process.c

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/*
 *  Derived from "arch/i386/kernel/process.c"
 *    Copyright (C) 1995  Linus Torvalds
 *
 *  Updated and modified by Cort Dougan ([email protected]) and
 *  Paul Mackerras ([email protected])
 *
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas ([email protected])
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/stddef.h>
#include <linux/unistd.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/init.h>
#include <linux/prctl.h>
#include <linux/init_task.h>
#include <linux/export.h>
#include <linux/kallsyms.h>
#include <linux/mqueue.h>
#include <linux/hardirq.h>
#include <linux/utsname.h>
#include <linux/ftrace.h>
#include <linux/kernel_stat.h>
#include <linux/personality.h>
#include <linux/random.h>
#include <linux/hw_breakpoint.h>

#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/mmu.h>
#include <asm/prom.h>
#include <asm/machdep.h>
#include <asm/time.h>
#include <asm/runlatch.h>
#include <asm/syscalls.h>
#include <asm/switch_to.h>
#include <asm/debug.h>
#ifdef CONFIG_PPC64
#include <asm/firmware.h>
#endif
#include <linux/kprobes.h>
#include <linux/kdebug.h>

extern unsigned long _get_SP(void);

#ifndef CONFIG_SMP
struct task_struct *last_task_used_math = NULL;
struct task_struct *last_task_used_altivec = NULL;
struct task_struct *last_task_used_vsx = NULL;
struct task_struct *last_task_used_spe = NULL;
#endif

/*
 * Make sure the floating-point register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_fp_to_thread(struct task_struct *tsk)
{
    if (tsk->thread.regs) {
        /*
         * We need to disable preemption here because if we didn't,
         * another process could get scheduled after the regs->msr
         * test but before we have finished saving the FP registers
         * to the thread_struct.  That process could take over the
         * FPU, and then when we get scheduled again we would store
         * bogus values for the remaining FP registers.
         */
        preempt_disable();
        if (tsk->thread.regs->msr & MSR_FP) {
#ifdef CONFIG_SMP
            /*
             * This should only ever be called for current or
             * for a stopped child process.  Since we save away
             * the FP register state on context switch on SMP,
             * there is something wrong if a stopped child appears
             * to still have its FP state in the CPU registers.
             */
            BUG_ON(tsk != current);
#endif
            giveup_fpu(tsk);
        }
        preempt_enable();
    }
}
EXPORT_SYMBOL_GPL(flush_fp_to_thread);

void enable_kernel_fp(void)
{
    WARN_ON(preemptible());

#ifdef CONFIG_SMP
    if (current->thread.regs && (current->thread.regs->msr & MSR_FP))
        giveup_fpu(current);
    else
        giveup_fpu(NULL);   /* just enables FP for kernel */
#else
    giveup_fpu(last_task_used_math);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_fp);

#ifdef CONFIG_ALTIVEC
void enable_kernel_altivec(void)
{
    WARN_ON(preemptible());

#ifdef CONFIG_SMP
    if (current->thread.regs && (current->thread.regs->msr & MSR_VEC))
        giveup_altivec(current);
    else
        giveup_altivec_notask();
#else
    giveup_altivec(last_task_used_altivec);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_altivec);

/*
 * Make sure the VMX/Altivec register state in the
 * the thread_struct is up to date for task tsk.
 */
void flush_altivec_to_thread(struct task_struct *tsk)
{
    if (tsk->thread.regs) {
        preempt_disable();
        if (tsk->thread.regs->msr & MSR_VEC) {
#ifdef CONFIG_SMP
            BUG_ON(tsk != current);
#endif
            giveup_altivec(tsk);
        }
        preempt_enable();
    }
}
EXPORT_SYMBOL_GPL(flush_altivec_to_thread);
#endif /* CONFIG_ALTIVEC */

#ifdef CONFIG_VSX
#if 0
/* not currently used, but some crazy RAID module might want to later */
void enable_kernel_vsx(void)
{
    WARN_ON(preemptible());

#ifdef CONFIG_SMP
    if (current->thread.regs && (current->thread.regs->msr & MSR_VSX))
        giveup_vsx(current);
    else
        giveup_vsx(NULL);   /* just enable vsx for kernel - force */
#else
    giveup_vsx(last_task_used_vsx);
#endif /* CONFIG_SMP */
}
EXPORT_SYMBOL(enable_kernel_vsx);
#endif

void giveup_vsx(struct task_struct *tsk)
{
    giveup_fpu(tsk);
    giveup_altivec(tsk);
    __giveup_vsx(tsk);
}

void flush_vsx_to_thread(struct task_struct *tsk)
{
    if (tsk->thread.regs) {
        preempt_disable();
        if (tsk->thread.regs->msr & MSR_VSX) {
#ifdef CONFIG_SMP
            BUG_ON(tsk != current);
#endif
            giveup_vsx(tsk);
        }
        preempt_enable();
    }
}
EXPORT_SYMBOL_GPL(flush_vsx_to_thread);
#endif /* CONFIG_VSX */

#ifdef CONFIG_SPE

void enable_kernel_spe(void)
{
    WARN_ON(preemptible());

