process_64.c

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/*  arch/sparc64/kernel/process.c
 *
 *  Copyright (C) 1995, 1996, 2008 David S. Miller ([email protected])
 *  Copyright (C) 1996       Eddie C. Dost   ([email protected])
 *  Copyright (C) 1997, 1998 Jakub Jelinek   ([email protected])
 */

/*
 * This file handles the architecture-dependent parts of process handling..
 */

#include <stdarg.h>

#include <linux/errno.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/delay.h>
#include <linux/compat.h>
#include <linux/tick.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/perf_event.h>
#include <linux/elfcore.h>
#include <linux/sysrq.h>
#include <linux/nmi.h>

#include <asm/uaccess.h>
#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/pstate.h>
#include <asm/elf.h>
#include <asm/fpumacro.h>
#include <asm/head.h>
#include <asm/cpudata.h>
#include <asm/mmu_context.h>
#include <asm/unistd.h>
#include <asm/hypervisor.h>
#include <asm/syscalls.h>
#include <asm/irq_regs.h>
#include <asm/smp.h>
#include <asm/pcr.h>

#include "kstack.h"

static void sparc64_yield(int cpu)
{
    if (tlb_type != hypervisor) {
        touch_nmi_watchdog();
        return;
    }

    clear_thread_flag(TIF_POLLING_NRFLAG);
    smp_mb__after_clear_bit();

    while (!need_resched() && !cpu_is_offline(cpu)) {
        unsigned long pstate;

        /* Disable interrupts. */
        __asm__ __volatile__(
            "rdpr %%pstate, %0\n\t"
            "andn %0, %1, %0\n\t"
            "wrpr %0, %%g0, %%pstate"
            : "=&r" (pstate)
            : "i" (PSTATE_IE));

        if (!need_resched() && !cpu_is_offline(cpu))
            sun4v_cpu_yield();

        /* Re-enable interrupts. */
        __asm__ __volatile__(
            "rdpr %%pstate, %0\n\t"
            "or %0, %1, %0\n\t"
            "wrpr %0, %%g0, %%pstate"
            : "=&r" (pstate)
            : "i" (PSTATE_IE));
    }

    set_thread_flag(TIF_POLLING_NRFLAG);
}

/* The idle loop on sparc64. */
void cpu_idle(void)
{
    int cpu = smp_processor_id();

    set_thread_flag(TIF_POLLING_NRFLAG);

    while(1) {
        tick_nohz_idle_enter();
        rcu_idle_enter();

        while (!need_resched() && !cpu_is_offline(cpu))
            sparc64_yield(cpu);

        rcu_idle_exit();
        tick_nohz_idle_exit();

#ifdef CONFIG_HOTPLUG_CPU
        if (cpu_is_offline(cpu)) {
            sched_preempt_enable_no_resched();
            cpu_play_dead();
        }
#endif
        schedule_preempt_disabled();
    }
}

#ifdef CONFIG_COMPAT
static void show_regwindow32(struct pt_regs *regs)
{
    struct reg_window32 __user *rw;
    struct reg_window32 r_w;
    mm_segment_t old_fs;
    
    __asm__ __volatile__ ("flushw");
    rw = compat_ptr((unsigned)regs->u_regs[14]);
    old_fs = get_fs();
    set_fs (USER_DS);
    if (copy_from_user (&r_w, rw, sizeof(r_w))) {
        set_fs (old_fs);
        return;
    }

    set_fs (old_fs);            
    printk("l0: %08x l1: %08x l2: %08x l3: %08x "
           "l4: %08x l5: %08x l6: %08x l7: %08x\n",
           r_w.locals[0], r_w.locals[1], r_w.locals[2], r_w.locals[3],
           r_w.locals[4], r_w.locals[5], r_w.locals[6], r_w.locals[7]);
    printk("i0: %08x i1: %08x i2: %08x i3: %08x "
           "i4: %08x i5: %08x i6: %08x i7: %08x\n",
           r_w.ins[0], r_w.ins[1], r_w.ins[2], r_w.ins[3],
           r_w.ins[4], r_w.ins[5], r_w.ins[6], r_w.ins[7]);
}
#else
#define show_regwindow32(regs)  do { } while (0)
#endif

