Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754616Ab1EaNQs (ORCPT ); Tue, 31 May 2011 09:16:48 -0400 Received: from DMZ-MAILSEC-SCANNER-5.MIT.EDU ([18.7.68.34]:47093 "EHLO dmz-mailsec-scanner-5.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754450Ab1EaNQo (ORCPT ); Tue, 31 May 2011 09:16:44 -0400 X-AuditID: 12074422-b7b0eae000007f48-23-4de4ea3ebdea From: Andy Lutomirski To: Ingo Molnar , x86@kernel.org Cc: Thomas Gleixner , linux-kernel@vger.kernel.org, Jesper Juhl , Borislav Petkov , Linus Torvalds , Andrew Morton , Arjan van de Ven , Jan Beulich , richard -rw- weinberger , Mikael Pettersson , Andi Kleen , Andy Lutomirski Subject: [PATCH v3 04/10] x86-64: Remove kernel.vsyscall64 sysctl Date: Tue, 31 May 2011 09:15:58 -0400 Message-Id: <2a1966052c8231877e67595e7caf95a9ae57838d.1306847455.git.luto@mit.edu> X-Mailer: git-send-email 1.7.5.1 In-Reply-To: References: In-Reply-To: References: X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrPKsWRmVeSWpSXmKPExsUixG6nrmv36omvwdL7NhZz1q9hs+i7cpTd 4si17+wWs67xWnze8I/N4sCvp2wW769uZ7O4vGsOm8WT5uuMFlsuNbNafJi4gc1i86apzBaP +t6yW/zY8JjVgc/je2sfi8exM4cZPW61/WH2mL/zI6PHzll32T02r9Dy+P/yCJvHplWdbB7v zp1j9zgx4zeLx/Ezzh6fN8kF8ERx2aSk5mSWpRbp2yVwZczZvIa1YL9BRefZ6ewNjK/Vuxg5 OSQETCR+d21jgrDFJC7cW8/WxcjFISSwj1Hi4vsjUM4GRomNhx8wQzjPmCQ6H68Ba2ETUJHo WPoAyObgEBHQl7j6mRGkhllgEovE4b+nWUBqhAUcJa6+f8oMYrMIqErcm74ZrJdXIEii9/Nu ZojVChJXrswDq+cUMJBoXrmGDcQWApp5/8kVZlziExgFFjAyrGKUTcmt0s1NzMwpTk3WLU5O zMtLLdI11cvNLNFLTSndxAiOGxelHYw/DyodYhTgYFTi4c0++NhXiDWxrLgy9xCjJAeTkiiv zMsnvkJ8SfkplRmJxRnxRaU5qcWHGCU4mJVEeL/xAeV4UxIrq1KL8mFS0hwsSuK8cyTVfYUE 0hNLUrNTUwtSi2CyMhwcShK8M0CGChalpqdWpGXmlCCkmTg4QYbzAA0PBanhLS5IzC3OTIfI n2LU5Whcu+MgoxBLXn5eqpQ4bxZIkQBIUUZpHtwcWLp7xSgO9JYwbz9IFQ8wVcJNegW0hAlo Se+7hyBLShIRUlINjGkhh8KT+A0/2/2z2meeeEZFuLJdv2G+i/ifXdNfP7s36dqs6J23Cpfc Pev/y9a6jreB7+BJhbl3Vt5h0+ncZ/SN/fmkbay5sl2vJjFvOaM1UynrrlJ3NktjlM3hu9JF aya1LLLgq8orfMy7NZWHIfe57mVJiSiHD1scUzxv60Xp/eP89b1JQomlOCPRUIu5qDgRANHQ BXZSAwAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6259 Lines: 198 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 --- 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 ee22180..3e8dac7 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, - .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; -- 1.7.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/