release/src-rt-6.x/linux/linux-2.6/arch/x86_64/kernel/vsyscall.c

   1 /*
   2  *  linux/arch/x86_64/kernel/vsyscall.c
   3  *
   4  *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE
   5  *  Copyright 2003 Andi Kleen, SuSE Labs.
   6  *
   7  *  Thanks to hpa@transmeta.com for some useful hint.
   8  *  Special thanks to Ingo Molnar for his early experience with
   9  *  a different vsyscall implementation for Linux/IA32 and for the name.
  10  *
  11  *  vsyscall 1 is located at -10Mbyte, vsyscall 2 is located
  12  *  at virtual address -10Mbyte+1024bytes etc... There are at max 4
  13  *  vsyscalls. One vsyscall can reserve more than 1 slot to avoid
  14  *  jumping out of line if necessary. We cannot add more with this
  15  *  mechanism because older kernels won't return -ENOSYS.
  16  *  If we want more than four we need a vDSO.
  17  *
  18  *  Note: the concept clashes with user mode linux. If you use UML and
  19  *  want per guest time just set the kernel.vsyscall64 sysctl to 0.
  20  */
  21
  22 #include <linux/time.h>
  23 #include <linux/init.h>
  24 #include <linux/kernel.h>
  25 #include <linux/timer.h>
  26 #include <linux/seqlock.h>
  27 #include <linux/jiffies.h>
  28 #include <linux/sysctl.h>
  29 #include <linux/clocksource.h>
  30 #include <linux/getcpu.h>
  31 #include <linux/cpu.h>
  32 #include <linux/smp.h>
  33 #include <linux/notifier.h>
  34
  35 #include <asm/vsyscall.h>
  36 #include <asm/pgtable.h>
  37 #include <asm/page.h>
  38 #include <asm/unistd.h>
  39 #include <asm/fixmap.h>
  40 #include <asm/errno.h>
  41 #include <asm/io.h>
  42 #include <asm/segment.h>
  43 #include <asm/desc.h>
  44 #include <asm/topology.h>
  45
  46 #define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))
  47 #define __syscall_clobber "r11","rcx","memory"
  48 #define __pa_vsymbol(x)                 \
  49         ({unsigned long v;              \
  50         extern char __vsyscall_0;       \
  51           asm("" : "=r" (v) : "0" (x)); \
  52           ((v - VSYSCALL_FIRST_PAGE) + __pa_symbol(&__vsyscall_0)); })
  53
  54 /*
  55  * vsyscall_gtod_data contains data that is :
  56  * - readonly from vsyscalls
  57  * - writen by timer interrupt or systcl (/proc/sys/kernel/vsyscall64)
  58  * Try to keep this structure as small as possible to avoid cache line ping pongs
  59  */
  60 struct vsyscall_gtod_data_t {
  61         seqlock_t       lock;
  62
  63         /* open coded 'struct timespec' */
  64         time_t          wall_time_sec;
  65         u32             wall_time_nsec;
  66
  67         int             sysctl_enabled;
  68         struct timezone sys_tz;
  69         struct { /* extract of a clocksource struct */
  70                 cycle_t (*vread)(void);
  71                 cycle_t cycle_last;
  72                 cycle_t mask;
  73                 u32     mult;
  74                 u32     shift;
  75         } clock;
  76 };
  77 int __vgetcpu_mode __section_vgetcpu_mode;
  78
  79 struct vsyscall_gtod_data_t __vsyscall_gtod_data __section_vsyscall_gtod_data =
  80 {
  81         .lock = SEQLOCK_UNLOCKED,
  82         .sysctl_enabled = 1,
  83 };
  84
  85 void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
  86 {
  87         unsigned long flags;
  88
  89         write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
  90         /* copy vsyscall data */
  91         vsyscall_gtod_data.clock.vread = clock->vread;
  92         vsyscall_gtod_data.clock.cycle_last = clock->cycle_last;
  93         vsyscall_gtod_data.clock.mask = clock->mask;
  94         vsyscall_gtod_data.clock.mult = clock->mult;
  95         vsyscall_gtod_data.clock.shift = clock->shift;
  96         vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec;
  97         vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec;
  98         vsyscall_gtod_data.sys_tz = sys_tz;
  99         write_sequnlock_irqrestore(&vsyscall_gtod_data.lock, flags);
 100 }
 101
 102 /* RED-PEN may want to readd seq locking, but then the variable should be
 103  * write-once.