static void show_regwindow(struct pt_regs *regs)
{
    struct reg_window __user *rw;
    struct reg_window *rwk;
    struct reg_window r_w;
    mm_segment_t old_fs;

    if ((regs->tstate & TSTATE_PRIV) || !(test_thread_flag(TIF_32BIT))) {
        __asm__ __volatile__ ("flushw");
        rw = (struct reg_window __user *)
            (regs->u_regs[14] + STACK_BIAS);
        rwk = (struct reg_window *)
            (regs->u_regs[14] + STACK_BIAS);
        if (!(regs->tstate & TSTATE_PRIV)) {
            old_fs = get_fs();
            set_fs (USER_DS);
            if (copy_from_user (&r_w, rw, sizeof(r_w))) {
                set_fs (old_fs);
                return;
            }
            rwk = &r_w;
            set_fs (old_fs);            
        }
    } else {
        show_regwindow32(regs);
        return;
    }
    printk("l0: %016lx l1: %016lx l2: %016lx l3: %016lx\n",
           rwk->locals[0], rwk->locals[1], rwk->locals[2], rwk->locals[3]);
    printk("l4: %016lx l5: %016lx l6: %016lx l7: %016lx\n",
           rwk->locals[4], rwk->locals[5], rwk->locals[6], rwk->locals[7]);
    printk("i0: %016lx i1: %016lx i2: %016lx i3: %016lx\n",
           rwk->ins[0], rwk->ins[1], rwk->ins[2], rwk->ins[3]);
    printk("i4: %016lx i5: %016lx i6: %016lx i7: %016lx\n",
           rwk->ins[4], rwk->ins[5], rwk->ins[6], rwk->ins[7]);
    if (regs->tstate & TSTATE_PRIV)
        printk("I7: <%pS>\n", (void *) rwk->ins[7]);
}

void show_regs(struct pt_regs *regs)
{
    printk("TSTATE: %016lx TPC: %016lx TNPC: %016lx Y: %08x    %s\n", regs->tstate,
           regs->tpc, regs->tnpc, regs->y, print_tainted());
    printk("TPC: <%pS>\n", (void *) regs->tpc);
    printk("g0: %016lx g1: %016lx g2: %016lx g3: %016lx\n",
           regs->u_regs[0], regs->u_regs[1], regs->u_regs[2],
           regs->u_regs[3]);
    printk("g4: %016lx g5: %016lx g6: %016lx g7: %016lx\n",
           regs->u_regs[4], regs->u_regs[5], regs->u_regs[6],
           regs->u_regs[7]);
    printk("o0: %016lx o1: %016lx o2: %016lx o3: %016lx\n",
           regs->u_regs[8], regs->u_regs[9], regs->u_regs[10],
           regs->u_regs[11]);
    printk("o4: %016lx o5: %016lx sp: %016lx ret_pc: %016lx\n",
           regs->u_regs[12], regs->u_regs[13], regs->u_regs[14],
           regs->u_regs[15]);
    printk("RPC: <%pS>\n", (void *) regs->u_regs[15]);
    show_regwindow(regs);
    show_stack(current, (unsigned long *) regs->u_regs[UREG_FP]);
}

union global_cpu_snapshot global_cpu_snapshot[NR_CPUS];
static DEFINE_SPINLOCK(global_cpu_snapshot_lock);

static void __global_reg_self(struct thread_info *tp, struct pt_regs *regs,
                  int this_cpu)
{
    struct global_reg_snapshot *rp;

    flushw_all();

    rp = &global_cpu_snapshot[this_cpu].reg;

    rp->tstate = regs->tstate;
    rp->tpc = regs->tpc;
    rp->tnpc = regs->tnpc;
    rp->o7 = regs->u_regs[UREG_I7];

    if (regs->tstate & TSTATE_PRIV) {
        struct reg_window *rw;

        rw = (struct reg_window *)
            (regs->u_regs[UREG_FP] + STACK_BIAS);
        if (kstack_valid(tp, (unsigned long) rw)) {
            rp->i7 = rw->ins[7];
            rw = (struct reg_window *)
                (rw->ins[6] + STACK_BIAS);
            if (kstack_valid(tp, (unsigned long) rw))
                rp->rpc = rw->ins[7];
        }
    } else {
        rp->i7 = 0;
        rp->rpc = 0;
    }
    rp->thread = tp;
}

