Patchwork [3/6] Avoid reading errno in syscall implementations

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Submitter H.J. Lu
Date Oct. 13, 2015, 7:04 p.m.
Message ID <CAMe9rOpCB72g6gDU2Zic2HK7d5i9Art97_y8UMEOjRe0-s48iQ@mail.gmail.com>
Download mbox | patch
Permalink /patch/9092/
State New
Headers show

Comments

H.J. Lu - Oct. 13, 2015, 7:04 p.m.
On Mon, Oct 12, 2015 at 4:19 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> Reading errno is expensive for x86 PIC.  With INTERNAL_SYSCALL,
> INTERNAL_SYSCALL_ERROR_P, INTERNAL_SYSCALL_ERRNO and
> INLINE_SYSCALL_ERROR_RETURN, we can avoid reading errno.
>
>         * sysdeps/unix/sysv/linux/eventfd.c (eventfd): Use
>         INTERNAL_SYSCALL, INTERNAL_SYSCALL_ERROR_P and
>         INTERNAL_SYSCALL_ERRNO to avoid reading errno.
>         * sysdeps/unix/sysv/linux/fstatfs64.c (__fstatfs64): Likewise.
>         * sysdeps/unix/sysv/linux/getrlimit64.c (__getrlimit64):
>         Likewise.
>         * sysdeps/unix/sysv/linux/setrlimit64.c (setrlimit64):
>         Likewise.
>         * sysdeps/unix/sysv/linux/signalfd.c (signalfd): Likewise.
>         * sysdeps/unix/sysv/linux/statfs64.c (__statfs64): Likewise.

First 2 patches have been checked into master.  Here is the updated
patch.  There is no code change in libc.so on x86-64.  OK for master?

Thanks.

Patch

From 4e66aee3711050ae863076542cf94a6e6367c665 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Fri, 21 Aug 2015 14:46:05 -0700
Subject: [PATCH 3/6] Avoid reading errno in syscall implementations

Reading errno is expensive for x86 PIC.  With INTERNAL_SYSCALL,
INTERNAL_SYSCALL_ERROR_P, INTERNAL_SYSCALL_ERRNO and
INLINE_SYSCALL_ERROR_RETURN_VALUE, we can avoid reading errno.

	* sysdeps/unix/sysv/linux/eventfd.c (eventfd): Use
	INTERNAL_SYSCALL, INTERNAL_SYSCALL_ERROR_P and
	INTERNAL_SYSCALL_ERRNO to avoid reading errno.
	* sysdeps/unix/sysv/linux/fstatfs64.c (__fstatfs64): Likewise.
	* sysdeps/unix/sysv/linux/getrlimit64.c (__getrlimit64):
	Likewise.
	* sysdeps/unix/sysv/linux/setrlimit64.c (setrlimit64):
	Likewise.
	* sysdeps/unix/sysv/linux/signalfd.c (signalfd): Likewise.
	* sysdeps/unix/sysv/linux/statfs64.c (__statfs64): Likewise.
---
 sysdeps/unix/sysv/linux/eventfd.c     | 10 +++++++---
 sysdeps/unix/sysv/linux/fstatfs64.c   | 12 ++++++++----
 sysdeps/unix/sysv/linux/getrlimit64.c |  7 +++++--
 sysdeps/unix/sysv/linux/lxstat64.c    |  7 +++++--
 sysdeps/unix/sysv/linux/setrlimit64.c |  7 +++++--
 sysdeps/unix/sysv/linux/signalfd.c    | 11 ++++++++---
 sysdeps/unix/sysv/linux/statfs64.c    | 13 +++++++++----
 7 files changed, 47 insertions(+), 20 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/eventfd.c b/sysdeps/unix/sysv/linux/eventfd.c
index efce282..a13be32 100644
--- a/sysdeps/unix/sysv/linux/eventfd.c
+++ b/sysdeps/unix/sysv/linux/eventfd.c
@@ -25,11 +25,15 @@  int
 eventfd (unsigned int count, int flags)
 {
 #ifdef __NR_eventfd2
-  int res = INLINE_SYSCALL (eventfd2, 2, count, flags);
 # ifndef __ASSUME_EVENTFD2
-  if (res != -1 || errno != ENOSYS)
-# endif
+  INTERNAL_SYSCALL_DECL (err);
+  int res = INTERNAL_SYSCALL (eventfd2, err, 2, count, flags);
+  if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err))
+      || INTERNAL_SYSCALL_ERRNO (res, err) != ENOSYS)
     return res;
+# else
+  return INLINE_SYSCALL (eventfd2, 2, count, flags);
+# endif
 #endif
 
