Merge branch 'tracing/hw-breakpoints' into perf/core

Conflicts:
	arch/x86/kernel/kprobes.c
	kernel/trace/Makefile

Merge reason: hw-breakpoints perf integration is looking
              good in testing and in reviews, plus conflicts
              are mounting up - so merge & resolve.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

39 files changed, 2512 insertions, 217 deletions

diff --git a/arch/Kconfig b/arch/Kconfig
index 7f418bbc261..eef3bbb9707 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -126,4 +126,11 @@ config HAVE_DMA_API_DEBUG
 config HAVE_DEFAULT_NO_SPIN_MUTEXES
 	bool
 
+config HAVE_HW_BREAKPOINT
+	bool
+	depends on HAVE_PERF_EVENTS
+	select ANON_INODES
+	select PERF_EVENTS
+
+
 source "kernel/gcov/Kconfig"
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 72ace9515a0..178084b4377 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -49,6 +49,7 @@ config X86
 	select HAVE_KERNEL_GZIP
 	select HAVE_KERNEL_BZIP2
 	select HAVE_KERNEL_LZMA
+	select HAVE_HW_BREAKPOINT
 	select HAVE_ARCH_KMEMCHECK
 
 config OUTPUT_FORMAT
diff --git a/arch/x86/include/asm/Kbuild b/arch/x86/include/asm/Kbuild
index 4a8e80cdcfa..9f828f87ca3 100644
--- a/arch/x86/include/asm/Kbuild
+++ b/arch/x86/include/asm/Kbuild
@@ -10,6 +10,7 @@ header-y += ptrace-abi.h
 header-y += sigcontext32.h
 header-y += ucontext.h
 header-y += processor-flags.h
+header-y += hw_breakpoint.h
 
 unifdef-y += e820.h
 unifdef-y += ist.h
diff --git a/arch/x86/include/asm/a.out-core.h b/arch/x86/include/asm/a.out-core.h
index bb70e397aa8..7a15588e45d 100644
--- a/arch/x86/include/asm/a.out-core.h
+++ b/arch/x86/include/asm/a.out-core.h
@@ -17,6 +17,7 @@
 
 #include <linux/user.h>
 #include <linux/elfcore.h>
+#include <asm/debugreg.h>
 
 /*
  * fill in the user structure for an a.out core dump
@@ -32,14 +33,7 @@ static inline void aout_dump_thread(struct pt_regs *regs, struct user *dump)
 			>> PAGE_SHIFT;
 	dump->u_dsize -= dump->u_tsize;
 	dump->u_ssize = 0;
-	dump->u_debugreg[0] = current->thread.debugreg0;
-	dump->u_debugreg[1] = current->thread.debugreg1;
-	dump->u_debugreg[2] = current->thread.debugreg2;
-	dump->u_debugreg[3] = current->thread.debugreg3;
-	dump->u_debugreg[4] = 0;
-	dump->u_debugreg[5] = 0;
-	dump->u_debugreg[6] = current->thread.debugreg6;
-	dump->u_debugreg[7] = current->thread.debugreg7;
+	aout_dump_debugregs(dump);
 
 	if (dump->start_stack < TASK_SIZE)
 		dump->u_ssize = ((unsigned long)(TASK_SIZE - dump->start_stack))
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
index 3ea6f37be9e..fdabd843576 100644
--- a/arch/x86/include/asm/debugreg.h
+++ b/arch/x86/include/asm/debugreg.h
@@ -18,6 +18,7 @@
 #define DR_TRAP1	(0x2)		/* db1 */
 #define DR_TRAP2	(0x4)		/* db2 */
 #define DR_TRAP3	(0x8)		/* db3 */
+#define DR_TRAP_BITS	(DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)
 
 #define DR_STEP		(0x4000)	/* single-step */
 #define DR_SWITCH	(0x8000)	/* task switch */
@@ -49,6 +50,8 @@
 
 #define DR_LOCAL_ENABLE_SHIFT 0    /* Extra shift to the local enable bit */
 #define DR_GLOBAL_ENABLE_SHIFT 1   /* Extra shift to the global enable bit */
+#define DR_LOCAL_ENABLE (0x1)      /* Local enable for reg 0 */
+#define DR_GLOBAL_ENABLE (0x2)     /* Global enable for reg 0 */
 #define DR_ENABLE_SIZE 2           /* 2 enable bits per register */
 
 #define DR_LOCAL_ENABLE_MASK (0x55)  /* Set  local bits for all 4 regs */
@@ -67,4 +70,34 @@
 #define DR_LOCAL_SLOWDOWN (0x100)   /* Local slow the pipeline */
 #define DR_GLOBAL_SLOWDOWN (0x200)  /* Global slow the pipeline */
 
+/*
+ * HW breakpoint additions
+ */
+#ifdef __KERNEL__
+
+DECLARE_PER_CPU(unsigned long, dr7);
+
+static inline void hw_breakpoint_disable(void)
+{
+	/* Zero the control register for HW Breakpoint */
+	set_debugreg(0UL, 7);
+
+	/* Zero-out the individual HW breakpoint address registers */
+	set_debugreg(0UL, 0);
+	set_debugreg(0UL, 1);
+	set_debugreg(0UL, 2);
+	set_debugreg(0UL, 3);
+}
+
+static inline int hw_breakpoint_active(void)
+{
+	return __get_cpu_var(dr7) & DR_GLOBAL_ENABLE_MASK;
+}
+
+extern void aout_dump_debugregs(struct user *dump);
+
+extern void hw_breakpoint_restore(void);
+
+#endif	/* __KERNEL__ */
+
 #endif /* _ASM_X86_DEBUGREG_H */
diff --git a/arch/x86/include/asm/hw_breakpoint.h b/arch/x86/include/asm/hw_breakpoint.h
new file mode 100644
index 00000000000..0675a7c4c20
--- /dev/null
+++ b/arch/x86/include/asm/hw_breakpoint.h
@@ -0,0 +1,73 @@
+#ifndef	_I386_HW_BREAKPOINT_H
+#define	_I386_HW_BREAKPOINT_H
+
+#ifdef	__KERNEL__
+#define	__ARCH_HW_BREAKPOINT_H
+
+/*
+ * The name should probably be something dealt in
+ * a higher level. While dealing with the user
+ * (display/resolving)
+ */
+struct arch_hw_breakpoint {
+	char		*name; /* Contains name of the symbol to set bkpt */
+	unsigned long	address;
+	u8		len;
+	u8		type;
+};
+
+#include <linux/kdebug.h>
+#include <linux/percpu.h>
+#include <linux/list.h>
+
+/* Available HW breakpoint length encodings */
+#define X86_BREAKPOINT_LEN_1		0x40
+#define X86_BREAKPOINT_LEN_2		0x44
+#define X86_BREAKPOINT_LEN_4		0x4c
+#define X86_BREAKPOINT_LEN_EXECUTE	0x40
+
+#ifdef CONFIG_X86_64
+#define X86_BREAKPOINT_LEN_8		0x48
+#endif
+
+/* Available HW breakpoint type encodings */
+
+/* trigger on instruction execute */
+#define X86_BREAKPOINT_EXECUTE	0x80
+/* trigger on memory write */
+#define X86_BREAKPOINT_WRITE	0x81
+/* trigger on memory read or write */
+#define X86_BREAKPOINT_RW	0x83
+
+/* Total number of available HW breakpoint registers */
+#define HBP_NUM 4
+
+struct perf_event;
+struct pmu;
+
+extern int arch_check_va_in_userspace(unsigned long va, u8 hbp_len);
+extern int arch_validate_hwbkpt_settings(struct perf_event *bp,
+					 struct task_struct *tsk);
+extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
+					   unsigned long val, void *data);
+
+
+int arch_install_hw_breakpoint(struct perf_event *bp);
+void arch_uninstall_hw_breakpoint(struct perf_event *bp);
+void hw_breakpoint_pmu_read(struct perf_event *bp);
+void hw_breakpoint_pmu_unthrottle(struct perf_event *bp);
+
+extern void
+arch_fill_perf_breakpoint(struct perf_event *bp);
+
+unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type);
+int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type);
+
+extern int arch_bp_generic_fields(int x86_len, int x86_type,
+				  int *gen_len, int *gen_type);
+
+extern struct pmu perf_ops_bp;
+
+#endif	/* __KERNEL__ */
+#endif	/* _I386_HW_BREAKPOINT_H */
+
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index c9786480f0f..6f8ec1c37e0 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -30,6 +30,7 @@ struct mm_struct;
 #include <linux/math64.h>
 #include <linux/init.h>
 