/* In order to avoid hangs we do not try to synchronize with the
 * global register dump client cpus.  The last store they make is to
 * the thread pointer, so do a short poll waiting for that to become
 * non-NULL.
 */
static void __global_reg_poll(struct global_reg_snapshot *gp)
{
    int limit = 0;

    while (!gp->thread && ++limit < 100) {
        barrier();
        udelay(1);
    }
}

void arch_trigger_all_cpu_backtrace(void)
{
    struct thread_info *tp = current_thread_info();
    struct pt_regs *regs = get_irq_regs();
    unsigned long flags;
    int this_cpu, cpu;

    if (!regs)
        regs = tp->kregs;

    spin_lock_irqsave(&global_cpu_snapshot_lock, flags);

    memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));

    this_cpu = raw_smp_processor_id();

    __global_reg_self(tp, regs, this_cpu);

    smp_fetch_global_regs();

    for_each_online_cpu(cpu) {
        struct global_reg_snapshot *gp = &global_cpu_snapshot[cpu].reg;

        __global_reg_poll(gp);

        tp = gp->thread;
        printk("%c CPU[%3d]: TSTATE[%016lx] TPC[%016lx] TNPC[%016lx] TASK[%s:%d]\n",
               (cpu == this_cpu ? '*' : ' '), cpu,
               gp->tstate, gp->tpc, gp->tnpc,
               ((tp && tp->task) ? tp->task->comm : "NULL"),
               ((tp && tp->task) ? tp->task->pid : -1));

        if (gp->tstate & TSTATE_PRIV) {
            printk("             TPC[%pS] O7[%pS] I7[%pS] RPC[%pS]\n",
                   (void *) gp->tpc,
                   (void *) gp->o7,
                   (void *) gp->i7,
                   (void *) gp->rpc);
        } else {
            printk("             TPC[%lx] O7[%lx] I7[%lx] RPC[%lx]\n",
                   gp->tpc, gp->o7, gp->i7, gp->rpc);
        }
    }

    memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));

    spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
}

#ifdef CONFIG_MAGIC_SYSRQ

static void sysrq_handle_globreg(int key)
{
    arch_trigger_all_cpu_backtrace();
}

static struct sysrq_key_op sparc_globalreg_op = {
    .handler    = sysrq_handle_globreg,
    .help_msg   = "global-regs(Y)",
    .action_msg = "Show Global CPU Regs",
};

static void __global_pmu_self(int this_cpu)
{
    struct global_pmu_snapshot *pp;
    int i, num;

    pp = &global_cpu_snapshot[this_cpu].pmu;

    num = 1;
    if (tlb_type == hypervisor &&
        sun4v_chip_type >= SUN4V_CHIP_NIAGARA4)
        num = 4;

    for (i = 0; i < num; i++) {
        pp->pcr[i] = pcr_ops->read_pcr(i);
        pp->pic[i] = pcr_ops->read_pic(i);
    }
}

static void __global_pmu_poll(struct global_pmu_snapshot *pp)
{
    int limit = 0;

    while (!pp->pcr[0] && ++limit < 100) {
        barrier();
        udelay(1);
    }
}

static void pmu_snapshot_all_cpus(void)
{
    unsigned long flags;
    int this_cpu, cpu;

    spin_lock_irqsave(&global_cpu_snapshot_lock, flags);

    memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));

    this_cpu = raw_smp_processor_id();

    __global_pmu_self(this_cpu);

    smp_fetch_global_pmu();

    for_each_online_cpu(cpu) {
        struct global_pmu_snapshot *pp = &global_cpu_snapshot[cpu].pmu;

