kprobes.c

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/*
 *  Kernel Probes (KProbes)
 *  arch/ia64/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
 * Copyright (C) Intel Corporation, 2005
 *
 * 2005-Apr     Rusty Lynch <[email protected]> and Anil S Keshavamurthy
 *              <[email protected]> adapted from i386
 */

#include <linux/kprobes.h>
#include <linux/ptrace.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/preempt.h>
#include <linux/moduleloader.h>
#include <linux/kdebug.h>

#include <asm/pgtable.h>
#include <asm/sections.h>
#include <asm/uaccess.h>

extern void jprobe_inst_return(void);

DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};

enum instruction_type {A, I, M, F, B, L, X, u};
static enum instruction_type bundle_encoding[32][3] = {
  { M, I, I },              /* 00 */
  { M, I, I },              /* 01 */
  { M, I, I },              /* 02 */
  { M, I, I },              /* 03 */
  { M, L, X },              /* 04 */
  { M, L, X },              /* 05 */
  { u, u, u },              /* 06 */
  { u, u, u },              /* 07 */
  { M, M, I },              /* 08 */
  { M, M, I },              /* 09 */
  { M, M, I },              /* 0A */
  { M, M, I },              /* 0B */
  { M, F, I },              /* 0C */
  { M, F, I },              /* 0D */
  { M, M, F },              /* 0E */
  { M, M, F },              /* 0F */
  { M, I, B },              /* 10 */
  { M, I, B },              /* 11 */
  { M, B, B },              /* 12 */
  { M, B, B },              /* 13 */
  { u, u, u },              /* 14 */
  { u, u, u },              /* 15 */
  { B, B, B },              /* 16 */
  { B, B, B },              /* 17 */
  { M, M, B },              /* 18 */
  { M, M, B },              /* 19 */
  { u, u, u },              /* 1A */
  { u, u, u },              /* 1B */
  { M, F, B },              /* 1C */
  { M, F, B },              /* 1D */
  { u, u, u },              /* 1E */
  { u, u, u },              /* 1F */
};

/* Insert a long branch code */
static void __kprobes set_brl_inst(void *from, void *to)
{
    s64 rel = ((s64) to - (s64) from) >> 4;
    bundle_t *brl;
    brl = (bundle_t *) ((u64) from & ~0xf);
    brl->quad0.template = 0x05; /* [MLX](stop) */
    brl->quad0.slot0 = NOP_M_INST;  /* nop.m 0x0 */
    brl->quad0.slot1_p0 = ((rel >> 20) & 0x7fffffffff) << 2;
    brl->quad1.slot1_p1 = (((rel >> 20) & 0x7fffffffff) << 2) >> (64 - 46);
    /* brl.cond.sptk.many.clr rel<<4 (qp=0) */
    brl->quad1.slot2 = BRL_INST(rel >> 59, rel & 0xfffff);
}

/*
 * In this function we check to see if the instruction
 * is IP relative instruction and update the kprobe
 * inst flag accordingly
 */
static void __kprobes update_kprobe_inst_flag(uint template, uint  slot,
                          uint major_opcode,
                          unsigned long kprobe_inst,
                          struct kprobe *p)
{
    p->ainsn.inst_flag = 0;
    p->ainsn.target_br_reg = 0;
    p->ainsn.slot = slot;

    /* Check for Break instruction
     * Bits 37:40 Major opcode to be zero
     * Bits 27:32 X6 to be zero
     * Bits 32:35 X3 to be zero
     */
    if ((!major_opcode) && (!((kprobe_inst >> 27) & 0x1FF)) ) {
        /* is a break instruction */
        p->ainsn.inst_flag |= INST_FLAG_BREAK_INST;
        return;
    }

    if (bundle_encoding[template][slot] == B) {
        switch (major_opcode) {
          case INDIRECT_CALL_OPCODE:
            p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
            p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
            break;
          case IP_RELATIVE_PREDICT_OPCODE:
          case IP_RELATIVE_BRANCH_OPCODE:
            p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
            break;
          case IP_RELATIVE_CALL_OPCODE:
            p->ainsn.inst_flag |= INST_FLAG_FIX_RELATIVE_IP_ADDR;
            p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
            p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
            break;
        }
    } else if (bundle_encoding[template][slot] == X) {
        switch (major_opcode) {
          case LONG_CALL_OPCODE:
            p->ainsn.inst_flag |= INST_FLAG_FIX_BRANCH_REG;
            p->ainsn.target_br_reg = ((kprobe_inst >> 6) & 0x7);
          break;
        }
    }
    return;
}

