// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Kernel Probes (KProbes)
 *  arch/ia64/kernel/kprobes.c
 *
 * Copyright (C) IBM Corporation, 2002, 2004
 * Copyright (C) Intel Corporation, 2005
 *
 * 2005-Apr     Rusty Lynch <rusty.lynch@intel.com> and Anil S Keshavamurthy
 *              <anil.s.keshavamurthy@intel.com> 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/extable.h>
#include <linux/kdebug.h>
#include <linux/pgtable.h>

#include <asm/sections.h>
#include <asm/exception.h>

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);
        __this_cpu_write(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)
{
        __this_cpu_write(current_kprobe, p);
}

static void kretprobe_trampoline(void)
{
}

int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
        regs->cr_iip = __kretprobe_trampoline_handler(regs, kretprobe_trampoline, NULL);
        /*
         * 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;
        ri->fp = NULL;

        /* 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 (!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)) {
                reset_current_kprobe();
                preempt_enable_no_resched();
                return 1;
        }

#if !defined(CONFIG_PREEMPTION)
        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:
                /*
                 * 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 == 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;
}

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

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;
}