#ifdef CONFIG_SMP
    if (current->thread.regs && (current->thread.regs->msr & MSR_SPE))
        giveup_spe(current);
    else
        giveup_spe(NULL);   /* just enable SPE for kernel - force */
#else
    giveup_spe(last_task_used_spe);
#endif /* __SMP __ */
}
EXPORT_SYMBOL(enable_kernel_spe);

void flush_spe_to_thread(struct task_struct *tsk)
{
    if (tsk->thread.regs) {
        preempt_disable();
        if (tsk->thread.regs->msr & MSR_SPE) {
#ifdef CONFIG_SMP
            BUG_ON(tsk != current);
#endif
            tsk->thread.spefscr = mfspr(SPRN_SPEFSCR);
            giveup_spe(tsk);
        }
        preempt_enable();
    }
}
#endif /* CONFIG_SPE */

#ifndef CONFIG_SMP
/*
 * If we are doing lazy switching of CPU state (FP, altivec or SPE),
 * and the current task has some state, discard it.
 */
void discard_lazy_cpu_state(void)
{
    preempt_disable();
    if (last_task_used_math == current)
        last_task_used_math = NULL;
#ifdef CONFIG_ALTIVEC
    if (last_task_used_altivec == current)
        last_task_used_altivec = NULL;
#endif /* CONFIG_ALTIVEC */
#ifdef CONFIG_VSX
    if (last_task_used_vsx == current)
        last_task_used_vsx = NULL;
#endif /* CONFIG_VSX */
#ifdef CONFIG_SPE
    if (last_task_used_spe == current)
        last_task_used_spe = NULL;
#endif
    preempt_enable();
}
#endif /* CONFIG_SMP */

#ifdef CONFIG_PPC_ADV_DEBUG_REGS
void do_send_trap(struct pt_regs *regs, unsigned long address,
          unsigned long error_code, int signal_code, int breakpt)
{
    siginfo_t info;

    current->thread.trap_nr = signal_code;
    if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
            11, SIGSEGV) == NOTIFY_STOP)
        return;

    /* Deliver the signal to userspace */
    info.si_signo = SIGTRAP;
    info.si_errno = breakpt;    /* breakpoint or watchpoint id */
    info.si_code = signal_code;
    info.si_addr = (void __user *)address;
    force_sig_info(SIGTRAP, &info, current);
}
#else   /* !CONFIG_PPC_ADV_DEBUG_REGS */
void do_dabr(struct pt_regs *regs, unsigned long address,
            unsigned long error_code)
{
    siginfo_t info;

    current->thread.trap_nr = TRAP_HWBKPT;
    if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
            11, SIGSEGV) == NOTIFY_STOP)
        return;

    if (debugger_dabr_match(regs))
        return;

    /* Clear the DABR */
    set_dabr(0, 0);

    /* Deliver the signal to userspace */
    info.si_signo = SIGTRAP;
    info.si_errno = 0;
    info.si_code = TRAP_HWBKPT;
    info.si_addr = (void __user *)address;
    force_sig_info(SIGTRAP, &info, current);
}
#endif  /* CONFIG_PPC_ADV_DEBUG_REGS */

static DEFINE_PER_CPU(unsigned long, current_dabr);

#ifdef CONFIG_PPC_ADV_DEBUG_REGS
/*
 * Set the debug registers back to their default "safe" values.
 */
static void set_debug_reg_defaults(struct thread_struct *thread)
{
    thread->iac1 = thread->iac2 = 0;
#if CONFIG_PPC_ADV_DEBUG_IACS > 2
    thread->iac3 = thread->iac4 = 0;
#endif
    thread->dac1 = thread->dac2 = 0;
#if CONFIG_PPC_ADV_DEBUG_DVCS > 0
    thread->dvc1 = thread->dvc2 = 0;
#endif
    thread->dbcr0 = 0;
#ifdef CONFIG_BOOKE
    /*
     * Force User/Supervisor bits to b11 (user-only MSR[PR]=1)
     */
    thread->dbcr1 = DBCR1_IAC1US | DBCR1_IAC2US |   \
            DBCR1_IAC3US | DBCR1_IAC4US;
    /*
     * Force Data Address Compare User/Supervisor bits to be User-only
     * (0b11 MSR[PR]=1) and set all other bits in DBCR2 register to be 0.
     */
    thread->dbcr2 = DBCR2_DAC1US | DBCR2_DAC2US;
#else
    thread->dbcr1 = 0;
#endif
}