/*
 * In this function we check to see if the instruction
 * (qp) cmpx.crel.ctype p1,p2=r2,r3
 * on which we are inserting kprobe is cmp instruction
 * with ctype as unc.
 */
static uint __kprobes is_cmp_ctype_unc_inst(uint template, uint slot,
                        uint major_opcode,
                        unsigned long kprobe_inst)
{
    cmp_inst_t cmp_inst;
    uint ctype_unc = 0;

    if (!((bundle_encoding[template][slot] == I) ||
        (bundle_encoding[template][slot] == M)))
        goto out;

    if (!((major_opcode == 0xC) || (major_opcode == 0xD) ||
        (major_opcode == 0xE)))
        goto out;

    cmp_inst.l = kprobe_inst;
    if ((cmp_inst.f.x2 == 0) || (cmp_inst.f.x2 == 1)) {
        /* Integer compare - Register Register (A6 type)*/
        if ((cmp_inst.f.tb == 0) && (cmp_inst.f.ta == 0)
                &&(cmp_inst.f.c == 1))
            ctype_unc = 1;
    } else if ((cmp_inst.f.x2 == 2)||(cmp_inst.f.x2 == 3)) {
        /* Integer compare - Immediate Register (A8 type)*/
        if ((cmp_inst.f.ta == 0) &&(cmp_inst.f.c == 1))
            ctype_unc = 1;
    }
out:
    return ctype_unc;
}

/*
 * In this function we check to see if the instruction
 * on which we are inserting kprobe is supported.
 * Returns qp value if supported
 * Returns -EINVAL if unsupported
 */
static int __kprobes unsupported_inst(uint template, uint  slot,
                      uint major_opcode,
                      unsigned long kprobe_inst,
                      unsigned long addr)
{
    int qp;

    qp = kprobe_inst & 0x3f;
    if (is_cmp_ctype_unc_inst(template, slot, major_opcode, kprobe_inst)) {
        if (slot == 1 && qp)  {
            printk(KERN_WARNING "Kprobes on cmp unc "
                    "instruction on slot 1 at <0x%lx> "
                    "is not supported\n", addr);
            return -EINVAL;

        }
        qp = 0;
    }
    else if (bundle_encoding[template][slot] == I) {
        if (major_opcode == 0) {
            /*
             * Check for Integer speculation instruction
             * - Bit 33-35 to be equal to 0x1
             */
            if (((kprobe_inst >> 33) & 0x7) == 1) {
                printk(KERN_WARNING
                    "Kprobes on speculation inst at <0x%lx> not supported\n",
                        addr);
                return -EINVAL;
            }
            /*
             * IP relative mov instruction
             *  - Bit 27-35 to be equal to 0x30
             */
            if (((kprobe_inst >> 27) & 0x1FF) == 0x30) {
                printk(KERN_WARNING
                    "Kprobes on \"mov r1=ip\" at <0x%lx> not supported\n",
                        addr);
                return -EINVAL;

            }
        }
        else if ((major_opcode == 5) && !(kprobe_inst & (0xFUl << 33)) &&
                (kprobe_inst & (0x1UL << 12))) {
            /* test bit instructions, tbit,tnat,tf
             * bit 33-36 to be equal to 0
             * bit 12 to be equal to 1
             */
            if (slot == 1 && qp) {
                printk(KERN_WARNING "Kprobes on test bit "
                        "instruction on slot at <0x%lx> "
                        "is not supported\n", addr);
                return -EINVAL;
            }
            qp = 0;
        }
    }
    else if (bundle_encoding[template][slot] == B) {
        if (major_opcode == 7) {
            /* IP-Relative Predict major code is 7 */
            printk(KERN_WARNING "Kprobes on IP-Relative"
                    "Predict is not supported\n");
            return -EINVAL;
        }
        else if (major_opcode == 2) {
            /* Indirect Predict, major code is 2
             * bit 27-32 to be equal to 10 or 11
             */
            int x6=(kprobe_inst >> 27) & 0x3F;
            if ((x6 == 0x10) || (x6 == 0x11)) {
                printk(KERN_WARNING "Kprobes on "
                    "Indirect Predict is not supported\n");
                return -EINVAL;
            }
        }
    }
    /* kernel does not use float instruction, here for safety kprobe
     * will judge whether it is fcmp/flass/float approximation instruction
     */
    else if (unlikely(bundle_encoding[template][slot] == F)) {
        if ((major_opcode == 4 || major_opcode == 5) &&
                (kprobe_inst  & (0x1 << 12))) {
            /* fcmp/fclass unc instruction */
            if (slot == 1 && qp) {
                printk(KERN_WARNING "Kprobes on fcmp/fclass "
                    "instruction on slot at <0x%lx> "
                    "is not supported\n", addr);
                return -EINVAL;

