/*
 *  Kernel Probes (KProbes)
 *  arch/ppc64/kernel/kprobes.c
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 *
 * 2002-Oct     Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
 *              Probes initial implementation ( includes contributions from
 *              Rusty Russell).
 * 2004-July    Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
 *              interface to access function arguments.
 * 2004-Nov     Ananth N Mavinakayanahalli <ananth@in.ibm.com> kprobes port
 *              for PPC64
 */

#include <linux/config.h>
#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <asm/kdebug.h>
#include <asm/sstep.h>

/* kprobe_status settings */
#define KPROBE_HIT_ACTIVE       0x00000001
#define KPROBE_HIT_SS           0x00000002

static struct kprobe *current_kprobe;
static unsigned long kprobe_status, kprobe_saved_msr;
static struct pt_regs jprobe_saved_regs;

int arch_prepare_kprobe(struct kprobe *p)
{
        kprobe_opcode_t insn = *p->addr;

        if (IS_MTMSRD(insn) || IS_RFID(insn))
                /* cannot put bp on RFID/MTMSRD */
                return 1;
        return 0;
}

void arch_copy_kprobe(struct kprobe *p)
{
        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
}

void arch_remove_kprobe(struct kprobe *p)
{
}

static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs)
{
        *p->addr = p->opcode;
        regs->nip = (unsigned long)p->addr;
}

static inline void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
        regs->msr |= MSR_SE;
        regs->nip = (unsigned long)&p->ainsn.insn;
}

static inline int kprobe_handler(struct pt_regs *regs)
{
        struct kprobe *p;
        int ret = 0;
        unsigned int *addr = (unsigned int *)regs->nip;

        /* We're in an interrupt, but this is clear and BUG()-safe. */
        preempt_disable();

        /* Check we're not actually recursing */
        if (kprobe_running()) {
                /* We *are* holding lock here, so this is safe.
                   Disarm the probe we just hit, and ignore it. */
                p = get_kprobe(addr);
                if (p) {
                        disarm_kprobe(p, regs);
                        ret = 1;
                } else {
                        p = current_kprobe;
                        if (p->break_handler && p->break_handler(p, regs)) {
                                goto ss_probe;
                        }
                }
                /* If it's not ours, can't be delete race, (we hold lock). */
                goto no_kprobe;
        }

        lock_kprobes();
        p = get_kprobe(addr);
        if (!p) {
                unlock_kprobes();
#if 0
                if (*addr != BREAKPOINT_INSTRUCTION) {
                        /*
                         * The breakpoint instruction was removed right
                         * after we hit it.  Another cpu has removed
                         * either a probepoint or a debugger breakpoint
                         * at this address.  In either case, no further
                         * handling of this interrupt is appropriate.
                         */
                        ret = 1;
                }
#endif
                /* Not one of ours: let kernel handle it */
                goto no_kprobe;
        }

        kprobe_status = KPROBE_HIT_ACTIVE;
        current_kprobe = p;
        kprobe_saved_msr = regs->msr;
        if (p->pre_handler(p, regs)) {
                /* handler has already set things up, so skip ss setup */
                return 1;
        }

ss_probe:
        prepare_singlestep(p, regs);
        kprobe_status = KPROBE_HIT_SS;
        return 1;

no_kprobe:
        preempt_enable_no_resched();
        return ret;
}

/*
 * Called after single-stepping.  p->addr is the address of the
 * instruction whose first byte has been replaced by the "breakpoint"
 * instruction.  To avoid the SMP problems that can occur when we
 * temporarily put back the original opcode to single-step, we
 * single-stepped a copy of the instruction.  The address of this
 * copy is p->ainsn.insn.
 */
static void resume_execution(struct kprobe *p, struct pt_regs *regs)
{
        int ret;

        regs->nip = (unsigned long)p->addr;
        ret = emulate_step(regs, p->ainsn.insn[0]);
        if (ret == 0)
                regs->nip = (unsigned long)p->addr + 4;

        regs->msr &= ~MSR_SE;
}

static inline int post_kprobe_handler(struct pt_regs *regs)
{
        if (!kprobe_running())
                return 0;

        if (current_kprobe->post_handler)
                current_kprobe->post_handler(current_kprobe, regs, 0);

        resume_execution(current_kprobe, regs);
        regs->msr |= kprobe_saved_msr;

        unlock_kprobes();
        preempt_enable_no_resched();

        /*
         * if somebody else is singlestepping across a probe point, msr
         * will have SE set, in which case, continue the remaining processing
         * of do_debug, as if this is not a probe hit.
         */
        if (regs->msr & MSR_SE)
                return 0;

        return 1;
}

/* Interrupts disabled, kprobe_lock held. */
static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
        if (current_kprobe->fault_handler
            && current_kprobe->fault_handler(current_kprobe, regs, trapnr))
                return 1;

        if (kprobe_status & KPROBE_HIT_SS) {
                resume_execution(current_kprobe, regs);
                regs->msr |= kprobe_saved_msr;

                unlock_kprobes();
                preempt_enable_no_resched();
        }
        return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val,
                             void *data)
{
        struct die_args *args = (struct die_args *)data;
        switch (val) {
        case DIE_IABR_MATCH:
        case DIE_DABR_MATCH:
        case DIE_BPT:
                if (kprobe_handler(args->regs))
                        return NOTIFY_STOP;
                break;
        case DIE_SSTEP:
                if (post_kprobe_handler(args->regs))
                        return NOTIFY_STOP;
                break;
        case DIE_GPF:
        case DIE_PAGE_FAULT:
                if (kprobe_running() &&
                    kprobe_fault_handler(args->regs, args->trapnr))
                        return NOTIFY_STOP;
                break;
        default:
                break;
        }
        return NOTIFY_DONE;
}

int setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct jprobe *jp = container_of(p, struct jprobe, kp);

        memcpy(&jprobe_saved_regs, regs, sizeof(struct pt_regs));

        /* setup return addr to the jprobe handler routine */
        regs->nip = (unsigned long)(((func_descr_t *)jp->entry)->entry);
        regs->gpr[2] = (unsigned long)(((func_descr_t *)jp->entry)->toc);

        return 1;
}

void jprobe_return(void)
{
        preempt_enable_no_resched();
        asm volatile("trap" ::: "memory");
}

void jprobe_return_end(void)
{
};

int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
        /*
         * FIXME - we should ideally be validating that we got here 'cos
         * of the "trap" in jprobe_return() above, before restoring the
         * saved regs...
         */
        memcpy(regs, &jprobe_saved_regs, sizeof(struct pt_regs));
        return 1;
}