+#define HBP_NUM 4
 /*
  * Default implementation of macro that returns current
  * instruction pointer ("program counter").
@@ -422,6 +423,8 @@ extern unsigned int xstate_size;
 extern void free_thread_xstate(struct task_struct *);
 extern struct kmem_cache *task_xstate_cachep;
 
+struct perf_event;
+
 struct thread_struct {
 	/* Cached TLS descriptors: */
 	struct desc_struct	tls_array[GDT_ENTRY_TLS_ENTRIES];
@@ -443,13 +446,10 @@ struct thread_struct {
 	unsigned long		fs;
 #endif
 	unsigned long		gs;
-	/* Hardware debugging registers: */
-	unsigned long		debugreg0;
-	unsigned long		debugreg1;
-	unsigned long		debugreg2;
-	unsigned long		debugreg3;
-	unsigned long		debugreg6;
-	unsigned long		debugreg7;
+	/* Save middle states of ptrace breakpoints */
+	struct perf_event	*ptrace_bps[HBP_NUM];
+	/* Debug status used for traps, single steps, etc... */
+	unsigned long           debugreg6;
 	/* Fault info: */
 	unsigned long		cr2;
 	unsigned long		trap_no;
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index d8e5d0cdd67..4f2e66e29ec 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -40,7 +40,7 @@ obj-$(CONFIG_X86_64)	+= sys_x86_64.o x8664_ksyms_64.o
 obj-$(CONFIG_X86_64)	+= syscall_64.o vsyscall_64.o
 obj-y			+= bootflag.o e820.o
 obj-y			+= pci-dma.o quirks.o i8237.o topology.o kdebugfs.o
-obj-y			+= alternative.o i8253.o pci-nommu.o
+obj-y			+= alternative.o i8253.o pci-nommu.o hw_breakpoint.o
 obj-y			+= tsc.o io_delay.o rtc.o
 
