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author | H.J. Lu <hjl.tools@gmail.com> | 2015-10-21 14:44:23 -0700 |
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committer | H.J. Lu <hjl.tools@gmail.com> | 2015-12-15 13:16:02 -0800 |
commit | b9eb92ab05204df772eb4929eccd018637c9f3e9 (patch) | |
tree | f272c9a3e0ef7232d0714cfda7e79b040a757fb9 | |
parent | c9afcaaafaf9126a973883528eed8d0058a264c0 (diff) | |
download | glibc-b9eb92ab05204df772eb4929eccd018637c9f3e9.zip glibc-b9eb92ab05204df772eb4929eccd018637c9f3e9.tar.gz glibc-b9eb92ab05204df772eb4929eccd018637c9f3e9.tar.bz2 |
Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIThjl/32bit/master
According to Silvermont software optimization guide, for 64-bit
applications, branch prediction performance can be negatively impacted
when the target of a branch is more than 4GB away from the branch. Add
the Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable
pages with MAP_32BIT first. NB: MAP_32BIT will map to lower 2GB, not
lower 4GB, address. Prefer_MAP_32BIT_EXEC reduces bits available for
address space layout randomization (ASLR), which is always disabled for
SUID programs and can only be enabled by setting environment variable,
LD_PREFER_MAP_32BIT_EXEC.
On Fedora 23, this patch speeds up GCC 5 testsuite by 3% on Silvermont.
[BZ #19367]
* sysdeps/unix/sysv/linux/wordsize-64/mmap.c: New file.
* sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h: Likewise.
* sysdeps/unix/sysv/linux/x86_64/64/mmap.c: Likewise.
* sysdeps/x86/cpu-features.h (bit_Prefer_MAP_32BIT_EXEC): New.
(index_Prefer_MAP_32BIT_EXEC): Likewise.
-rw-r--r-- | sysdeps/unix/sysv/linux/wordsize-64/mmap.c | 40 | ||||
-rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 44 | ||||
-rw-r--r-- | sysdeps/unix/sysv/linux/x86_64/64/mmap.c | 37 | ||||
-rw-r--r-- | sysdeps/x86/cpu-features.h | 3 |
4 files changed, 124 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/wordsize-64/mmap.c b/sysdeps/unix/sysv/linux/wordsize-64/mmap.c new file mode 100644 index 0000000..e098976 --- /dev/null +++ b/sysdeps/unix/sysv/linux/wordsize-64/mmap.c @@ -0,0 +1,40 @@ +/* Linux mmap system call. 64-bit version. + Copyright (C) 2015 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 + <http://www.gnu.org/licenses/>. */ + +#include <sys/types.h> +#include <sys/mman.h> +#include <errno.h> +#include <sysdep.h> + +/* An architecture may override this. */ +#ifndef MMAP_PREPARE +# define MMAP_PREPARE(addr, len, prot, flags, fd, offset) +#endif + +__ptr_t +__mmap (__ptr_t addr, size_t len, int prot, int flags, int fd, off_t offset) +{ + MMAP_PREPARE (addr, len, prot, flags, fd, offset); + return (__ptr_t) INLINE_SYSCALL (mmap, 6, addr, len, prot, flags, + fd, offset); +} + +weak_alias (__mmap, mmap) +weak_alias (__mmap, mmap64) +weak_alias (__mmap, __mmap64) diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h new file mode 100644 index 0000000..159d0f1 --- /dev/null +++ b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h @@ -0,0 +1,44 @@ +/* Optional code to distinguish library flavours. x86-64 version. + Copyright (C) 2015 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 + <http://www.gnu.org/licenses/>. */ + +#ifndef _DL_LIBRECON_H + +#include <sysdeps/unix/sysv/linux/dl-librecon.h> + +/* Recognizing extra environment variables. For 64-bit applications, + branch prediction performance may be negatively impacted when the + target of a branch is more than 4GB away from the branch. Add the + Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable + pages with MAP_32BIT first. NB: MAP_32BIT will map to lower 2GB, + not lower 4GB, address. Prefer_MAP_32BIT_EXEC reduces bits available + for address space layout randomization (ASLR). Prefer_MAP_32BIT_EXEC + is always disabled for SUID programs and can be enabled by setting + environment variable, LD_PREFER_MAP_32BIT_EXEC. */ +#define EXTRA_LD_ENVVARS \ + case 21: \ + if (memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0) \ + GLRO(dl_x86_cpu_features).feature[index_Prefer_MAP_32BIT_EXEC] \ + = bit_Prefer_MAP_32BIT_EXEC; \ + break; + +/* Extra unsecure variables. The names are all stuffed in a single + string which means they have to be terminated with a '\0' explicitly. */ +#define EXTRA_UNSECURE_ENVVARS \ + "LD_PREFER_MAP_32BIT_EXEC\0" + +#endif /* dl-librecon.h */ diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap.c b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c new file mode 100644 index 0000000..031316c --- /dev/null +++ b/sysdeps/unix/sysv/linux/x86_64/64/mmap.c @@ -0,0 +1,37 @@ +/* Linux mmap system call. x86-64 version. + Copyright (C) 2015 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 + <http://www.gnu.org/licenses/>. */ + +#include <ldsodefs.h> + +/* If the Prefer_MAP_32BIT_EXEC bit is set, try to map executable pages + with MAP_32BIT first. */ +#define MMAP_PREPARE(addr, len, prot, flags, fd, offset) \ + if ((addr) == NULL \ + && ((prot) & PROT_EXEC) != 0 \ + && HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC)) \ + { \ + __ptr_t ret = (__ptr_t) INLINE_SYSCALL (mmap, 6, (addr), (len), \ + (prot), \ + (flags) | MAP_32BIT, \ + (fd), (offset)); \ + if (ret != MAP_FAILED) \ + return ret; \ + } + +#include <sysdeps/unix/sysv/linux/wordsize-64/mmap.c> diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h index 80edbee..93bee69 100644 --- a/sysdeps/x86/cpu-features.h +++ b/sysdeps/x86/cpu-features.h @@ -33,6 +33,7 @@ #define bit_AVX512DQ_Usable (1 << 13) #define bit_I586 (1 << 14) #define bit_I686 (1 << 15) +#define bit_Prefer_MAP_32BIT_EXEC (1 << 16) /* CPUID Feature flags. */ @@ -97,6 +98,7 @@ # define index_AVX512DQ_Usable FEATURE_INDEX_1*FEATURE_SIZE # define index_I586 FEATURE_INDEX_1*FEATURE_SIZE # define index_I686 FEATURE_INDEX_1*FEATURE_SIZE +# define index_Prefer_MAP_32BIT_EXEC FEATURE_INDEX_1*FEATURE_SIZE # if defined (_LIBC) && !IS_IN (nonlib) # ifdef __x86_64__ @@ -248,6 +250,7 @@ extern const struct cpu_features *__get_cpu_features (void) # define index_AVX512DQ_Usable FEATURE_INDEX_1 # define index_I586 FEATURE_INDEX_1 # define index_I686 FEATURE_INDEX_1 +# define index_Prefer_MAP_32BIT_EXEC FEATURE_INDEX_1 #endif /* !__ASSEMBLER__ */ |