static void prime_debug_regs(struct thread_struct *thread)
{
    mtspr(SPRN_IAC1, thread->iac1);
    mtspr(SPRN_IAC2, thread->iac2);
#if CONFIG_PPC_ADV_DEBUG_IACS > 2
    mtspr(SPRN_IAC3, thread->iac3);
    mtspr(SPRN_IAC4, thread->iac4);
#endif
    mtspr(SPRN_DAC1, thread->dac1);
    mtspr(SPRN_DAC2, thread->dac2);
#if CONFIG_PPC_ADV_DEBUG_DVCS > 0
    mtspr(SPRN_DVC1, thread->dvc1);
    mtspr(SPRN_DVC2, thread->dvc2);
#endif
    mtspr(SPRN_DBCR0, thread->dbcr0);
    mtspr(SPRN_DBCR1, thread->dbcr1);
#ifdef CONFIG_BOOKE
    mtspr(SPRN_DBCR2, thread->dbcr2);
#endif
}
/*
 * Unless neither the old or new thread are making use of the
 * debug registers, set the debug registers from the values
 * stored in the new thread.
 */
static void switch_booke_debug_regs(struct thread_struct *new_thread)
{
    if ((current->thread.dbcr0 & DBCR0_IDM)
        || (new_thread->dbcr0 & DBCR0_IDM))
            prime_debug_regs(new_thread);
}
#else   /* !CONFIG_PPC_ADV_DEBUG_REGS */
#ifndef CONFIG_HAVE_HW_BREAKPOINT
static void set_debug_reg_defaults(struct thread_struct *thread)
{
    if (thread->dabr) {
        thread->dabr = 0;
        thread->dabrx = 0;
        set_dabr(0, 0);
    }
}
#endif /* !CONFIG_HAVE_HW_BREAKPOINT */
#endif  /* CONFIG_PPC_ADV_DEBUG_REGS */

int set_dabr(unsigned long dabr, unsigned long dabrx)
{
    __get_cpu_var(current_dabr) = dabr;

    if (ppc_md.set_dabr)
        return ppc_md.set_dabr(dabr, dabrx);

    /* XXX should we have a CPU_FTR_HAS_DABR ? */
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
    mtspr(SPRN_DAC1, dabr);
#ifdef CONFIG_PPC_47x
    isync();
#endif
#elif defined(CONFIG_PPC_BOOK3S)
    mtspr(SPRN_DABR, dabr);
    mtspr(SPRN_DABRX, dabrx);
#endif
    return 0;
}

#ifdef CONFIG_PPC64
DEFINE_PER_CPU(struct cpu_usage, cpu_usage_array);
#endif

struct task_struct *__switch_to(struct task_struct *prev,
    struct task_struct *new)
{
    struct thread_struct *new_thread, *old_thread;
    unsigned long flags;
    struct task_struct *last;
#ifdef CONFIG_PPC_BOOK3S_64
    struct ppc64_tlb_batch *batch;
#endif

#ifdef CONFIG_SMP
    /* avoid complexity of lazy save/restore of fpu
     * by just saving it every time we switch out if
     * this task used the fpu during the last quantum.
     *
     * If it tries to use the fpu again, it'll trap and
     * reload its fp regs.  So we don't have to do a restore
     * every switch, just a save.
     *  -- Cort
     */
    if (prev->thread.regs && (prev->thread.regs->msr & MSR_FP))
        giveup_fpu(prev);
#ifdef CONFIG_ALTIVEC
    /*
     * If the previous thread used altivec in the last quantum
     * (thus changing altivec regs) then save them.
     * We used to check the VRSAVE register but not all apps
     * set it, so we don't rely on it now (and in fact we need
     * to save & restore VSCR even if VRSAVE == 0).  -- paulus
     *
     * On SMP we always save/restore altivec regs just to avoid the
     * complexity of changing processors.
     *  -- Cort
     */
    if (prev->thread.regs && (prev->thread.regs->msr & MSR_VEC))
        giveup_altivec(prev);
#endif /* CONFIG_ALTIVEC */
#ifdef CONFIG_VSX
    if (prev->thread.regs && (prev->thread.regs->msr & MSR_VSX))
        /* VMX and FPU registers are already save here */
        __giveup_vsx(prev);
#endif /* CONFIG_VSX */
#ifdef CONFIG_SPE
    /*
     * If the previous thread used spe in the last quantum
     * (thus changing spe regs) then save them.
     *
     * On SMP we always save/restore spe regs just to avoid the
     * complexity of changing processors.
     */
    if ((prev->thread.regs && (prev->thread.regs->msr & MSR_SPE)))
        giveup_spe(prev);
#endif /* CONFIG_SPE */

#else  /* CONFIG_SMP */
#ifdef CONFIG_ALTIVEC
    /* Avoid the trap.  On smp this this never happens since
     * we don't set last_task_used_altivec -- Cort
     */
    if (new->thread.regs && last_task_used_altivec == new)
        new->thread.regs->msr |= MSR_VEC;
#endif /* CONFIG_ALTIVEC */
#ifdef CONFIG_VSX
    if (new->thread.regs && last_task_used_vsx == new)
        new->thread.regs->msr |= MSR_VSX;
#endif /* CONFIG_VSX */
#ifdef CONFIG_SPE
    /* Avoid the trap.  On smp this this never happens since
     * we don't set last_task_used_spe
     */
    if (new->thread.regs && last_task_used_spe == new)
        new->thread.regs->msr |= MSR_SPE;
#endif /* CONFIG_SPE */

#endif /* CONFIG_SMP */

#ifdef CONFIG_PPC_ADV_DEBUG_REGS
    switch_booke_debug_regs(&new->thread);
#else
/*
 * For PPC_BOOK3S_64, we use the hw-breakpoint interfaces that would
 * schedule DABR
 */
#ifndef CONFIG_HAVE_HW_BREAKPOINT
    if (unlikely(__get_cpu_var(current_dabr) != new->thread.dabr))
        set_dabr(new->thread.dabr, new->thread.dabrx);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
#endif


    new_thread = &new->thread;
    old_thread = &current->thread;

