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/*
* linux/arch/x86_64/kernel/vsyscall.c
*
* Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
* Copyright 2003 Andi Kleen, SuSE Labs.
*
* Thanks to hpa@transmeta.com for some useful hint.
* Special thanks to Ingo Molnar for his early experience with
* a different vsyscall implementation for Linux/IA32 and for the name.
*
* vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
* at virtual address -10Mbyte+1024bytes etc... There are at max 4
* vsyscalls. One vsyscall can reserve more than 1 slot to avoid
* jumping out of line if necessary. We cannot add more with this
* mechanism because older kernels won't return -ENOSYS.
* If we want more than four we need a vDSO.
*
* Note: the concept clashes with user mode linux. If you use UML and
* want per guest time just set the kernel.vsyscall64 sysctl to 0.
*/
#include <linux/time.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/seqlock.h>
#include <linux/jiffies.h>
#include <linux/sysctl.h>
#include <asm/vsyscall.h>
#include <asm/pgtable.h>
#include <asm/page.h>
#include <asm/fixmap.h>
#include <asm/errno.h>
#include <asm/io.h>
#define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
#define force_inline __attribute__((always_inline)) inline
int __sysctl_vsyscall __section_sysctl_vsyscall = 1;
seqlock_t __xtime_lock __section_xtime_lock = SEQLOCK_UNLOCKED;
#include <asm/unistd.h>
static force_inline void timeval_normalize(struct timeval * tv)
{
time_t __sec;
__sec = tv->tv_usec / 1000000;
if (__sec) {
tv->tv_usec %= 1000000;
tv->tv_sec += __sec;
}
}
static force_inline void do_vgettimeofday(struct timeval * tv)
{
long sequence, t;
unsigned long sec, usec;
do {
sequence = read_seqbegin(&__xtime_lock);
sec = __xtime.tv_sec;
usec = (__xtime.tv_nsec / 1000) +
(__jiffies - __wall_jiffies) * (1000000 / HZ);
if (__vxtime.mode == VXTIME_TSC) {
sync_core();
rdtscll(t);
if (t < __vxtime.last_tsc)
t = __vxtime.last_tsc;
usec += ((t - __vxtime.last_tsc) *
__vxtime.tsc_quot) >> 32;
/* See comment in x86_64 do_gettimeofday. */
} else {
usec += ((readl((void *)fix_to_virt(VSYSCALL_HPET) + 0xf0) -
__vxtime.last) * __vxtime.quot) >> 32;
}
} while (read_seqretry(&__xtime_lock, sequence));
tv->tv_sec = sec + usec / 1000000;
tv->tv_usec = usec % 1000000;
}
/* RED-PEN may want to readd seq locking, but then the variable should be write-once. */
static force_inline void do_get_tz(struct timezone * tz)
{
*tz = __sys_tz;
}
static force_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
{
int ret;
asm volatile("vsysc2: syscall"
: "=a" (ret)
: "0" (__NR_gettimeofday),"D" (tv),"S" (tz) : __syscall_clobber );
return ret;
}
static force_inline long time_syscall(long *t)
{
long secs;
asm volatile("vsysc1: syscall"
: "=a" (secs)
: "0" (__NR_time),"D" (t) : __syscall_clobber);
return secs;
}
static int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)
{
if (unlikely(!__sysctl_vsyscall))
return gettimeofday(tv,tz);
if (tv)
do_vgettimeofday(tv);
if (tz)
do_get_tz(tz);
return 0;
}
/* This will break when the xtime seconds get inaccurate, but that is
* unlikely */
static time_t __vsyscall(1) vtime(time_t *t)
{
if (unlikely(!__sysctl_vsyscall))
return time_syscall(t);
else if (t)
*t = __xtime.tv_sec;
return __xtime.tv_sec;
}
static long __vsyscall(2) venosys_0(void)
{
return -ENOSYS;
}
static long __vsyscall(3) venosys_1(void)
{
return -ENOSYS;
}
#ifdef CONFIG_SYSCTL
#define SYSCALL 0x050f
#define NOP2 0x9090
/*
* NOP out syscall in vsyscall page when not needed.
*/
static int vsyscall_sysctl_change(ctl_table *ctl, int write, struct file * filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
extern u16 vsysc1, vsysc2;
u16 *map1, *map2;
int ret = proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
if (!write)
return ret;
/* gcc has some trouble with __va(__pa()), so just do it this
way. */
map1 = ioremap(__pa_symbol(&vsysc1), 2);
if (!map1)
return -ENOMEM;
map2 = ioremap(__pa_symbol(&vsysc2), 2);
if (!map2) {
ret = -ENOMEM;
goto out;
}
if (!sysctl_vsyscall) {
*map1 = SYSCALL;
*map2 = SYSCALL;
} else {
*map1 = NOP2;
*map2 = NOP2;
}
iounmap(map2);
out:
iounmap(map1);
return ret;
}
static int vsyscall_sysctl_nostrat(ctl_table *t, int __user *name, int nlen,
void __user *oldval, size_t __user *oldlenp,
void __user *newval, size_t newlen,
void **context)
{
return -ENOSYS;
}
static ctl_table kernel_table2[] = {
{ .ctl_name = 99, .procname = "vsyscall64",
.data = &sysctl_vsyscall, .maxlen = sizeof(int), .mode = 0644,
.strategy = vsyscall_sysctl_nostrat,
.proc_handler = vsyscall_sysctl_change },
{ 0, }
};
static ctl_table kernel_root_table2[] = {
{ .ctl_name = CTL_KERN, .procname = "kernel", .mode = 0555,
.child = kernel_table2 },
{ 0 },
};
#endif
static void __init map_vsyscall(void)
{
extern char __vsyscall_0;
unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
__set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);
}
static int __init vsyscall_init(void)
{
BUG_ON(((unsigned long) &vgettimeofday !=
VSYSCALL_ADDR(__NR_vgettimeofday)));
BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
map_vsyscall();
sysctl_vsyscall = 1;
register_sysctl_table(kernel_root_table2, 0);
return 0;
}
__initcall(vsyscall_init);
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