310 строки
8.5 KiB
C
310 строки
8.5 KiB
C
/*
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* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
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* Copyright 2003 Andi Kleen, SuSE Labs.
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*
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* Thanks to hpa@transmeta.com for some useful hint.
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* Special thanks to Ingo Molnar for his early experience with
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* a different vsyscall implementation for Linux/IA32 and for the name.
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*
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* vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
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* at virtual address -10Mbyte+1024bytes etc... There are at max 4
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* vsyscalls. One vsyscall can reserve more than 1 slot to avoid
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* jumping out of line if necessary. We cannot add more with this
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* mechanism because older kernels won't return -ENOSYS.
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* If we want more than four we need a vDSO.
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*
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* Note: the concept clashes with user mode linux. If you use UML and
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* want per guest time just set the kernel.vsyscall64 sysctl to 0.
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*/
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/timer.h>
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#include <linux/seqlock.h>
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#include <linux/jiffies.h>
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#include <linux/sysctl.h>
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#include <linux/clocksource.h>
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#include <linux/getcpu.h>
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#include <linux/cpu.h>
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#include <linux/smp.h>
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#include <linux/notifier.h>
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#include <asm/vsyscall.h>
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#include <asm/pgtable.h>
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#include <asm/page.h>
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#include <asm/unistd.h>
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#include <asm/fixmap.h>
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#include <asm/errno.h>
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#include <asm/io.h>
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#include <asm/segment.h>
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#include <asm/desc.h>
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#include <asm/topology.h>
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#include <asm/vgtod.h>
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#define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
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#define __syscall_clobber "r11","cx","memory"
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/*
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* vsyscall_gtod_data contains data that is :
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* - readonly from vsyscalls
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* - written by timer interrupt or systcl (/proc/sys/kernel/vsyscall64)
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* Try to keep this structure as small as possible to avoid cache line ping pongs
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*/
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int __vgetcpu_mode __section_vgetcpu_mode;
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struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
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{
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.lock = SEQLOCK_UNLOCKED,
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.sysctl_enabled = 1,
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};
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void update_vsyscall_tz(void)
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{
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unsigned long flags;
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write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
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/* sys_tz has changed */
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vsyscall_gtod_data.sys_tz = sys_tz;
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write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
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}
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void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
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{
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unsigned long flags;
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write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
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/* copy vsyscall data */
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vsyscall_gtod_data.clock.vread = clock->vread;
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vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
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vsyscall_gtod_data.clock.mask = clock->mask;
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vsyscall_gtod_data.clock.mult = clock->mult;
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vsyscall_gtod_data.clock.shift = clock->shift;
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vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
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vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
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vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
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write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
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}
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/* RED-PEN may want to readd seq locking, but then the variable should be
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* write-once.
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*/
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static __always_inline void do_get_tz(struct timezone * tz)
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{
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*tz = __vsyscall_gtod_data.sys_tz;
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}
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static __always_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
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{
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int ret;
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asm volatile("syscall"
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: "=a" (ret)
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: "0" (__NR_gettimeofday),"D" (tv),"S" (tz)
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: __syscall_clobber );
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return ret;
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}
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static __always_inline long time_syscall(long *t)
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{
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long secs;
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asm volatile("syscall"
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: "=a" (secs)
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: "0" (__NR_time),"D" (t) : __syscall_clobber);
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return secs;
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}
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static __always_inline void do_vgettimeofday(struct timeval * tv)
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{
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cycle_t now, base, mask, cycle_delta;
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unsigned seq;
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unsigned long mult, shift, nsec;
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cycle_t (*vread)(void);
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do {
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seq = read_seqbegin(&__vsyscall_gtod_data.lock);
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vread = __vsyscall_gtod_data.clock.vread;
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if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
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gettimeofday(tv,NULL);
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return;
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}
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now = vread();
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base = __vsyscall_gtod_data.clock.cycle_last;
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mask = __vsyscall_gtod_data.clock.mask;
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mult = __vsyscall_gtod_data.clock.mult;
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shift = __vsyscall_gtod_data.clock.shift;
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tv->tv_sec = __vsyscall_gtod_data.wall_time_sec;
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nsec = __vsyscall_gtod_data.wall_time_nsec;
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} while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
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/* calculate interval: */
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cycle_delta = (now - base) & mask;
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/* convert to nsecs: */
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nsec += (cycle_delta * mult) >> shift;
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while (nsec >= NSEC_PER_SEC) {
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tv->tv_sec += 1;
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nsec -= NSEC_PER_SEC;
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}
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tv->tv_usec = nsec / NSEC_PER_USEC;
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}
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int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)
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{
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if (tv)
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do_vgettimeofday(tv);
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if (tz)
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do_get_tz(tz);
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return 0;
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}
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/* This will break when the xtime seconds get inaccurate, but that is
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* unlikely */
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time_t __vsyscall(1) vtime(time_t *t)
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{
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struct timeval tv;
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time_t result;
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if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
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return time_syscall(t);
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vgettimeofday(&tv, NULL);
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result = tv.tv_sec;
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if (t)
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*t = result;
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return result;
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}
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/* Fast way to get current CPU and node.