        __global_pmu_poll(pp);

        printk("%c CPU[%3d]: PCR[%08lx:%08lx:%08lx:%08lx] PIC[%08lx:%08lx:%08lx:%08lx]\n",
               (cpu == this_cpu ? '*' : ' '), cpu,
               pp->pcr[0], pp->pcr[1], pp->pcr[2], pp->pcr[3],
               pp->pic[0], pp->pic[1], pp->pic[2], pp->pic[3]);
    }

    memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot));

    spin_unlock_irqrestore(&global_cpu_snapshot_lock, flags);
}

static void sysrq_handle_globpmu(int key)
{
    pmu_snapshot_all_cpus();
}

static struct sysrq_key_op sparc_globalpmu_op = {
    .handler    = sysrq_handle_globpmu,
    .help_msg   = "global-pmu(X)",
    .action_msg = "Show Global PMU Regs",
};

static int __init sparc_sysrq_init(void)
{
    int ret = register_sysrq_key('y', &sparc_globalreg_op);

    if (!ret)
        ret = register_sysrq_key('x', &sparc_globalpmu_op);
    return ret;
}

core_initcall(sparc_sysrq_init);

#endif

unsigned long thread_saved_pc(struct task_struct *tsk)
{
    struct thread_info *ti = task_thread_info(tsk);
    unsigned long ret = 0xdeadbeefUL;
    
    if (ti && ti->ksp) {
        unsigned long *sp;
        sp = (unsigned long *)(ti->ksp + STACK_BIAS);
        if (((unsigned long)sp & (sizeof(long) - 1)) == 0UL &&
            sp[14]) {
            unsigned long *fp;
            fp = (unsigned long *)(sp[14] + STACK_BIAS);
            if (((unsigned long)fp & (sizeof(long) - 1)) == 0UL)
                ret = fp[15];
        }
    }
    return ret;
}

/* Free current thread data structures etc.. */
void exit_thread(void)
{
    struct thread_info *t = current_thread_info();

    if (t->utraps) {
        if (t->utraps[0] < 2)
            kfree (t->utraps);
        else
            t->utraps[0]--;
    }
}

void flush_thread(void)
{
    struct thread_info *t = current_thread_info();
    struct mm_struct *mm;

    mm = t->task->mm;
    if (mm)
        tsb_context_switch(mm);

    set_thread_wsaved(0);

    /* Clear FPU register state. */
    t->fpsaved[0] = 0;
}

/* It's a bit more tricky when 64-bit tasks are involved... */
static unsigned long clone_stackframe(unsigned long csp, unsigned long psp)
{
    bool stack_64bit = test_thread_64bit_stack(psp);
    unsigned long fp, distance, rval;

    if (stack_64bit) {
        csp += STACK_BIAS;
        psp += STACK_BIAS;
        __get_user(fp, &(((struct reg_window __user *)psp)->ins[6]));
        fp += STACK_BIAS;
        if (test_thread_flag(TIF_32BIT))
            fp &= 0xffffffff;
    } else
        __get_user(fp, &(((struct reg_window32 __user *)psp)->ins[6]));

    /* Now align the stack as this is mandatory in the Sparc ABI
     * due to how register windows work.  This hides the
     * restriction from thread libraries etc.
     */
    csp &= ~15UL;

    distance = fp - psp;
    rval = (csp - distance);
    if (copy_in_user((void __user *) rval, (void __user *) psp, distance))
        rval = 0;
    else if (!stack_64bit) {
        if (put_user(((u32)csp),
                 &(((struct reg_window32 __user *)rval)->ins[6])))
            rval = 0;
    } else {
        if (put_user(((u64)csp - STACK_BIAS),
                 &(((struct reg_window __user *)rval)->ins[6])))
            rval = 0;
        else
            rval = rval - STACK_BIAS;
    }

    return rval;
}

/* Standard stuff. */
static inline void shift_window_buffer(int first_win, int last_win,
                       struct thread_info *t)
{
    int i;

    for (i = first_win; i < last_win; i++) {
        t->rwbuf_stkptrs[i] = t->rwbuf_stkptrs[i+1];
        memcpy(&t->reg_window[i], &t->reg_window[i+1],
               sizeof(struct reg_window));
    }
}

void synchronize_user_stack(void)
{
    struct thread_info *t = current_thread_info();
    unsigned long window;

    flush_user_windows();
    if ((window = get_thread_wsaved()) != 0) {
        window -= 1;
        do {
            struct reg_window *rwin = &t->reg_window[window];
            int winsize = sizeof(struct reg_window);
            unsigned long sp;

            sp = t->rwbuf_stkptrs[window];

