x86_64: move kernel

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 749 insertions, 0 deletions

diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
new file mode 100644
index 000000000000..a30e004682e2
--- /dev/null
+++ b/arch/x86/kernel/kprobes_64.c
@@ -0,0 +1,749 @@
+/*
+ *  Kernel Probes (KProbes)
+ *  arch/x86_64/kernel/kprobes.c
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ *
+ * 2002-Oct	Created by Vamsi Krishna S <vamsi_krishna@in.ibm.com> Kernel
+ *		Probes initial implementation ( includes contributions from
+ *		Rusty Russell).
+ * 2004-July	Suparna Bhattacharya <suparna@in.ibm.com> added jumper probes
+ *		interface to access function arguments.
+ * 2004-Oct	Jim Keniston <kenistoj@us.ibm.com> and Prasanna S Panchamukhi
+ *		<prasanna@in.ibm.com> adapted for x86_64
+ * 2005-Mar	Roland McGrath <roland@redhat.com>
+ *		Fixed to handle %rip-relative addressing mode correctly.
+ * 2005-May     Rusty Lynch <rusty.lynch@intel.com>
+ *              Added function return probes functionality
+ */
+
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/preempt.h>
+#include <linux/module.h>
+#include <linux/kdebug.h>
+
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/alternative.h>
+
+void jprobe_return_end(void);
+static void __kprobes arch_copy_kprobe(struct kprobe *p);
+
+DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
+DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
+
+/*
+ * returns non-zero if opcode modifies the interrupt flag.
+ */
+static __always_inline int is_IF_modifier(kprobe_opcode_t *insn)
+{
+	switch (*insn) {
+	case 0xfa:		/* cli */
+	case 0xfb:		/* sti */
+	case 0xcf:		/* iret/iretd */
+	case 0x9d:		/* popf/popfd */
+		return 1;
+	}
+
+	if (*insn  >= 0x40 && *insn <= 0x4f && *++insn == 0xcf)
+		return 1;
+	return 0;
+}
+
+int __kprobes arch_prepare_kprobe(struct kprobe *p)
+{
+	/* insn: must be on special executable page on x86_64. */
+	p->ainsn.insn = get_insn_slot();
+	if (!p->ainsn.insn) {
+		return -ENOMEM;
+	}
+	arch_copy_kprobe(p);
+	return 0;
+}
+
+/*
+ * Determine if the instruction uses the %rip-relative addressing mode.
+ * If it does, return the address of the 32-bit displacement word.
+ * If not, return null.
+ */
+static s32 __kprobes *is_riprel(u8 *insn)
+{
+#define W(row,b0,b1,b2,b3,b4,b5,b6,b7,b8,b9,ba,bb,bc,bd,be,bf)		      \
+	(((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) |   \
+	  (b4##UL << 0x4)|(b5##UL << 0x5)|(b6##UL << 0x6)|(b7##UL << 0x7) |   \
+	  (b8##UL << 0x8)|(b9##UL << 0x9)|(ba##UL << 0xa)|(bb##UL << 0xb) |   \
+	  (bc##UL << 0xc)|(bd##UL << 0xd)|(be##UL << 0xe)|(bf##UL << 0xf))    \
+	 << (row % 64))
+	static const u64 onebyte_has_modrm[256 / 64] = {
+		/*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+		/*      -------------------------------         */
+		W(0x00, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 00 */
+		W(0x10, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 10 */
+		W(0x20, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0)| /* 20 */
+		W(0x30, 1,1,1,1,0,0,0,0,1,1,1,1,0,0,0,0), /* 30 */
+		W(0x40, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 40 */
+		W(0x50, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 50 */
+		W(0x60, 0,0,1,1,0,0,0,0,0,1,0,1,0,0,0,0)| /* 60 */
+		W(0x70, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 70 */
+		W(0x80, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 80 */
+		W(0x90, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 90 */