 obj-$(CONFIG_X86_TRAMPOLINE)	+= trampoline.o
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
new file mode 100644
index 00000000000..752daebe91c
--- /dev/null
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -0,0 +1,545 @@
+/*
+ * 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) 2007 Alan Stern
+ * Copyright (C) 2009 IBM Corporation
+ * Copyright (C) 2009 Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ */
+
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/irqflags.h>
+#include <linux/notifier.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>
+#include <linux/percpu.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+
+#include <asm/hw_breakpoint.h>
+#include <asm/processor.h>
+#include <asm/debugreg.h>
+
+/* Per cpu debug control register value */
+DEFINE_PER_CPU(unsigned long, dr7);
+EXPORT_PER_CPU_SYMBOL(dr7);
+
+/* Per cpu debug address registers values */
+static DEFINE_PER_CPU(unsigned long, cpu_debugreg[HBP_NUM]);
+
+/*
+ * Stores the breakpoints currently in use on each breakpoint address
+ * register for each cpus
+ */
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM]);
+
+
+/*
+ * Encode the length, type, Exact, and Enable bits for a particular breakpoint
+ * as stored in debug register 7.
+ */
+unsigned long encode_dr7(int drnum, unsigned int len, unsigned int type)
+{
+	unsigned long bp_info;
+
+	bp_info = (len | type) & 0xf;
+	bp_info <<= (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
+	bp_info |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE)) |
+				DR_GLOBAL_SLOWDOWN;
+	return bp_info;
+}
+
+/*
+ * Decode the length and type bits for a particular breakpoint as
+ * stored in debug register 7.  Return the "enabled" status.
+ */
+int decode_dr7(unsigned long dr7, int bpnum, unsigned *len, unsigned *type)
+{
+	int bp_info = dr7 >> (DR_CONTROL_SHIFT + bpnum * DR_CONTROL_SIZE);
+
+	*len = (bp_info & 0xc) | 0x40;
+	*type = (bp_info & 0x3) | 0x80;
+
+	return (dr7 >> (bpnum * DR_ENABLE_SIZE)) & 0x3;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ *
+ * We seek a free debug address register and use it for this
+ * breakpoint. Eventually we enable it in the debug control register.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	unsigned long *dr7;
+	int i;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
+
+		if (!*slot) {
+			*slot = bp;
+			break;
+		}
+	}
+
+	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+		return -EBUSY;
+
+	set_debugreg(info->address, i);
+	__get_cpu_var(cpu_debugreg[i]) = info->address;
+
+	dr7 = &__get_cpu_var(dr7);
+	*dr7 |= encode_dr7(i, info->len, info->type);
+
+	set_debugreg(*dr7, 7);
+
+	return 0;
+}
+
+/*
+ * Uninstall the breakpoint contained in the given counter.
+ *
+ * First we search the debug address register it uses and then we disable
+ * it.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	unsigned long *dr7;
+	int i;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		struct perf_event **slot = &__get_cpu_var(bp_per_reg[i]);
+
+		if (*slot == bp) {
+			*slot = NULL;
+			break;
+		}
+	}
+
+	if (WARN_ONCE(i == HBP_NUM, "Can't find any breakpoint slot"))
+		return;
+
+	dr7 = &__get_cpu_var(dr7);
+	*dr7 &= ~encode_dr7(i, info->len, info->type);
+
+	set_debugreg(*dr7, 7);
+}
+
+static int get_hbp_len(u8 hbp_len)
+{
+	unsigned int len_in_bytes = 0;
+
+	switch (hbp_len) {
+	case X86_BREAKPOINT_LEN_1:
+		len_in_bytes = 1;
+		break;
+	case X86_BREAKPOINT_LEN_2:
+		len_in_bytes = 2;
+		break;
+	case X86_BREAKPOINT_LEN_4:
+		len_in_bytes = 4;
+		break;
+#ifdef CONFIG_X86_64
+	case X86_BREAKPOINT_LEN_8:
+		len_in_bytes = 8;
+		break;
+#endif
+	}
+	return len_in_bytes;
+}
+
+/*
+ * Check for virtual address in user space.
+ */
+int arch_check_va_in_userspace(unsigned long va, u8 hbp_len)
+{
+	unsigned int len;
+
+	len = get_hbp_len(hbp_len);
+
+	return (va <= TASK_SIZE - len);
+}
+
+/*
+ * Check for virtual address in kernel space.
+ */
+static int arch_check_va_in_kernelspace(unsigned long va, u8 hbp_len)
+{
+	unsigned int len;
+
+	len = get_hbp_len(hbp_len);
+
+	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+}
+
+/*
+ * Store a breakpoint's encoded address, length, and type.
+ */
+static int arch_store_info(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	/*
+	 * For kernel-addresses, either the address or symbol name can be
+	 * specified.
+	 */
+	if (info->name)
+		info->address = (unsigned long)
+				kallsyms_lookup_name(info->name);
+	if (info->address)
+		return 0;
+
+	return -EINVAL;
+}
+
+int arch_bp_generic_fields(int x86_len, int x86_type,
+			   int *gen_len, int *gen_type)
+{
+	/* Len */
+	switch (x86_len) {
+	case X86_BREAKPOINT_LEN_1:
+		*gen_len = HW_BREAKPOINT_LEN_1;
+		break;
+	case X86_BREAKPOINT_LEN_2:
+		*gen_len = HW_BREAKPOINT_LEN_2;
+		break;
+	case X86_BREAKPOINT_LEN_4:
+		*gen_len = HW_BREAKPOINT_LEN_4;
+		break;
+#ifdef CONFIG_X86_64
+	case X86_BREAKPOINT_LEN_8:
+		*gen_len = HW_BREAKPOINT_LEN_8;
+		break;
+#endif
+	default:
+		return -EINVAL;
+	}
+
+	/* Type */
+	switch (x86_type) {
+	case X86_BREAKPOINT_EXECUTE:
+		*gen_type = HW_BREAKPOINT_X;
+		break;
+	case X86_BREAKPOINT_WRITE:
+		*gen_type = HW_BREAKPOINT_W;
+		break;
+	case X86_BREAKPOINT_RW:
+		*gen_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+
+static int arch_build_bp_info(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+
+	info->address = bp->attr.bp_addr;
+
+	/* Len */
+	switch (bp->attr.bp_len) {
+	case HW_BREAKPOINT_LEN_1:
+		info->len = X86_BREAKPOINT_LEN_1;
+		break;
+	case HW_BREAKPOINT_LEN_2:
+		info->len = X86_BREAKPOINT_LEN_2;
+		break;
+	case HW_BREAKPOINT_LEN_4:
+		info->len = X86_BREAKPOINT_LEN_4;
+		break;
+#ifdef CONFIG_X86_64
+	case HW_BREAKPOINT_LEN_8:
+		info->len = X86_BREAKPOINT_LEN_8;
+		break;
+#endif
+	default:
+		return -EINVAL;
+	}
+
+	/* Type */
+	switch (bp->attr.bp_type) {
+	case HW_BREAKPOINT_W:
+		info->type = X86_BREAKPOINT_WRITE;
+		break;
+	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+		info->type = X86_BREAKPOINT_RW;
+		break;
+	case HW_BREAKPOINT_X:
+		info->type = X86_BREAKPOINT_EXECUTE;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int arch_validate_hwbkpt_settings(struct perf_event *bp,
+				  struct task_struct *tsk)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	unsigned int align;
+	int ret;
+
+
+	ret = arch_build_bp_info(bp);
+	if (ret)
+		return ret;
+
+	ret = -EINVAL;
+
+	if (info->type == X86_BREAKPOINT_EXECUTE)
+		/*
+		 * Ptrace-refactoring code
+		 * For now, we'll allow instruction breakpoint only for user-space
+		 * addresses
+		 */
+		if ((!arch_check_va_in_userspace(info->address, info->len)) &&
+			info->len != X86_BREAKPOINT_EXECUTE)
+			return ret;
+
+	switch (info->len) {
+	case X86_BREAKPOINT_LEN_1:
+		align = 0;
+		break;
+	case X86_BREAKPOINT_LEN_2:
+		align = 1;
+		break;
+	case X86_BREAKPOINT_LEN_4:
+		align = 3;
+		break;
+#ifdef CONFIG_X86_64
+	case X86_BREAKPOINT_LEN_8:
+		align = 7;
+		break;
+#endif
+	default:
+		return ret;
+	}
+
+	if (bp->callback)
+		ret = arch_store_info(bp);
+
+	if (ret < 0)
+		return ret;
+	/*
+	 * Check that the low-order bits of the address are appropriate
+	 * for the alignment implied by len.
+	 */
+	if (info->address & align)
+		return -EINVAL;
+
+	/* Check that the virtual address is in the proper range */
+	if (tsk) {
+		if (!arch_check_va_in_userspace(info->address, info->len))
+			return -EFAULT;
+	} else {
+		if (!arch_check_va_in_kernelspace(info->address, info->len))
+			return -EFAULT;
+	}
+
+	return 0;
+}
+
+/*
+ * Dump the debug register contents to the user.
+ * We can't dump our per cpu values because it
+ * may contain cpu wide breakpoint, something that
+ * doesn't belong to the current task.
+ *
+ * TODO: include non-ptrace user breakpoints (perf)
+ */
+void aout_dump_debugregs(struct user *dump)
+{
+	int i;
+	int dr7 = 0;
+	struct perf_event *bp;
+	struct arch_hw_breakpoint *info;
+	struct thread_struct *thread = &current->thread;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		bp = thread->ptrace_bps[i];
+
+		if (bp && !bp->attr.disabled) {
+			dump->u_debugreg[i] = bp->attr.bp_addr;
+			info = counter_arch_bp(bp);
+			dr7 |= encode_dr7(i, info->len, info->type);
+		} else {
+			dump->u_debugreg[i] = 0;
+		}
+	}
+
+	dump->u_debugreg[4] = 0;
+	dump->u_debugreg[5] = 0;
+	dump->u_debugreg[6] = current->thread.debugreg6;
+
+	dump->u_debugreg[7] = dr7;
+}
+EXPORT_SYMBOL_GPL(aout_dump_debugregs);
+
+/*
+ * Release the user breakpoints used by ptrace
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+	int i;
+	struct thread_struct *t = &tsk->thread;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		unregister_hw_breakpoint(t->ptrace_bps[i]);
+		t->ptrace_bps[i] = NULL;
+	}
+}
+
+void hw_breakpoint_restore(void)
+{
+	set_debugreg(__get_cpu_var(cpu_debugreg[0]), 0);
+	set_debugreg(__get_cpu_var(cpu_debugreg[1]), 1);
+	set_debugreg(__get_cpu_var(cpu_debugreg[2]), 2);
+	set_debugreg(__get_cpu_var(cpu_debugreg[3]), 3);
+	set_debugreg(current->thread.debugreg6, 6);
+	set_debugreg(__get_cpu_var(dr7), 7);
+}
+EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
+
+/*
+ * Handle debug exception notifications.
+ *
+ * Return value is either NOTIFY_STOP or NOTIFY_DONE as explained below.
+ *
+ * NOTIFY_DONE returned if one of the following conditions is true.
+ * i) When the causative address is from user-space and the exception
+ * is a valid one, i.e. not triggered as a result of lazy debug register
+ * switching
+ * ii) When there are more bits than trap<n> set in DR6 register (such
+ * as BD, BS or BT) indicating that more than one debug condition is
+ * met and requires some more action in do_debug().
+ *
+ * NOTIFY_STOP returned for all other cases
+ *
+ */
+static int __kprobes hw_breakpoint_handler(struct die_args *args)
+{
+	int i, cpu, rc = NOTIFY_STOP;
+	struct perf_event *bp;
+	unsigned long dr7, dr6;
+	unsigned long *dr6_p;
+
+	/* The DR6 value is pointed by args->err */
+	dr6_p = (unsigned long *)ERR_PTR(args->err);
+	dr6 = *dr6_p;
+
+	/* Do an early return if no trap bits are set in DR6 */
+	if ((dr6 & DR_TRAP_BITS) == 0)
+		return NOTIFY_DONE;
+
+	get_debugreg(dr7, 7);
+	/* Disable breakpoints during exception handling */
+	set_debugreg(0UL, 7);
+	/*
+	 * Assert that local interrupts are disabled
+	 * Reset the DRn bits in the virtualized register value.
+	 * The ptrace trigger routine will add in whatever is needed.
+	 */
+	current->thread.debugreg6 &= ~DR_TRAP_BITS;
+	cpu = get_cpu();
+
+	/* Handle all the breakpoints that were triggered */
+	for (i = 0; i < HBP_NUM; ++i) {
+		if (likely(!(dr6 & (DR_TRAP0 << i))))
+			continue;
+
+		/*
+		 * The counter may be concurrently released but that can only
+		 * occur from a call_rcu() path. We can then safely fetch
+		 * the breakpoint, use its callback, touch its counter
+		 * while we are in an rcu_read_lock() path.
+		 */
+		rcu_read_lock();
+
+		bp = per_cpu(bp_per_reg[i], cpu);
+		if (bp)
+			rc = NOTIFY_DONE;
+		/*
+		 * Reset the 'i'th TRAP bit in dr6 to denote completion of
+		 * exception handling
+		 */
+		(*dr6_p) &= ~(DR_TRAP0 << i);
+		/*
+		 * bp can be NULL due to lazy debug register switching
+		 * or due to concurrent perf counter removing.
+		 */
+		if (!bp) {
+			rcu_read_unlock();
+			break;
+		}
+
+		(bp->callback)(bp, args->regs);
+
+		rcu_read_unlock();
+	}
+	if (dr6 & (~DR_TRAP_BITS))
+		rc = NOTIFY_DONE;
+
+	set_debugreg(dr7, 7);
+	put_cpu();
+
+	return rc;
+}
+
+/*
+ * Handle debug exception notifications.
+ */
+int __kprobes hw_breakpoint_exceptions_notify(
+		struct notifier_block *unused, unsigned long val, void *data)
+{
+	if (val != DIE_DEBUG)
+		return NOTIFY_DONE;
+
+	return hw_breakpoint_handler(data);
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+	/* TODO */
+}
+
+void hw_breakpoint_pmu_unthrottle(struct perf_event *bp)
+{
+	/* TODO */
+}
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 8d82a77a3f3..34e86b67550 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -43,6 +43,7 @@
 #include <linux/smp.h>
 #include <linux/nmi.h>
 
