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gettimeofday / vdso / aarch64 question
- From: Steve Ellcey <sellcey at cavium dot com>
- To: libc-alpha <libc-alpha at sourceware dot org>
- Date: Wed, 09 May 2018 16:25:19 -0700
- Subject: gettimeofday / vdso / aarch64 question
- Reply-to: sellcey at cavium dot com
- Spamdiagnosticmetadata: NSPM
- Spamdiagnosticoutput: 1:99
I was wondering if someone could look at my proposed getimeofday.c
implementation for aarch64 and help me figure out what I am doing
wrong. I am trying to use the VDSO interface to speed it up and
it looks like that should be supported starting with Linux 2.6.39
(according to sysdeps/unix/sysv/linux/aarch64/init-first.c) but
when I include this gettimeofday.c in sysdeps/unix/sysv/linux/aarch64
I get a link failure with undefined references to __GI___gettimeofday.
I think something is wrong with my use of the various symbol macros,
probably with libc_ifunc_hidden or __hidden_ver1, but I can't seem to
figure out what the right incantation is.
Steve Ellcey
sellcey@cavium.com
diff --git a/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c b/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
index e69de29..7631322 100644
--- a/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/aarch64/gettimeofday.c
@@ -0,0 +1,66 @@
+/* Copyright (C) 2018 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/>. */
+
+/* Get the current time of day and timezone information,
+ putting it into *tv and *tz. If tz is null, *tz is not filled.
+ Returns 0 on success, -1 on errors. */
+
+#ifdef SHARED
+
+# define __gettimeofday __redirect___gettimeofday
+# include <sys/time.h>
+# undef __gettimeofday
+# include <dl-vdso.h>
+static int
+__gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
+{
+ /* Should this be INLINE_SYSCALL or INLINE_VSYSCALL? */
+ return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
+}
+/* PREPARE_VERSION will need an __LP64__ ifdef when ILP32 support
+ goes in. See _libc_vdso_platform_setup in
+ sysdeps/unix/sysv/linux/aarch64/init-first.c. */
+
+# undef INIT_ARCH
+# define INIT_ARCH() \
+ PREPARE_VERSION (linux_version, "LINUX_2.6.39", 123718537); \
+ void *vdso_gettimeofday = \
+ _dl_vdso_vsym ("__kernel_gettimeofday", &linux_version);
+
+libc_ifunc_hidden (__redirect___gettimeofday, __gettimeofday,
+ vdso_gettimeofday ?: (void *) __gettimeofday_syscall)
+# undef libc_hidden_def
+# define libc_hidden_def(name) \
+ __hidden_ver1 (__gettimeofday_syscall, __GI___gettimeofday, \
+ __gettimeofday_syscall);
+weak_alias (__gettimeofday, gettimeofday)
+libc_hidden_weak (gettimeofday)
+
+#else
+
+# include <sys/time.h>
+# include <sysdep.h>
+int
+__gettimeofday (struct timeval *tv, struct timezone *tz)
+{
+ return INLINE_SYSCALL (gettimeofday, 2, tv, tz);
+}
+libc_hidden_def (__gettimeofday)
+weak_alias (__gettimeofday, gettimeofday)
+libc_hidden_weak (gettimeofday)
+#endif