[mirror_ubuntu-zesty-kernel.git] / arch / ia64 / kernel / kprobes.c

/*
 *  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 <rusty.lynch@intel.com> and Anil S Keshavamurthy
 *              <anil.s.keshavamurthy@intel.com> adapted from i386
 */

#include <linux/config.h>
#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 <asm/pgtable.h>
#include <asm/kdebug.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);

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 */
};

/*
 * 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;

        /* 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
 * on which we are inserting kprobe is supported.
 * Returns 0 if supported
 * Returns -EINVAL if unsupported
 */
static int __kprobes unsupported_inst(uint template, uint  slot,
                                      uint major_opcode,
                                      unsigned long kprobe_inst,
                                      struct kprobe *p)
{
        unsigned long addr = (unsigned long)p->addr;

        if (bundle_encoding[template][slot] == I) {
                switch (major_opcode) {
                        case 0x0: //I_UNIT_MISC_OPCODE:
                        /*
                         * 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;

                        }
                }
        }
        return 0;
}


/*
 * 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)) {
                /* Integere 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)) {
                /* Integere 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 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)
{
        unsigned long break_inst = BREAK_INST;
        bundle_t *bundle = &p->ainsn.insn.bundle;

        /*
         * Copy the original kprobe_inst qualifying predicate(qp)
         * to the break instruction iff !is_cmp_ctype_unc_inst
         * because for cmp instruction with ctype equal to unc,
         * which is a special instruction always needs to be
         * executed regradless of qp
         */
        if (!is_cmp_ctype_unc_inst(template, slot, major_opcode, kprobe_inst))
                break_inst |= (0x3f & kprobe_inst);

        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 inline void 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 inline int 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;
        }

        if (slot == 1 && bundle_encoding[template][1] != L) {
                printk(KERN_WARNING "Inserting kprobes on slot #1 "
                       "is not supported\n");
                return -EINVAL;
        }

        return 0;
}

static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
        kcb->prev_kprobe.kp = kprobe_running();
        kcb->prev_kprobe.status = kcb->kprobe_status;
}

static inline void restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
        __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
        kcb->kprobe_status = kcb->prev_kprobe.status;
}

static inline void 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;
        struct hlist_node *node, *tmp;
        unsigned long flags, orig_ret_address = 0;
        unsigned long trampoline_address =
                ((struct fnptr *)kretprobe_trampoline)->ip;

        spin_lock_irqsave(&kretprobe_lock, flags);
        head = kretprobe_inst_table_head(current);

        /*
         * 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 then 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;

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

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

                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;
        }

        BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
        regs->cr_iip = orig_ret_address;

        reset_current_kprobe();
        spin_unlock_irqrestore(&kretprobe_lock, flags);
        preempt_enable_no_resched();

        /*
         * 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;
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
                                      struct pt_regs *regs)
{
        struct kretprobe_instance *ri;

        if ((ri = get_free_rp_inst(rp)) != NULL) {
                ri->rp = rp;
                ri->task = current;
                ri->ret_addr = (kprobe_opcode_t *)regs->b0;

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

                add_rp_inst(ri);
        } else {
                rp->nmissed++;
        }
}

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 = &p->ainsn.insn.bundle;

        memcpy(&p->opcode.bundle, kprobe_addr, sizeof(bundle_t));
        memcpy(&p->ainsn.insn.bundle, kprobe_addr, sizeof(bundle_t));

        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);

        if (unsupported_inst(template, slot, major_opcode, kprobe_inst, p))
                        return -EINVAL;

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

        return 0;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
        unsigned long addr = (unsigned long)p->addr;
        unsigned long arm_addr = addr & ~0xFULL;

        memcpy((char *)arm_addr, &p->ainsn.insn.bundle, sizeof(bundle_t));
        flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t));
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
        unsigned long addr = (unsigned long)p->addr;
        unsigned long arm_addr = addr & ~0xFULL;

        /* p->opcode contains the original unaltered bundle */
        memcpy((char *) arm_addr, (char *) &p->opcode.bundle, sizeof(bundle_t));
        flush_icache_range(arm_addr, arm_addr + sizeof(bundle_t));
}

/*
 * 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->opcode.bundle)) & ~0xFULL;
        unsigned long resume_addr = (unsigned long)p->addr & ~0xFULL;
        unsigned long template;
        int slot = ((unsigned long)p->addr & 0xf);

        template = p->opcode.bundle.quad0.template;

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

        if (p->ainsn.inst_flag) {

                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->opcode.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 int template, major_opcode;
        unsigned long kprobe_inst;
        unsigned long *kprobe_addr = (unsigned long *)regs->cr_iip;
        bundle_t bundle;

        memcpy(&bundle, kprobe_addr, sizeof(bundle_t));
        template = bundle.quad0.template;

        /* 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;
}

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:
        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;
}

static int __kprobes kprobes_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;

                /*
                 * 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 == 0x80200 || args->err == 0x80300 || 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;
        case DIE_PAGE_FAULT:
                /* kprobe_running() needs smp_processor_id() */
                preempt_disable();
                if (kprobe_running() &&
                        kprobes_fault_handler(args->regs, args->trapnr))
                        ret = NOTIFY_STOP;
                preempt_enable();
        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 = 0;
        lp->cfm = 0;
        return;
}

int __kprobes setjmp_pre_handler(struct kprobe *p, struct pt_regs *regs)
{
        struct jprobe *jp = container_of(p, struct jprobe, kp);
        unsigned long addr = ((struct fnptr *)(jp->entry))->ip;
        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 transfering 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;
}

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);
}