#ifdef CONFIG_PPC64
    /*
     * Collect processor utilization data per process
     */
    if (firmware_has_feature(FW_FEATURE_SPLPAR)) {
        struct cpu_usage *cu = &__get_cpu_var(cpu_usage_array);
        long unsigned start_tb, current_tb;
        start_tb = old_thread->start_tb;
        cu->current_tb = current_tb = mfspr(SPRN_PURR);
        old_thread->accum_tb += (current_tb - start_tb);
        new_thread->start_tb = current_tb;
    }
#endif /* CONFIG_PPC64 */

#ifdef CONFIG_PPC_BOOK3S_64
    batch = &__get_cpu_var(ppc64_tlb_batch);
    if (batch->active) {
        current_thread_info()->local_flags |= _TLF_LAZY_MMU;
        if (batch->index)
            __flush_tlb_pending(batch);
        batch->active = 0;
    }
#endif /* CONFIG_PPC_BOOK3S_64 */

    local_irq_save(flags);

    /*
     * We can't take a PMU exception inside _switch() since there is a
     * window where the kernel stack SLB and the kernel stack are out
     * of sync. Hard disable here.
     */
    hard_irq_disable();
    last = _switch(old_thread, new_thread);

#ifdef CONFIG_PPC_BOOK3S_64
    if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
        current_thread_info()->local_flags &= ~_TLF_LAZY_MMU;
        batch = &__get_cpu_var(ppc64_tlb_batch);
        batch->active = 1;
    }
#endif /* CONFIG_PPC_BOOK3S_64 */

    local_irq_restore(flags);

    return last;
}

static int instructions_to_print = 16;

static void show_instructions(struct pt_regs *regs)
{
    int i;
    unsigned long pc = regs->nip - (instructions_to_print * 3 / 4 *
            sizeof(int));

    printk("Instruction dump:");

    for (i = 0; i < instructions_to_print; i++) {
        int instr;

        if (!(i % 8))
            printk("\n");

#if !defined(CONFIG_BOOKE)
        /* If executing with the IMMU off, adjust pc rather
         * than print XXXXXXXX.
         */
        if (!(regs->msr & MSR_IR))
            pc = (unsigned long)phys_to_virt(pc);
#endif

        /* We use __get_user here *only* to avoid an OOPS on a
         * bad address because the pc *should* only be a
         * kernel address.
         */
        if (!__kernel_text_address(pc) ||
             __get_user(instr, (unsigned int __user *)pc)) {
            printk(KERN_CONT "XXXXXXXX ");
        } else {
            if (regs->nip == pc)
                printk(KERN_CONT "<%08x> ", instr);
            else
                printk(KERN_CONT "%08x ", instr);
        }

        pc += sizeof(int);
    }

    printk("\n");
}

static struct regbit {
    unsigned long bit;
    const char *name;
} msr_bits[] = {
#if defined(CONFIG_PPC64) && !defined(CONFIG_BOOKE)
    {MSR_SF,    "SF"},
    {MSR_HV,    "HV"},
#endif
    {MSR_VEC,   "VEC"},
    {MSR_VSX,   "VSX"},
#ifdef CONFIG_BOOKE
    {MSR_CE,    "CE"},
#endif
    {MSR_EE,    "EE"},
    {MSR_PR,    "PR"},
    {MSR_FP,    "FP"},
    {MSR_ME,    "ME"},
#ifdef CONFIG_BOOKE
    {MSR_DE,    "DE"},
#else
    {MSR_SE,    "SE"},
    {MSR_BE,    "BE"},
#endif
    {MSR_IR,    "IR"},
    {MSR_DR,    "DR"},
    {MSR_PMM,   "PMM"},
#ifndef CONFIG_BOOKE
    {MSR_RI,    "RI"},
    {MSR_LE,    "LE"},
#endif
    {0,     NULL}
};

static void printbits(unsigned long val, struct regbit *bits)
{
    const char *sep = "";

    printk("<");
    for (; bits->bit; ++bits)
        if (val & bits->bit) {
            printk("%s%s", sep, bits->name);
            sep = ",";
        }
    printk(">");
}

#ifdef CONFIG_PPC64
#define REG     "%016lx"
#define REGS_PER_LINE   4
#define LAST_VOLATILE   13
#else
#define REG     "%08lx"
#define REGS_PER_LINE   8
#define LAST_VOLATILE   12
#endif

void show_regs(struct pt_regs * regs)
{
    int i, trap;

    printk("NIP: "REG" LR: "REG" CTR: "REG"\n",
           regs->nip, regs->link, regs->ctr);
    printk("REGS: %p TRAP: %04lx   %s  (%s)\n",
           regs, regs->trap, print_tainted(), init_utsname()->release);
    printk("MSR: "REG" ", regs->msr);
    printbits(regs->msr, msr_bits);
    printk("  CR: %08lx  XER: %08lx\n", regs->ccr, regs->xer);
#ifdef CONFIG_PPC64
    printk("SOFTE: %ld\n", regs->softe);
#endif
    trap = TRAP(regs);
    if ((regs->trap != 0xc00) && cpu_has_feature(CPU_FTR_CFAR))
        printk("CFAR: "REG"\n", regs->orig_gpr3);
    if (trap == 0x300 || trap == 0x600)
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
        printk("DEAR: "REG", ESR: "REG"\n", regs->dar, regs->dsisr);
#else
        printk("DAR: "REG", DSISR: %08lx\n", regs->dar, regs->dsisr);
#endif
    printk("TASK = %p[%d] '%s' THREAD: %p",
           current, task_pid_nr(current), current->comm, task_thread_info(current));

