1 files changed, 228 insertions, 242 deletions

diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c
index 2564793ec2b6..1d05d669107c 100644
--- a/arch/s390/kernel/kprobes.c
+++ b/arch/s390/kernel/kprobes.c
@@ -32,34 +32,14 @@
 #include <linux/slab.h>
 #include <linux/hardirq.h>
 
-DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe *, current_kprobe);
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
-struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
+struct kretprobe_blackpoint kretprobe_blacklist[] = { };
 
-int __kprobes arch_prepare_kprobe(struct kprobe *p)
-{
-        /* Make sure the probe isn't going on a difficult instruction */
-        if (is_prohibited_opcode((kprobe_opcode_t *) p->addr))
-                return -EINVAL;
-
-        if ((unsigned long)p->addr & 0x01)
-                return -EINVAL;
-
-        /* Use the get_insn_slot() facility for correctness */
-        if (!(p->ainsn.insn = get_insn_slot()))
-                return -ENOMEM;
-
-        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
-
-        get_instruction_type(&p->ainsn);
-        p->opcode = *p->addr;
-        return 0;
-}
-
-int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
+static int __kprobes is_prohibited_opcode(kprobe_opcode_t *insn)
 {
-        switch (*(__u8 *) instruction) {
+        switch (insn[0] >> 8) {
         case 0x0c:      /* bassm */
         case 0x0b:      /* bsm   */
         case 0x83:      /* diag  */
@@ -68,7 +48,7 @@ int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
         case 0xad:      /* stosm */
                 return -EINVAL;
         }
-        switch (*(__u16 *) instruction) {
+        switch (insn[0]) {
         case 0x0101:    /* pr    */
         case 0xb25a:    /* bsa   */
         case 0xb240:    /* bakr  */
@@ -81,93 +61,92 @@ int __kprobes is_prohibited_opcode(kprobe_opcode_t *instruction)
         return 0;
 }
 
-void __kprobes get_instruction_type(struct arch_specific_insn *ainsn)
+static int __kprobes get_fixup_type(kprobe_opcode_t *insn)
 {
         /* default fixup method */
-        ainsn->fixup = FIXUP_PSW_NORMAL;
-
-        /* save r1 operand */
-        ainsn->reg = (*ainsn->insn & 0xf0) >> 4;
+        int fixup = FIXUP_PSW_NORMAL;
 