 #ifndef __ASSUME_EVENTFD2
diff --git a/sysdeps/unix/sysv/linux/fstatfs64.c b/sysdeps/unix/sysv/linux/fstatfs64.c
index af83830..eb21d42 100644
--- a/sysdeps/unix/sysv/linux/fstatfs64.c
+++ b/sysdeps/unix/sysv/linux/fstatfs64.c
@@ -35,12 +35,16 @@  __fstatfs64 (int fd, struct statfs64 *buf)
   if (! __no_statfs64)
 # endif
     {
-      int result = INLINE_SYSCALL (fstatfs64, 3, fd, sizeof (*buf), buf);
-
 # if __ASSUME_STATFS64 == 0
-      if (result == 0 || errno != ENOSYS)
-# endif
+      INTERNAL_SYSCALL_DECL (err);
+      int result = INTERNAL_SYSCALL (fstatfs64, err, 3, fd,
+				     sizeof (*buf), buf);
+      if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err))
+	  || INTERNAL_SYSCALL_ERRNO (result, err) != ENOSYS)
 	return result;
+# else
+      return INLINE_SYSCALL (fstatfs64, 3, fd, sizeof (*buf), buf);
+# endif
 
 # if __ASSUME_STATFS64 == 0
       __no_statfs64 = 1;
diff --git a/sysdeps/unix/sysv/linux/getrlimit64.c b/sysdeps/unix/sysv/linux/getrlimit64.c
index 100ba62..cca1265 100644
--- a/sysdeps/unix/sysv/linux/getrlimit64.c
+++ b/sysdeps/unix/sysv/linux/getrlimit64.c
@@ -30,8 +30,11 @@  __getrlimit64 (enum __rlimit_resource resource, struct rlimit64 *rlimits)
   return INLINE_SYSCALL (prlimit64, 4, 0, resource, NULL, rlimits);
 #else
 # ifdef __NR_prlimit64
-  int res = INLINE_SYSCALL (prlimit64, 4, 0, resource, NULL, rlimits);
-  if (res == 0 || errno != ENOSYS)
+  INTERNAL_SYSCALL_DECL (err);
+  int res = INTERNAL_SYSCALL (prlimit64, err, 4, 0, resource, NULL,
+			      rlimits);
+  if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err))
+      || INTERNAL_SYSCALL_ERRNO (res, err) != ENOSYS)
     return res;
 # endif
   struct rlimit rlimits32;
diff --git a/sysdeps/unix/sysv/linux/lxstat64.c b/sysdeps/unix/sysv/linux/lxstat64.c
index 5d0c051..63959cf 100644
--- a/sysdeps/unix/sysv/linux/lxstat64.c
+++ b/sysdeps/unix/sysv/linux/lxstat64.c
@@ -30,8 +30,11 @@ 
 int
 ___lxstat64 (int vers, const char *name, struct stat64 *buf)
 {
-  int result;
-  result = INLINE_SYSCALL (lstat64, 2, name, buf);
+  INTERNAL_SYSCALL_DECL (err);
+  int result = INTERNAL_SYSCALL (lstat64, err, 2, name, buf);
+  if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err)))
+    return INLINE_SYSCALL_ERROR_RETURN_VALUE (INTERNAL_SYSCALL_ERRNO (result,
+								      err));
 #if defined _HAVE_STAT64___ST_INO && __ASSUME_ST_INO_64_BIT == 0
   if (__builtin_expect (!result, 1) && buf->__st_ino != (__ino_t) buf->st_ino)
     buf->st_ino = buf->__st_ino;