#ifdef CONFIG_SMP
    printk(" CPU: %d", raw_smp_processor_id());
#endif /* CONFIG_SMP */

    for (i = 0;  i < 32;  i++) {
        if ((i % REGS_PER_LINE) == 0)
            printk("\nGPR%02d: ", i);
        printk(REG " ", regs->gpr[i]);
        if (i == LAST_VOLATILE && !FULL_REGS(regs))
            break;
    }
    printk("\n");
#ifdef CONFIG_KALLSYMS
    /*
     * Lookup NIP late so we have the best change of getting the
     * above info out without failing
     */
    printk("NIP ["REG"] %pS\n", regs->nip, (void *)regs->nip);
    printk("LR ["REG"] %pS\n", regs->link, (void *)regs->link);
#endif
    show_stack(current, (unsigned long *) regs->gpr[1]);
    if (!user_mode(regs))
        show_instructions(regs);
}

void exit_thread(void)
{
    discard_lazy_cpu_state();
}

void flush_thread(void)
{
    discard_lazy_cpu_state();

#ifdef CONFIG_HAVE_HW_BREAKPOINT
    flush_ptrace_hw_breakpoint(current);
#else /* CONFIG_HAVE_HW_BREAKPOINT */
    set_debug_reg_defaults(&current->thread);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
}

void
release_thread(struct task_struct *t)
{
}

/*
 * this gets called so that we can store coprocessor state into memory and
 * copy the current task into the new thread.
 */
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
    flush_fp_to_thread(src);
    flush_altivec_to_thread(src);
    flush_vsx_to_thread(src);
    flush_spe_to_thread(src);
#ifdef CONFIG_HAVE_HW_BREAKPOINT
    flush_ptrace_hw_breakpoint(src);
#endif /* CONFIG_HAVE_HW_BREAKPOINT */

    *dst = *src;
    return 0;
}

/*
 * Copy a thread..
 */
extern unsigned long dscr_default; /* defined in arch/powerpc/kernel/sysfs.c */

int copy_thread(unsigned long clone_flags, unsigned long usp,
        unsigned long arg, struct task_struct *p,
        struct pt_regs *regs)
{
    struct pt_regs *childregs, *kregs;
    extern void ret_from_fork(void);
    extern void ret_from_kernel_thread(void);
    void (*f)(void);
    unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;

    /* Copy registers */
    sp -= sizeof(struct pt_regs);
    childregs = (struct pt_regs *) sp;
    if (!regs) {
        /* for kernel thread, set `current' and stackptr in new task */
        memset(childregs, 0, sizeof(struct pt_regs));
        childregs->gpr[1] = sp + sizeof(struct pt_regs);
#ifdef CONFIG_PPC64
        childregs->gpr[14] = *(unsigned long *)usp;
        childregs->gpr[2] = ((unsigned long *)usp)[1],
        clear_tsk_thread_flag(p, TIF_32BIT);
#else
        childregs->gpr[14] = usp;   /* function */
        childregs->gpr[2] = (unsigned long) p;
#endif
        childregs->gpr[15] = arg;
        p->thread.regs = NULL;  /* no user register state */
        f = ret_from_kernel_thread;
    } else {
        CHECK_FULL_REGS(regs);
        *childregs = *regs;
        childregs->gpr[1] = usp;
        p->thread.regs = childregs;
        childregs->gpr[3] = 0;  /* Result from fork() */
        if (clone_flags & CLONE_SETTLS) {
#ifdef CONFIG_PPC64
            if (!is_32bit_task())
                childregs->gpr[13] = childregs->gpr[6];
            else
#endif
                childregs->gpr[2] = childregs->gpr[6];
        }

        f = ret_from_fork;
    }
    sp -= STACK_FRAME_OVERHEAD;

    /*
     * The way this works is that at some point in the future
     * some task will call _switch to switch to the new task.
     * That will pop off the stack frame created below and start
     * the new task running at ret_from_fork.  The new task will
     * do some house keeping and then return from the fork or clone
     * system call, using the stack frame created above.
     */
    sp -= sizeof(struct pt_regs);
    kregs = (struct pt_regs *) sp;
    sp -= STACK_FRAME_OVERHEAD;
    p->thread.ksp = sp;
    p->thread.ksp_limit = (unsigned long)task_stack_page(p) +
                _ALIGN_UP(sizeof(struct thread_info), 16);

