1 files changed, 225 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
new file mode 100644
index 000000000000..b4b8dc59663a
--- /dev/null
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -0,0 +1,225 @@
+/*
+ *  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);