+		W(0xa0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* a0 */
+		W(0xb0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* b0 */
+		W(0xc0, 1,1,0,0,1,1,1,1,0,0,0,0,0,0,0,0)| /* c0 */
+		W(0xd0, 1,1,1,1,0,0,0,0,1,1,1,1,1,1,1,1)| /* d0 */
+		W(0xe0, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* e0 */
+		W(0xf0, 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1)  /* f0 */
+		/*      -------------------------------         */
+		/*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+	};
+	static const u64 twobyte_has_modrm[256 / 64] = {
+		/*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+		/*      -------------------------------         */
+		W(0x00, 1,1,1,1,0,0,0,0,0,0,0,0,0,1,0,1)| /* 0f */
+		W(0x10, 1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0)| /* 1f */
+		W(0x20, 1,1,1,1,1,0,1,0,1,1,1,1,1,1,1,1)| /* 2f */
+		W(0x30, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0), /* 3f */
+		W(0x40, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 4f */
+		W(0x50, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 5f */
+		W(0x60, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 6f */
+		W(0x70, 1,1,1,1,1,1,1,0,0,0,0,0,1,1,1,1), /* 7f */
+		W(0x80, 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)| /* 8f */
+		W(0x90, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* 9f */
+		W(0xa0, 0,0,0,1,1,1,1,1,0,0,0,1,1,1,1,1)| /* af */
+		W(0xb0, 1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1), /* bf */
+		W(0xc0, 1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0)| /* cf */
+		W(0xd0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* df */
+		W(0xe0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1)| /* ef */
+		W(0xf0, 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0)  /* ff */
+		/*      -------------------------------         */
+		/*      0 1 2 3 4 5 6 7 8 9 a b c d e f         */
+	};
+#undef	W
+	int need_modrm;
+
+	/* Skip legacy instruction prefixes.  */
+	while (1) {
+		switch (*insn) {
+		case 0x66:
+		case 0x67:
+		case 0x2e:
+		case 0x3e:
+		case 0x26:
+		case 0x64:
+		case 0x65:
+		case 0x36:
+		case 0xf0:
+		case 0xf3:
+		case 0xf2:
+			++insn;
+			continue;
+		}
+		break;
+	}
+
+	/* Skip REX instruction prefix.  */
+	if ((*insn & 0xf0) == 0x40)
+		++insn;
+
+	if (*insn == 0x0f) {	/* Two-byte opcode.  */
+		++insn;
+		need_modrm = test_bit(*insn, twobyte_has_modrm);
+	} else {		/* One-byte opcode.  */
+		need_modrm = test_bit(*insn, onebyte_has_modrm);
+	}
+
+	if (need_modrm) {
+		u8 modrm = *++insn;
+		if ((modrm & 0xc7) == 0x05) { /* %rip+disp32 addressing mode */
+			/* Displacement follows ModRM byte.  */
+			return (s32 *) ++insn;
+		}
+	}
+
+	/* No %rip-relative addressing mode here.  */
+	return NULL;
+}
+
+static void __kprobes arch_copy_kprobe(struct kprobe *p)
+{
+	s32 *ripdisp;
+	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
+	ripdisp = is_riprel(p->ainsn.insn);
+	if (ripdisp) {
+		/*
+		 * The copied instruction uses the %rip-relative
+		 * addressing mode.  Adjust the displacement for the
+		 * difference between the original location of this
+		 * instruction and the location of the copy that will
+		 * actually be run.  The tricky bit here is making sure
+		 * that the sign extension happens correctly in this
+		 * calculation, since we need a signed 32-bit result to
+		 * be sign-extended to 64 bits when it's added to the
+		 * %rip value and yield the same 64-bit result that the
+		 * sign-extension of the original signed 32-bit
+		 * displacement would have given.
