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[RFC] [PATCH] MIPS: Add VDSO support


From: Alex Smith <alex.smith@imgtec.com>

This patch adds support for using the implementations of gettimeofday()
and clock_gettime() provided by the kernel in the VDSO. The VDSO will
always provide clock_gettime() as CLOCK_{REALTIME,MONOTONIC}_COARSE can
be implemented regardless of platform. CLOCK_{REALTIME,MONOTONIC}, along
with gettimeofday(), are only implemented on platforms which make use of
either the CP0 count or GIC as their clocksource. On other platforms,
the VDSO does not provide the __vdso_gettimeofday symbol, as it is
never useful.

The VDSO functions return ENOSYS when they encounter an unsupported
request, in which case glibc should fall back to the standard syscall.

	* sysdeps/unix/sysv/linux/mips/Makefile (sysdep_routines):
	Include dl-vdso.
	* sysdeps/unix/sysv/linux/mips/Versions: Add
	__vdso_clock_gettime.
	* sysdeps/unix/sysv/linux/mips/init-first.c: New file.
	* sysdeps/unix/sysv/linux/mips/libc-vdso.h: New file.
	* sysdeps/unix/sysv/linux/mips/mips32/sysdep.h:
	(INTERNAL_VSYSCALL_CALL): Define to be compatible with MIPS
	definitions of INTERNAL_SYSCALL_{ERROR_P,ERRNO}.
	(HAVE_CLOCK_GETTIME_VSYSCALL): Define.
	(HAVE_GETTIMEOFDAY_VSYSCALL): Define.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h: Likewise.

---
Hi,

The kernel patches for vdso support are already upstream.

I'm picking up this patch to upstream vdso support for MIPS in glibc.

Rebased this patch on glibc-2.23

Tested with upstream kernel 4.5 and QEMU emulating Malta.

 ./vdsotest gettimeofday bench
gettimeofday: syscall: 1021 nsec/call
gettimeofday:    libc: 262 nsec/call
gettimeofday:    vdso: 174 nsec/call

Regards,
ZubairLK

---
 sysdeps/unix/sysv/linux/mips/Makefile            |  2 ++
 sysdeps/unix/sysv/linux/mips/Versions            |  4 +++
 sysdeps/unix/sysv/linux/mips/init-first.c        | 44 ++++++++++++++++++++++++
 sysdeps/unix/sysv/linux/mips/libc-vdso.h         | 33 ++++++++++++++++++
 sysdeps/unix/sysv/linux/mips/mips32/sysdep.h     | 16 +++++++++
 sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h | 17 +++++++++
 sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h | 17 +++++++++
 7 files changed, 133 insertions(+)
 create mode 100644 sysdeps/unix/sysv/linux/mips/init-first.c
 create mode 100644 sysdeps/unix/sysv/linux/mips/libc-vdso.h

diff --git a/sysdeps/unix/sysv/linux/mips/Makefile b/sysdeps/unix/sysv/linux/mips/Makefile
index 8127025..c6729c1 100644
--- a/sysdeps/unix/sysv/linux/mips/Makefile
+++ b/sysdeps/unix/sysv/linux/mips/Makefile
@@ -96,6 +96,8 @@ ifeq ($(subdir),elf)
 ifeq ($(build-shared),yes)
 # This is needed for DSO loading from static binaries.
 sysdep-dl-routines += dl-static
+
+sysdep_routines += dl-vdso
 endif
 endif
 