#ifdef CONFIG_PPC_STD_MMU_64
    if (mmu_has_feature(MMU_FTR_SLB)) {
        unsigned long sp_vsid;
        unsigned long llp = mmu_psize_defs[mmu_linear_psize].sllp;

        if (mmu_has_feature(MMU_FTR_1T_SEGMENT))
            sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_1T)
                << SLB_VSID_SHIFT_1T;
        else
            sp_vsid = get_kernel_vsid(sp, MMU_SEGSIZE_256M)
                << SLB_VSID_SHIFT;
        sp_vsid |= SLB_VSID_KERNEL | llp;
        p->thread.ksp_vsid = sp_vsid;
    }
#endif /* CONFIG_PPC_STD_MMU_64 */
#ifdef CONFIG_PPC64 
    if (cpu_has_feature(CPU_FTR_DSCR)) {
        p->thread.dscr_inherit = current->thread.dscr_inherit;
        p->thread.dscr = current->thread.dscr;
    }
#endif
    /*
     * The PPC64 ABI makes use of a TOC to contain function 
     * pointers.  The function (ret_from_except) is actually a pointer
     * to the TOC entry.  The first entry is a pointer to the actual
     * function.
     */
#ifdef CONFIG_PPC64
    kregs->nip = *((unsigned long *)f);
#else
    kregs->nip = (unsigned long)f;
#endif
    return 0;
}

/*
 * Set up a thread for executing a new program
 */
void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
{
#ifdef CONFIG_PPC64
    unsigned long load_addr = regs->gpr[2]; /* saved by ELF_PLAT_INIT */
#endif

    /*
     * If we exec out of a kernel thread then thread.regs will not be
     * set.  Do it now.
     */
    if (!current->thread.regs) {
        struct pt_regs *regs = task_stack_page(current) + THREAD_SIZE;
        current->thread.regs = regs - 1;
    }

    memset(regs->gpr, 0, sizeof(regs->gpr));
    regs->ctr = 0;
    regs->link = 0;
    regs->xer = 0;
    regs->ccr = 0;
    regs->gpr[1] = sp;

    /*
     * We have just cleared all the nonvolatile GPRs, so make
     * FULL_REGS(regs) return true.  This is necessary to allow
     * ptrace to examine the thread immediately after exec.
     */
    regs->trap &= ~1UL;

#ifdef CONFIG_PPC32
    regs->mq = 0;
    regs->nip = start;
    regs->msr = MSR_USER;
#else
    if (!is_32bit_task()) {
        unsigned long entry, toc;

        /* start is a relocated pointer to the function descriptor for
         * the elf _start routine.  The first entry in the function
         * descriptor is the entry address of _start and the second
         * entry is the TOC value we need to use.
         */
        __get_user(entry, (unsigned long __user *)start);
        __get_user(toc, (unsigned long __user *)start+1);

        /* Check whether the e_entry function descriptor entries
         * need to be relocated before we can use them.
         */
        if (load_addr != 0) {
            entry += load_addr;
            toc   += load_addr;
        }
        regs->nip = entry;
        regs->gpr[2] = toc;
        regs->msr = MSR_USER64;
    } else {
        regs->nip = start;
        regs->gpr[2] = 0;
        regs->msr = MSR_USER32;
    }
#endif

    discard_lazy_cpu_state();
#ifdef CONFIG_VSX
    current->thread.used_vsr = 0;
#endif
    memset(current->thread.fpr, 0, sizeof(current->thread.fpr));
    current->thread.fpscr.val = 0;
#ifdef CONFIG_ALTIVEC
    memset(current->thread.vr, 0, sizeof(current->thread.vr));
    memset(&current->thread.vscr, 0, sizeof(current->thread.vscr));
    current->thread.vscr.u[3] = 0x00010000; /* Java mode disabled */
    current->thread.vrsave = 0;
    current->thread.used_vr = 0;
#endif /* CONFIG_ALTIVEC */
#ifdef CONFIG_SPE
    memset(current->thread.evr, 0, sizeof(current->thread.evr));
    current->thread.acc = 0;
    current->thread.spefscr = 0;
    current->thread.used_spe = 0;
#endif /* CONFIG_SPE */
}

#define PR_FP_ALL_EXCEPT (PR_FP_EXC_DIV | PR_FP_EXC_OVF | PR_FP_EXC_UND \
        | PR_FP_EXC_RES | PR_FP_EXC_INV)

int set_fpexc_mode(struct task_struct *tsk, unsigned int val)
{
    struct pt_regs *regs = tsk->thread.regs;

    /* This is a bit hairy.  If we are an SPE enabled  processor
     * (have embedded fp) we store the IEEE exception enable flags in
     * fpexc_mode.  fpexc_mode is also used for setting FP exception
     * mode (asyn, precise, disabled) for 'Classic' FP. */
    if (val & PR_FP_EXC_SW_ENABLE) {
#ifdef CONFIG_SPE
        if (cpu_has_feature(CPU_FTR_SPE)) {
            tsk->thread.fpexc_mode = val &
                (PR_FP_EXC_SW_ENABLE | PR_FP_ALL_EXCEPT);
            return 0;
        } else {
            return -EINVAL;
        }
#else
        return -EINVAL;
#endif
    }

