also, change sources.redhat.com to sourceware.org. This patch was automatically generated by running the following shell script, which uses GNU sed, and which avoids modifying files imported from upstream: sed -ri ' s,(http|ftp)(://(.*\.)?(gnu|fsf|sourceware)\.org($|[^.]|\.[^a-z])),https\2,g s,(http|ftp)(://(.*\.)?)sources\.redhat\.com($|[^.]|\.[^a-z]),https\2sourceware.org\4,g ' \ $(find $(git ls-files) -prune -type f \ ! -name '*.po' \ ! -name 'ChangeLog*' \ ! -path COPYING ! -path COPYING.LIB \ ! -path manual/fdl-1.3.texi ! -path manual/lgpl-2.1.texi \ ! -path manual/texinfo.tex ! -path scripts/config.guess \ ! -path scripts/config.sub ! -path scripts/install-sh \ ! -path scripts/mkinstalldirs ! -path scripts/move-if-change \ ! -path INSTALL ! -path locale/programs/charmap-kw.h \ ! -path po/libc.pot ! -path sysdeps/gnu/errlist.c \ ! '(' -name configure \ -execdir test -f configure.ac -o -f configure.in ';' ')' \ ! '(' -name preconfigure \ -execdir test -f preconfigure.ac ';' ')' \ -print) and then by running 'make dist-prepare' to regenerate files built from the altered files, and then executing the following to cleanup: chmod a+x sysdeps/unix/sysv/linux/riscv/configure # Omit irrelevant whitespace and comment-only changes, # perhaps from a slightly-different Autoconf version. git checkout -f \ sysdeps/csky/configure \ sysdeps/hppa/configure \ sysdeps/riscv/configure \ sysdeps/unix/sysv/linux/csky/configure # Omit changes that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/powerpc/powerpc64/ppc-mcount.S: trailing lines git checkout -f \ sysdeps/powerpc/powerpc64/ppc-mcount.S \ sysdeps/unix/sysv/linux/s390/s390-64/syscall.S # Omit change that caused a pre-commit check to fail like this: # remote: *** error: sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S: last line does not end in newline git checkout -f sysdeps/sparc/sparc64/multiarch/memcpy-ultra3.S
2019-09-07 05:40:42 +00:00
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <support/blob_repeat.h>
#include <support/check.h>
#include <support/test-driver.h>
#include <support/support.h>
#include <support/xunistd.h>
#include <sys/mman.h>
#include <unistd.h>
#include <wchar.h>
/* Small allocations should use malloc directly instead of the mmap
optimization because mappings carry a lot of overhead. */
static const size_t maximum_small_size = 4 * 1024 * 1024;
/* Internal helper for fill. */
static void
fill0 (char *target, const char *element, size_t element_size,
size_t count)
{
while (count > 0)
{
memcpy (target, element, element_size);
target += element_size;
--count;
}
}
/* Fill the buffer at TARGET with COUNT copies of the ELEMENT_SIZE
bytes starting at ELEMENT. */
static void
fill (char *target, const char *element, size_t element_size,
size_t count)
{
if (element_size == 0 || count == 0)
return;
else if (element_size == 1)
memset (target, element[0], count);
else if (element_size == sizeof (wchar_t))
{
wchar_t wc;
memcpy (&wc, element, sizeof (wc));
wmemset ((wchar_t *) target, wc, count);
}
else if (element_size < 1024 && count > 4096)
{
/* Use larger copies for really small element sizes. */
char buffer[8192];
size_t buffer_count = sizeof (buffer) / element_size;
fill0 (buffer, element, element_size, buffer_count);
while (count > 0)
{
size_t copy_count = buffer_count;
if (copy_count > count)
copy_count = count;
size_t copy_bytes = copy_count * element_size;
memcpy (target, buffer, copy_bytes);
target += copy_bytes;
count -= copy_count;
}
}
else
fill0 (target, element, element_size, count);
}
/* Use malloc instead of mmap for small allocations and unusual size
combinations. */
static struct support_blob_repeat
allocate_malloc (size_t total_size, const void *element, size_t element_size,
size_t count)
{
void *buffer = malloc (total_size);
if (buffer == NULL)
return (struct support_blob_repeat) { 0 };
fill (buffer, element, element_size, count);
return (struct support_blob_repeat)
{
.start = buffer,
.size = total_size,
.use_malloc = true
};
}
/* Return the least common multiple of PAGE_SIZE and ELEMENT_SIZE,
avoiding overflow. This assumes that PAGE_SIZE is a power of
two. */
static size_t
minimum_stride_size (size_t page_size, size_t element_size)
{
TEST_VERIFY_EXIT (page_size > 0);
TEST_VERIFY_EXIT (element_size > 0);
/* Compute the number of trailing zeros common to both sizes. */
unsigned int common_zeros = __builtin_ctzll (page_size | element_size);
/* In the product, this power of two appears twice, but in the least
common multiple, it appears only once. Therefore, shift one
factor. */
size_t multiple;
if (__builtin_mul_overflow (page_size >> common_zeros, element_size,
&multiple))
return 0;
return multiple;
}
/* Allocations larger than maximum_small_size potentially use mmap