-        /* save the instruction length (pop 5-5) in bytes */
-        switch (*(__u8 *) (ainsn->insn) >> 6) {
-        case 0:
-                ainsn->ilen = 2;
-                break;
-        case 1:
-        case 2:
-                ainsn->ilen = 4;
-                break;
-        case 3:
-                ainsn->ilen = 6;
-                break;
-        }
-
-        switch (*(__u8 *) ainsn->insn) {
+        switch (insn[0] >> 8) {
         case 0x05:      /* balr */
         case 0x0d:      /* basr */
-                ainsn->fixup = FIXUP_RETURN_REGISTER;
+                fixup = FIXUP_RETURN_REGISTER;
                 /* if r2 = 0, no branch will be taken */
-                if ((*ainsn->insn & 0x0f) == 0)
-                        ainsn->fixup |= FIXUP_BRANCH_NOT_TAKEN;
+                if ((insn[0] & 0x0f) == 0)
+                        fixup |= FIXUP_BRANCH_NOT_TAKEN;
                 break;
         case 0x06:      /* bctr */
         case 0x07:      /* bcr  */
-                ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
+                fixup = FIXUP_BRANCH_NOT_TAKEN;
                 break;
         case 0x45:      /* bal  */
         case 0x4d:      /* bas  */
-                ainsn->fixup = FIXUP_RETURN_REGISTER;
+                fixup = FIXUP_RETURN_REGISTER;
                 break;
         case 0x47:      /* bc   */
         case 0x46:      /* bct  */
         case 0x86:      /* bxh  */
         case 0x87:      /* bxle */
-                ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
+                fixup = FIXUP_BRANCH_NOT_TAKEN;
                 break;
         case 0x82:      /* lpsw */
-                ainsn->fixup = FIXUP_NOT_REQUIRED;
+                fixup = FIXUP_NOT_REQUIRED;
                 break;
         case 0xb2:      /* lpswe */
-                if (*(((__u8 *) ainsn->insn) + 1) == 0xb2) {
-                        ainsn->fixup = FIXUP_NOT_REQUIRED;
-                }
+                if ((insn[0] & 0xff) == 0xb2)
+                        fixup = FIXUP_NOT_REQUIRED;
                 break;
         case 0xa7:      /* bras */
-                if ((*ainsn->insn & 0x0f) == 0x05) {
-                        ainsn->fixup |= FIXUP_RETURN_REGISTER;
-                }
+                if ((insn[0] & 0x0f) == 0x05)
+                        fixup |= FIXUP_RETURN_REGISTER;
                 break;
         case 0xc0:
-                if ((*ainsn->insn & 0x0f) == 0x00  /* larl  */
-                        || (*ainsn->insn & 0x0f) == 0x05) /* brasl */
-                ainsn->fixup |= FIXUP_RETURN_REGISTER;
+                if ((insn[0] & 0x0f) == 0x00 || /* larl  */
+                    (insn[0] & 0x0f) == 0x05)   /* brasl */
+                fixup |= FIXUP_RETURN_REGISTER;
                 break;
         case 0xeb:
-                if (*(((__u8 *) ainsn->insn) + 5 ) == 0x44 ||   /* bxhg  */
-                        *(((__u8 *) ainsn->insn) + 5) == 0x45) {/* bxleg */
-                        ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
-                }
+                if ((insn[2] & 0xff) == 0x44 || /* bxhg  */
+                    (insn[2] & 0xff) == 0x45)   /* bxleg */
+                        fixup = FIXUP_BRANCH_NOT_TAKEN;
                 break;
         case 0xe3:      /* bctg */
-                if (*(((__u8 *) ainsn->insn) + 5) == 0x46) {
-                        ainsn->fixup = FIXUP_BRANCH_NOT_TAKEN;
-                }
+                if ((insn[2] & 0xff) == 0x46)
+                        fixup = FIXUP_BRANCH_NOT_TAKEN;
                 break;
         }
+        return fixup;
+}
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+        if ((unsigned long) p->addr & 0x01)
+                return -EINVAL;
+
+        /* Make sure the probe isn't going on a difficult instruction */
+        if (is_prohibited_opcode(p->addr))
+                return -EINVAL;
+
+        p->opcode = *p->addr;
+        memcpy(p->ainsn.insn, p->addr, ((p->opcode >> 14) + 3) & -2);
+
+        return 0;
 }
 
+struct ins_replace_args {
+        kprobe_opcode_t *ptr;
+        kprobe_opcode_t opcode;
+};
+
 static int __kprobes swap_instruction(void *aref)
 {
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
         unsigned long status = kcb->kprobe_status;
         struct ins_replace_args *args = aref;
-        int rc;
 
         kcb->kprobe_status = KPROBE_SWAP_INST;
-        rc = probe_kernel_write(args->ptr, &args->new, sizeof(args->new));
+        probe_kernel_write(args->ptr, &args->opcode, sizeof(args->opcode));
         kcb->kprobe_status = status;
-        return rc;
+        return 0;
 }
 
 void __kprobes arch_arm_kprobe(struct kprobe *p)
@@ -175,8 +154,7 @@ void __kprobes arch_arm_kprobe(struct kprobe *p)
         struct ins_replace_args args;
 
         args.ptr = p->addr;
-        args.old = p->opcode;
-        args.new = BREAKPOINT_INSTRUCTION;
+        args.opcode = BREAKPOINT_INSTRUCTION;
         stop_machine(swap_instruction, &args, NULL);
 }
 
@@ -185,64 +163,69 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p)
         struct ins_replace_args args;
 
         args.ptr = p->addr;
-        args.old = BREAKPOINT_INSTRUCTION;
-        args.new = p->opcode;
+        args.opcode = p->opcode;
         stop_machine(swap_instruction, &args, NULL);
 }
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)
 {
-        if (p->ainsn.insn) {
-                free_insn_slot(p->ainsn.insn, 0);
-                p->ainsn.insn = NULL;
-        }
 }
 