+#include <asm/debugreg.h>
 #include <asm/apicdef.h>
 #include <asm/system.h>
 
@@ -434,6 +435,11 @@ single_step_cont(struct pt_regs *regs, struct die_args *args)
 			"resuming...\n");
 	kgdb_arch_handle_exception(args->trapnr, args->signr,
 				   args->err, "c", "", regs);
+	/*
+	 * Reset the BS bit in dr6 (pointed by args->err) to
+	 * denote completion of processing
+	 */
+	(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 
 	return NOTIFY_STOP;
 }
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index c5f1f117e0c..3fe86d706a1 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -56,6 +56,7 @@
 #include <asm/uaccess.h>
 #include <asm/alternative.h>
 #include <asm/insn.h>
+#include <asm/debugreg.h>
 
 void jprobe_return_end(void);
 
@@ -945,8 +946,14 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 			ret = NOTIFY_STOP;
 		break;
 	case DIE_DEBUG:
-		if (post_kprobe_handler(args->regs))
+		if (post_kprobe_handler(args->regs)) {
+			/*
+			 * Reset the BS bit in dr6 (pointed by args->err) to
+			 * denote completion of processing
+			 */
+			(*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;
 			ret = NOTIFY_STOP;
+		}
 		break;
 	case DIE_GPF:
 		/*
diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c
index c1c429d0013..c843f8406da 100644
--- a/arch/x86/kernel/machine_kexec_32.c
+++ b/arch/x86/kernel/machine_kexec_32.c
@@ -25,6 +25,7 @@
 #include <asm/desc.h>
 #include <asm/system.h>
 #include <asm/cacheflush.h>
+#include <asm/debugreg.h>
 
 static void set_idt(void *newidt, __u16 limit)
 {
@@ -202,6 +203,7 @@ void machine_kexec(struct kimage *image)
 
 	/* Interrupts aren't acceptable while we reboot */
 	local_irq_disable();
+	hw_breakpoint_disable();
 
 	if (image->preserve_context) {
 #ifdef CONFIG_X86_IO_APIC
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 84c3bf209e9..4a8bb82248a 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -18,6 +18,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/mmu_context.h>
+#include <asm/debugreg.h>
 
 static int init_one_level2_page(struct kimage *image, pgd_t *pgd,
 				unsigned long addr)
@@ -282,6 +283,7 @@ void machine_kexec(struct kimage *image)
 
 	/* Interrupts aren't acceptable while we reboot */
 	local_irq_disable();
+	hw_breakpoint_disable();
 
 	if (image->preserve_context) {
 #ifdef CONFIG_X86_IO_APIC
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 5284cd2b577..744508e7cfd 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -10,6 +10,7 @@
 #include <linux/clockchips.h>
 #include <linux/random.h>
 #include <trace/events/power.h>
+#include <linux/hw_breakpoint.h>
 #include <asm/system.h>
 #include <asm/apic.h>
 #include <asm/syscalls.h>
@@ -17,6 +18,7 @@
 #include <asm/uaccess.h>
 #include <asm/i387.h>
 #include <asm/ds.h>
+#include <asm/debugreg.h>
 
 unsigned long idle_halt;
 EXPORT_SYMBOL(idle_halt);
@@ -103,14 +105,7 @@ void flush_thread(void)
 	}
 #endif
 
-	clear_tsk_thread_flag(tsk, TIF_DEBUG);
-
-	tsk->thread.debugreg0 = 0;
-	tsk->thread.debugreg1 = 0;
-	tsk->thread.debugreg2 = 0;
-	tsk->thread.debugreg3 = 0;
-	tsk->thread.debugreg6 = 0;
-	tsk->thread.debugreg7 = 0;
+	flush_ptrace_hw_breakpoint(tsk);
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 	/*
 	 * Forget coprocessor state..
@@ -192,16 +187,6 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p,
 	else if (next->debugctlmsr != prev->debugctlmsr)
 		update_debugctlmsr(next->debugctlmsr);
 
-	if (test_tsk_thread_flag(next_p, TIF_DEBUG)) {
-		set_debugreg(next->debugreg0, 0);
-		set_debugreg(next->debugreg1, 1);
-		set_debugreg(next->debugreg2, 2);
-		set_debugreg(next->debugreg3, 3);
-		/* no 4 and 5 */
-		set_debugreg(next->debugreg6, 6);
-		set_debugreg(next->debugreg7, 7);
-	}
-
 	if (test_tsk_thread_flag(prev_p, TIF_NOTSC) ^
 	    test_tsk_thread_flag(next_p, TIF_NOTSC)) {
 		/* prev and next are different */
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 4cf79567cda..d5bd3132ee7 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -58,6 +58,7 @@
 #include <asm/idle.h>
 #include <asm/syscalls.h>
 #include <asm/ds.h>
+#include <asm/debugreg.h>
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
@@ -259,7 +260,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 
 	task_user_gs(p) = get_user_gs(regs);
 
+	p->thread.io_bitmap_ptr = NULL;
 	tsk = current;
+	err = -ENOMEM;
+
+	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
+
 	if (unlikely(test_tsk_thread_flag(tsk, TIF_IO_BITMAP))) {
 		p->thread.io_bitmap_ptr = kmemdup(tsk->thread.io_bitmap_ptr,
 						IO_BITMAP_BYTES, GFP_KERNEL);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index eb62cbcaa49..70cf15873f3 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -52,6 +52,7 @@
 #include <asm/idle.h>
 #include <asm/syscalls.h>
 #include <asm/ds.h>
+#include <asm/debugreg.h>
 
 asmlinkage extern void ret_from_fork(void);
 
@@ -297,12 +298,16 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 
 	p->thread.fs = me->thread.fs;
 	p->thread.gs = me->thread.gs;
+	p->thread.io_bitmap_ptr = NULL;
 
 	savesegment(gs, p->thread.gsindex);
 	savesegment(fs, p->thread.fsindex);
 	savesegment(es, p->thread.es);
 	savesegment(ds, p->thread.ds);
 
+	err = -ENOMEM;
+	memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
+
 	if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) {
 		p->thread.io_bitmap_ptr = kmalloc(IO_BITMAP_BYTES, GFP_KERNEL);
 		if (!p->thread.io_bitmap_ptr) {
@@ -341,6 +346,7 @@ out:
 		kfree(p->thread.io_bitmap_ptr);
 		p->thread.io_bitmap_max = 0;
 	}
+
 	return err;
 }
 
@@ -495,6 +501,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	 */
 	if (preload_fpu)
 		__math_state_restore();
+
 	return prev_p;
 }
 
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index c4f76d275ee..b25f8947ed7 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -22,6 +22,8 @@
 #include <linux/seccomp.h>
 #include <linux/signal.h>
 #include <linux/workqueue.h>
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -34,6 +36,7 @@
 #include <asm/prctl.h>
 #include <asm/proto.h>
 #include <asm/ds.h>
+#include <asm/hw_breakpoint.h>
 
 #include "tls.h"
 
@@ -249,11 +252,6 @@ static int set_segment_reg(struct task_struct *task,
 	return 0;
 }
 
-static unsigned long debugreg_addr_limit(struct task_struct *task)
-{
-	return TASK_SIZE - 3;
-}
-
 #else  /* CONFIG_X86_64 */
 
 #define FLAG_MASK		(FLAG_MASK_32 | X86_EFLAGS_NT)
@@ -378,15 +376,6 @@ static int set_segment_reg(struct task_struct *task,
 	return 0;
 }
 
-static unsigned long debugreg_addr_limit(struct task_struct *task)
-{
-#ifdef CONFIG_IA32_EMULATION
-	if (test_tsk_thread_flag(task, TIF_IA32))
-		return IA32_PAGE_OFFSET - 3;
-#endif
-	return TASK_SIZE_MAX - 7;
-}
-
 #endif	/* CONFIG_X86_32 */
 
 static unsigned long get_flags(struct task_struct *task)
@@ -566,99 +555,229 @@ static int genregs_set(struct task_struct *target,
 	return ret;
 }
 