            if (test_thread_64bit_stack(sp))
                sp += STACK_BIAS;
            else
                winsize = sizeof(struct reg_window32);

            if (!copy_to_user((char __user *)sp, rwin, winsize)) {
                shift_window_buffer(window, get_thread_wsaved() - 1, t);
                set_thread_wsaved(get_thread_wsaved() - 1);
            }
        } while (window--);
    }
}

static void stack_unaligned(unsigned long sp)
{
    siginfo_t info;

    info.si_signo = SIGBUS;
    info.si_errno = 0;
    info.si_code = BUS_ADRALN;
    info.si_addr = (void __user *) sp;
    info.si_trapno = 0;
    force_sig_info(SIGBUS, &info, current);
}

void fault_in_user_windows(void)
{
    struct thread_info *t = current_thread_info();
    unsigned long window;

    flush_user_windows();
    window = get_thread_wsaved();

    if (likely(window != 0)) {
        window -= 1;
        do {
            struct reg_window *rwin = &t->reg_window[window];
            int winsize = sizeof(struct reg_window);
            unsigned long sp;

            sp = t->rwbuf_stkptrs[window];

            if (test_thread_64bit_stack(sp))
                sp += STACK_BIAS;
            else
                winsize = sizeof(struct reg_window32);

            if (unlikely(sp & 0x7UL))
                stack_unaligned(sp);

            if (unlikely(copy_to_user((char __user *)sp,
                          rwin, winsize)))
                goto barf;
        } while (window--);
    }
    set_thread_wsaved(0);
    return;

barf:
    set_thread_wsaved(window + 1);
    do_exit(SIGILL);
}

asmlinkage long sparc_do_fork(unsigned long clone_flags,
                  unsigned long stack_start,
                  struct pt_regs *regs,
                  unsigned long stack_size)
{
    int __user *parent_tid_ptr, *child_tid_ptr;
    unsigned long orig_i1 = regs->u_regs[UREG_I1];
    long ret;

#ifdef CONFIG_COMPAT
    if (test_thread_flag(TIF_32BIT)) {
        parent_tid_ptr = compat_ptr(regs->u_regs[UREG_I2]);
        child_tid_ptr = compat_ptr(regs->u_regs[UREG_I4]);
    } else
#endif
    {
        parent_tid_ptr = (int __user *) regs->u_regs[UREG_I2];
        child_tid_ptr = (int __user *) regs->u_regs[UREG_I4];
    }

    ret = do_fork(clone_flags, stack_start,
              regs, stack_size,
              parent_tid_ptr, child_tid_ptr);

    /* If we get an error and potentially restart the system
     * call, we're screwed because copy_thread() clobbered
     * the parent's %o1.  So detect that case and restore it
     * here.
     */
    if ((unsigned long)ret >= -ERESTART_RESTARTBLOCK)
        regs->u_regs[UREG_I1] = orig_i1;

    return ret;
}

/* Copy a Sparc thread.  The fork() return value conventions
 * under SunOS are nothing short of bletcherous:
 * Parent -->  %o0 == childs  pid, %o1 == 0
 * Child  -->  %o0 == parents pid, %o1 == 1
 */
int copy_thread(unsigned long clone_flags, unsigned long sp,
        unsigned long unused,
        struct task_struct *p, struct pt_regs *regs)
{
    struct thread_info *t = task_thread_info(p);
    struct sparc_stackf *parent_sf;
    unsigned long child_stack_sz;
    char *child_trap_frame;
    int kernel_thread;

    kernel_thread = (regs->tstate & TSTATE_PRIV) ? 1 : 0;
    parent_sf = ((struct sparc_stackf *) regs) - 1;