            }
            qp = 0;
        }
        if ((major_opcode == 0 || major_opcode == 1) &&
            (kprobe_inst & (0x1UL << 33))) {
            /* float Approximation instruction */
            if (slot == 1 && qp) {
                printk(KERN_WARNING "Kprobes on float Approx "
                    "instr at <0x%lx> is not supported\n",
                        addr);
                return -EINVAL;
            }
            qp = 0;
        }
    }
    return qp;
}

/*
 * In this function we override the bundle with
 * the break instruction at the given slot.
 */
static void __kprobes prepare_break_inst(uint template, uint  slot,
                     uint major_opcode,
                     unsigned long kprobe_inst,
                     struct kprobe *p,
                     int qp)
{
    unsigned long break_inst = BREAK_INST;
    bundle_t *bundle = &p->opcode.bundle;

    /*
     * Copy the original kprobe_inst qualifying predicate(qp)
     * to the break instruction
     */
    break_inst |= qp;

    switch (slot) {
      case 0:
        bundle->quad0.slot0 = break_inst;
        break;
      case 1:
        bundle->quad0.slot1_p0 = break_inst;
        bundle->quad1.slot1_p1 = break_inst >> (64-46);
        break;
      case 2:
        bundle->quad1.slot2 = break_inst;
        break;
    }

    /*
     * Update the instruction flag, so that we can
     * emulate the instruction properly after we
     * single step on original instruction
     */
    update_kprobe_inst_flag(template, slot, major_opcode, kprobe_inst, p);
}

static void __kprobes get_kprobe_inst(bundle_t *bundle, uint slot,
            unsigned long *kprobe_inst, uint *major_opcode)
{
    unsigned long kprobe_inst_p0, kprobe_inst_p1;
    unsigned int template;

    template = bundle->quad0.template;

    switch (slot) {
      case 0:
        *major_opcode = (bundle->quad0.slot0 >> SLOT0_OPCODE_SHIFT);
        *kprobe_inst = bundle->quad0.slot0;
          break;
      case 1:
        *major_opcode = (bundle->quad1.slot1_p1 >> SLOT1_p1_OPCODE_SHIFT);
        kprobe_inst_p0 = bundle->quad0.slot1_p0;
        kprobe_inst_p1 = bundle->quad1.slot1_p1;
        *kprobe_inst = kprobe_inst_p0 | (kprobe_inst_p1 << (64-46));
        break;
      case 2:
        *major_opcode = (bundle->quad1.slot2 >> SLOT2_OPCODE_SHIFT);
        *kprobe_inst = bundle->quad1.slot2;
        break;
    }
}

/* Returns non-zero if the addr is in the Interrupt Vector Table */
static int __kprobes in_ivt_functions(unsigned long addr)
{
    return (addr >= (unsigned long)__start_ivt_text
        && addr < (unsigned long)__end_ivt_text);
}

static int __kprobes valid_kprobe_addr(int template, int slot,
                       unsigned long addr)
{
    if ((slot > 2) || ((bundle_encoding[template][1] == L) && slot > 1)) {
        printk(KERN_WARNING "Attempting to insert unaligned kprobe "
                "at 0x%lx\n", addr);
        return -EINVAL;
    }

    if (in_ivt_functions(addr)) {
        printk(KERN_WARNING "Kprobes can't be inserted inside "
                "IVT functions at 0x%lx\n", addr);
        return -EINVAL;
    }

    return 0;
}

static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
    unsigned int i;
    i = atomic_add_return(1, &kcb->prev_kprobe_index);
    kcb->prev_kprobe[i-1].kp = kprobe_running();
    kcb->prev_kprobe[i-1].status = kcb->kprobe_status;
}