+		 */
+		s64 disp = (u8 *) p->addr + *ripdisp - (u8 *) p->ainsn.insn;
+		BUG_ON((s64) (s32) disp != disp); /* Sanity check.  */
+		*ripdisp = disp;
+	}
+	p->opcode = *p->addr;
+}
+
+void __kprobes arch_arm_kprobe(struct kprobe *p)
+{
+	text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);
+}
+
+void __kprobes arch_disarm_kprobe(struct kprobe *p)
+{
+	text_poke(p->addr, &p->opcode, 1);
+}
+
+void __kprobes arch_remove_kprobe(struct kprobe *p)
+{
+	mutex_lock(&kprobe_mutex);
+	free_insn_slot(p->ainsn.insn, 0);
+	mutex_unlock(&kprobe_mutex);
+}
+
+static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	kcb->prev_kprobe.kp = kprobe_running();
+	kcb->prev_kprobe.status = kcb->kprobe_status;
+	kcb->prev_kprobe.old_rflags = kcb->kprobe_old_rflags;
+	kcb->prev_kprobe.saved_rflags = kcb->kprobe_saved_rflags;
+}
+
+static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
+{
+	__get_cpu_var(current_kprobe) = kcb->prev_kprobe.kp;
+	kcb->kprobe_status = kcb->prev_kprobe.status;
+	kcb->kprobe_old_rflags = kcb->prev_kprobe.old_rflags;
+	kcb->kprobe_saved_rflags = kcb->prev_kprobe.saved_rflags;
+}
+
+static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
+				struct kprobe_ctlblk *kcb)
+{
+	__get_cpu_var(current_kprobe) = p;
+	kcb->kprobe_saved_rflags = kcb->kprobe_old_rflags
+		= (regs->eflags & (TF_MASK | IF_MASK));
+	if (is_IF_modifier(p->ainsn.insn))
+		kcb->kprobe_saved_rflags &= ~IF_MASK;
+}
+
+static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
+{
+	regs->eflags |= TF_MASK;
+	regs->eflags &= ~IF_MASK;
+	/*single step inline if the instruction is an int3*/
+	if (p->opcode == BREAKPOINT_INSTRUCTION)
+		regs->rip = (unsigned long)p->addr;
+	else
+		regs->rip = (unsigned long)p->ainsn.insn;
+}
+
+/* Called with kretprobe_lock held */
+void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
+				      struct pt_regs *regs)
+{
+	unsigned long *sara = (unsigned long *)regs->rsp;
+
+	ri->ret_addr = (kprobe_opcode_t *) *sara;
+	/* Replace the return addr with trampoline addr */
+	*sara = (unsigned long) &kretprobe_trampoline;
+}
+
+int __kprobes kprobe_handler(struct pt_regs *regs)
+{
+	struct kprobe *p;
+	int ret = 0;
+	kprobe_opcode_t *addr = (kprobe_opcode_t *)(regs->rip - sizeof(kprobe_opcode_t));
+	struct kprobe_ctlblk *kcb;
+
+	/*
+	 * We don't want to be preempted for the entire
+	 * duration of kprobe processing
+	 */
+	preempt_disable();
+	kcb = get_kprobe_ctlblk();
+
+	/* 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->eflags &= ~TF_MASK;
+				regs->eflags |= kcb->kprobe_saved_rflags;
+				goto no_kprobe;
+			} else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) {
+				/* TODO: Provide re-entrancy from
+				 * post_kprobes_handler() and avoid exception
+				 * stack corruption while single-stepping on
+				 * the instruction of the new probe.
+				 */
+				arch_disarm_kprobe(p);
+				regs->rip = (unsigned long)p->addr;
+				reset_current_kprobe();
+				ret = 1;
+			} else {
+				/* We have reentered the kprobe_handler(), since
+				 * another probe was hit while within the
+				 * handler. We here save the original kprobe
+				 * variables and just single step on instruction
+				 * of the new probe without calling any user
+				 * handlers.
