Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 | /*
* 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))) notrace
#define __syscall_clobber "r11","cx","memory"
/*
* vsyscall_gtod_data contains data that is :
* - readonly from vsyscalls
* - written 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_tz(void)
{
unsigned long flags;
write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
/* sys_tz has changed */
vsyscall_gtod_data.sys_tz = sys_tz;
write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
}
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.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("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("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, NULL);
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 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 */
native_read_tscp(&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;
}
static long __vsyscall(3) venosys_1(void)
{
return -ENOSYS;
}
#ifdef CONFIG_SYSCTL
static int
vsyscall_sysctl_change(ctl_table *ctl, int write, struct file * filp,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
}
static ctl_table kernel_table2[] = {
{ .procname = "vsyscall64",
.data = &vsyscall_gtod_data.sysctl_enabled, .maxlen = sizeof(int),
.mode = 0644,
.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 = 0x0f40000000000ULL;
d |= cpu;
d |= (node & 0xf) << 12;
d |= (node >> 4) << 48;
write_gdt_entry(get_cpu_gdt_table(cpu), GDT_ENTRY_PER_CPU, &d, DESCTYPE_S);
}
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, 1);
return NOTIFY_DONE;
}
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));
#ifdef CONFIG_SYSCTL
register_sysctl_table(kernel_root_table2);
#endif
on_each_cpu(cpu_vsyscall_init, NULL, 1);
hotcpu_notifier(cpu_vsyscall_notifier, 0);
return 0;
}
__initcall(vsyscall_init);
|