+static void ptrace_triggered(struct perf_event *bp, void *data)
+{
+	int i;
+	struct thread_struct *thread = &(current->thread);
+
+	/*
+	 * Store in the virtual DR6 register the fact that the breakpoint
+	 * was hit so the thread's debugger will see it.
+	 */
+	for (i = 0; i < HBP_NUM; i++) {
+		if (thread->ptrace_bps[i] == bp)
+			break;
+	}
+
+	thread->debugreg6 |= (DR_TRAP0 << i);
+}
+
 /*
- * This function is trivial and will be inlined by the compiler.
- * Having it separates the implementation details of debug
- * registers from the interface details of ptrace.
+ * Walk through every ptrace breakpoints for this thread and
+ * build the dr7 value on top of their attributes.
+ *
  */
-static unsigned long ptrace_get_debugreg(struct task_struct *child, int n)
+static unsigned long ptrace_get_dr7(struct perf_event *bp[])
 {
-	switch (n) {
-	case 0:		return child->thread.debugreg0;
-	case 1:		return child->thread.debugreg1;
-	case 2:		return child->thread.debugreg2;
-	case 3:		return child->thread.debugreg3;
-	case 6:		return child->thread.debugreg6;
-	case 7:		return child->thread.debugreg7;
+	int i;
+	int dr7 = 0;
+	struct arch_hw_breakpoint *info;
+
+	for (i = 0; i < HBP_NUM; i++) {
+		if (bp[i] && !bp[i]->attr.disabled) {
+			info = counter_arch_bp(bp[i]);
+			dr7 |= encode_dr7(i, info->len, info->type);
+		}
 	}
-	return 0;
+
+	return dr7;
 }
 
-static int ptrace_set_debugreg(struct task_struct *child,
-			       int n, unsigned long data)
+/*
+ * Handle ptrace writes to debug register 7.
+ */
+static int ptrace_write_dr7(struct task_struct *tsk, unsigned long data)
 {
-	int i;
+	struct thread_struct *thread = &(tsk->thread);
+	unsigned long old_dr7;
+	int i, orig_ret = 0, rc = 0;
+	int enabled, second_pass = 0;
+	unsigned len, type;
+	int gen_len, gen_type;
+	struct perf_event *bp;
+
+	data &= ~DR_CONTROL_RESERVED;
+	old_dr7 = ptrace_get_dr7(thread->ptrace_bps);
+restore:
+	/*
+	 * Loop through all the hardware breakpoints, making the
+	 * appropriate changes to each.
+	 */
+	for (i = 0; i < HBP_NUM; i++) {
+		enabled = decode_dr7(data, i, &len, &type);
+		bp = thread->ptrace_bps[i];
+
+		if (!enabled) {
+			if (bp) {
+				/*
+				 * Don't unregister the breakpoints right-away,
+				 * unless all register_user_hw_breakpoint()
+				 * requests have succeeded. This prevents
+				 * any window of opportunity for debug
+				 * register grabbing by other users.
+				 */
+				if (!second_pass)
+					continue;
+				thread->ptrace_bps[i] = NULL;
+				unregister_hw_breakpoint(bp);
+			}
+			continue;
+		}
 
-	if (unlikely(n == 4 || n == 5))
-		return -EIO;
+		/*
+		 * We shoud have at least an inactive breakpoint at this
+		 * slot. It means the user is writing dr7 without having
+		 * written the address register first
+		 */
+		if (!bp) {
+			rc = -EINVAL;
+			break;
+		}
 
-	if (n < 4 && unlikely(data >= debugreg_addr_limit(child)))
-		return -EIO;
+		rc = arch_bp_generic_fields(len, type, &gen_len, &gen_type);
+		if (rc)
+			break;
 
-	switch (n) {
-	case 0:		child->thread.debugreg0 = data; break;
-	case 1:		child->thread.debugreg1 = data; break;
-	case 2:		child->thread.debugreg2 = data; break;
-	case 3:		child->thread.debugreg3 = data; break;
+		/*
+		 * This is a temporary thing as bp is unregistered/registered
+		 * to simulate modification
+		 */
+		bp = modify_user_hw_breakpoint(bp, bp->attr.bp_addr, gen_len,
+					       gen_type, bp->callback,
+					       tsk, true);
+		thread->ptrace_bps[i] = NULL;
 
-	case 6:
-		if ((data & ~0xffffffffUL) != 0)
-			return -EIO;
-		child->thread.debugreg6 = data;
-		break;
+		if (!bp) { /* incorrect bp, or we have a bug in bp API */
+			rc = -EINVAL;
+			break;
+		}
+		if (IS_ERR(bp)) {
+			rc = PTR_ERR(bp);
+			bp = NULL;
+			break;
+		}
+		thread->ptrace_bps[i] = bp;
+	}
+	/*
+	 * Make a second pass to free the remaining unused breakpoints
+	 * or to restore the original breakpoints if an error occurred.
+	 */
+	if (!second_pass) {
+		second_pass = 1;
+		if (rc < 0) {
+			orig_ret = rc;
+			data = old_dr7;
+		}
+		goto restore;
+	}
+	return ((orig_ret < 0) ? orig_ret : rc);
+}
 
-	case 7:
+/*
+ * Handle PTRACE_PEEKUSR calls for the debug register area.
+ */
+static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
+{
+	struct thread_struct *thread = &(tsk->thread);
+	unsigned long val = 0;
+
+	if (n < HBP_NUM) {
+		struct perf_event *bp;
+		bp = thread->ptrace_bps[n];
+		if (!bp)
+			return 0;
+		val = bp->hw.info.address;
+	} else if (n == 6) {
+		val = thread->debugreg6;
+	 } else if (n == 7) {
+		val = ptrace_get_dr7(thread->ptrace_bps);
+	}
+	return val;
+}
+
+static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
+				      unsigned long addr)
+{
+	struct perf_event *bp;
+	struct thread_struct *t = &tsk->thread;
+
+	if (!t->ptrace_bps[nr]) {
 		/*
-		 * Sanity-check data. Take one half-byte at once with
-		 * check = (val >> (16 + 4*i)) & 0xf. It contains the
-		 * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
-		 * 2 and 3 are LENi. Given a list of invalid values,
-		 * we do mask |= 1 << invalid_value, so that
-		 * (mask >> check) & 1 is a correct test for invalid
-		 * values.
-		 *
-		 * R/Wi contains the type of the breakpoint /
-		 * watchpoint, LENi contains the length of the watched
-		 * data in the watchpoint case.
-		 *
-		 * The invalid values are:
-		 * - LENi == 0x10 (undefined), so mask |= 0x0f00.	[32-bit]
-		 * - R/Wi == 0x10 (break on I/O reads or writes), so
-		 *   mask |= 0x4444.
-		 * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
-		 *   0x1110.
-		 *
-		 * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
-		 *
-		 * See the Intel Manual "System Programming Guide",
-		 * 15.2.4
-		 *
-		 * Note that LENi == 0x10 is defined on x86_64 in long
-		 * mode (i.e. even for 32-bit userspace software, but
-		 * 64-bit kernel), so the x86_64 mask value is 0x5454.
-		 * See the AMD manual no. 24593 (AMD64 System Programming)
+		 * Put stub len and type to register (reserve) an inactive but
+		 * correct bp
 		 */
-#ifdef CONFIG_X86_32
-#define	DR7_MASK	0x5f54
-#else
-#define	DR7_MASK	0x5554
-#endif
-		data &= ~DR_CONTROL_RESERVED;
-		for (i = 0; i < 4; i++)
-			if ((DR7_MASK >> ((data >> (16 + 4*i)) & 0xf)) & 1)
-				return -EIO;
-		child->thread.debugreg7 = data;
-		if (data)
-			set_tsk_thread_flag(child, TIF_DEBUG);
-		else
-			clear_tsk_thread_flag(child, TIF_DEBUG);
-		break;
+		bp = register_user_hw_breakpoint(addr, HW_BREAKPOINT_LEN_1,
+						 HW_BREAKPOINT_W,
+						 ptrace_triggered, tsk,
+						 false);
+	} else {
+		bp = t->ptrace_bps[nr];
+		t->ptrace_bps[nr] = NULL;
+		bp = modify_user_hw_breakpoint(bp, addr, bp->attr.bp_len,
+					       bp->attr.bp_type,
+					       bp->callback,
+					       tsk,
+					       bp->attr.disabled);
 	}
 
