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From: Andy Lutomirski <luto@MIT.EDU>
To: Ingo Molnar <mingo@elte.hu>, x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,
	linux-kernel@vger.kernel.org, Jesper Juhl <jj@chaosbits.net>,
	Borislav Petkov <bp@alien8.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arjan van de Ven <arjan@infradead.org>,
	Jan Beulich <JBeulich@novell.com>,
	richard -rw- weinberger <richard.weinberger@gmail.com>,
	Mikael Pettersson <mikpe@it.uu.se>,
	Andi Kleen <andi@firstfloor.org>, Brian Gerst <brgerst@gmail.com>,
	Louis Rilling <Louis.Rilling@kerlabs.com>,
	Valdis.Kletnieks@vt.edu, pageexec@freemail.hu,
	Andy Lutomirski <luto@MIT.EDU>
Subject: [PATCH v5 4/9] x86-64: Remove kernel.vsyscall64 sysctl
Date: Sun,  5 Jun 2011 13:50:20 -0400
Message-ID: <973ae803fe76f712da4b2740e66dccf452d3b1e4.1307292171.git.luto@mit.edu> (raw)
In-Reply-To: <cover.1307292171.git.luto@mit.edu>
In-Reply-To: <cover.1307292171.git.luto@mit.edu>

It's unnecessary overhead in code that's supposed to be highly
optimized.  Removing it allows us to remove one of the two syscall
instructions in the vsyscall page.

The only sensible use for it is for UML users, and it doesn't fully
address inconsistent vsyscall results on UML.  The real fix for UML
is to stop using vsyscalls entirely.

Signed-off-by: Andy Lutomirski <luto@mit.edu>
---
 arch/x86/include/asm/vgtod.h   |    1 -
 arch/x86/kernel/vsyscall_64.c  |   34 +------------------------
 arch/x86/vdso/vclock_gettime.c |   55 +++++++++++++++------------------------
 3 files changed, 22 insertions(+), 68 deletions(-)

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 646b4c1..aa5add8 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -11,7 +11,6 @@ struct vsyscall_gtod_data {
 	time_t		wall_time_sec;
 	u32		wall_time_nsec;
 
-	int		sysctl_enabled;
 	struct timezone sys_tz;
 	struct { /* extract of a clocksource struct */
 		cycle_t (*vread)(void);
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 3cf1cef..9b2f3f5 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -53,7 +53,6 @@ DEFINE_VVAR(int, vgetcpu_mode);
 DEFINE_VVAR(struct vsyscall_gtod_data, vsyscall_gtod_data) =
 {
 	.lock = __SEQLOCK_UNLOCKED(__vsyscall_gtod_data.lock),
-	.sysctl_enabled = 1,
 };
 
 void update_vsyscall_tz(void)
@@ -103,15 +102,6 @@ static __always_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
 	return ret;
 }
 
-static __always_inline long time_syscall(long *t)
-{
-	long secs;
-	asm volatile("syscall"
-		: "=a" (secs)
-		: "0" (__NR_time),"D" (t) : __syscall_clobber);
-	return secs;
-}
-
 static __always_inline void do_vgettimeofday(struct timeval * tv)
 {
 	cycle_t now, base, mask, cycle_delta;
@@ -122,8 +112,7 @@ static __always_inline void do_vgettimeofday(struct timeval * tv)
 		seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);
 
 		vread = VVAR(vsyscall_gtod_data).clock.vread;
-		if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled ||
-			     !vread)) {
+		if (unlikely(!vread)) {
 			gettimeofday(tv,NULL);
 			return;
 		}
@@ -165,8 +154,6 @@ time_t __vsyscall(1) vtime(time_t *t)
 {
 	unsigned seq;
 	time_t result;
-	if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
-		return time_syscall(t);
 
 	do {
 		seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock);
@@ -227,22 +214,6 @@ static long __vsyscall(3) venosys_1(void)
 	return -ENOSYS;
 }
 
-#ifdef CONFIG_SYSCTL
-static ctl_table kernel_table2[] = {
-	{ .procname = "vsyscall64",
-	  .data = &vsyscall_gtod_data.sysctl_enabled, .maxlen = sizeof(int),
-	  .mode = 0644,
-	  .proc_handler = proc_dointvec },
-	{}
-};
-
-static ctl_table kernel_root_table2[] = {
-	{ .procname = "kernel", .mode = 0555,
-	  .child = kernel_table2 },
-	{}
-};
-#endif
-
 /* Assume __initcall executes before all user space. Hopefully kmod
    doesn't violate that. We'll find out if it does. */
 static void __cpuinit vsyscall_set_cpu(int cpu)
@@ -301,9 +272,6 @@ static int __init vsyscall_init(void)
 	BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
 	BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
 	BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu));
-#ifdef CONFIG_SYSCTL
-	register_sysctl_table(kernel_root_table2);
-#endif
 	on_each_cpu(cpu_vsyscall_init, NULL, 1);
 	/* notifier priority > KVM */
 	hotcpu_notifier(cpu_vsyscall_notifier, 30);
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index a724905..cf54813 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -116,21 +116,21 @@ notrace static noinline int do_monotonic_coarse(struct timespec *ts)
 
 notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
-	if (likely(gtod->sysctl_enabled))
-		switch (clock) {
-		case CLOCK_REALTIME:
-			if (likely(gtod->clock.vread))
-				return do_realtime(ts);
-			break;
-		case CLOCK_MONOTONIC:
-			if (likely(gtod->clock.vread))
-				return do_monotonic(ts);
-			break;
-		case CLOCK_REALTIME_COARSE:
-			return do_realtime_coarse(ts);
-		case CLOCK_MONOTONIC_COARSE:
-			return do_monotonic_coarse(ts);
-		}
+	switch (clock) {
+	case CLOCK_REALTIME:
+		if (likely(gtod->clock.vread))
+			return do_realtime(ts);
+		break;
+	case CLOCK_MONOTONIC:
+		if (likely(gtod->clock.vread))
+			return do_monotonic(ts);
+		break;
+	case CLOCK_REALTIME_COARSE:
+		return do_realtime_coarse(ts);
+	case CLOCK_MONOTONIC_COARSE:
+		return do_monotonic_coarse(ts);
+	}
+
 	return vdso_fallback_gettime(clock, ts);
 }
 int clock_gettime(clockid_t, struct timespec *)
@@ -139,7 +139,7 @@ int clock_gettime(clockid_t, struct timespec *)
 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
 	long ret;
-	if (likely(gtod->sysctl_enabled && gtod->clock.vread)) {
+	if (likely(gtod->clock.vread)) {
 		if (likely(tv != NULL)) {
 			BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
 				     offsetof(struct timespec, tv_nsec) ||
@@ -161,27 +161,14 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 int gettimeofday(struct timeval *, struct timezone *)
 	__attribute__((weak, alias("__vdso_gettimeofday")));
 
-/* This will break when the xtime seconds get inaccurate, but that is
- * unlikely */
-
-static __always_inline long time_syscall(long *t)
-{
-	long secs;
-	asm volatile("syscall"
-		     : "=a" (secs)
-		     : "0" (__NR_time), "D" (t) : "cc", "r11", "cx", "memory");
-	return secs;
-}
-
+/*
+ * This will break when the xtime seconds get inaccurate, but that is
+ * unlikely
+ */
 notrace time_t __vdso_time(time_t *t)
 {
-	time_t result;
-
-	if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled))
-		return time_syscall(t);
-
 	/* This is atomic on x86_64 so we don't need any locks. */
-	result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec);
+	time_t result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec);
 