diff --git a/sysdeps/unix/sysv/linux/setrlimit64.c b/sysdeps/unix/sysv/linux/setrlimit64.c
index 17f95cb..33e1500 100644
--- a/sysdeps/unix/sysv/linux/setrlimit64.c
+++ b/sysdeps/unix/sysv/linux/setrlimit64.c
@@ -33,8 +33,11 @@  setrlimit64 (resource, rlimits)
   return INLINE_SYSCALL (prlimit64, 4, 0, resource, rlimits, NULL);
 #else
 # ifdef __NR_prlimit64
-  int res = INLINE_SYSCALL (prlimit64, 4, 0, resource, rlimits, NULL);
-  if (res == 0 || errno != ENOSYS)
+  INTERNAL_SYSCALL_DECL (err);
+  int res = INTERNAL_SYSCALL (prlimit64, err, 4, 0, resource, rlimits,
+			      NULL);
+  if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err))
+      || INTERNAL_SYSCALL_ERRNO (res, err) != ENOSYS)
     return res;
 # endif
   struct rlimit rlimits32;
diff --git a/sysdeps/unix/sysv/linux/signalfd.c b/sysdeps/unix/sysv/linux/signalfd.c
index 8573450..d58edc7 100644
--- a/sysdeps/unix/sysv/linux/signalfd.c
+++ b/sysdeps/unix/sysv/linux/signalfd.c
@@ -26,11 +26,16 @@  int
 signalfd (int fd, const sigset_t *mask, int flags)
 {
 #ifdef __NR_signalfd4
-  int res = INLINE_SYSCALL (signalfd4, 4, fd, mask, _NSIG / 8, flags);
 # ifndef __ASSUME_SIGNALFD4
-  if (res != -1 || errno != ENOSYS)
-# endif
+  INTERNAL_SYSCALL_DECL (err);
+  int res = INTERNAL_SYSCALL (signalfd4, err, 4, fd, mask, _NSIG / 8,
+			      flags);
+  if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (res, err))
+      || INTERNAL_SYSCALL_ERRNO (res, err) != ENOSYS)
     return res;
+# else
+  return INLINE_SYSCALL (signalfd4, 4, fd, mask, _NSIG / 8, flags);
+# endif
 #endif
 
 #ifndef __ASSUME_SIGNALFD4
diff --git a/sysdeps/unix/sysv/linux/statfs64.c b/sysdeps/unix/sysv/linux/statfs64.c
index ac5c33f..fdd1667 100644
--- a/sysdeps/unix/sysv/linux/statfs64.c
+++ b/sysdeps/unix/sysv/linux/statfs64.c
@@ -37,12 +37,17 @@  __statfs64 (const char *file, struct statfs64 *buf)
   if (! __no_statfs64)
 # endif
     {
-      int result = INLINE_SYSCALL (statfs64, 3, file, sizeof (*buf), buf);
-
 # if __ASSUME_STATFS64 == 0
-      if (result == 0 || errno != ENOSYS)
-# endif
+      INTERNAL_SYSCALL_DECL (err);
+      int result = INTERNAL_SYSCALL (statfs64, err, 3, file,
+				     sizeof (*buf), buf);
+
+      if (!__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err))
+	  || INTERNAL_SYSCALL_ERRNO (result, err) != ENOSYS)
 	return result;
+# else
+      return INLINE_SYSCALL (statfs64, 3, file, sizeof (*buf), buf);
+# endif
 
 # if __ASSUME_STATFS64 == 0
       __no_statfs64 = 1;
-- 
2.4.3