+	if (!bp)
+		return -EIO;
+	/*
+	 * CHECKME: the previous code returned -EIO if the addr wasn't a
+	 * valid task virtual addr. The new one will return -EINVAL in this
+	 * case.
+	 * -EINVAL may be what we want for in-kernel breakpoints users, but
+	 * -EIO looks better for ptrace, since we refuse a register writing
+	 * for the user. And anyway this is the previous behaviour.
+	 */
+	if (IS_ERR(bp))
+		return PTR_ERR(bp);
+
+	t->ptrace_bps[nr] = bp;
+
 	return 0;
 }
 
 /*
+ * Handle PTRACE_POKEUSR calls for the debug register area.
+ */
+int ptrace_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
+{
+	struct thread_struct *thread = &(tsk->thread);
+	int rc = 0;
+
+	/* There are no DR4 or DR5 registers */
+	if (n == 4 || n == 5)
+		return -EIO;
+
+	if (n == 6) {
+		thread->debugreg6 = val;
+		goto ret_path;
+	}
+	if (n < HBP_NUM) {
+		rc = ptrace_set_breakpoint_addr(tsk, n, val);
+		if (rc)
+			return rc;
+	}
+	/* All that's left is DR7 */
+	if (n == 7)
+		rc = ptrace_write_dr7(tsk, val);
+
+ret_path:
+	return rc;
+}
+
+/*
  * These access the current or another (stopped) task's io permission
  * bitmap for debugging or core dump.
  */
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 6a44a76055a..fbf3b07c856 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -799,15 +799,6 @@ static void do_signal(struct pt_regs *regs)
 
 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 	if (signr > 0) {
-		/*
-		 * Re-enable any watchpoints before delivering the
-		 * signal to user space. The processor register will
-		 * have been cleared if the watchpoint triggered
-		 * inside the kernel.
-		 */
-		if (current->thread.debugreg7)
-			set_debugreg(current->thread.debugreg7, 7);
-
 		/* Whee! Actually deliver the signal.  */
 		if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
 			/*
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 7e37dcee0cc..33399176512 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -529,77 +529,56 @@ asmlinkage __kprobes struct pt_regs *sync_regs(struct pt_regs *eregs)
 dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code)
 {
 	struct task_struct *tsk = current;
-	unsigned long condition;
+	unsigned long dr6;
 	int si_code;
 
-	get_debugreg(condition, 6);
+	get_debugreg(dr6, 6);
 
 	/* Catch kmemcheck conditions first of all! */
-	if (condition & DR_STEP && kmemcheck_trap(regs))
+	if ((dr6 & DR_STEP) && kmemcheck_trap(regs))
 		return;
 
+	/* DR6 may or may not be cleared by the CPU */
+	set_debugreg(0, 6);
 	/*
 	 * The processor cleared BTF, so don't mark that we need it set.
 	 */
 	clear_tsk_thread_flag(tsk, TIF_DEBUGCTLMSR);
 	tsk->thread.debugctlmsr = 0;
 
-	if (notify_die(DIE_DEBUG, "debug", regs, condition, error_code,
-						SIGTRAP) == NOTIFY_STOP)
+	/* Store the virtualized DR6 value */
+	tsk->thread.debugreg6 = dr6;
+
+	if (notify_die(DIE_DEBUG, "debug", regs, PTR_ERR(&dr6), error_code,
+							SIGTRAP) == NOTIFY_STOP)
 		return;
 
 	/* It's safe to allow irq's after DR6 has been saved */
 	preempt_conditional_sti(regs);
 
-	/* Mask out spurious debug traps due to lazy DR7 setting */
-	if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
-		if (!tsk->thread.debugreg7)
-			goto clear_dr7;
+	if (regs->flags & X86_VM_MASK) {
+		handle_vm86_trap((struct kernel_vm86_regs *) regs,
+				error_code, 1);
+		return;
 	}
 
-#ifdef CONFIG_X86_32
-	if (regs->flags & X86_VM_MASK)
-		goto debug_vm86;
-#endif
-
-	/* Save debug status register where ptrace can see it */
-	tsk->thread.debugreg6 = condition;
-
 	/*
-	 * Single-stepping through TF: make sure we ignore any events in
-	 * kernel space (but re-enable TF when returning to user mode).
+	 * Single-stepping through system calls: ignore any exceptions in
+	 * kernel space, but re-enable TF when returning to user mode.
+	 *
+	 * We already checked v86 mode above, so we can check for kernel mode
+	 * by just checking the CPL of CS.
 	 */
-	if (condition & DR_STEP) {
-		if (!user_mode(regs))
-			goto clear_TF_reenable;
+	if ((dr6 & DR_STEP) && !user_mode(regs)) {
+		tsk->thread.debugreg6 &= ~DR_STEP;
+		set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
+		regs->flags &= ~X86_EFLAGS_TF;
 	}
-
-	si_code = get_si_code(condition);
-	/* Ok, finally something we can handle */
-	send_sigtrap(tsk, regs, error_code, si_code);
-
-	/*
-	 * Disable additional traps. They'll be re-enabled when
-	 * the signal is delivered.
-	 */
-clear_dr7:
-	set_debugreg(0, 7);
+	si_code = get_si_code(tsk->thread.debugreg6);
+	if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS))
+		send_sigtrap(tsk, regs, error_code, si_code);
 	preempt_conditional_cli(regs);
-	return;
 
-#ifdef CONFIG_X86_32
-debug_vm86:
-	/* reenable preemption: handle_vm86_trap() might sleep */
-	dec_preempt_count();
-	handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1);
-	conditional_cli(regs);
-	return;
-#endif
-
-clear_TF_reenable:
-	set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
-	regs->flags &= ~X86_EFLAGS_TF;
-	preempt_conditional_cli(regs);
 	return;
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ae07d261527..4fc80174191 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -42,6 +42,7 @@
 #define CREATE_TRACE_POINTS
 #include "trace.h"
 
+#include <asm/debugreg.h>
 #include <asm/uaccess.h>
 #include <asm/msr.h>
 #include <asm/desc.h>
@@ -3643,14 +3644,15 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 	trace_kvm_entry(vcpu->vcpu_id);
 	kvm_x86_ops->run(vcpu, kvm_run);
 
-	if (unlikely(vcpu->arch.switch_db_regs || test_thread_flag(TIF_DEBUG))) {
-		set_debugreg(current->thread.debugreg0, 0);
-		set_debugreg(current->thread.debugreg1, 1);
-		set_debugreg(current->thread.debugreg2, 2);
-		set_debugreg(current->thread.debugreg3, 3);
-		set_debugreg(current->thread.debugreg6, 6);
-		set_debugreg(current->thread.debugreg7, 7);
-	}
+	/*
+	 * If the guest has used debug registers, at least dr7
+	 * will be disabled while returning to the host.
+	 * If we don't have active breakpoints in the host, we don't
+	 * care about the messed up debug address registers. But if
+	 * we have some of them active, restore the old state.
+	 */
+	if (hw_breakpoint_active())
+		hw_breakpoint_restore();
 
 	set_bit(KVM_REQ_KICK, &vcpu->requests);
 	local_irq_enable();
diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c
index 16ccbd77917..11a4ad4d625 100644
--- a/arch/x86/mm/kmmio.c
+++ b/arch/x86/mm/kmmio.c
@@ -540,8 +540,14 @@ kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args)
 	struct die_args *arg = args;
 
 	if (val == DIE_DEBUG && (arg->err & DR_STEP))
-		if (post_kmmio_handler(arg->err, arg->regs) == 1)
+		if (post_kmmio_handler(arg->err, arg->regs) == 1) {
+			/*
+			 * Reset the BS bit in dr6 (pointed by args->err) to
+			 * denote completion of processing
+			 */
+			(*(unsigned long *)ERR_PTR(arg->err)) &= ~DR_STEP;
 			return NOTIFY_STOP;
+		}
 
 	return NOTIFY_DONE;
 }
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 8aa85f17667..0a979f3e5b8 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -18,6 +18,7 @@
 #include <asm/mce.h>
 #include <asm/xcr.h>
 #include <asm/suspend.h>
+#include <asm/debugreg.h>
 
