powerpc: switch to generic fork/clone/vfork

[deliverable/linux.git] / arch / powerpc / kernel / process.c

/*
 *  Derived from "arch/i386/kernel/process.c"
 *    Copyright (C) 1995  Linus Torvalds
 *
 *  Updated and modified by Cort Dougan (cort@cs.nmt.edu) and
 *  Paul Mackerras (paulus@cs.anu.edu.au)
 *
 *  PowerPC version
 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
 *
 *  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 (unlikely(p->flags & PF_KTHREAD)) {
                struct thread_info *ti = (void *)task_stack_page(p);
                memset(childregs, 0, sizeof(struct pt_regs));
                childregs->gpr[1] = sp + sizeof(struct pt_regs);
                childregs->gpr[14] = usp;       /* function */
#ifdef CONFIG_PPC64
                clear_tsk_thread_flag(p, TIF_32BIT);
                childregs->softe = 1;
#endif
                childregs->gpr[15] = arg;
                p->thread.regs = NULL;  /* no user register state */
                ti->flags |= _TIF_RESTOREALL;
                f = ret_from_kernel_thread;
        } else {
                CHECK_FULL_REGS(regs);
                *childregs = *regs;
                if (usp)
                        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);
}

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;
}