aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorNathan Lynch <nathan_lynch@codesourcery.com>2015-06-04 21:10:43 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-06-04 21:10:43 +0000
commitb65d3e5f0f452e86f81d21d59b065feeb31357be (patch)
tree6ac6681b12e442b6d6fa73093ef0ad60811491d7
parent34caaafd1ae38c9295325a1da491d75a92b205b0 (diff)
downloadglibc-b65d3e5f0f452e86f81d21d59b065feeb31357be.tar
glibc-b65d3e5f0f452e86f81d21d59b065feeb31357be.tar.gz
glibc-b65d3e5f0f452e86f81d21d59b065feeb31357be.tar.bz2
glibc-b65d3e5f0f452e86f81d21d59b065feeb31357be.zip
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.
-rw-r--r--ChangeLog15
-rw-r--r--sysdeps/unix/sysv/linux/arm/Makefile1
-rw-r--r--sysdeps/unix/sysv/linux/arm/Versions2
-rw-r--r--sysdeps/unix/sysv/linux/arm/init-first.c44
-rw-r--r--sysdeps/unix/sysv/linux/arm/libc-vdso.h33
-rw-r--r--sysdeps/unix/sysv/linux/arm/sysdep.h4
6 files changed, 99 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog
index 89c4bcfb14..0d807909c6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+2015-06-04 Nathan Lynch <nathan_lynch@codesourcery.com>
+
+ * 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 <adhemerval.zanella@linaro.org>
* 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
+ <http://www.gnu.org/licenses/>. */
+
+#ifdef SHARED
+# include <dl-vdso.h>
+# include <libc-vdso.h>
+
+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 <csu/init-first.c>
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
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _LIBC_VDSO_H
+#define _LIBC_VDSO_H
+
+#ifdef SHARED
+
+# include <sysdep-vdso.h>
+
+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) \