static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
    unsigned int i;
    i = atomic_read(&kcb->prev_kprobe_index);
    __get_cpu_var(current_kprobe) = kcb->prev_kprobe[i-1].kp;
    kcb->kprobe_status = kcb->prev_kprobe[i-1].status;
    atomic_sub(1, &kcb->prev_kprobe_index);
}

static void __kprobes set_current_kprobe(struct kprobe *p,
            struct kprobe_ctlblk *kcb)
{
    __get_cpu_var(current_kprobe) = p;
}

static void kretprobe_trampoline(void)
{
}

/*
 * At this point the target function has been tricked into
 * returning into our trampoline.  Lookup the associated instance
 * and then:
 *    - call the handler function
 *    - cleanup by marking the instance as unused
 *    - long jump back to the original return address
 */
int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
    struct kretprobe_instance *ri = NULL;
    struct hlist_head *head, empty_rp;
    struct hlist_node *node, *tmp;
    unsigned long flags, orig_ret_address = 0;
    unsigned long trampoline_address =
        ((struct fnptr *)kretprobe_trampoline)->ip;

    INIT_HLIST_HEAD(&empty_rp);
    kretprobe_hash_lock(current, &head, &flags);

    /*
     * It is possible to have multiple instances associated with a given
     * task either because an multiple functions in the call path
     * have a return probe installed on them, and/or more than one return
     * return probe was registered for a target function.
     *
     * We can handle this because:
     *     - instances are always inserted at the head of the list
     *     - when multiple return probes are registered for the same
     *       function, the first instance's ret_addr will point to the
     *       real return address, and all the rest will point to
     *       kretprobe_trampoline
     */
    hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
        if (ri->task != current)
            /* another task is sharing our hash bucket */
            continue;

        orig_ret_address = (unsigned long)ri->ret_addr;
        if (orig_ret_address != trampoline_address)
            /*
             * This is the real return address. Any other
             * instances associated with this task are for
             * other calls deeper on the call stack
             */
            break;
    }

    regs->cr_iip = orig_ret_address;

    hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
        if (ri->task != current)
            /* another task is sharing our hash bucket */
            continue;

        if (ri->rp && ri->rp->handler)
            ri->rp->handler(ri, regs);

        orig_ret_address = (unsigned long)ri->ret_addr;
        recycle_rp_inst(ri, &empty_rp);

        if (orig_ret_address != trampoline_address)
            /*
             * This is the real return address. Any other
             * instances associated with this task are for
             * other calls deeper on the call stack
             */
            break;
    }

    kretprobe_assert(ri, orig_ret_address, trampoline_address);

    reset_current_kprobe();
    kretprobe_hash_unlock(current, &flags);
    preempt_enable_no_resched();

    hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
        hlist_del(&ri->hlist);
        kfree(ri);
    }
    /*
     * By returning a non-zero value, we are telling
     * kprobe_handler() that we don't want the post_handler
     * to run (and have re-enabled preemption)
     */
    return 1;
}

void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
                      struct pt_regs *regs)
{
    ri->ret_addr = (kprobe_opcode_t *)regs->b0;

    /* Replace the return addr with trampoline addr */
    regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
}

/* Check the instruction in the slot is break */
static int __kprobes __is_ia64_break_inst(bundle_t *bundle, uint slot)
{
    unsigned int major_opcode;
    unsigned int template = bundle->quad0.template;
    unsigned long kprobe_inst;

    /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */
    if (slot == 1 && bundle_encoding[template][1] == L)
        slot++;

    /* Get Kprobe probe instruction at given slot*/
    get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode);

    /* For break instruction,
     * Bits 37:40 Major opcode to be zero
     * Bits 27:32 X6 to be zero
     * Bits 32:35 X3 to be zero
     */
    if (major_opcode || ((kprobe_inst >> 27) & 0x1FF)) {
        /* Not a break instruction */
        return 0;
    }

