diff options
Diffstat (limited to 'arch/x86/kernel/vsyscall_64.c')
| -rw-r--r-- | arch/x86/kernel/vsyscall_64.c | 349 |
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 000000000000..06c34949bfdc --- /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); |