 	if (t)
 		*t = result;
-- 
1.7.5.2


  parent reply index

Thread overview: 112+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-05 17:50 [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 1/9] x86-64: Fix alignment of jiffies variable Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 2/9] x86-64: Document some of entry_64.S Andy Lutomirski
2011-06-06  8:31   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 3/9] x86-64: Give vvars their own page Andy Lutomirski
2011-06-06  8:32   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` Andy Lutomirski [this message]
2011-06-06  8:32   ` [tip:x86/vdso] x86-64: Remove kernel.vsyscall64 sysctl tip-bot for Andy Lutomirski
2011-12-05 18:27   ` [PATCH v5 4/9] " Matthew Maurer
2011-06-05 17:50 ` [PATCH v5 5/9] x86-64: Map the HPET NX Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 6/9] x86-64: Remove vsyscall number 3 (venosys) Andy Lutomirski
2011-06-06  8:33   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 7/9] x86-64: Fill unused parts of the vsyscall page with 0xcc Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls Andy Lutomirski
2011-06-05 19:30   ` Ingo Molnar
2011-06-05 20:01     ` Andrew Lutomirski
2011-06-06  7:39       ` Ingo Molnar
2011-06-06  9:42       ` pageexec
2011-06-06 11:19         ` Andrew Lutomirski
2011-06-06 11:56           ` pageexec
2011-06-06 12:43             ` Andrew Lutomirski
2011-06-06 13:58               ` pageexec
2011-06-06 14:07                 ` Brian Gerst
2011-06-07 23:32                   ` pageexec
2011-06-07 23:49                     ` Andrew Lutomirski
2011-06-08  6:32                       ` pageexec
2011-06-06 15:26                 ` Ingo Molnar
2011-06-06 15:48                   ` pageexec
2011-06-06 15:59                     ` Ingo Molnar
2011-06-06 16:19                       ` pageexec
2011-06-06 16:47                         ` Ingo Molnar
2011-06-06 22:49                           ` pageexec
2011-06-06 22:57                             ` david
2011-06-07  9:07                               ` Ingo Molnar
2011-06-07  6:59                             ` Pekka Enberg
2011-06-07  8:30                             ` Ingo Molnar
2011-06-07 23:24                               ` pageexec
2011-06-08  5:55                                 ` Pekka Enberg
2011-06-08  6:19                                   ` pageexec
2011-06-08  6:48                                 ` Ingo Molnar
2011-06-08  9:02                                   ` pageexec
2011-06-08  9:11                                     ` Andi Kleen
2011-06-08  9:35                                       ` pageexec
2011-06-08 10:06                                         ` Andi Kleen
2011-06-08 10:26                                           ` pageexec
2011-06-08 10:39                                             ` Ingo Molnar
2011-06-08 10:35                                           ` Ingo Molnar
2011-06-08  9:15                                     ` Ingo Molnar
2011-06-08  7:16                                 ` Ingo Molnar
2011-06-08  9:29                                   ` pageexec
2011-06-06 14:01             ` Linus Torvalds
2011-06-06 14:55               ` pageexec
2011-06-06 15:33                 ` Ingo Molnar
2011-06-06 15:58                   ` pageexec
2011-06-06 15:41         ` Ingo Molnar
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:35   ` [tip:x86/vdso] x86-64, vdso, seccomp: Fix !CONFIG_SECCOMP build tip-bot for Ingo Molnar
2011-06-07  7:49   ` [tip:x86/vdso] x86-64: Emulate legacy vsyscalls tip-bot for Andy Lutomirski
2011-06-07  8:03   ` tip-bot for Andy Lutomirski
2011-06-05 17:50 ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule Andy Lutomirski
2011-06-06  8:34   ` [tip:x86/vdso] " tip-bot for Andy Lutomirski
2011-06-06  8:46   ` [PATCH v5 9/9] " Linus Torvalds
2011-06-06  9:31     ` Andi Kleen
2011-06-06 10:39       ` pageexec
2011-06-06 13:56         ` Linus Torvalds
2011-06-06 18:46           ` pageexec
2011-06-06 20:40             ` Linus Torvalds
2011-06-06 20:51               ` Andrew Lutomirski
2011-06-06 21:54                 ` Ingo Molnar
2011-06-06 21:45               ` Ingo Molnar
2011-06-06 21:48                 ` Ingo Molnar
     [not found]                 ` <BANLkTi==uw_h78oaep1cCOCzwY0edLUU_Q@mail.gmail.com>
2011-06-07  8:03                   ` [PATCH, v6] x86-64: Emulate legacy vsyscalls Ingo Molnar
2011-06-06 21:53               ` [PATCH v5 9/9] x86-64: Add CONFIG_UNSAFE_VSYSCALLS to feature-removal-schedule pageexec
2011-06-06 14:44         ` Ingo Molnar
2011-06-06 15:01           ` pageexec
2011-06-06 15:15             ` Ingo Molnar
2011-06-06 15:29               ` pageexec
2011-06-06 16:54                 ` Ingo Molnar
2011-06-06 18:59           ` pageexec
2011-06-06 19:25             ` Ingo Molnar
2011-06-07  0:34               ` pageexec
2011-06-07  9:51                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-10 11:19                     ` Ingo Molnar
2011-06-14  0:48                       ` pageexec
2011-06-15 19:42                         ` Valdis.Kletnieks
2011-06-06 14:52         ` Ingo Molnar
2011-06-06 10:24     ` [PATCH] x86-64, vsyscalls: Rename UNSAFE_VSYSCALLS to COMPAT_VSYSCALLS Ingo Molnar
2011-06-06 11:20       ` pageexec
2011-06-06 12:47         ` Ingo Molnar
2011-06-06 12:48           ` Ingo Molnar
2011-06-06 18:04           ` pageexec
2011-06-06 19:12             ` Ingo Molnar
2011-06-07  0:02               ` pageexec
2011-06-07  9:56                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  6:48                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:05                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-09  7:02                     ` Ingo Molnar
2011-06-09 23:33                       ` pageexec
2011-06-07 10:13                 ` Ingo Molnar
2011-06-07 23:24                   ` pageexec
2011-06-06 12:19       ` Ted Ts'o
2011-06-06 12:33         ` Andrew Lutomirski
2011-06-06 12:37         ` Ingo Molnar
2011-06-06 14:34     ` [tip:x86/vdso] " tip-bot for Ingo Molnar
2011-06-05 20:05 ` [PATCH v5 0/9] Remove syscall instructions at fixed addresses Andrew Lutomirski

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