    /* Is a break instruction */
    return 1;
}

/*
 * In this function, we check whether the target bundle modifies IP or
 * it triggers an exception. If so, it cannot be boostable.
 */
static int __kprobes can_boost(bundle_t *bundle, uint slot,
                   unsigned long bundle_addr)
{
    unsigned int template = bundle->quad0.template;

    do {
        if (search_exception_tables(bundle_addr + slot) ||
            __is_ia64_break_inst(bundle, slot))
            return 0;   /* exception may occur in this bundle*/
    } while ((++slot) < 3);
    template &= 0x1e;
    if (template >= 0x10 /* including B unit */ ||
        template == 0x04 /* including X unit */ ||
        template == 0x06) /* undefined */
        return 0;

    return 1;
}

/* Prepare long jump bundle and disables other boosters if need */
static void __kprobes prepare_booster(struct kprobe *p)
{
    unsigned long addr = (unsigned long)p->addr & ~0xFULL;
    unsigned int slot = (unsigned long)p->addr & 0xf;
    struct kprobe *other_kp;

    if (can_boost(&p->ainsn.insn[0].bundle, slot, addr)) {
        set_brl_inst(&p->ainsn.insn[1].bundle, (bundle_t *)addr + 1);
        p->ainsn.inst_flag |= INST_FLAG_BOOSTABLE;
    }

    /* disables boosters in previous slots */
    for (; addr < (unsigned long)p->addr; addr++) {
        other_kp = get_kprobe((void *)addr);
        if (other_kp)
            other_kp->ainsn.inst_flag &= ~INST_FLAG_BOOSTABLE;
    }
}

int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
    unsigned long addr = (unsigned long) p->addr;
    unsigned long *kprobe_addr = (unsigned long *)(addr & ~0xFULL);
    unsigned long kprobe_inst=0;
    unsigned int slot = addr & 0xf, template, major_opcode = 0;
    bundle_t *bundle;
    int qp;

    bundle = &((kprobe_opcode_t *)kprobe_addr)->bundle;
    template = bundle->quad0.template;

    if(valid_kprobe_addr(template, slot, addr))
        return -EINVAL;

    /* Move to slot 2, if bundle is MLX type and kprobe slot is 1 */
    if (slot == 1 && bundle_encoding[template][1] == L)
        slot++;

    /* Get kprobe_inst and major_opcode from the bundle */
    get_kprobe_inst(bundle, slot, &kprobe_inst, &major_opcode);

    qp = unsupported_inst(template, slot, major_opcode, kprobe_inst, addr);
    if (qp < 0)
        return -EINVAL;

    p->ainsn.insn = get_insn_slot();
    if (!p->ainsn.insn)
        return -ENOMEM;
    memcpy(&p->opcode, kprobe_addr, sizeof(kprobe_opcode_t));
    memcpy(p->ainsn.insn, kprobe_addr, sizeof(kprobe_opcode_t));

    prepare_break_inst(template, slot, major_opcode, kprobe_inst, p, qp);

    prepare_booster(p);

    return 0;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
    unsigned long arm_addr;
    bundle_t *src, *dest;

    arm_addr = ((unsigned long)p->addr) & ~0xFUL;
    dest = &((kprobe_opcode_t *)arm_addr)->bundle;
    src = &p->opcode.bundle;

    flush_icache_range((unsigned long)p->ainsn.insn,
               (unsigned long)p->ainsn.insn +
               sizeof(kprobe_opcode_t) * MAX_INSN_SIZE);

    switch (p->ainsn.slot) {
        case 0:
            dest->quad0.slot0 = src->quad0.slot0;
            break;
        case 1:
            dest->quad1.slot1_p1 = src->quad1.slot1_p1;
            break;
        case 2:
            dest->quad1.slot2 = src->quad1.slot2;
            break;
    }
    flush_icache_range(arm_addr, arm_addr + sizeof(kprobe_opcode_t));
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
    unsigned long arm_addr;
    bundle_t *src, *dest;

    arm_addr = ((unsigned long)p->addr) & ~0xFUL;
    dest = &((kprobe_opcode_t *)arm_addr)->bundle;
    /* p->ainsn.insn contains the original unaltered kprobe_opcode_t */
    src = &p->ainsn.insn->bundle;
    switch (p->ainsn.slot) {
        case 0:
            dest->quad0.slot0 = src->quad0.slot0;
            break;
        case 1:
            dest->quad1.slot1_p1 = src->quad1.slot1_p1;
            break;
        case 2:
            dest->quad1.slot2 = src->quad1.slot2;
            break;
    }
    flush_icache_range(arm_addr, arm_addr + sizeof(kprobe_opcode_t));
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
    if (p->ainsn.insn) {
        free_insn_slot(p->ainsn.insn,
                   p->ainsn.inst_flag & INST_FLAG_BOOSTABLE);
        p->ainsn.insn = NULL;
    }
}
/*
 * We are resuming execution after a single step fault, so the pt_regs
 * structure reflects the register state after we executed the instruction
 * located in the kprobe (p->ainsn.insn->bundle).  We still need to adjust
 * the ip to point back to the original stack address. To set the IP address
 * to original stack address, handle the case where we need to fixup the
 * relative IP address and/or fixup branch register.
 */
static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
{
    unsigned long bundle_addr = (unsigned long) (&p->ainsn.insn->bundle);
    unsigned long resume_addr = (unsigned long)p->addr & ~0xFULL;
    unsigned long template;
    int slot = ((unsigned long)p->addr & 0xf);