+				 */
+				save_previous_kprobe(kcb);
+				set_current_kprobe(p, regs, kcb);
+				kprobes_inc_nmissed_count(p);
+				prepare_singlestep(p, regs);
+				kcb->kprobe_status = KPROBE_REENTER;
+				return 1;
+			}
+		} else {
+			if (*addr != BREAKPOINT_INSTRUCTION) {
+			/* The breakpoint instruction was removed by
+			 * another cpu right after we hit, no further
+			 * handling of this interrupt is appropriate
+			 */
+				regs->rip = (unsigned long)addr;
+				ret = 1;
+				goto no_kprobe;
+			}
+			p = __get_cpu_var(current_kprobe);
+			if (p->break_handler && p->break_handler(p, regs)) {
+				goto ss_probe;
+			}
+		}
+		goto no_kprobe;
+	}
+
+	p = get_kprobe(addr);
+	if (!p) {
+		if (*addr != BREAKPOINT_INSTRUCTION) {
+			/*
+			 * The breakpoint instruction was removed right
+			 * after we hit it.  Another cpu has removed
+			 * either a probepoint or a debugger breakpoint
+			 * at this address.  In either case, no further
+			 * handling of this interrupt is appropriate.
+			 * Back up over the (now missing) int3 and run
+			 * the original instruction.
+			 */
+			regs->rip = (unsigned long)addr;
+			ret = 1;
+		}
+		/* Not one of ours: let kernel handle it */
+		goto no_kprobe;
+	}
+
+	set_current_kprobe(p, regs, kcb);
+	kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+
+	if (p->pre_handler && p->pre_handler(p, regs))
+		/* handler has already set things up, so skip ss setup */
+		return 1;
+
+ss_probe:
+	prepare_singlestep(p, regs);
+	kcb->kprobe_status = KPROBE_HIT_SS;
+	return 1;
+
+no_kprobe:
+	preempt_enable_no_resched();
+	return ret;
+}
+
+/*
+ * For function-return probes, init_kprobes() establishes a probepoint
+ * here. When a retprobed function returns, this probe is hit and
+ * trampoline_probe_handler() runs, calling the kretprobe's handler.
+ */
+ void kretprobe_trampoline_holder(void)
+ {
+ 	asm volatile (  ".global kretprobe_trampoline\n"
+ 			"kretprobe_trampoline: \n"
+ 			"nop\n");
+ }
+
+/*
+ * Called when we hit the probe point at kretprobe_trampoline
+ */
+int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kretprobe_instance *ri = NULL;
+	struct hlist_head *head, empty_rp;
+	struct hlist_node *node, *tmp;
+	unsigned long flags, orig_ret_address = 0;
+	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
+
+	INIT_HLIST_HEAD(&empty_rp);
+	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, &empty_rp);
+
+		if (orig_ret_address != trampoline_address)
+			/*
+			 * This is the real return address. Any other
+			 * instances associated with this task are for
+			 * other calls deeper on the call stack
+			 */
+			break;
+	}
+
+	kretprobe_assert(ri, orig_ret_address, trampoline_address);
+	regs->rip = orig_ret_address;
+
+	reset_current_kprobe();
+	spin_unlock_irqrestore(&kretprobe_lock, flags);
+	preempt_enable_no_resched();
+
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
+	/*
+	 * By returning a non-zero value, we are telling
+	 * kprobe_handler() that we don't want the post_handler
+	 * to run (and have re-enabled preemption)
+	 */
+	return 1;
+}
+
+/*
+ * Called after single-stepping.  p->addr is the address of the
+ * instruction whose first byte has been replaced by the "int 3"
+ * instruction.  To avoid the SMP problems that can occur when we
+ * temporarily put back the original opcode to single-step, we
+ * single-stepped a copy of the instruction.  The address of this
+ * copy is p->ainsn.insn.
