1 files changed, 349 insertions, 0 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
new file mode 100644
index 0000000..06c3494
--- /dev/null
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -0,0 +1,349 @@
+/*
+ *  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 <linux/clocksource.h>
+#include <linux/getcpu.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+#include <linux/notifier.h>
+
+#include <asm/vsyscall.h>
+#include <asm/pgtable.h>
+#include <asm/page.h>
+#include <asm/unistd.h>
+#include <asm/fixmap.h>
+#include <asm/errno.h>
+#include <asm/io.h>
+#include <asm/segment.h>
+#include <asm/desc.h>
+#include <asm/topology.h>
+#include <asm/vgtod.h>
+
+#define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
+#define __syscall_clobber "r11","rcx","memory"
+#define __pa_vsymbol(x)			\
+	({unsigned long v;  		\
+	extern char __vsyscall_0; 	\
+	  asm("" : "=r" (v) : "0" (x)); \
+	  ((v - VSYSCALL_FIRST_PAGE) + __pa_symbol(&__vsyscall_0)); })
+
+/*
+ * vsyscall_gtod_data contains data that is :
+ * - readonly from vsyscalls
+ * - writen by timer interrupt or systcl (/proc/sys/kernel/vsyscall64)
+ * Try to keep this structure as small as possible to avoid cache line ping pongs
+ */
+int __vgetcpu_mode __section_vgetcpu_mode;
+
+struct vsyscall_gtod_data __vsyscall_gtod_data __section_vsyscall_gtod_data =
+{
+	.lock = SEQLOCK_UNLOCKED,
+	.sysctl_enabled = 1,
+};
+
+void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
+{
+	unsigned long flags;
+
+	write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
+	/* copy vsyscall data */
+	vsyscall_gtod_data.clock.vread = clock->vread;
+	vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
+	vsyscall_gtod_data.clock.mask = clock->mask;
+	vsyscall_gtod_data.clock.mult = clock->mult;
+	vsyscall_gtod_data.clock.shift = clock->shift;
+	vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
+	vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
+	vsyscall_gtod_data.sys_tz = sys_tz;
+	vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
+	vsyscall_gtod_data.wall_to_monotonic = wall_to_monotonic;
+	write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
+}
+
+/* RED-PEN may want to readd seq locking, but then the variable should be
+ * write-once.
+ */
+static __always_inline void do_get_tz(struct timezone * tz)
+{
+	*tz = __vsyscall_gtod_data.sys_tz;
+}
+
+static __always_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 __always_inline long time_syscall(long *t)
+{
+	long secs;
+	asm volatile("vsysc1: 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;
+	unsigned seq;
+	unsigned long mult, shift, nsec;
+	cycle_t (*vread)(void);
+	do {
+		seq = read_seqbegin(&__vsyscall_gtod_data.lock);
+
+		vread = __vsyscall_gtod_data.clock.vread;
+		if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
+			gettimeofday(tv,NULL);
+			return;
+		}
+		now = vread();
+		base = __vsyscall_gtod_data.clock.cycle_last;
+		mask = __vsyscall_gtod_data.clock.mask;
+		mult = __vsyscall_gtod_data.clock.mult;
+		shift = __vsyscall_gtod_data.clock.shift;
+
+		tv->tv_sec = __vsyscall_gtod_data.wall_time_sec;
+		nsec = __vsyscall_gtod_data.wall_time_nsec;
+	} while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
+
+	/* calculate interval: */
+	cycle_delta = (now - base) & mask;
+	/* convert to nsecs: */
+	nsec += (cycle_delta * mult) >> shift;
+
+	while (nsec >= NSEC_PER_SEC) {
+		tv->tv_sec += 1;
+		nsec -= NSEC_PER_SEC;
+	}
+	tv->tv_usec = nsec / NSEC_PER_USEC;
+}
+
+int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * 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 */
+time_t __vsyscall(1) vtime(time_t *t)
+{
+	struct timeval tv;
+	time_t result;
+	if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
+		return time_syscall(t);
+
+	vgettimeofday(&tv, 0);
+	result = tv.tv_sec;
+	if (t)
+		*t = result;
+	return result;
+}
+
+/* Fast way to get current CPU and node.