-static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+static void __kprobes enable_singlestep(struct kprobe_ctlblk *kcb,
+                                        struct pt_regs *regs,
+                                        unsigned long ip)
 {
-        per_cr_bits kprobe_per_regs[1];
+        struct per_regs per_kprobe;
 
-        memset(kprobe_per_regs, 0, sizeof(per_cr_bits));
-        regs->psw.addr = (unsigned long)p->ainsn.insn | PSW_ADDR_AMODE;
+        /* Set up the PER control registers %cr9-%cr11 */
+        per_kprobe.control = PER_EVENT_IFETCH;
+        per_kprobe.start = ip;
+        per_kprobe.end = ip;
 
-        /* Set up the per control reg info, will pass to lctl */
-        kprobe_per_regs[0].em_instruction_fetch = 1;
-        kprobe_per_regs[0].starting_addr = (unsigned long)p->ainsn.insn;
-        kprobe_per_regs[0].ending_addr = (unsigned long)p->ainsn.insn + 1;
+        /* Save control regs and psw mask */
+        __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
+        kcb->kprobe_saved_imask = regs->psw.mask &
+                (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
 
-        /* Set the PER control regs, turns on single step for this address */
-        __ctl_load(kprobe_per_regs, 9, 11);
+        /* Set PER control regs, turns on single step for the given address */
+        __ctl_load(per_kprobe, 9, 11);
         regs->psw.mask |= PSW_MASK_PER;
         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
+        regs->psw.addr = ip | PSW_ADDR_AMODE;
 }
 
-static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+static void __kprobes disable_singlestep(struct kprobe_ctlblk *kcb,
+                                         struct pt_regs *regs,
+                                         unsigned long ip)
 {
-        kcb->prev_kprobe.kp = kprobe_running();
-        kcb->prev_kprobe.status = kcb->kprobe_status;
-        kcb->prev_kprobe.kprobe_saved_imask = kcb->kprobe_saved_imask;
-        memcpy(kcb->prev_kprobe.kprobe_saved_ctl, kcb->kprobe_saved_ctl,
-                                        sizeof(kcb->kprobe_saved_ctl));
+        /* Restore control regs and psw mask, set new psw address */
+        __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
+        regs->psw.mask &= ~PSW_MASK_PER;
+        regs->psw.mask |= kcb->kprobe_saved_imask;
+        regs->psw.addr = ip | PSW_ADDR_AMODE;
 }
 
-static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+/*
+ * Activate a kprobe by storing its pointer to current_kprobe. The
+ * previous kprobe is stored in kcb->prev_kprobe. A stack of up to
+ * two kprobes can be active, see KPROBE_REENTER.
+ */
+static void __kprobes push_kprobe(struct kprobe_ctlblk *kcb, struct kprobe *p)
 {
-        __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
-        kcb->kprobe_status = kcb->prev_kprobe.status;
-        kcb->kprobe_saved_imask = kcb->prev_kprobe.kprobe_saved_imask;
-        memcpy(kcb->kprobe_saved_ctl, kcb->prev_kprobe.kprobe_saved_ctl,
-                                        sizeof(kcb->kprobe_saved_ctl));
+        kcb->prev_kprobe.kp = __get_cpu_var(current_kprobe);
+        kcb->prev_kprobe.status = kcb->kprobe_status;
+        __get_cpu_var(current_kprobe) = p;
 }
 
-static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
-                                                struct kprobe_ctlblk *kcb)
+/*
+ * Deactivate a kprobe by backing up to the previous state. If the
+ * current state is KPROBE_REENTER prev_kprobe.kp will be non-NULL,
+ * for any other state prev_kprobe.kp will be NULL.
+ */
+static void __kprobes pop_kprobe(struct kprobe_ctlblk *kcb)
 {
-        __get_cpu_var(current_kprobe) = p;
-        /* Save the interrupt and per flags */
-        kcb->kprobe_saved_imask = regs->psw.mask &
-                (PSW_MASK_PER | PSW_MASK_IO | PSW_MASK_EXT);
-        /* Save the control regs that govern PER */
-        __ctl_store(kcb->kprobe_saved_ctl, 9, 11);
+        __get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
+        kcb->kprobe_status = kcb->prev_kprobe.status;
 }
 
 void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
@@ -251,79 +234,104 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
         ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];
 