+ *
+ * This function prepares to return from the post-single-step
+ * interrupt.  We have to fix up the stack as follows:
+ *
+ * 0) Except in the case of absolute or indirect jump or call instructions,
+ * the new rip is relative to the copied instruction.  We need to make
+ * it relative to the original instruction.
+ *
+ * 1) If the single-stepped instruction was pushfl, then the TF and IF
+ * flags are set in the just-pushed eflags, and may need to be cleared.
+ *
+ * 2) If the single-stepped instruction was a call, the return address
+ * that is atop the stack is the address following the copied instruction.
+ * We need to make it the address following the original instruction.
+ */
+static void __kprobes resume_execution(struct kprobe *p,
+		struct pt_regs *regs, struct kprobe_ctlblk *kcb)
+{
+	unsigned long *tos = (unsigned long *)regs->rsp;
+	unsigned long next_rip = 0;
+	unsigned long copy_rip = (unsigned long)p->ainsn.insn;
+	unsigned long orig_rip = (unsigned long)p->addr;
+	kprobe_opcode_t *insn = p->ainsn.insn;
+
+	/*skip the REX prefix*/
+	if (*insn >= 0x40 && *insn <= 0x4f)
+		insn++;
+
+	switch (*insn) {
+	case 0x9c:		/* pushfl */
+		*tos &= ~(TF_MASK | IF_MASK);
+		*tos |= kcb->kprobe_old_rflags;
+		break;
+	case 0xc3:		/* ret/lret */
+	case 0xcb:
+	case 0xc2:
+	case 0xca:
+		regs->eflags &= ~TF_MASK;
+		/* rip is already adjusted, no more changes required*/
+		return;
+	case 0xe8:		/* call relative - Fix return addr */
+		*tos = orig_rip + (*tos - copy_rip);
+		break;
+	case 0xff:
+		if ((insn[1] & 0x30) == 0x10) {
+			/* call absolute, indirect */
+			/* Fix return addr; rip is correct. */
+			next_rip = regs->rip;
+			*tos = orig_rip + (*tos - copy_rip);
+		} else if (((insn[1] & 0x31) == 0x20) ||	/* jmp near, absolute indirect */
+			   ((insn[1] & 0x31) == 0x21)) {	/* jmp far, absolute indirect */
+			/* rip is correct. */
+			next_rip = regs->rip;
+		}
+		break;
+	case 0xea:		/* jmp absolute -- rip is correct */
+		next_rip = regs->rip;
+		break;
+	default:
+		break;
+	}
+
+	regs->eflags &= ~TF_MASK;
+	if (next_rip) {
+		regs->rip = next_rip;
+	} else {
+		regs->rip = orig_rip + (regs->rip - copy_rip);
+	}
+}
+
+int __kprobes post_kprobe_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, kcb);
+	regs->eflags |= kcb->kprobe_saved_rflags;
+
+	/* Restore 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();
+
+	/*
+	 * if somebody else is singlestepping across a probe point, eflags
+	 * will have TF set, in which case, continue the remaining processing
+	 * of do_debug, as if this is not a probe hit.
+	 */
+	if (regs->eflags & TF_MASK)
+		return 0;
+
+	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();
+	const struct exception_table_entry *fixup;
+
+	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 rip points back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		regs->rip = (unsigned long)cur->addr;
+		regs->eflags |= kcb->kprobe_old_rflags;
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			restore_previous_kprobe(kcb);
+		else
+			reset_current_kprobe();
+		preempt_enable_no_resched();
+		break;
+	case KPROBE_HIT_ACTIVE:
+	case KPROBE_HIT_SSDONE:
+		/*
+		 * We increment the nmissed count for accounting,
+		 * we can also use npre/npostfault count for accouting
+		 * these specific fault cases.
+		 */
+		kprobes_inc_nmissed_count(cur);
+
+		/*
+		 * We come here because instructions in the pre/post
+		 * handler caused the page_fault, this could happen
+		 * if handler tries to access user space by
+		 * copy_from_user(), get_user() etc. Let the
+		 * user-specified handler try to fix it first.
