From patchwork Tue Dec 15 20:08:31 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "H.J. Lu" X-Patchwork-Id: 10025 Received: (qmail 51605 invoked by alias); 15 Dec 2015 20:08:36 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 51527 invoked by uid 89); 15 Dec 2015 20:08:36 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.6 required=5.0 tests=AWL, BAYES_00, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW, SPF_PASS, UNSUBSCRIBE_BODY autolearn=no version=3.3.2 X-HELO: mail-oi0-f53.google.com MIME-Version: 1.0 X-Received: by 10.202.49.9 with SMTP id x9mr11260903oix.75.1450210111970; Tue, 15 Dec 2015 12:08:31 -0800 (PST) In-Reply-To: <56705E40.3030307@redhat.com> References: <87egeszoq3.fsf@tassilo.jf.intel.com> <20151211222913.GT15533@two.firstfloor.org> <566B55DF.2040200@redhat.com> <20151212001449.GU15533@two.firstfloor.org> <566B8008.6010106@redhat.com> <56705B8F.7000303@redhat.com> <56705E40.3030307@redhat.com> Date: Tue, 15 Dec 2015 12:08:31 -0800 Message-ID: Subject: Re: [PATCH] Add Prefer_MAP_32BIT_EXEC for Silvermont From: "H.J. Lu" To: "Carlos O'Donell" Cc: Jeff Law , Zack Weinberg , Andi Kleen , Adhemerval Zanella , GNU C Library On Tue, Dec 15, 2015 at 10:38 AM, Carlos O'Donell wrote: > On 12/15/2015 01:27 PM, Carlos O'Donell wrote: >> + cpu_features->feature[index_Prefer_MAP_32BIT_EXEC] >> + |= get_prefer_map_32bit_exec (); >> >> You wouldn't need get_prefer_map_32bit_exec, since this is all part of >> the code, like dl-librecon.h, which parses the extra env var. > > To be clear: > > * Add new bit flag definitions for cpu_features. > * Add a sysdeps/unix/sysv/linux/x86_64/dl-silvermont.h > * Fill in EXTRA_LD_ENVVARS or add new ones. > * Write to rtld's GLRO cpu_features the bit you need based > on __libc_enable_secure. > > That should simplify and concentrate the Silvermont fixes to > just two files, making future maintenance and documentation > easier. > > This is the updated patch. I put EXTRA_LD_ENVVARS and EXTRA_UNSECURE_ENVVARS in x86_64/64/dl-librecon.h to be consistent with i386/dl-librecon.h. If we ever need to update EXTRA_LD_ENVVARS/EXTRA_UNSECURE_ENVVARS in the future, we have a single file to change. Tested on x86-64. OK for master? Thanks for all the feedbacks and suggestions. From 940a29897c4018a5c13bef99d0918311629b5f10 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Wed, 21 Oct 2015 14:44:23 -0700 Subject: [PATCH] Add Prefer_MAP_32BIT_EXEC to map executable pages with MAP_32BIT 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. * 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. --- sysdeps/unix/sysv/linux/wordsize-64/mmap.c | 40 ++++++++++++++++++++++ sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h | 44 +++++++++++++++++++++++++ sysdeps/unix/sysv/linux/x86_64/64/mmap.c | 37 +++++++++++++++++++++ sysdeps/x86/cpu-features.h | 3 ++ 4 files changed, 124 insertions(+) create mode 100644 sysdeps/unix/sysv/linux/wordsize-64/mmap.c create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/mmap.c 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 + . */ + +#include +#include +#include +#include + +/* 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 + . */ + +#ifndef _DL_LIBRECON_H + +#include + +/* 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 + . */ + +#include + +/* 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 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__ */ -- 2.5.0