From b65d3e5f0f452e86f81d21d59b065feeb31357be Mon Sep 17 00:00:00 2001 From: Nathan Lynch Date: Thu, 4 Jun 2015 21:10:43 +0000 Subject: [PATCH] ARM: VDSO support 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. * 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. --- ChangeLog | 15 ++++++++ sysdeps/unix/sysv/linux/arm/Makefile | 1 + sysdeps/unix/sysv/linux/arm/Versions | 2 ++ sysdeps/unix/sysv/linux/arm/init-first.c | 44 ++++++++++++++++++++++++ sysdeps/unix/sysv/linux/arm/libc-vdso.h | 33 ++++++++++++++++++ sysdeps/unix/sysv/linux/arm/sysdep.h | 4 +++ 6 files changed, 99 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/ChangeLog b/ChangeLog index 89c4bcfb14..0d807909c6 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,18 @@ +2015-06-04 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. + 2015-06-04 Adhemerval Zanella * sysdeps/unix/sysv/linux/not-cancel.h (open_not_cancel): Rewrite to diff --git a/sysdeps/unix/sysv/linux/arm/Makefile b/sysdeps/unix/sysv/linux/arm/Makefile index 50410b67b5..270cb73f70 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 a251b0fd7d..5ff2225f24 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 0000000000..2fa4fb75a7 --- /dev/null +++ b/sysdeps/unix/sysv/linux/arm/init-first.c @@ -0,0 +1,44 @@ +/* Initialization code run first thing by the ELF startup code. Linux/ARM. + 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 0000000000..17baea6e46 --- /dev/null +++ b/sysdeps/unix/sysv/linux/arm/libc-vdso.h @@ -0,0 +1,33 @@ +/* VDSO function pointer declarations. Linux/ARM. + 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 37eac192b1..200f77a62e 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) \ -- 2.43.5