 104  */
 105 static __always_inline void do_get_tz(struct timezone * tz)
 106 {
 107         *tz = __vsyscall_gtod_data.sys_tz;
 108 }
 109
 110 static __always_inline int gettimeofday(struct timeval *tv, struct timezone *tz)
 111 {
 112         int ret;
 113         asm volatile("vsysc2: syscall"
 114                 : "=a" (ret)
 115                 : "0" (__NR_gettimeofday),"D" (tv),"S" (tz)
 116                 : __syscall_clobber );
 117         return ret;
 118 }
 119
 120 static __always_inline long time_syscall(long *t)
 121 {
 122         long secs;
 123         asm volatile("vsysc1: syscall"
 124                 : "=a" (secs)
 125                 : "0" (__NR_time),"D" (t) : __syscall_clobber);
 126         return secs;
 127 }
 128
 129 static __always_inline void do_vgettimeofday(struct timeval * tv)
 130 {
 131         cycle_t now, base, mask, cycle_delta;
 132         unsigned seq;
 133         unsigned long mult, shift, nsec;
 134         cycle_t (*vread)(void);
 135         do {
 136                 seq = read_seqbegin(&__vsyscall_gtod_data.lock);
 137
 138                 vread = __vsyscall_gtod_data.clock.vread;
 139                 if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
 140                         gettimeofday(tv,NULL);
 141                         return;
 142                 }
 143                 now = vread();
 144                 base = __vsyscall_gtod_data.clock.cycle_last;
 145                 mask = __vsyscall_gtod_data.clock.mask;
 146                 mult = __vsyscall_gtod_data.clock.mult;
 147                 shift = __vsyscall_gtod_data.clock.shift;
 148
 149                 tv->tv_sec = __vsyscall_gtod_data.wall_time_sec;
 150                 nsec = __vsyscall_gtod_data.wall_time_nsec;
 151         } while (read_seqretry(&__vsyscall_gtod_data.lock, seq));
 152
 153         /* calculate interval: */
 154         cycle_delta = (now - base) & mask;
 155         /* convert to nsecs: */
 156         nsec += (cycle_delta * mult) >> shift;
 157
 158         while (nsec >= NSEC_PER_SEC) {
 159                 tv->tv_sec += 1;
 160                 nsec -= NSEC_PER_SEC;
 161         }
 162         tv->tv_usec = nsec / NSEC_PER_USEC;
 163 }
 164
 165 int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)
 166 {
 167         if (tv)
 168                 do_vgettimeofday(tv);
 169         if (tz)
 170                 do_get_tz(tz);
 171         return 0;
 172 }
 173
 174 /* This will break when the xtime seconds get inaccurate, but that is
 175  * unlikely */
 176 time_t __vsyscall(1) vtime(time_t *t)
 177 {
 178         struct timeval tv;
 179         time_t result;
 180         if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
 181                 return time_syscall(t);
 182
 183         vgettimeofday(&tv, 0);
 184         result = tv.tv_sec;
 185         if (t)
 186                 *t = result;
 187         return result;
 188 }
 189
 190 /* Fast way to get current CPU and node.
 191    This helps to do per node and per CPU caches in user space.
 192    The result is not guaranteed without CPU affinity, but usually
 193    works out because the scheduler tries to keep a thread on the same
 194    CPU.
 195
 196    tcache must point to a two element sized long array.
 197    All arguments can be NULL. */
 198 long __vsyscall(2)
 199 vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
 200 {
 201         unsigned int dummy, p;
 202         unsigned long j = 0;
 203
 204         /* Fast cache - only recompute value once per jiffies and avoid
 205            relatively costly rdtscp/cpuid otherwise.
 206            This works because the scheduler usually keeps the process
 207            on the same CPU and this syscall doesn't guarantee its
 208            results anyways.
 209            We do this here because otherwise user space would do it on
 210            its own in a likely inferior way (no access to jiffies).
 211            If you don't like it pass NULL. */
 212         if (tcache && tcache->blob[0] == (j = __jiffies)) {
 213                 p = tcache->blob[1];
 214         } else if (__vgetcpu_mode == VGETCPU_RDTSCP) {
 215                 /* Load per CPU data from RDTSCP */
 216                 rdtscp(dummy, dummy, p);
 217         } else {
 218                 /* Load per CPU data from GDT */
 219                 asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
 220         }
 221         if (tcache) {
 222                 tcache->blob[0] = j;
 223                 tcache->blob[1] = p;
 224         }
 225         if (cpu)
 226                 *cpu = p & 0xfff;
 227         if (node)
 228                 *node = p >> 12;
 229         return 0;
 230 }
 231
 232 long __vsyscall(3) venosys_1(void)
 233 {
 234         return -ENOSYS;
 235 }
 236
 237 #ifdef CONFIG_SYSCTL
 238
 239 #define SYSCALL 0x050f
 240 #define NOP2    0x9090
 241
 242 /*
 243  * NOP out syscall in vsyscall page when not needed.