 #ifdef CONFIG_X86_32
 static struct saved_context saved_context;
@@ -142,31 +143,6 @@ static void fix_processor_context(void)
 #endif
 	load_TR_desc();				/* This does ltr */
 	load_LDT(&current->active_mm->context);	/* This does lldt */
-
-	/*
-	 * Now maybe reload the debug registers
-	 */
-	if (current->thread.debugreg7) {
-#ifdef CONFIG_X86_32
-		set_debugreg(current->thread.debugreg0, 0);
-		set_debugreg(current->thread.debugreg1, 1);
-		set_debugreg(current->thread.debugreg2, 2);
-		set_debugreg(current->thread.debugreg3, 3);
-		/* no 4 and 5 */
-		set_debugreg(current->thread.debugreg6, 6);
-		set_debugreg(current->thread.debugreg7, 7);
-#else
-		/* CONFIG_X86_64 */
-		loaddebug(&current->thread, 0);
-		loaddebug(&current->thread, 1);
-		loaddebug(&current->thread, 2);
-		loaddebug(&current->thread, 3);
-		/* no 4 and 5 */
-		loaddebug(&current->thread, 6);
-		loaddebug(&current->thread, 7);
-#endif
-	}
-
 }
 
 /**
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
new file mode 100644
index 00000000000..0b98cbf76da
--- /dev/null
+++ b/include/linux/hw_breakpoint.h
@@ -0,0 +1,137 @@
+#ifndef _LINUX_HW_BREAKPOINT_H
+#define _LINUX_HW_BREAKPOINT_H
+
+#include <linux/perf_event.h>
+
+enum {
+	HW_BREAKPOINT_LEN_1 = 1,
+	HW_BREAKPOINT_LEN_2 = 2,
+	HW_BREAKPOINT_LEN_4 = 4,
+	HW_BREAKPOINT_LEN_8 = 8,
+};
+
+enum {
+	HW_BREAKPOINT_R = 1,
+	HW_BREAKPOINT_W = 2,
+	HW_BREAKPOINT_X = 4,
+};
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+
+static inline unsigned long hw_breakpoint_addr(struct perf_event *bp)
+{
+	return bp->attr.bp_addr;
+}
+
+static inline int hw_breakpoint_type(struct perf_event *bp)
+{
+	return bp->attr.bp_type;
+}
+
+static inline int hw_breakpoint_len(struct perf_event *bp)
+{
+	return bp->attr.bp_len;
+}
+
+extern struct perf_event *
+register_user_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    struct task_struct *tsk,
+			    bool active);
+
+/* FIXME: only change from the attr, and don't unregister */
+extern struct perf_event *
+modify_user_hw_breakpoint(struct perf_event *bp,
+			  unsigned long addr,
+			  int len,
+			  int type,
+			  perf_callback_t triggered,
+			  struct task_struct *tsk,
+			  bool active);
+
+/*
+ * Kernel breakpoints are not associated with any particular thread.
+ */
+extern struct perf_event *
+register_wide_hw_breakpoint_cpu(unsigned long addr,
+				int len,
+				int type,
+				perf_callback_t triggered,
+				int cpu,
+				bool active);
+
+extern struct perf_event **
+register_wide_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    bool active);
+
+extern int register_perf_hw_breakpoint(struct perf_event *bp);
+extern int __register_perf_hw_breakpoint(struct perf_event *bp);
+extern void unregister_hw_breakpoint(struct perf_event *bp);
+extern void unregister_wide_hw_breakpoint(struct perf_event **cpu_events);
+
+extern int reserve_bp_slot(struct perf_event *bp);
+extern void release_bp_slot(struct perf_event *bp);
+
+extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
+
+static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
+{
+	return &bp->hw.info;
+}
+
+#else /* !CONFIG_HAVE_HW_BREAKPOINT */
+
+static inline struct perf_event *
+register_user_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    struct task_struct *tsk,
+			    bool active)		{ return NULL; }
+static inline struct perf_event *
+modify_user_hw_breakpoint(struct perf_event *bp,
+			  unsigned long addr,
+			  int len,
+			  int type,
+			  perf_callback_t triggered,
+			  struct task_struct *tsk,
+			  bool active)			{ return NULL; }
+static inline struct perf_event *
+register_wide_hw_breakpoint_cpu(unsigned long addr,
+				int len,
+				int type,
+				perf_callback_t triggered,
+				int cpu,
+				bool active)		{ return NULL; }
+static inline struct perf_event **
+register_wide_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    bool active)		{ return NULL; }
+static inline int
+register_perf_hw_breakpoint(struct perf_event *bp)	{ return -ENOSYS; }
+static inline int
+__register_perf_hw_breakpoint(struct perf_event *bp) 	{ return -ENOSYS; }
+static inline void unregister_hw_breakpoint(struct perf_event *bp)	{ }
+static inline void
+unregister_wide_hw_breakpoint(struct perf_event **cpu_events)		{ }
+static inline int
+reserve_bp_slot(struct perf_event *bp)			{return -ENOSYS; }
+static inline void release_bp_slot(struct perf_event *bp) 		{ }
+
+static inline void flush_ptrace_hw_breakpoint(struct task_struct *tsk)	{ }
+
+static inline struct arch_hw_breakpoint *counter_arch_bp(struct perf_event *bp)
+{
+	return NULL;
+}
+
+#endif /* CONFIG_HAVE_HW_BREAKPOINT */
+
+#endif /* _LINUX_HW_BREAKPOINT_H */
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 7f87563c848..b5cdac0de37 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -18,6 +18,10 @@
 #include <linux/ioctl.h>
 #include <asm/byteorder.h>
 
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+#include <asm/hw_breakpoint.h>
+#endif
+
 /*
  * User-space ABI bits:
  */
@@ -31,6 +35,7 @@ enum perf_type_id {
 	PERF_TYPE_TRACEPOINT			= 2,
 	PERF_TYPE_HW_CACHE			= 3,
 	PERF_TYPE_RAW				= 4,
+	PERF_TYPE_BREAKPOINT			= 5,
 
 	PERF_TYPE_MAX,				/* non-ABI */
 };
@@ -209,6 +214,15 @@ struct perf_event_attr {
 		__u32		wakeup_events;	  /* wakeup every n events */
 		__u32		wakeup_watermark; /* bytes before wakeup   */
 	};
+
+	union {
+		struct { /* Hardware breakpoint info */
+			__u64		bp_addr;
+			__u32		bp_type;
+			__u32		bp_len;
+		};
+	};
+
 	__u32			__reserved_2;
 
 	__u64			__reserved_3;
@@ -478,6 +492,11 @@ struct hw_perf_event {
 			s64		remaining;
 			struct hrtimer	hrtimer;
 		};
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+		union { /* breakpoint */
+			struct arch_hw_breakpoint	info;
+		};
+#endif
 	};
 	atomic64_t			prev_count;
 	u64				sample_period;
@@ -546,6 +565,8 @@ struct perf_pending_entry {
 	void (*func)(struct perf_pending_entry *);
 };
 
+typedef void (*perf_callback_t)(struct perf_event *, void *);
+
 /**
  * struct perf_event - performance event kernel representation:
  */
@@ -588,7 +609,7 @@ struct perf_event {
 	u64				tstamp_running;
 	u64				tstamp_stopped;
 
-	struct perf_event_attr	attr;
+	struct perf_event_attr		attr;
 	struct hw_perf_event		hw;
 
 	struct perf_event_context	*ctx;
@@ -641,6 +662,10 @@ struct perf_event {
 	struct event_filter		*filter;
 #endif
 
+	perf_callback_t			callback;
+
+	perf_callback_t			event_callback;
+
 #endif /* CONFIG_PERF_EVENTS */
 };
 
@@ -745,6 +770,13 @@ extern int hw_perf_group_sched_in(struct perf_event *group_leader,
 	       struct perf_cpu_context *cpuctx,
 	       struct perf_event_context *ctx, int cpu);
 extern void perf_event_update_userpage(struct perf_event *event);
+extern int perf_event_release_kernel(struct perf_event *event);
+extern struct perf_event *
+perf_event_create_kernel_counter(struct perf_event_attr *attr,
+				int cpu,
+				pid_t pid,
+				perf_callback_t callback);
+extern u64 perf_event_read_value(struct perf_event *event);
 
 struct perf_sample_data {
 	u64				type;
@@ -821,6 +853,7 @@ extern int sysctl_perf_event_sample_rate;
 extern void perf_event_init(void);
 extern void perf_tp_event(int event_id, u64 addr, u64 count,
 				 void *record, int entry_size);
+extern void perf_bp_event(struct perf_event *event, void *data);
 