    template = p->ainsn.insn->bundle.quad0.template;

    if (slot == 1 && bundle_encoding[template][1] == L)
        slot = 2;

    if (p->ainsn.inst_flag & ~INST_FLAG_BOOSTABLE) {

        if (p->ainsn.inst_flag & INST_FLAG_FIX_RELATIVE_IP_ADDR) {
            /* Fix relative IP address */
            regs->cr_iip = (regs->cr_iip - bundle_addr) +
                    resume_addr;
        }

        if (p->ainsn.inst_flag & INST_FLAG_FIX_BRANCH_REG) {
        /*
         * Fix target branch register, software convention is
         * to use either b0 or b6 or b7, so just checking
         * only those registers
         */
            switch (p->ainsn.target_br_reg) {
            case 0:
                if ((regs->b0 == bundle_addr) ||
                    (regs->b0 == bundle_addr + 0x10)) {
                    regs->b0 = (regs->b0 - bundle_addr) +
                        resume_addr;
                }
                break;
            case 6:
                if ((regs->b6 == bundle_addr) ||
                    (regs->b6 == bundle_addr + 0x10)) {
                    regs->b6 = (regs->b6 - bundle_addr) +
                        resume_addr;
                }
                break;
            case 7:
                if ((regs->b7 == bundle_addr) ||
                    (regs->b7 == bundle_addr + 0x10)) {
                    regs->b7 = (regs->b7 - bundle_addr) +
                        resume_addr;
                }
                break;
            } /* end switch */
        }
        goto turn_ss_off;
    }

    if (slot == 2) {
        if (regs->cr_iip == bundle_addr + 0x10) {
            regs->cr_iip = resume_addr + 0x10;
        }
    } else {
        if (regs->cr_iip == bundle_addr) {
            regs->cr_iip = resume_addr;
        }
    }

turn_ss_off:
    /* Turn off Single Step bit */
    ia64_psr(regs)->ss = 0;
}

static void __kprobes prepare_ss(struct kprobe *p, struct pt_regs *regs)
{
    unsigned long bundle_addr = (unsigned long) &p->ainsn.insn->bundle;
    unsigned long slot = (unsigned long)p->addr & 0xf;

    /* single step inline if break instruction */
    if (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)
        regs->cr_iip = (unsigned long)p->addr & ~0xFULL;
    else
        regs->cr_iip = bundle_addr & ~0xFULL;

    if (slot > 2)
        slot = 0;

    ia64_psr(regs)->ri = slot;

    /* turn on single stepping */
    ia64_psr(regs)->ss = 1;
}

static int __kprobes is_ia64_break_inst(struct pt_regs *regs)
{
    unsigned int slot = ia64_psr(regs)->ri;
    unsigned long *kprobe_addr = (unsigned long *)regs->cr_iip;
    bundle_t bundle;

    memcpy(&bundle, kprobe_addr, sizeof(bundle_t));

    return __is_ia64_break_inst(&bundle, slot);
}

static int __kprobes pre_kprobes_handler(struct die_args *args)
{
    struct kprobe *p;
    int ret = 0;
    struct pt_regs *regs = args->regs;
    kprobe_opcode_t *addr = (kprobe_opcode_t *)instruction_pointer(regs);
    struct kprobe_ctlblk *kcb;

    /*
     * We don't want to be preempted for the entire
     * duration of kprobe processing
     */
    preempt_disable();
    kcb = get_kprobe_ctlblk();