         /* Replace the return addr with trampoline addr */
-        regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
+        regs->gprs[14] = (unsigned long) &kretprobe_trampoline;
+}
+
+static void __kprobes kprobe_reenter_check(struct kprobe_ctlblk *kcb,
+                                           struct kprobe *p)
+{
+        switch (kcb->kprobe_status) {
+        case KPROBE_HIT_SSDONE:
+        case KPROBE_HIT_ACTIVE:
+                kprobes_inc_nmissed_count(p);
+                break;
+        case KPROBE_HIT_SS:
+        case KPROBE_REENTER:
+        default:
+                /*
+                 * A kprobe on the code path to single step an instruction
+                 * is a BUG. The code path resides in the .kprobes.text
+                 * section and is executed with interrupts disabled.
+                 */
+                printk(KERN_EMERG "Invalid kprobe detected at %p.\n", p->addr);
+                dump_kprobe(p);
+                BUG();
+        }
 }
 
 static int __kprobes kprobe_handler(struct pt_regs *regs)
 {
-        struct kprobe *p;
-        int ret = 0;
-        unsigned long *addr = (unsigned long *)
-                ((regs->psw.addr & PSW_ADDR_INSN) - 2);
         struct kprobe_ctlblk *kcb;
+        struct kprobe *p;
 
         /*
-         * We don't want to be preempted for the entire
-         * duration of kprobe processing
+         * We want to disable preemption for the entire duration of kprobe
+         * processing. That includes the calls to the pre/post handlers
+         * and single stepping the kprobe instruction.
          */
         preempt_disable();
         kcb = get_kprobe_ctlblk();
+        p = get_kprobe((void *)((regs->psw.addr & PSW_ADDR_INSN) - 2));
 
-        /* Check we're not actually recursing */
-        if (kprobe_running()) {
-                p = get_kprobe(addr);
-                if (p) {
-                        if (kcb->kprobe_status == KPROBE_HIT_SS &&
-                            *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
-                                regs->psw.mask &= ~PSW_MASK_PER;
-                                regs->psw.mask |= kcb->kprobe_saved_imask;
-                                goto no_kprobe;
-                        }
-                        /* We have reentered the 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.
+        if (p) {
+                if (kprobe_running()) {
+                        /*
+                         * We have hit a kprobe while another is still
+                         * active. This can happen in the pre and post
+                         * handler. Single step the instruction of the
+                         * new probe but do not call any handler function
+                         * of this secondary kprobe.
+                         * push_kprobe and pop_kprobe saves and restores
+                         * the currently active kprobe.
                          */
-                        save_previous_kprobe(kcb);
-                        set_current_kprobe(p, regs, kcb);
-                        kprobes_inc_nmissed_count(p);
-                        prepare_singlestep(p, regs);
+                        kprobe_reenter_check(kcb, p);
+                        push_kprobe(kcb, p);
                         kcb->kprobe_status = KPROBE_REENTER;
-                        return 1;
                 } else {
-                        p = __get_cpu_var(current_kprobe);
-                        if (p->break_handler && p->break_handler(p, regs)) {
-                                goto ss_probe;
-                        }
+                        /*
+                         * If we have no pre-handler or it returned 0, we
+                         * continue with single stepping. If we have a
+                         * pre-handler and it returned non-zero, it prepped
+                         * for calling the break_handler below on re-entry
+                         * for jprobe processing, so get out doing nothing
+                         * more here.
+                         */
+                        push_kprobe(kcb, p);
+                        kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+                        if (p->pre_handler && p->pre_handler(p, regs))
+                                return 1;
+                        kcb->kprobe_status = KPROBE_HIT_SS;
                 }
-                goto no_kprobe;
-        }
-
-        p = get_kprobe(addr);
-        if (!p)
-                /*
-                 * No kprobe at this address. The fault has not been
-                 * caused by a kprobe breakpoint. The race of breakpoint
-                 * vs. kprobe remove does not exist because on s390 we
-                 * use stop_machine to arm/disarm the breakpoints.
-                 */
-                goto no_kprobe;
-
-        kcb->kprobe_status = KPROBE_HIT_ACTIVE;
-        set_current_kprobe(p, regs, kcb);
-        if (p->pre_handler && p->pre_handler(p, regs))
-                /* handler has already set things up, so skip ss setup */
+                enable_singlestep(kcb, regs, (unsigned long) p->ainsn.insn);
                 return 1;
-
-ss_probe:
-        prepare_singlestep(p, regs);
-        kcb->kprobe_status = KPROBE_HIT_SS;
-        return 1;
-
-no_kprobe:
+        } else if (kprobe_running()) {
+                p = __get_cpu_var(current_kprobe);
+                if (p->break_handler && p->break_handler(p, regs)) {
+                        /*
+                         * Continuation after the jprobe completed and
+                         * caused the jprobe_return trap. The jprobe
+                         * break_handler "returns" to the original
+                         * function that still has the kprobe breakpoint
+                         * installed. We continue with single stepping.
+                         */
+                        kcb->kprobe_status = KPROBE_HIT_SS;
+                        enable_singlestep(kcb, regs,
+                                          (unsigned long) p->ainsn.insn);
+                        return 1;
+                } /* else:
+                   * No kprobe at this address and the current kprobe
+                   * has no break handler (no jprobe!). The kernel just
+                   * exploded, let the standard trap handler pick up the
+                   * pieces.
+                   */
+        } /* else:
+           * No kprobe at this address and no active kprobe. The trap has
+           * not been caused by a kprobe breakpoint. The race of breakpoint
+           * vs. kprobe remove does not exist because on s390 as we use
+           * stop_machine to arm/disarm the breakpoints.
+           */
         preempt_enable_no_resched();
-        return ret;
+        return 0;
 }
 
