From patchwork Tue Jun 2 16:08:48 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Lynch X-Patchwork-Id: 7011 Received: (qmail 53756 invoked by alias); 2 Jun 2015 16:08:56 -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 53743 invoked by uid 89); 2 Jun 2015 16:08:55 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.5 required=5.0 tests=AWL, BAYES_00, RCVD_IN_DNSWL_LOW, SPF_PASS autolearn=ham version=3.3.2 X-HELO: relay1.mentorg.com From: Nathan Lynch To: Subject: [PATCH v3] ARM: VDSO support Date: Tue, 2 Jun 2015 11:08:48 -0500 Message-ID: <1433261328-17335-1-git-send-email-nathan_lynch@codesourcery.com> MIME-Version: 1.0 Beginning with the upcoming 4.1 release, Linux on a subset of 32-bit ARM hardware will provide fast user-space implementations of the following system calls: - gettimeofday - clock_gettime The kernel implementation depends on the ARMv7 Generic Timers Extension to accelerate these system calls. So CPUs such as Cortex-A15 and -A7 benefit, while Cortex-A9, -A8, and pre-v7 CPUs do not. On systems where the VDSO does not provide any speedup, the kernel prevents the relevant symbol lookups from succeeding. On OMAP5 (Cortex-A15) gettimeofday latency decreases from ~350ns to ~120ns. On BeagleBone Black (Cortex-A8) it goes from ~650ns to ~660ns, which to my mind is an acceptable cost. Verified that no new test failures are introduced on kernels with and without the VDSO. 2015-06-02 Nathan Lynch * sysdeps/unix/sysv/linux/arm/Makefile: (sysdep_routines): Include dl-vdso. * sysdeps/unix/sysv/linux/arm/init-first.c: New file: Use VDSO routines for gettimeofday, clock_gettime if available. * sysdeps/unix/sysv/linux/arm/libc-vdso.h: New file: Declare VDSO symbols. * sysdeps/unix/sysv/linux/arm/sysdep.h: [HAVE_GETTIMEOFDAY_VSYSCALL]: Define. [HAVE_CLOCK_GETTIME_VSYSCALL]: Define. * sysdeps/unix/sysv/linux/arm/Versions: Add __vdso_clock_gettime. --- Changes since v2: - Added comment explaining export of __vdso_clock_gettime. - Removed export of __vdso_gettimeofday. - Coding style fixes. Changes since v1: - Reworked on top of Adhemerval's VDSO refactoring. sysdeps/unix/sysv/linux/arm/Makefile | 1 + sysdeps/unix/sysv/linux/arm/Versions | 2 ++ sysdeps/unix/sysv/linux/arm/init-first.c | 43 ++++++++++++++++++++++++++++++++ sysdeps/unix/sysv/linux/arm/libc-vdso.h | 32 ++++++++++++++++++++++++ sysdeps/unix/sysv/linux/arm/sysdep.h | 4 +++ 5 files changed, 82 insertions(+) create mode 100644 sysdeps/unix/sysv/linux/arm/init-first.c create mode 100644 sysdeps/unix/sysv/linux/arm/libc-vdso.h diff --git a/sysdeps/unix/sysv/linux/arm/Makefile b/sysdeps/unix/sysv/linux/arm/Makefile index 50410b67b5fc..270cb73f70e5 100644 --- a/sysdeps/unix/sysv/linux/arm/Makefile +++ b/sysdeps/unix/sysv/linux/arm/Makefile @@ -1,4 +1,5 @@ ifeq ($(subdir),elf) +sysdep_routines += dl-vdso sysdep-rtld-routines += aeabi_read_tp libc-do-syscall endif diff --git a/sysdeps/unix/sysv/linux/arm/Versions b/sysdeps/unix/sysv/linux/arm/Versions index a251b0fd7d87..5ff2225f2490 100644 --- a/sysdeps/unix/sysv/linux/arm/Versions +++ b/sysdeps/unix/sysv/linux/arm/Versions @@ -10,5 +10,7 @@ libc { GLIBC_PRIVATE { # A copy of sigaction lives in libpthread, and needs these. __default_sa_restorer; __default_rt_sa_restorer; + # nptl/pthread_cond_timedwait.c uses INTERNAL_VSYSCALL(clock_gettime). + __vdso_clock_gettime; } } diff --git a/sysdeps/unix/sysv/linux/arm/init-first.c b/sysdeps/unix/sysv/linux/arm/init-first.c new file mode 100644 index 000000000000..981d0aed058f --- /dev/null +++ b/sysdeps/unix/sysv/linux/arm/init-first.c @@ -0,0 +1,43 @@ +/* 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 + . */ + +#ifdef SHARED +# include +# include + +int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *) attribute_hidden; +int (*VDSO_SYMBOL(clock_gettime)) (clockid_t, struct timespec *); + +static inline void +_libc_vdso_platform_setup (void) +{ + PREPARE_VERSION_KNOWN (linux26, LINUX_2_6); + + void *p = _dl_vdso_vsym ("__vdso_gettimeofday", &linux26); + PTR_MANGLE (p); + VDSO_SYMBOL (gettimeofday) = p; + + p = _dl_vdso_vsym ("__vdso_clock_gettime", &linux26); + PTR_MANGLE (p); + VDSO_SYMBOL (clock_gettime) = p; +} + +# define VDSO_SETUP _libc_vdso_platform_setup +#endif + +#include diff --git a/sysdeps/unix/sysv/linux/arm/libc-vdso.h b/sysdeps/unix/sysv/linux/arm/libc-vdso.h new file mode 100644 index 000000000000..2ebcc62cd284 --- /dev/null +++ b/sysdeps/unix/sysv/linux/arm/libc-vdso.h @@ -0,0 +1,32 @@ +/* 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 _LIBC_VDSO_H +#define _LIBC_VDSO_H + +#ifdef SHARED + +# include + +extern int (*VDSO_SYMBOL(gettimeofday)) (struct timeval *, void *) + attribute_hidden; +extern int (*VDSO_SYMBOL(clock_gettime)) (clockid_t, struct timespec *); + +#endif + +#endif /* _LIBC_VDSO_H */ diff --git a/sysdeps/unix/sysv/linux/arm/sysdep.h b/sysdeps/unix/sysv/linux/arm/sysdep.h index 37eac192b1e2..200f77a62ef1 100644 --- a/sysdeps/unix/sysv/linux/arm/sysdep.h +++ b/sysdeps/unix/sysv/linux/arm/sysdep.h @@ -387,6 +387,10 @@ __local_syscall_error: \ #undef INTERNAL_SYSCALL_ERRNO #define INTERNAL_SYSCALL_ERRNO(val, err) (-(val)) +/* List of system calls which are supported as vsyscalls. */ +#define HAVE_CLOCK_GETTIME_VSYSCALL 1 +#define HAVE_GETTIMEOFDAY_VSYSCALL 1 + #define LOAD_ARGS_0() #define ASM_ARGS_0 #define LOAD_ARGS_1(a1) \