+		 */
+		if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
+			return 1;
+
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		fixup = search_exception_tables(regs->rip);
+		if (fixup) {
+			regs->rip = fixup->fixup;
+			return 1;
+		}
+
+		/*
+		 * fixup() could not handle it,
+		 * Let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
+	}
+	return 0;
+}
+
+/*
+ * Wrapper routine for handling exceptions.
+ */
+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_INT3:
+		if (kprobe_handler(args->regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_DEBUG:
+		if (post_kprobe_handler(args->regs))
+			ret = NOTIFY_STOP;
+		break;
+	case DIE_GPF:
+	case DIE_PAGE_FAULT:
+		/* kprobe_running() needs smp_processor_id() */
+		preempt_disable();
+		if (kprobe_running() &&
+		    kprobe_fault_handler(args->regs, args->trapnr))
+			ret = NOTIFY_STOP;
+		preempt_enable();
+		break;
+	default:
+		break;
+	}
+	return ret;
+}
+
+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();
+
+	kcb->jprobe_saved_regs = *regs;
+	kcb->jprobe_saved_rsp = (long *) regs->rsp;
+	addr = (unsigned long)(kcb->jprobe_saved_rsp);
+	/*
+	 * As Linus pointed out, gcc assumes that the callee
+	 * owns the argument space and could overwrite it, e.g.
+	 * tailcall optimization. So, to be absolutely safe
+	 * we also save and restore enough stack bytes to cover
+	 * the argument area.
+	 */
+	memcpy(kcb->jprobes_stack, (kprobe_opcode_t *)addr,
+			MIN_STACK_SIZE(addr));
+	regs->eflags &= ~IF_MASK;
+	regs->rip = (unsigned long)(jp->entry);
+	return 1;
+}
+
+void __kprobes jprobe_return(void)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+
+	asm volatile ("       xchg   %%rbx,%%rsp     \n"
+		      "       int3			\n"
+		      "       .globl jprobe_return_end	\n"
+		      "       jprobe_return_end:	\n"
+		      "       nop			\n"::"b"
+		      (kcb->jprobe_saved_rsp):"memory");
+}
+
+int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
+{
+	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	u8 *addr = (u8 *) (regs->rip - 1);
+	unsigned long stack_addr = (unsigned long)(kcb->jprobe_saved_rsp);
+	struct jprobe *jp = container_of(p, struct jprobe, kp);
+
+	if ((addr > (u8 *) jprobe_return) && (addr < (u8 *) jprobe_return_end)) {
+		if ((long *)regs->rsp != kcb->jprobe_saved_rsp) {
+			struct pt_regs *saved_regs =
+			    container_of(kcb->jprobe_saved_rsp,
+					    struct pt_regs, rsp);
+			printk("current rsp %p does not match saved rsp %p\n",
+			       (long *)regs->rsp, kcb->jprobe_saved_rsp);
+			printk("Saved registers for jprobe %p\n", jp);
+			show_registers(saved_regs);
+			printk("Current registers\n");
+			show_registers(regs);
+			BUG();
+		}
+		*regs = kcb->jprobe_saved_regs;
+		memcpy((kprobe_opcode_t *) stack_addr, kcb->jprobes_stack,
+		       MIN_STACK_SIZE(stack_addr));
+		preempt_enable_no_resched();
+		return 1;
+	}
+	return 0;
+}
+
+static struct kprobe trampoline_p = {
+	.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
+	.pre_handler = trampoline_probe_handler
+};
+
+int __init arch_init_kprobes(void)
+{
+	return register_kprobe(&trampoline_p);
+}
+
+int __kprobes arch_trampoline_kprobe(struct kprobe *p)
+{
+	if (p->addr == (kprobe_opcode_t *)&kretprobe_trampoline)
+		return 1;
+
+	return 0;
+}