syscalls_64.c

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/*
 * Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Copyright 2003 PathScale, Inc.
 *
 * Licensed under the GPL
 */

#include <linux/sched.h>
#include <asm/prctl.h> /* XXX This should get the constants from libc */
#include <os.h>

long arch_prctl(struct task_struct *task, int code, unsigned long __user *addr)
{
    unsigned long *ptr = addr, tmp;
    long ret;
    int pid = task->mm->context.id.u.pid;

    /*
     * With ARCH_SET_FS (and ARCH_SET_GS is treated similarly to
     * be safe), we need to call arch_prctl on the host because
     * setting %fs may result in something else happening (like a
     * GDT or thread.fs being set instead).  So, we let the host
     * fiddle the registers and thread struct and restore the
     * registers afterwards.
     *
     * So, the saved registers are stored to the process (this
     * needed because a stub may have been the last thing to run),
     * arch_prctl is run on the host, then the registers are read
     * back.
     */
    switch (code) {
    case ARCH_SET_FS:
    case ARCH_SET_GS:
        ret = restore_registers(pid, &current->thread.regs.regs);
        if (ret)
            return ret;
        break;
    case ARCH_GET_FS:
    case ARCH_GET_GS:
        /*
         * With these two, we read to a local pointer and
         * put_user it to the userspace pointer that we were
         * given.  If addr isn't valid (because it hasn't been
         * faulted in or is just bogus), we want put_user to
         * fault it in (or return -EFAULT) instead of having
         * the host return -EFAULT.
         */
        ptr = &tmp;
    }

    ret = os_arch_prctl(pid, code, ptr);
    if (ret)
        return ret;

    switch (code) {
    case ARCH_SET_FS:
        current->thread.arch.fs = (unsigned long) ptr;
        ret = save_registers(pid, &current->thread.regs.regs);
        break;
    case ARCH_SET_GS:
        ret = save_registers(pid, &current->thread.regs.regs);
        break;
    case ARCH_GET_FS:
        ret = put_user(tmp, addr);
        break;
    case ARCH_GET_GS:
        ret = put_user(tmp, addr);
        break;
    }

    return ret;
}

long sys_arch_prctl(int code, unsigned long addr)
{
    return arch_prctl(current, code, (unsigned long __user *) addr);
}

void arch_switch_to(struct task_struct *to)
{
    if ((to->thread.arch.fs == 0) || (to->mm == NULL))
        return;

    arch_prctl(to, ARCH_SET_FS, (void __user *) to->thread.arch.fs);
}