 244  */
 245 static int vsyscall_sysctl_change(ctl_table *ctl, int write, struct file * filp,
 246                         void __user *buffer, size_t *lenp, loff_t *ppos)
 247 {
 248         extern u16 vsysc1, vsysc2;
 249         u16 __iomem *map1;
 250         u16 __iomem *map2;
 251         int ret = proc_dointvec(ctl, write, filp, buffer, lenp, ppos);
 252         if (!write)
 253                 return ret;
 254         /* gcc has some trouble with __va(__pa()), so just do it this
 255            way. */
 256         map1 = ioremap(__pa_vsymbol(&vsysc1), 2);
 257         if (!map1)
 258                 return -ENOMEM;
 259         map2 = ioremap(__pa_vsymbol(&vsysc2), 2);
 260         if (!map2) {
 261                 ret = -ENOMEM;
 262                 goto out;
 263         }
 264         if (!vsyscall_gtod_data.sysctl_enabled) {
 265                 writew(SYSCALL, map1);
 266                 writew(SYSCALL, map2);
 267         } else {
 268                 writew(NOP2, map1);
 269                 writew(NOP2, map2);
 270         }
 271         iounmap(map2);
 272 out:
 273         iounmap(map1);
 274         return ret;
 275 }
 276
 277 static int vsyscall_sysctl_nostrat(ctl_table *t, int __user *name, int nlen,
 278                                 void __user *oldval, size_t __user *oldlenp,
 279                                 void __user *newval, size_t newlen)
 280 {
 281         return -ENOSYS;
 282 }
 283
 284 static ctl_table kernel_table2[] = {
 285         { .ctl_name = 99, .procname = "vsyscall64",
 286           .data = &vsyscall_gtod_data.sysctl_enabled, .maxlen = sizeof(int),
 287           .mode = 0644,
 288           .strategy = vsyscall_sysctl_nostrat,
 289           .proc_handler = vsyscall_sysctl_change },
 290         {}
 291 };
 292
 293 static ctl_table kernel_root_table2[] = {
 294         { .ctl_name = CTL_KERN, .procname = "kernel", .mode = 0555,
 295           .child = kernel_table2 },
 296         {}
 297 };
 298
 299 #endif
 300
 301 /* Assume __initcall executes before all user space. Hopefully kmod
 302    doesn't violate that. We'll find out if it does. */
 303 static void __cpuinit vsyscall_set_cpu(int cpu)
 304 {
 305         unsigned long *d;
 306         unsigned long node = 0;
 307 #ifdef CONFIG_NUMA
 308         node = cpu_to_node[cpu];
 309 #endif
 310         if (cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP))
 311                 write_rdtscp_aux((node << 12) | cpu);
 312
 313         /* Store cpu number in limit so that it can be loaded quickly
 314            in user space in vgetcpu.
 315            12 bits for the CPU and 8 bits for the node. */
 316         d = (unsigned long *)(cpu_gdt(cpu) + GDT_ENTRY_PER_CPU);
 317         *d = 0x0f40000000000ULL;
 318         *d |= cpu;
 319         *d |= (node & 0xf) << 12;
 320         *d |= (node >> 4) << 48;
 321 }
 322
 323 static void __cpuinit cpu_vsyscall_init(void *arg)
 324 {
 325         /* preemption should be already off */
 326         vsyscall_set_cpu(raw_smp_processor_id());
 327 }
 328
 329 static int __cpuinit
 330 cpu_vsyscall_notifier(struct notifier_block *n, unsigned long action, void *arg)
 331 {
 332         long cpu = (long)arg;
 333         if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN)
 334                 smp_call_function_single(cpu, cpu_vsyscall_init, NULL, 0, 1);
 335         return NOTIFY_DONE;
 336 }
 337
 338 static void __init map_vsyscall(void)
 339 {
 340         extern char __vsyscall_0;
 341         unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
 342
 343         /* Note that VSYSCALL_MAPPED_PAGES must agree with the code below. */
 344         __set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);
 345 }
 346
 347 static int __init vsyscall_init(void)
 348 {
 349         BUG_ON(((unsigned long) &vgettimeofday !=
 350                         VSYSCALL_ADDR(__NR_vgettimeofday)));
 351         BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
 352         BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
 353         BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu));
 354         map_vsyscall();
 355 #ifdef CONFIG_SYSCTL
 356         register_sysctl_table(kernel_root_table2);
 357 #endif
 358         on_each_cpu(cpu_vsyscall_init, NULL, 0, 1);
 359         hotcpu_notifier(cpu_vsyscall_notifier, 0);
 360         return 0;
 361 }
 362
 363 __initcall(vsyscall_init);