    /* on a CONFIG_SPE this does not hurt us.  The bits that
     * __pack_fe01 use do not overlap with bits used for
     * PR_FP_EXC_SW_ENABLE.  Additionally, the MSR[FE0,FE1] bits
     * on CONFIG_SPE implementations are reserved so writing to
     * them does not change anything */
    if (val > PR_FP_EXC_PRECISE)
        return -EINVAL;
    tsk->thread.fpexc_mode = __pack_fe01(val);
    if (regs != NULL && (regs->msr & MSR_FP) != 0)
        regs->msr = (regs->msr & ~(MSR_FE0|MSR_FE1))
            | tsk->thread.fpexc_mode;
    return 0;
}

int get_fpexc_mode(struct task_struct *tsk, unsigned long adr)
{
    unsigned int val;

    if (tsk->thread.fpexc_mode & PR_FP_EXC_SW_ENABLE)
#ifdef CONFIG_SPE
        if (cpu_has_feature(CPU_FTR_SPE))
            val = tsk->thread.fpexc_mode;
        else
            return -EINVAL;
#else
        return -EINVAL;
#endif
    else
        val = __unpack_fe01(tsk->thread.fpexc_mode);
    return put_user(val, (unsigned int __user *) adr);
}

int set_endian(struct task_struct *tsk, unsigned int val)
{
    struct pt_regs *regs = tsk->thread.regs;

    if ((val == PR_ENDIAN_LITTLE && !cpu_has_feature(CPU_FTR_REAL_LE)) ||
        (val == PR_ENDIAN_PPC_LITTLE && !cpu_has_feature(CPU_FTR_PPC_LE)))
        return -EINVAL;

    if (regs == NULL)
        return -EINVAL;

    if (val == PR_ENDIAN_BIG)
        regs->msr &= ~MSR_LE;
    else if (val == PR_ENDIAN_LITTLE || val == PR_ENDIAN_PPC_LITTLE)
        regs->msr |= MSR_LE;
    else
        return -EINVAL;

    return 0;
}

int get_endian(struct task_struct *tsk, unsigned long adr)
{
    struct pt_regs *regs = tsk->thread.regs;
    unsigned int val;

    if (!cpu_has_feature(CPU_FTR_PPC_LE) &&
        !cpu_has_feature(CPU_FTR_REAL_LE))
        return -EINVAL;

    if (regs == NULL)
        return -EINVAL;

    if (regs->msr & MSR_LE) {
        if (cpu_has_feature(CPU_FTR_REAL_LE))
            val = PR_ENDIAN_LITTLE;
        else
            val = PR_ENDIAN_PPC_LITTLE;
    } else
        val = PR_ENDIAN_BIG;

    return put_user(val, (unsigned int __user *)adr);
}

int set_unalign_ctl(struct task_struct *tsk, unsigned int val)
{
    tsk->thread.align_ctl = val;
    return 0;
}

int get_unalign_ctl(struct task_struct *tsk, unsigned long adr)
{
    return put_user(tsk->thread.align_ctl, (unsigned int __user *)adr);
}

#define TRUNC_PTR(x)    ((typeof(x))(((unsigned long)(x)) & 0xffffffff))

int sys_clone(unsigned long clone_flags, unsigned long usp,
          int __user *parent_tidp, void __user *child_threadptr,
          int __user *child_tidp, int p6,
          struct pt_regs *regs)
{
    CHECK_FULL_REGS(regs);
    if (usp == 0)
        usp = regs->gpr[1]; /* stack pointer for child */
#ifdef CONFIG_PPC64
    if (is_32bit_task()) {
        parent_tidp = TRUNC_PTR(parent_tidp);
        child_tidp = TRUNC_PTR(child_tidp);
    }
#endif
    return do_fork(clone_flags, usp, regs, 0, parent_tidp, child_tidp);
}

int sys_fork(unsigned long p1, unsigned long p2, unsigned long p3,
         unsigned long p4, unsigned long p5, unsigned long p6,
         struct pt_regs *regs)
{
    CHECK_FULL_REGS(regs);
    return do_fork(SIGCHLD, regs->gpr[1], regs, 0, NULL, NULL);
}

int sys_vfork(unsigned long p1, unsigned long p2, unsigned long p3,
          unsigned long p4, unsigned long p5, unsigned long p6,
          struct pt_regs *regs)
{
    CHECK_FULL_REGS(regs);
    return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, regs->gpr[1],
            regs, 0, NULL, NULL);
}

void __ret_from_kernel_execve(struct pt_regs *normal)
__noreturn;

void ret_from_kernel_execve(struct pt_regs *normal)
{
    set_thread_flag(TIF_RESTOREALL);
    __ret_from_kernel_execve(normal);
}

static inline int valid_irq_stack(unsigned long sp, struct task_struct *p,
                  unsigned long nbytes)
{
    unsigned long stack_page;
    unsigned long cpu = task_cpu(p);

    /*
     * Avoid crashing if the stack has overflowed and corrupted
     * task_cpu(p), which is in the thread_info struct.
     */
    if (cpu < NR_CPUS && cpu_possible(cpu)) {
        stack_page = (unsigned long) hardirq_ctx[cpu];
        if (sp >= stack_page + sizeof(struct thread_struct)
            && sp <= stack_page + THREAD_SIZE - nbytes)
            return 1;

        stack_page = (unsigned long) softirq_ctx[cpu];
        if (sp >= stack_page + sizeof(struct thread_struct)
            && sp <= stack_page + THREAD_SIZE - nbytes)
            return 1;
    }
    return 0;
}

int validate_sp(unsigned long sp, struct task_struct *p,
               unsigned long nbytes)
{
    unsigned long stack_page = (unsigned long)task_stack_page(p);

    if (sp >= stack_page + sizeof(struct thread_struct)
        && sp <= stack_page + THREAD_SIZE - nbytes)
        return 1;