    /* Handle recursion cases */
    if (kprobe_running()) {
        p = get_kprobe(addr);
        if (p) {
            if ((kcb->kprobe_status == KPROBE_HIT_SS) &&
                 (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) {
                ia64_psr(regs)->ss = 0;
                goto no_kprobe;
            }
            /* We have reentered the pre_kprobe_handler(), since
             * another probe was hit while within the handler.
             * We here save the original kprobes variables and
             * just single step on the instruction of the new probe
             * without calling any user handlers.
             */
            save_previous_kprobe(kcb);
            set_current_kprobe(p, kcb);
            kprobes_inc_nmissed_count(p);
            prepare_ss(p, regs);
            kcb->kprobe_status = KPROBE_REENTER;
            return 1;
        } else if (args->err == __IA64_BREAK_JPROBE) {
            /*
             * jprobe instrumented function just completed
             */
            p = __get_cpu_var(current_kprobe);
            if (p->break_handler && p->break_handler(p, regs)) {
                goto ss_probe;
            }
        } else if (!is_ia64_break_inst(regs)) {
            /* The breakpoint instruction was removed by
             * another cpu right after we hit, no further
             * handling of this interrupt is appropriate
             */
            ret = 1;
            goto no_kprobe;
        } else {
            /* Not our break */
            goto no_kprobe;
        }
    }

    p = get_kprobe(addr);
    if (!p) {
        if (!is_ia64_break_inst(regs)) {
            /*
             * 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;

        }

        /* Not one of our break, let kernel handle it */
        goto no_kprobe;
    }

    set_current_kprobe(p, kcb);
    kcb->kprobe_status = KPROBE_HIT_ACTIVE;

    if (p->pre_handler && p->pre_handler(p, regs))
        /*
         * Our pre-handler is specifically requesting that we just
         * do a return.  This is used for both the jprobe pre-handler
         * and the kretprobe trampoline
         */
        return 1;

ss_probe:
#if !defined(CONFIG_PREEMPT)
    if (p->ainsn.inst_flag == INST_FLAG_BOOSTABLE && !p->post_handler) {
        /* Boost up -- we can execute copied instructions directly */
        ia64_psr(regs)->ri = p->ainsn.slot;
        regs->cr_iip = (unsigned long)&p->ainsn.insn->bundle & ~0xFULL;
        /* turn single stepping off */
        ia64_psr(regs)->ss = 0;

        reset_current_kprobe();
        preempt_enable_no_resched();
        return 1;
    }
#endif
    prepare_ss(p, regs);
    kcb->kprobe_status = KPROBE_HIT_SS;
    return 1;

no_kprobe:
    preempt_enable_no_resched();
    return ret;
}

static int __kprobes post_kprobes_handler(struct pt_regs *regs)
{
    struct kprobe *cur = kprobe_running();
    struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

    if (!cur)
        return 0;

    if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
        kcb->kprobe_status = KPROBE_HIT_SSDONE;
        cur->post_handler(cur, regs, 0);
    }

    resume_execution(cur, regs);

    /*Restore back the original saved kprobes variables and continue. */
    if (kcb->kprobe_status == KPROBE_REENTER) {
        restore_previous_kprobe(kcb);
        goto out;
    }
    reset_current_kprobe();

out:
    preempt_enable_no_resched();
    return 1;
}

int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
    struct kprobe *cur = kprobe_running();
    struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();


    switch(kcb->kprobe_status) {
    case KPROBE_HIT_SS:
    case KPROBE_REENTER:
        /*
         * We are here because the instruction being single
         * stepped caused a page fault. We reset the current
         * kprobe and the instruction pointer points back to
         * the probe address and allow the page fault handler
         * to continue as a normal page fault.
         */
        regs->cr_iip = ((unsigned long)cur->addr) & ~0xFULL;
        ia64_psr(regs)->ri = ((unsigned long)cur->addr) & 0xf;
        if (kcb->kprobe_status == KPROBE_REENTER)
            restore_previous_kprobe(kcb);
        else
            reset_current_kprobe();
        preempt_enable_no_resched();
        break;
    case KPROBE_HIT_ACTIVE:
    case KPROBE_HIT_SSDONE:
        /*
         * We increment the nmissed count for accounting,
         * we can also use npre/npostfault count for accouting
         * these specific fault cases.
         */
        kprobes_inc_nmissed_count(cur);

        /*
         * We come here because instructions in the pre/post
         * handler caused the page_fault, this could happen
         * if handler tries to access user space by
         * copy_from_user(), get_user() etc. Let the
         * user-specified handler try to fix it first.
         */
        if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
            return 1;
        /*
         * In case the user-specified fault handler returned
         * zero, try to fix up.
         */
        if (ia64_done_with_exception(regs))
            return 1;