 /*
@@ -344,12 +352,12 @@ static void __used kretprobe_trampoline_holder(void)
 static int __kprobes trampoline_probe_handler(struct kprobe *p,
                                               struct pt_regs *regs)
 {
-        struct kretprobe_instance *ri = NULL;
+        struct kretprobe_instance *ri;
         struct hlist_head *head, empty_rp;
         struct hlist_node *node, *tmp;
-        unsigned long flags, orig_ret_address = 0;
-        unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
-        kprobe_opcode_t *correct_ret_addr = NULL;
+        unsigned long flags, orig_ret_address;
+        unsigned long trampoline_address;
+        kprobe_opcode_t *correct_ret_addr;
 
         INIT_HLIST_HEAD(&empty_rp);
         kretprobe_hash_lock(current, &head, &flags);
@@ -367,12 +375,16 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
          *       real return address, and all the rest will point to
          *       kretprobe_trampoline
          */
+        ri = NULL;
+        orig_ret_address = 0;
+        correct_ret_addr = NULL;
+        trampoline_address = (unsigned long) &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;
+                orig_ret_address = (unsigned long) ri->ret_addr;
 
                 if (orig_ret_address != trampoline_address)
                         /*
@@ -391,7 +403,7 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
                         /* another task is sharing our hash bucket */
                         continue;
 
-                orig_ret_address = (unsigned long)ri->ret_addr;
+                orig_ret_address = (unsigned long) ri->ret_addr;
 
                 if (ri->rp && ri->rp->handler) {
                         ri->ret_addr = correct_ret_addr;
@@ -400,19 +412,18 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
 
                 recycle_rp_inst(ri, &empty_rp);
 
-                if (orig_ret_address != trampoline_address) {
+                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->psw.addr = orig_ret_address | PSW_ADDR_AMODE;
 
-        reset_current_kprobe();
+        pop_kprobe(get_kprobe_ctlblk());
         kretprobe_hash_unlock(current, &flags);
         preempt_enable_no_resched();
 
@@ -439,55 +450,42 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
 static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
 {
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+        unsigned long ip = regs->psw.addr & PSW_ADDR_INSN;
+        int fixup = get_fixup_type(p->ainsn.insn);
 