    /* Calculate offset to stack_frame & pt_regs */
    child_stack_sz = ((STACKFRAME_SZ + TRACEREG_SZ) +
              (kernel_thread ? STACKFRAME_SZ : 0));
    child_trap_frame = (task_stack_page(p) +
                (THREAD_SIZE - child_stack_sz));
    memcpy(child_trap_frame, parent_sf, child_stack_sz);

    t->flags = (t->flags & ~((0xffUL << TI_FLAG_CWP_SHIFT) |
                 (0xffUL << TI_FLAG_CURRENT_DS_SHIFT))) |
        (((regs->tstate + 1) & TSTATE_CWP) << TI_FLAG_CWP_SHIFT);
    t->new_child = 1;
    t->ksp = ((unsigned long) child_trap_frame) - STACK_BIAS;
    t->kregs = (struct pt_regs *) (child_trap_frame +
                       sizeof(struct sparc_stackf));
    t->fpsaved[0] = 0;

    if (kernel_thread) {
        struct sparc_stackf *child_sf = (struct sparc_stackf *)
            (child_trap_frame + (STACKFRAME_SZ + TRACEREG_SZ));

        /* Zero terminate the stack backtrace.  */
        child_sf->fp = NULL;
        t->kregs->u_regs[UREG_FP] =
          ((unsigned long) child_sf) - STACK_BIAS;

        t->flags |= ((long)ASI_P << TI_FLAG_CURRENT_DS_SHIFT);
        t->kregs->u_regs[UREG_G6] = (unsigned long) t;
        t->kregs->u_regs[UREG_G4] = (unsigned long) t->task;
    } else {
        if (t->flags & _TIF_32BIT) {
            sp &= 0x00000000ffffffffUL;
            regs->u_regs[UREG_FP] &= 0x00000000ffffffffUL;
        }
        t->kregs->u_regs[UREG_FP] = sp;
        t->flags |= ((long)ASI_AIUS << TI_FLAG_CURRENT_DS_SHIFT);
        if (sp != regs->u_regs[UREG_FP]) {
            unsigned long csp;

            csp = clone_stackframe(sp, regs->u_regs[UREG_FP]);
            if (!csp)
                return -EFAULT;
            t->kregs->u_regs[UREG_FP] = csp;
        }
        if (t->utraps)
            t->utraps[0]++;
    }

    /* Set the return value for the child. */
    t->kregs->u_regs[UREG_I0] = current->pid;
    t->kregs->u_regs[UREG_I1] = 1;

    /* Set the second return value for the parent. */
    regs->u_regs[UREG_I1] = 0;

    if (clone_flags & CLONE_SETTLS)
        t->kregs->u_regs[UREG_G7] = regs->u_regs[UREG_I3];

    return 0;
}

/*
 * This is the mechanism for creating a new kernel thread.
 *
 * NOTE! Only a kernel-only process(ie the swapper or direct descendants
 * who haven't done an "execve()") should use this: it will work within
 * a system call from a "real" process, but the process memory space will
 * not be freed until both the parent and the child have exited.
 */
pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
    long retval;

    /* If the parent runs before fn(arg) is called by the child,
     * the input registers of this function can be clobbered.
     * So we stash 'fn' and 'arg' into global registers which
     * will not be modified by the parent.
     */
    __asm__ __volatile__("mov %4, %%g2\n\t"    /* Save FN into global */
                 "mov %5, %%g3\n\t"    /* Save ARG into global */
                 "mov %1, %%g1\n\t"    /* Clone syscall nr. */
                 "mov %2, %%o0\n\t"    /* Clone flags. */
                 "mov 0, %%o1\n\t"     /* usp arg == 0 */
                 "t 0x6d\n\t"      /* Linux/Sparc clone(). */
                 "brz,a,pn %%o1, 1f\n\t" /* Parent, just return. */
                 " mov %%o0, %0\n\t"
                 "jmpl %%g2, %%o7\n\t"   /* Call the function. */
                 " mov %%g3, %%o0\n\t"   /* Set arg in delay. */
                 "mov %3, %%g1\n\t"
                 "t 0x6d\n\t"      /* Linux/Sparc exit(). */
                 /* Notreached by child. */
                 "1:" :
                 "=r" (retval) :
                 "i" (__NR_clone), "r" (flags | CLONE_VM | CLONE_UNTRACED),
                 "i" (__NR_exit),  "r" (fn), "r" (arg) :
                 "g1", "g2", "g3", "o0", "o1", "memory", "cc");
    return retval;
}
EXPORT_SYMBOL(kernel_thread);

typedef struct {
    union {
        unsigned int    pr_regs[32];
        unsigned long   pr_dregs[16];
    } pr_fr;
    unsigned int __unused;
    unsigned int    pr_fsr;
    unsigned char   pr_qcnt;
    unsigned char   pr_q_entrysize;
    unsigned char   pr_en;
    unsigned int    pr_q[64];
} elf_fpregset_t32;