    return valid_irq_stack(sp, p, nbytes);
}

EXPORT_SYMBOL(validate_sp);

unsigned long get_wchan(struct task_struct *p)
{
    unsigned long ip, sp;
    int count = 0;

    if (!p || p == current || p->state == TASK_RUNNING)
        return 0;

    sp = p->thread.ksp;
    if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD))
        return 0;

    do {
        sp = *(unsigned long *)sp;
        if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD))
            return 0;
        if (count > 0) {
            ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE];
            if (!in_sched_functions(ip))
                return ip;
        }
    } while (count++ < 16);
    return 0;
}

static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;

void show_stack(struct task_struct *tsk, unsigned long *stack)
{
    unsigned long sp, ip, lr, newsp;
    int count = 0;
    int firstframe = 1;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    int curr_frame = current->curr_ret_stack;
    extern void return_to_handler(void);
    unsigned long rth = (unsigned long)return_to_handler;
    unsigned long mrth = -1;
#ifdef CONFIG_PPC64
    extern void mod_return_to_handler(void);
    rth = *(unsigned long *)rth;
    mrth = (unsigned long)mod_return_to_handler;
    mrth = *(unsigned long *)mrth;
#endif
#endif

    sp = (unsigned long) stack;
    if (tsk == NULL)
        tsk = current;
    if (sp == 0) {
        if (tsk == current)
            asm("mr %0,1" : "=r" (sp));
        else
            sp = tsk->thread.ksp;
    }

    lr = 0;
    printk("Call Trace:\n");
    do {
        if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))
            return;

        stack = (unsigned long *) sp;
        newsp = stack[0];
        ip = stack[STACK_FRAME_LR_SAVE];
        if (!firstframe || ip != lr) {
            printk("["REG"] ["REG"] %pS", sp, ip, (void *)ip);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
            if ((ip == rth || ip == mrth) && curr_frame >= 0) {
                printk(" (%pS)",
                       (void *)current->ret_stack[curr_frame].ret);
                curr_frame--;
            }
#endif
            if (firstframe)
                printk(" (unreliable)");
            printk("\n");
        }
        firstframe = 0;

        /*
         * See if this is an exception frame.
         * We look for the "regshere" marker in the current frame.
         */
        if (validate_sp(sp, tsk, STACK_INT_FRAME_SIZE)
            && stack[STACK_FRAME_MARKER] == STACK_FRAME_REGS_MARKER) {
            struct pt_regs *regs = (struct pt_regs *)
                (sp + STACK_FRAME_OVERHEAD);
            lr = regs->link;
            printk("--- Exception: %lx at %pS\n    LR = %pS\n",
                   regs->trap, (void *)regs->nip, (void *)lr);
            firstframe = 1;
        }

        sp = newsp;
    } while (count++ < kstack_depth_to_print);
}

void dump_stack(void)
{
    show_stack(current, NULL);
}
EXPORT_SYMBOL(dump_stack);

#ifdef CONFIG_PPC64
/* Called with hard IRQs off */
void __ppc64_runlatch_on(void)
{
    struct thread_info *ti = current_thread_info();
    unsigned long ctrl;

    ctrl = mfspr(SPRN_CTRLF);
    ctrl |= CTRL_RUNLATCH;
    mtspr(SPRN_CTRLT, ctrl);

    ti->local_flags |= _TLF_RUNLATCH;
}

/* Called with hard IRQs off */
void __ppc64_runlatch_off(void)
{
    struct thread_info *ti = current_thread_info();
    unsigned long ctrl;

    ti->local_flags &= ~_TLF_RUNLATCH;

    ctrl = mfspr(SPRN_CTRLF);
    ctrl &= ~CTRL_RUNLATCH;
    mtspr(SPRN_CTRLT, ctrl);
}
#endif /* CONFIG_PPC64 */

unsigned long arch_align_stack(unsigned long sp)
{
    if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
        sp -= get_random_int() & ~PAGE_MASK;
    return sp & ~0xf;
}

static inline unsigned long brk_rnd(void)
{
        unsigned long rnd = 0;

    /* 8MB for 32bit, 1GB for 64bit */
    if (is_32bit_task())
        rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT)));
    else
        rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT)));

    return rnd << PAGE_SHIFT;
}

unsigned long arch_randomize_brk(struct mm_struct *mm)
{
    unsigned long base = mm->brk;
    unsigned long ret;

#ifdef CONFIG_PPC_STD_MMU_64
    /*
     * If we are using 1TB segments and we are allowed to randomise
     * the heap, we can put it above 1TB so it is backed by a 1TB
     * segment. Otherwise the heap will be in the bottom 1TB
     * which always uses 256MB segments and this may result in a
     * performance penalty.
     */
    if (!is_32bit_task() && (mmu_highuser_ssize == MMU_SEGSIZE_1T))
        base = max_t(unsigned long, mm->brk, 1UL << SID_SHIFT_1T);
#endif

    ret = PAGE_ALIGN(base + brk_rnd());

    if (ret < mm->brk)
        return mm->brk;

    return ret;
}

unsigned long randomize_et_dyn(unsigned long base)
{
    unsigned long ret = PAGE_ALIGN(base + brk_rnd());

    if (ret < base)
        return base;

    return ret;
}