-        regs->psw.addr &= PSW_ADDR_INSN;
-
-        if (p->ainsn.fixup & FIXUP_PSW_NORMAL)
-                regs->psw.addr = (unsigned long)p->addr +
-                                ((unsigned long)regs->psw.addr -
-                                 (unsigned long)p->ainsn.insn);
+        if (fixup & FIXUP_PSW_NORMAL)
+                ip += (unsigned long) p->addr - (unsigned long) p->ainsn.insn;
 
-        if (p->ainsn.fixup & FIXUP_BRANCH_NOT_TAKEN)
-                if ((unsigned long)regs->psw.addr -
-                    (unsigned long)p->ainsn.insn == p->ainsn.ilen)
-                        regs->psw.addr = (unsigned long)p->addr + p->ainsn.ilen;
+        if (fixup & FIXUP_BRANCH_NOT_TAKEN) {
+                int ilen = ((p->ainsn.insn[0] >> 14) + 3) & -2;
+                if (ip - (unsigned long) p->ainsn.insn == ilen)
+                        ip = (unsigned long) p->addr + ilen;
+        }
 
-        if (p->ainsn.fixup & FIXUP_RETURN_REGISTER)
-                regs->gprs[p->ainsn.reg] = ((unsigned long)p->addr +
-                                                (regs->gprs[p->ainsn.reg] -
-                                                (unsigned long)p->ainsn.insn))
-                                                | PSW_ADDR_AMODE;
+        if (fixup & FIXUP_RETURN_REGISTER) {
+                int reg = (p->ainsn.insn[0] & 0xf0) >> 4;
+                regs->gprs[reg] += (unsigned long) p->addr -
+                                   (unsigned long) p->ainsn.insn;
+        }
 
-        regs->psw.addr |= PSW_ADDR_AMODE;
-        /* turn off PER mode */
-        regs->psw.mask &= ~PSW_MASK_PER;
-        /* Restore the original per control regs */
-        __ctl_load(kcb->kprobe_saved_ctl, 9, 11);
-        regs->psw.mask |= kcb->kprobe_saved_imask;
+        disable_singlestep(kcb, regs, ip);
 }
 
 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 {
-        struct kprobe *cur = kprobe_running();
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+        struct kprobe *p = kprobe_running();
 
-        if (!cur)
+        if (!p)
                 return 0;
 
-        if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
+        if (kcb->kprobe_status != KPROBE_REENTER && p->post_handler) {
                 kcb->kprobe_status = KPROBE_HIT_SSDONE;
-                cur->post_handler(cur, regs, 0);
+                p->post_handler(p, 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:
+        resume_execution(p, regs);
+        pop_kprobe(kcb);
         preempt_enable_no_resched();
 
         /*
@@ -495,17 +493,16 @@ out:
          * will have PER set, in which case, continue the remaining processing
          * of do_single_step, as if this is not a probe hit.
          */
-        if (regs->psw.mask & PSW_MASK_PER) {
+        if (regs->psw.mask & PSW_MASK_PER)
                 return 0;
-        }
 
         return 1;
 }
 
 static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 {
-        struct kprobe *cur = kprobe_running();
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+        struct kprobe *p = kprobe_running();
         const struct exception_table_entry *entry;
 
         switch(kcb->kprobe_status) {
@@ -521,14 +518,8 @@ static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
                  * and allow the page fault handler to continue as a
                  * normal page fault.
                  */
-                regs->psw.addr = (unsigned long)cur->addr | PSW_ADDR_AMODE;
-                regs->psw.mask &= ~PSW_MASK_PER;
-                regs->psw.mask |= kcb->kprobe_saved_imask;
-                if (kcb->kprobe_status == KPROBE_REENTER)
-                        restore_previous_kprobe(kcb);
-                else {
-                        reset_current_kprobe();
-                }
+                disable_singlestep(kcb, regs, (unsigned long) p->addr);
+                pop_kprobe(kcb);
                 preempt_enable_no_resched();
                 break;
         case KPROBE_HIT_ACTIVE:
@@ -538,7 +529,7 @@ static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
                  * we can also use npre/npostfault count for accouting
                  * these specific fault cases.
                  */
-                kprobes_inc_nmissed_count(cur);
+                kprobes_inc_nmissed_count(p);
 