/*
 * fill in the fpu structure for a core dump.
 */
int dump_fpu (struct pt_regs * regs, elf_fpregset_t * fpregs)
{
    unsigned long *kfpregs = current_thread_info()->fpregs;
    unsigned long fprs = current_thread_info()->fpsaved[0];

    if (test_thread_flag(TIF_32BIT)) {
        elf_fpregset_t32 *fpregs32 = (elf_fpregset_t32 *)fpregs;

        if (fprs & FPRS_DL)
            memcpy(&fpregs32->pr_fr.pr_regs[0], kfpregs,
                   sizeof(unsigned int) * 32);
        else
            memset(&fpregs32->pr_fr.pr_regs[0], 0,
                   sizeof(unsigned int) * 32);
        fpregs32->pr_qcnt = 0;
        fpregs32->pr_q_entrysize = 8;
        memset(&fpregs32->pr_q[0], 0,
               (sizeof(unsigned int) * 64));
        if (fprs & FPRS_FEF) {
            fpregs32->pr_fsr = (unsigned int) current_thread_info()->xfsr[0];
            fpregs32->pr_en = 1;
        } else {
            fpregs32->pr_fsr = 0;
            fpregs32->pr_en = 0;
        }
    } else {
        if(fprs & FPRS_DL)
            memcpy(&fpregs->pr_regs[0], kfpregs,
                   sizeof(unsigned int) * 32);
        else
            memset(&fpregs->pr_regs[0], 0,
                   sizeof(unsigned int) * 32);
        if(fprs & FPRS_DU)
            memcpy(&fpregs->pr_regs[16], kfpregs+16,
                   sizeof(unsigned int) * 32);
        else
            memset(&fpregs->pr_regs[16], 0,
                   sizeof(unsigned int) * 32);
        if(fprs & FPRS_FEF) {
            fpregs->pr_fsr = current_thread_info()->xfsr[0];
            fpregs->pr_gsr = current_thread_info()->gsr[0];
        } else {
            fpregs->pr_fsr = fpregs->pr_gsr = 0;
        }
        fpregs->pr_fprs = fprs;
    }
    return 1;
}
EXPORT_SYMBOL(dump_fpu);

/*
 * sparc_execve() executes a new program after the asm stub has set
 * things up for us.  This should basically do what I want it to.
 */
asmlinkage int sparc_execve(struct pt_regs *regs)
{
    int error, base = 0;
    struct filename *filename;

    /* User register window flush is done by entry.S */

    /* Check for indirect call. */
    if (regs->u_regs[UREG_G1] == 0)
        base = 1;

    filename = getname((char __user *)regs->u_regs[base + UREG_I0]);
    error = PTR_ERR(filename);
    if (IS_ERR(filename))
        goto out;
    error = do_execve(filename->name,
              (const char __user *const __user *)
              regs->u_regs[base + UREG_I1],
              (const char __user *const __user *)
              regs->u_regs[base + UREG_I2], regs);
    putname(filename);
    if (!error) {
        fprs_write(0);
        current_thread_info()->xfsr[0] = 0;
        current_thread_info()->fpsaved[0] = 0;
        regs->tstate &= ~TSTATE_PEF;
    }
out:
    return error;
}

unsigned long get_wchan(struct task_struct *task)
{
    unsigned long pc, fp, bias = 0;
    struct thread_info *tp;
    struct reg_window *rw;
        unsigned long ret = 0;
    int count = 0; 

    if (!task || task == current ||
            task->state == TASK_RUNNING)
        goto out;

    tp = task_thread_info(task);
    bias = STACK_BIAS;
    fp = task_thread_info(task)->ksp + bias;

    do {
        if (!kstack_valid(tp, fp))
            break;
        rw = (struct reg_window *) fp;
        pc = rw->ins[7];
        if (!in_sched_functions(pc)) {
            ret = pc;
            goto out;
        }
        fp = rw->ins[6] + bias;
    } while (++count < 16);

out:
    return ret;
}