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This helps to do per node and per CPU caches in user space.
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The result is not guaranteed without CPU affinity, but usually
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works out because the scheduler tries to keep a thread on the same
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CPU.
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tcache must point to a two element sized long array.
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All arguments can be NULL. */
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long __vsyscall(2)
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vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
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{
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unsigned int p;
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unsigned long j = 0;
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/* Fast cache - only recompute value once per jiffies and avoid
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relatively costly rdtscp/cpuid otherwise.
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This works because the scheduler usually keeps the process
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on the same CPU and this syscall doesn't guarantee its
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results anyways.
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We do this here because otherwise user space would do it on
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its own in a likely inferior way (no access to jiffies).
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If you don't like it pass NULL. */
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if (tcache && tcache->blob[0] == (j = __jiffies)) {
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p = tcache->blob[1];
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} else if (__vgetcpu_mode == VGETCPU_RDTSCP) {
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/* Load per CPU data from RDTSCP */
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native_read_tscp(&p);
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} else {
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/* Load per CPU data from GDT */
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asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
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}
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if (tcache) {
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tcache->blob[0] = j;
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tcache->blob[1] = p;
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}
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if (cpu)
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*cpu = p & 0xfff;
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if (node)
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*node = p >> 12;
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return 0;
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}
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static long __vsyscall(3) venosys_1(void)
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{
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return -ENOSYS;
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}
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#ifdef CONFIG_SYSCTL
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static int
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vsyscall_sysctl_change(ctl_table *ctl, int write, struct file * filp,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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return proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
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}
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static ctl_table kernel_table2[] = {
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{ .procname = "vsyscall64",
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.data = &vsyscall_gtod_data.sysctl_enabled, .maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = vsyscall_sysctl_change },
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{}
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};
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static ctl_table kernel_root_table2[] = {
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{ .ctl_name = CTL_KERN, .procname = "kernel", .mode = 0555,
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.child = kernel_table2 },
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{}
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};
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#endif
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/* Assume __initcall executes before all user space. Hopefully kmod
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doesn't violate that. We'll find out if it does. */
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static void __cpuinit vsyscall_set_cpu(int cpu)
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{
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unsigned long *d;
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unsigned long node = 0;
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#ifdef CONFIG_NUMA
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node = cpu_to_node(cpu);
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#endif
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if (cpu_has(&cpu_data(cpu), X86_FEATURE_RDTSCP))
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write_rdtscp_aux((node << 12) | cpu);
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/* Store cpu number in limit so that it can be loaded quickly
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in user space in vgetcpu.
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12 bits for the CPU and 8 bits for the node. */
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d = (unsigned long *)(get_cpu_gdt_table(cpu) + GDT_ENTRY_PER_CPU);
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*d = 0x0f40000000000ULL;
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*d |= cpu;
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*d |= (node & 0xf) << 12;
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*d |= (node >> 4) << 48;
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}
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static void __cpuinit cpu_vsyscall_init(void *arg)
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{
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/* preemption should be already off */
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vsyscall_set_cpu(raw_smp_processor_id());
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}
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static int __cpuinit
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cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
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{
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long cpu = (long)arg;
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if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
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smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 0, 1);
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return NOTIFY_DONE;
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}
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void __init map_vsyscall(void)
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{
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extern char __vsyscall_0;
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unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
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/* Note that VSYSCALL_MAPPED_PAGES must agree with the code below. */
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__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);
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}
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static int __init vsyscall_init(void)
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{
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BUG_ON(((unsigned long) &vgettimeofday !=
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VSYSCALL_ADDR(__NR_vgettimeofday)));
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BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
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BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
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BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu));
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#ifdef CONFIG_SYSCTL
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register_sysctl_table(kernel_root_table2);
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#endif
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on_each_cpu(cpu_vsyscall_init, NULL, 0, 1);
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hotcpu_notifier(cpu_vsyscall_notifier, 0);
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return 0;
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}
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__initcall(vsyscall_init);
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