                 /*
                  * We come here because instructions in the pre/post
@@ -547,7 +538,7 @@ static int __kprobes kprobe_trap_handler(struct pt_regs *regs, int trapnr)
                  * 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))
+                if (p->fault_handler && p->fault_handler(p, regs, trapnr))
                         return 1;
 
                 /*
@@ -589,7 +580,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
                                        unsigned long val, void *data)
 {
-        struct die_args *args = (struct die_args *)data;
+        struct die_args *args = (struct die_args *) data;
         struct pt_regs *regs = args->regs;
         int ret = NOTIFY_DONE;
 
@@ -598,16 +589,16 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 
         switch (val) {
         case DIE_BPT:
-                if (kprobe_handler(args->regs))
+                if (kprobe_handler(regs))
                         ret = NOTIFY_STOP;
                 break;
         case DIE_SSTEP:
-                if (post_kprobe_handler(args->regs))
+                if (post_kprobe_handler(regs))
                         ret = NOTIFY_STOP;
                 break;
         case DIE_TRAP:
                 if (!preemptible() && kprobe_running() &&
-                    kprobe_trap_handler(args->regs, args->trapnr))
+                    kprobe_trap_handler(regs, args->trapnr))
                         ret = NOTIFY_STOP;
                 break;
         default:
@@ -623,23 +614,19 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 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 kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+        unsigned long stack;
 
         memcpy(&kcb->jprobe_saved_regs, regs, sizeof(struct pt_regs));
 
         /* setup return addr to the jprobe handler routine */
-        regs->psw.addr = (unsigned long)(jp->entry) | PSW_ADDR_AMODE;
+        regs->psw.addr = (unsigned long) jp->entry | PSW_ADDR_AMODE;
         regs->psw.mask &= ~(PSW_MASK_IO | PSW_MASK_EXT);
 
-        /* r14 is the function return address */
-        kcb->jprobe_saved_r14 = (unsigned long)regs->gprs[14];
         /* r15 is the stack pointer */
-        kcb->jprobe_saved_r15 = (unsigned long)regs->gprs[15];
-        addr = (unsigned long)kcb->jprobe_saved_r15;
+        stack = (unsigned long) regs->gprs[15];
 
-        memcpy(kcb->jprobes_stack, (kprobe_opcode_t *) addr,
-               MIN_STACK_SIZE(addr));
+        memcpy(kcb->jprobes_stack, (void *) stack, MIN_STACK_SIZE(stack));
         return 1;
 }
 
@@ -656,30 +643,29 @@ void __kprobes jprobe_return_end(void)
 int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 {
         struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-        unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_r15);
+        unsigned long stack;
+
+        stack = (unsigned long) kcb->jprobe_saved_regs.gprs[15];
 
         /* Put the regs back */
         memcpy(regs, &kcb->jprobe_saved_regs, sizeof(struct pt_regs));
         /* put the stack back */
-        memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
-               MIN_STACK_SIZE(stack_addr));
+        memcpy((void *) stack, kcb->jprobes_stack, MIN_STACK_SIZE(stack));
         preempt_enable_no_resched();
         return 1;
 }
 
-static struct kprobe trampoline_p = {
-        .addr = (kprobe_opcode_t *) & kretprobe_trampoline,
+static struct kprobe trampoline = {
+        .addr = (kprobe_opcode_t *) &kretprobe_trampoline,
         .pre_handler = trampoline_probe_handler
 };
 
 int __init arch_init_kprobes(void)
 {
-        return register_kprobe(&trampoline_p);
+        return register_kprobe(&trampoline);
 }
 
 int __kprobes arch_trampoline_kprobe(struct kprobe *p)
 {
-        if (p->addr == (kprobe_opcode_t *) & kretprobe_trampoline)
-                return 1;
-        return 0;
+        return p->addr == (kprobe_opcode_t *) &kretprobe_trampoline;
 }