with alias mappings. If SHARED, the alias mappings are created
using MAP_SHARED instead of MAP_PRIVATE. */
static struct support_blob_repeat
allocate_big (size_t total_size, const void *element, size_t element_size,
size_t count, bool shared)
{
unsigned long page_size = xsysconf (_SC_PAGESIZE);
size_t stride_size = minimum_stride_size (page_size, element_size);
if (stride_size == 0)
{
errno = EOVERFLOW;
return (struct support_blob_repeat) { 0 };
}
/* Ensure that the stride size is at least maximum_small_size. This
is necessary to reduce the number of distinct mappings. */
if (stride_size < maximum_small_size)
stride_size
= ((maximum_small_size + stride_size - 1) / stride_size) * stride_size;
if (stride_size > total_size)
/* The mmap optimization would not save anything. */
return allocate_malloc (total_size, element, element_size, count);
/* Reserve the memory region. If we cannot create the mapping,
there is no reason to set up the backing file. */
void *target = mmap (NULL, total_size, PROT_NONE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (target == MAP_FAILED)
return (struct support_blob_repeat) { 0 };
/* Create the backing file for the repeated mapping. Call mkstemp
directly to remove the resources backing the temporary file
immediately, once support_blob_repeat_free is called. Using
create_temp_file would result in a warning during post-test
cleanup. */
int fd;
{
char *temppath = xasprintf ("%s/support_blob_repeat-XXXXXX", test_dir);
fd = mkstemp (temppath);
if (fd < 0)
FAIL_EXIT1 ("mkstemp (\"%s\"): %m", temppath);
xunlink (temppath);
free (temppath);
}
/* Make sure that there is backing storage, so that the fill
operation will not fault. */
if (posix_fallocate (fd, 0, stride_size) != 0)
FAIL_EXIT1 ("posix_fallocate (%zu): %m", stride_size);
/* The stride size must still be a multiple of the page size and
element size. */
TEST_VERIFY_EXIT ((stride_size % page_size) == 0);
TEST_VERIFY_EXIT ((stride_size % element_size) == 0);
/* Fill the backing store. */
{
void *ptr = mmap (target, stride_size, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_FILE | MAP_SHARED, fd, 0);
if (ptr == MAP_FAILED)
{
int saved_errno = errno;
xmunmap (target, total_size);
xclose (fd);
errno = saved_errno;
return (struct support_blob_repeat) { 0 };
}
if (ptr != target)
FAIL_EXIT1 ("mapping of %zu bytes moved from %p to %p",
stride_size, target, ptr);
/* Write the repeating data. */
fill (target, element, element_size, stride_size / element_size);
/* Return to a PROT_NONE mapping, just to be on the safe side. */
ptr = mmap (target, stride_size, PROT_NONE,
MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (ptr == MAP_FAILED)
FAIL_EXIT1 ("Failed to reinstate PROT_NONE mapping: %m");
if (ptr != target)
FAIL_EXIT1 ("PROT_NONE mapping of %zu bytes moved from %p to %p",
stride_size, target, ptr);
}
/* Create the alias mappings. */
{
size_t remaining_size = total_size;
char *current = target;
int flags = MAP_FIXED | MAP_FILE;
if (shared)
flags |= MAP_SHARED;
else
flags |= MAP_PRIVATE;
#ifdef MAP_NORESERVE
flags |= MAP_NORESERVE;
#endif
while (remaining_size > 0)
{
size_t to_map = stride_size;
if (to_map > remaining_size)
to_map = remaining_size;
void *ptr = mmap (current, to_map, PROT_READ | PROT_WRITE,
flags, fd, 0);
if (ptr == MAP_FAILED)
{
int saved_errno = errno;
xmunmap (target, total_size);
xclose (fd);
errno = saved_errno;
return (struct support_blob_repeat) { 0 };
}
if (ptr != current)
FAIL_EXIT1 ("MAP_PRIVATE mapping of %zu bytes moved from %p to %p",
to_map, target, ptr);
remaining_size -= to_map;
current += to_map;
}
}
xclose (fd);
return (struct support_blob_repeat)
{
.start = target,
.size = total_size,
.use_malloc = false
};
}
struct support_blob_repeat
repeat_allocate (const void *element, size_t element_size,
size_t count, bool shared)
{
size_t total_size;
if (__builtin_mul_overflow (element_size, count, &total_size))
{
errno = EOVERFLOW;
return (struct support_blob_repeat) { 0 };
}
if (total_size <= maximum_small_size)
return allocate_malloc (total_size, element, element_size, count);
else
return allocate_big (total_size, element, element_size, count, shared);
}
struct support_blob_repeat
support_blob_repeat_allocate (const void *element, size_t element_size,
size_t count)
{
return repeat_allocate (element, element_size, count, false);
}
struct support_blob_repeat
support_blob_repeat_allocate_shared (const void *element, size_t element_size,
size_t count)
{
return repeat_allocate (element, element_size, count, true);
}
void
support_blob_repeat_free (struct support_blob_repeat *blob)
{
if (blob->size > 0)
{
int saved_errno = errno;
if (blob->use_malloc)
free (blob->start);
else
xmunmap (blob->start, blob->size);
errno = saved_errno;
}
*blob = (struct support_blob_repeat) { 0 };
}