2012-09-25 08:40:29 +00:00
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/* System-specific malloc support functions. Linux version.
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2023-01-06 21:08:04 +00:00
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Copyright (C) 2012-2023 Free Software Foundation, Inc.
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2012-09-25 08:40:29 +00:00
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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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
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<https://www.gnu.org/licenses/>. */
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2012-09-25 08:40:29 +00:00
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#include <fcntl.h>
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#include <not-cancel.h>
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/* The Linux kernel overcommits address space by default and if there is not
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enough memory available, it uses various parameters to decide the process to
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kill. It is however possible to disable or curb this overcommit behavior
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by setting the proc sysctl vm.overcommit_memory to the value '2' and with
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that, a process is only allowed to use the maximum of a pre-determined
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fraction of the total address space. In such a case, we want to make sure
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that we are judicious with our heap usage as well, and explicitly give away
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the freed top of the heap to reduce our commit charge. See the proc(5) man
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page to know more about overcommit behavior.
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Other than that, we also force an unmap in a secure exec. */
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static inline bool
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check_may_shrink_heap (void)
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{
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static int may_shrink_heap = -1;
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if (__builtin_expect (may_shrink_heap >= 0, 1))
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return may_shrink_heap;
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may_shrink_heap = __libc_enable_secure;
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if (__builtin_expect (may_shrink_heap == 0, 1))
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{
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2017-07-03 14:11:24 +00:00
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int fd = __open_nocancel ("/proc/sys/vm/overcommit_memory",
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O_RDONLY | O_CLOEXEC);
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2012-09-25 08:40:29 +00:00
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if (fd >= 0)
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{
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char val;
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2017-07-03 17:20:46 +00:00
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ssize_t n = __read_nocancel (fd, &val, 1);
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2012-09-25 08:40:29 +00:00
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may_shrink_heap = n > 0 && val == '2';
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2017-07-03 18:22:58 +00:00
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__close_nocancel_nostatus (fd);
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2012-09-25 08:40:29 +00:00
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}
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}
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return may_shrink_heap;
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}
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2013-01-17 20:08:12 +00:00
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#define HAVE_MREMAP 1
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