        /*
         * Let ia64_do_page_fault() fix it.
         */
        break;
    default:
        break;
    }

    return 0;
}

int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
                       unsigned long val, void *data)
{
    struct die_args *args = (struct die_args *)data;
    int ret = NOTIFY_DONE;

    if (args->regs && user_mode(args->regs))
        return ret;

    switch(val) {
    case DIE_BREAK:
        /* err is break number from ia64_bad_break() */
        if ((args->err >> 12) == (__IA64_BREAK_KPROBE >> 12)
            || args->err == __IA64_BREAK_JPROBE
            || args->err == 0)
            if (pre_kprobes_handler(args))
                ret = NOTIFY_STOP;
        break;
    case DIE_FAULT:
        /* err is vector number from ia64_fault() */
        if (args->err == 36)
            if (post_kprobes_handler(args->regs))
                ret = NOTIFY_STOP;
        break;
    default:
        break;
    }
    return ret;
}

struct param_bsp_cfm {
    unsigned long ip;
    unsigned long *bsp;
    unsigned long cfm;
};

static void ia64_get_bsp_cfm(struct unw_frame_info *info, void *arg)
{
    unsigned long ip;
    struct param_bsp_cfm *lp = arg;

    do {
        unw_get_ip(info, &ip);
        if (ip == 0)
            break;
        if (ip == lp->ip) {
            unw_get_bsp(info, (unsigned long*)&lp->bsp);
            unw_get_cfm(info, (unsigned long*)&lp->cfm);
            return;
        }
    } while (unw_unwind(info) >= 0);
    lp->bsp = NULL;
    lp->cfm = 0;
    return;
}

unsigned long arch_deref_entry_point(void *entry)
{
    return ((struct fnptr *)entry)->ip;
}

int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
    struct jprobe *jp = container_of(p, struct jprobe, kp);
    unsigned long addr = arch_deref_entry_point(jp->entry);
    struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
    struct param_bsp_cfm pa;
    int bytes;

    /*
     * Callee owns the argument space and could overwrite it, eg
     * tail call optimization. So to be absolutely safe
     * we save the argument space before transferring the control
     * to instrumented jprobe function which runs in
     * the process context
     */
    pa.ip = regs->cr_iip;
    unw_init_running(ia64_get_bsp_cfm, &pa);
    bytes = (char *)ia64_rse_skip_regs(pa.bsp, pa.cfm & 0x3f)
                - (char *)pa.bsp;
    memcpy( kcb->jprobes_saved_stacked_regs,
        pa.bsp,
        bytes );
    kcb->bsp = pa.bsp;
    kcb->cfm = pa.cfm;

    /* save architectural state */
    kcb->jprobe_saved_regs = *regs;

    /* after rfi, execute the jprobe instrumented function */
    regs->cr_iip = addr & ~0xFULL;
    ia64_psr(regs)->ri = addr & 0xf;
    regs->r1 = ((struct fnptr *)(jp->entry))->gp;

    /*
     * fix the return address to our jprobe_inst_return() function
     * in the jprobes.S file
     */
    regs->b0 = ((struct fnptr *)(jprobe_inst_return))->ip;

    return 1;
}

/* ia64 does not need this */
void __kprobes jprobe_return(void)
{
}

int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
{
    struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
    int bytes;

    /* restoring architectural state */
    *regs = kcb->jprobe_saved_regs;

    /* restoring the original argument space */
    flush_register_stack();
    bytes = (char *)ia64_rse_skip_regs(kcb->bsp, kcb->cfm & 0x3f)
                - (char *)kcb->bsp;
    memcpy( kcb->bsp,
        kcb->jprobes_saved_stacked_regs,
        bytes );
    invalidate_stacked_regs();

    preempt_enable_no_resched();
    return 1;
}

static struct kprobe trampoline_p = {
    .pre_handler = trampoline_probe_handler
};

int __init arch_init_kprobes(void)
{
    trampoline_p.addr =
        (kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip;
    return register_kprobe(&trampoline_p);
}

int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
    if (p->addr ==
        (kprobe_opcode_t *)((struct fnptr *)kretprobe_trampoline)->ip)
        return 1;

    return 0;
}