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/*

 *  linux/arch/x86_64/kernel/vsyscall.c

 *

 *  Copyright (C) 2001 Andrea Arcangeli <andrea@suse.de> SuSE

 *

 *  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 8192

 *  vsyscalls. One vsyscall can reserve more than 1 slot to avoid

 *  jumping out of line if necessary.

 *

 *  $Id: vsyscall.c,v 1.1.1.1 2004-04-15 01:36:42 phoenix Exp $

 */

/*

 * TODO 2001-03-20:

 *

 * 1) make page fault handler detect faults on page1-page-last of the vsyscall

 *    virtual space, and make it increase %rip and write -ENOSYS in %rax (so

 *    we'll be able to upgrade to a new glibc without upgrading kernel after

 *    we add more vsyscalls.

 * 2) Possibly we need a fixmap table for the vsyscalls too if we want

 *    to avoid SIGSEGV and we want to return -EFAULT from the vsyscalls as well.

 *    Can we segfault inside a "syscall"? We can fix this anytime and those fixes

 *    won't be visible for userspace. Not fixing this is a noop for correct programs,

 *    broken programs will segfault and there's no security risk until we choose to

 *    fix it.

 *

 * These are not urgent things that we need to address only before shipping the first

 * production binary kernels.

 */

#include <linux/time.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/mm.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>

#include <asm/msr.h>

#include <asm/unistd.h>

#define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr)))

#define force_inline inline __attribute__((always_inline))

long __vxtime_sequence[2] __section_vxtime_sequence;

static force_inline void do_vgettimeofday(struct timeval * tv)

{

        long sequence, t;

        unsigned long sec, usec;

        do {

                sequence = __vxtime_sequence[1];

                rmb();

                sec = __xtime.tv_sec;

                usec = __xtime.tv_usec + (__jiffies - __wall_jiffies) * (1000000 / HZ);

                switch (__vxtime.mode) {

                        case VXTIME_TSC:

                                sync_core();

                                rdtscll(t);

                                usec += (((t  - __vxtime.last_tsc) * __vxtime.tsc_quot) >> 32);

                                break;

                        case VXTIME_HPET:

                                usec += ((readl(fix_to_virt(VSYSCALL_HPET) + 0xf0) - __vxtime.last) * __vxtime.quot) >> 32;

                                break;

                }

                rmb();

        } while (sequence != __vxtime_sequence[0]);

        tv->tv_sec = sec + usec / 1000000;

        tv->tv_usec = usec % 1000000;

}

static force_inline void do_get_tz(struct timezone * tz)

{

        long sequence;

        do {

                sequence = __vxtime_sequence[1];

                rmb();

                *tz = __sys_tz;

                rmb();

        } while (sequence != __vxtime_sequence[0]);

}

static long __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)

{

        if (tv)

                        do_vgettimeofday(tv);

        if (tz)

                do_get_tz(tz);

        return 0;

}

static time_t __vsyscall(1) vtime(time_t * tp)

{

        struct timeval tv;

        vgettimeofday(&tv, NULL);

        if (tp) *tp = tv.tv_sec;

        return tv.tv_sec;

}

static long __vsyscall(2) venosys_0(void)

{

        return -ENOSYS;

}

static long __vsyscall(3) venosys_1(void)

{

        return -ENOSYS;

}

extern char vsyscall_syscall[], __vsyscall_0[];

static void __init map_vsyscall(void)

{

        unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);

        __set_fixmap(VSYSCALL_FIRST_PAGE, physaddr_page0, PAGE_KERNEL_VSYSCALL);

        if (hpet_address)

                __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VSYSCALL);

}

static int __init vsyscall_init(void)

{

        if ((unsigned long) &vgettimeofday != VSYSCALL_ADDR(__NR_vgettimeofday))

                panic("vgettimeofday link addr broken");

        if ((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime))

                panic("vtime link addr broken");

        if (VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE))

                panic("fixmap first vsyscall %lx should be %lx", __fix_to_virt(VSYSCALL_FIRST_PAGE),

                        VSYSCALL_ADDR(0));

        map_vsyscall();

        return 0;

}

__initcall(vsyscall_init);