diff --git a/sysdeps/unix/sysv/linux/mips/Versions b/sysdeps/unix/sysv/linux/mips/Versions
index a56322a..453f276 100644
--- a/sysdeps/unix/sysv/linux/mips/Versions
+++ b/sysdeps/unix/sysv/linux/mips/Versions
@@ -37,4 +37,8 @@ libc {
   GLIBC_2.11 {
     fallocate64;
   }
+  GLIBC_PRIVATE {
+    # nptl/pthread_cond_timedwait.c uses INTERNAL_VSYSCALL(clock_gettime).
+    __vdso_clock_gettime;
+  }
 }
diff --git a/sysdeps/unix/sysv/linux/mips/init-first.c b/sysdeps/unix/sysv/linux/mips/init-first.c
new file mode 100644
index 0000000..46dba69
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/mips/init-first.c
@@ -0,0 +1,44 @@
+/* Initialization code run first thing by the ELF startup code.
+   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/mips/libc-vdso.h b/sysdeps/unix/sysv/linux/mips/libc-vdso.h
new file mode 100644
index 0000000..1580de8
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/mips/libc-vdso.h
@@ -0,0 +1,33 @@
+/* VDSO function pointer declarations.
+   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/mips/mips32/sysdep.h b/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
index 2160df7..2335409 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/mips/mips32/sysdep.h
@@ -371,6 +371,22 @@
 #define __SYSCALL_CLOBBERS "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \
 	"$14", "$15", "$24", "$25", "hi", "lo", "memory"
 
+/* Standard MIPS syscalls have an error flag, and return a positive errno
+   when the error flag is set. Emulate this behaviour for vsyscalls so that
+   the INTERNAL_SYSCALL_{ERROR_P,ERRNO} macros work correctly.  */
+#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...)		\
+  ({									\
+    long _ret = funcptr (args);						\
+    err = ((unsigned long) (_ret) >= (unsigned long) -4095L);		\
+    if (err)								\
+      _ret = -_ret;							\
+    _ret;								\
+  })
+
+/* List of system calls which are supported as vsyscalls.  */
+#define HAVE_CLOCK_GETTIME_VSYSCALL	1
+#define HAVE_GETTIMEOFDAY_VSYSCALL	1
+
 #endif /* __ASSEMBLER__ */
 
 /* Pointer mangling is not yet supported for MIPS.  */
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h b/sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h
index 466dcde..661b3dc 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/sysdep.h
@@ -295,6 +295,23 @@
 
 #define __SYSCALL_CLOBBERS "$1", "$3", "$10", "$11", "$12", "$13", \
 	"$14", "$15", "$24", "$25", "hi", "lo", "memory"
+
+/* Standard MIPS syscalls have an error flag, and return a positive errno
+   when the error flag is set. Emulate this behaviour for vsyscalls so that
+   the INTERNAL_SYSCALL_{ERROR_P,ERRNO} macros work correctly.  */
+#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...)		\
+  ({									\
+    long _ret = funcptr (args);						\
+    err = ((unsigned long) (_ret) >= (unsigned long) -4095L);		\
+    if (err)								\
+      _ret = -_ret;							\
+    _ret;								\
+  })
+
+/* List of system calls which are supported as vsyscalls.  */
+#define HAVE_CLOCK_GETTIME_VSYSCALL	1
+#define HAVE_GETTIMEOFDAY_VSYSCALL	1
+
 #endif /* __ASSEMBLER__ */
 
 /* Pointer mangling is not yet supported for MIPS.  */
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h b/sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h
index db8b237..476eca3 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/sysdep.h
@@ -291,6 +291,23 @@
 
 #define __SYSCALL_CLOBBERS "$1", "$3", "$10", "$11", "$12", "$13", \
 	"$14", "$15", "$24", "$25", "hi", "lo", "memory"
+
+/* Standard MIPS syscalls have an error flag, and return a positive errno
+   when the error flag is set. Emulate this behaviour for vsyscalls so that
+   the INTERNAL_SYSCALL_{ERROR_P,ERRNO} macros work correctly.  */
+#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...)		\
+  ({									\
+    long _ret = funcptr (args);						\
+    err = ((unsigned long) (_ret) >= (unsigned long) -4095L);		\
+    if (err)								\
+      _ret = -_ret;							\
+    _ret;								\
+  })
+
+/* List of system calls which are supported as vsyscalls.  */
+#define HAVE_CLOCK_GETTIME_VSYSCALL	1
+#define HAVE_GETTIMEOFDAY_VSYSCALL	1
+
 #endif /* __ASSEMBLER__ */
 
 /* Pointer mangling is not yet supported for MIPS.  */
-- 
1.9.1


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