+   This helps to do per node and per CPU caches in user space.
+   The result is not guaranteed without CPU affinity, but usually
+   works out because the scheduler tries to keep a thread on the same
+   CPU.
+
+   tcache must point to a two element sized long array.
+   All arguments can be NULL. */
+long __vsyscall(2)
+vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
+{
+	unsigned int dummy, p;
+	unsigned long j = 0;
+
+	/* Fast cache - only recompute value once per jiffies and avoid
+	   relatively costly rdtscp/cpuid otherwise.
+	   This works because the scheduler usually keeps the process
+	   on the same CPU and this syscall doesn't guarantee its
+	   results anyways.
+	   We do this here because otherwise user space would do it on
+	   its own in a likely inferior way (no access to jiffies).
+	   If you don't like it pass NULL. */
+	if (tcache && tcache->blob[0] == (j = __jiffies)) {
+		p = tcache->blob[1];
+	} else if (__vgetcpu_mode == VGETCPU_RDTSCP) {
+		/* Load per CPU data from RDTSCP */
+		rdtscp(dummy, dummy, p);
+	} else {
+		/* Load per CPU data from GDT */
+		asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
+	}
+	if (tcache) {
+		tcache->blob[0] = j;
+		tcache->blob[1] = p;
+	}
+	if (cpu)
+		*cpu = p & 0xfff;
+	if (node)
+		*node = p >> 12;
+	return 0;
+}
+
+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 __iomem *map1;
+	u16 __iomem *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_vsymbol(&vsysc1), 2);
+	if (!map1)
+		return -ENOMEM;
+	map2 = ioremap(__pa_vsymbol(&vsysc2), 2);
+	if (!map2) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	if (!vsyscall_gtod_data.sysctl_enabled) {
+		writew(SYSCALL, map1);
+		writew(SYSCALL, map2);
+	} else {
+		writew(NOP2, map1);
+		writew(NOP2, map2);
+	}
+	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)
+{
+	return -ENOSYS;
+}
+
+static ctl_table kernel_table2[] = {
+	{ .ctl_name = 99, .procname = "vsyscall64",
+	  .data = &vsyscall_gtod_data.sysctl_enabled, .maxlen = sizeof(int),
+	  .mode = 0644,
+	  .strategy = vsyscall_sysctl_nostrat,
+	  .proc_handler = vsyscall_sysctl_change },
+	{}
+};
+
+static ctl_table kernel_root_table2[] = {
+	{ .ctl_name = CTL_KERN, .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)
+{
+	unsigned long *d;
+	unsigned long node = 0;
+#ifdef CONFIG_NUMA
+	node = cpu_to_node[cpu];
+#endif
+	if (cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP))
+		write_rdtscp_aux((node << 12) | cpu);
+
+	/* Store cpu number in limit so that it can be loaded quickly
+	   in user space in vgetcpu.
+	   12 bits for the CPU and 8 bits for the node. */
+	d = (unsigned long *)(cpu_gdt(cpu) + GDT_ENTRY_PER_CPU);
+	*d = 0x0f40000000000ULL;
+	*d |= cpu;
+	*d |= (node & 0xf) << 12;
+	*d |= (node >> 4) << 48;
+}
+
+static void __cpuinit cpu_vsyscall_init(void *arg)
+{
+	/* preemption should be already off */
+	vsyscall_set_cpu(raw_smp_processor_id());
+}
+
+static int __cpuinit
+cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
+{
+	long cpu = (long)arg;
+	if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
+		smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 0, 1);
+	return NOTIFY_DONE;
+}
+
+static void __init map_vsyscall(void)
+{
+	extern char __vsyscall_0;
+	unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
+
+	/* Note that VSYSCALL_MAPPED_PAGES must agree with the code below. */
+	__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)));
+	BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu));
+	map_vsyscall();
+#ifdef CONFIG_SYSCTL
+	register_sysctl_table(kernel_root_table2);
+#endif
+	on_each_cpu(cpu_vsyscall_init, NULL, 0, 1);
+	hotcpu_notifier(cpu_vsyscall_notifier, 0);
+	return 0;
+}
+
+__initcall(vsyscall_init);