 #ifndef perf_misc_flags
 #define perf_misc_flags(regs)	(user_mode(regs) ? PERF_RECORD_MISC_USER : \
@@ -855,6 +888,8 @@ static inline int perf_event_task_enable(void)				{ return -EINVAL; }
 static inline void
 perf_sw_event(u32 event_id, u64 nr, int nmi,
 		     struct pt_regs *regs, u64 addr)			{ }
+static inline void
+perf_bp_event(struct perf_event *event, void *data)		{ }
 
 static inline void perf_event_mmap(struct vm_area_struct *vma)		{ }
 static inline void perf_event_comm(struct task_struct *tsk)		{ }
diff --git a/kernel/Makefile b/kernel/Makefile
index b8d4cd8ac0b..17b575ec7d0 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -95,6 +95,7 @@ obj-$(CONFIG_RING_BUFFER) += trace/
 obj-$(CONFIG_SMP) += sched_cpupri.o
 obj-$(CONFIG_SLOW_WORK) += slow-work.o
 obj-$(CONFIG_PERF_EVENTS) += perf_event.o
+obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
 
 ifneq ($(CONFIG_SCHED_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff --git a/kernel/exit.c b/kernel/exit.c
index f7864ac2ecc..3f45e3cf931 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -49,6 +49,7 @@
 #include <linux/init_task.h>
 #include <linux/perf_event.h>
 #include <trace/events/sched.h>
+#include <linux/hw_breakpoint.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -978,6 +979,10 @@ NORET_TYPE void do_exit(long code)
 	proc_exit_connector(tsk);
 
 	/*
+	 * FIXME: do that only when needed, using sched_exit tracepoint
+	 */
+	flush_ptrace_hw_breakpoint(tsk);
+	/*
 	 * Flush inherited counters to the parent - before the parent
 	 * gets woken up by child-exit notifications.
 	 */
diff --git a/kernel/hw_breakpoint.c b/kernel/hw_breakpoint.c
new file mode 100644
index 00000000000..9ea9414e0e5
--- /dev/null
+++ b/kernel/hw_breakpoint.c
@@ -0,0 +1,494 @@
+/*
+ * 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) 2007 Alan Stern
+ * Copyright (C) IBM Corporation, 2009
+ * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Thanks to Ingo Molnar for his many suggestions.
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ * This file contains the arch-independent routines.
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kallsyms.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/smp.h>
+
+#include <linux/hw_breakpoint.h>
+
+#include <asm/processor.h>
+
+#ifdef CONFIG_X86
+#include <asm/debugreg.h>
+#endif
+
+/*
+ * Constraints data
+ */
+
+/* Number of pinned cpu breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
+
+/* Number of pinned task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, task_bp_pinned[HBP_NUM]);
+
+/* Number of non-pinned cpu/task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
+
+/* Gather the number of total pinned and un-pinned bp in a cpuset */
+struct bp_busy_slots {
+	unsigned int pinned;
+	unsigned int flexible;
+};
+
+/* Serialize accesses to the above constraints */
+static DEFINE_MUTEX(nr_bp_mutex);
+
+/*
+ * Report the maximum number of pinned breakpoints a task
+ * have in this cpu
+ */
+static unsigned int max_task_bp_pinned(int cpu)
+{
+	int i;
+	unsigned int *tsk_pinned = per_cpu(task_bp_pinned, cpu);
+
+	for (i = HBP_NUM -1; i >= 0; i--) {
+		if (tsk_pinned[i] > 0)
+			return i + 1;
+	}
+
+	return 0;
+}
+
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void fetch_bp_busy_slots(struct bp_busy_slots *slots, int cpu)
+{
+	if (cpu >= 0) {
+		slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
+		slots->pinned += max_task_bp_pinned(cpu);
+		slots->flexible = per_cpu(nr_bp_flexible, cpu);
+
+		return;
+	}
+
+	for_each_online_cpu(cpu) {
+		unsigned int nr;
+
+		nr = per_cpu(nr_cpu_bp_pinned, cpu);
+		nr += max_task_bp_pinned(cpu);
+
+		if (nr > slots->pinned)
+			slots->pinned = nr;
+
+		nr = per_cpu(nr_bp_flexible, cpu);
+
+		if (nr > slots->flexible)
+			slots->flexible = nr;
+	}
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
+{
+	int count = 0;
+	struct perf_event *bp;
+	struct perf_event_context *ctx = tsk->perf_event_ctxp;
+	unsigned int *task_bp_pinned;
+	struct list_head *list;
+	unsigned long flags;
+
+	if (WARN_ONCE(!ctx, "No perf context for this task"))
+		return;
+
+	list = &ctx->event_list;
+
+	spin_lock_irqsave(&ctx->lock, flags);
+
+	/*
+	 * The current breakpoint counter is not included in the list
+	 * at the open() callback time
+	 */
+	list_for_each_entry(bp, list, event_entry) {
+		if (bp->attr.type == PERF_TYPE_BREAKPOINT)
+			count++;
+	}
+
+	spin_unlock_irqrestore(&ctx->lock, flags);
+
+	if (WARN_ONCE(count < 0, "No breakpoint counter found in the counter list"))
+		return;
+
+	task_bp_pinned = per_cpu(task_bp_pinned, cpu);
+	if (enable) {
+		task_bp_pinned[count]++;
+		if (count > 0)
+			task_bp_pinned[count-1]--;
+	} else {
+		task_bp_pinned[count]--;
+		if (count > 0)
+			task_bp_pinned[count-1]++;
+	}
+}
+
+/*
+ * Add/remove the given breakpoint in our constraint table
+ */
+static void toggle_bp_slot(struct perf_event *bp, bool enable)
+{
+	int cpu = bp->cpu;
+	struct task_struct *tsk = bp->ctx->task;
+
+	/* Pinned counter task profiling */
+	if (tsk) {
+		if (cpu >= 0) {
+			toggle_bp_task_slot(tsk, cpu, enable);
+			return;
+		}
+
+		for_each_online_cpu(cpu)
+			toggle_bp_task_slot(tsk, cpu, enable);
+		return;
+	}
+
+	/* Pinned counter cpu profiling */
+	if (enable)
+		per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
+	else
+		per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
+}
+
+/*
+ * Contraints to check before allowing this new breakpoint counter:
+ *
+ *  == Non-pinned counter == (Considered as pinned for now)
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
+ *           + max(per_cpu(task_bp_pinned, cpu)))) < HBP_NUM
+ *
+ *       -> If there are already non-pinned counters in this cpu, it means
+ *          there is already a free slot for them.
+ *          Otherwise, we check that the maximum number of per task
+ *          breakpoints (for this cpu) plus the number of per cpu breakpoint
+ *          (for this cpu) doesn't cover every registers.
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
+ *           + max(per_cpu(task_bp_pinned, *)))) < HBP_NUM
+ *
+ *       -> This is roughly the same, except we check the number of per cpu
+ *          bp for every cpu and we keep the max one. Same for the per tasks
+ *          breakpoints.
+ *
+ *
+ * == Pinned counter ==
+ *
+ *   - If attached to a single cpu, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
+ *            + max(per_cpu(task_bp_pinned, cpu))) < HBP_NUM
+ *
+ *       -> Same checks as before. But now the nr_bp_flexible, if any, must keep
+ *          one register at least (or they will never be fed).
+ *
+ *   - If attached to every cpus, check:
+ *
+ *       ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
+ *            + max(per_cpu(task_bp_pinned, *))) < HBP_NUM
+ */
+int reserve_bp_slot(struct perf_event *bp)
+{
+	struct bp_busy_slots slots = {0};
+	int ret = 0;
+
+	mutex_lock(&nr_bp_mutex);
+
+	fetch_bp_busy_slots(&slots, bp->cpu);
+
+	/* Flexible counters need to keep at least one slot */
+	if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
+		ret = -ENOSPC;
+		goto end;
+	}
+
+	toggle_bp_slot(bp, true);
+
+end:
+	mutex_unlock(&nr_bp_mutex);
+
+	return ret;
+}
+
+void release_bp_slot(struct perf_event *bp)
+{
+	mutex_lock(&nr_bp_mutex);
+
+	toggle_bp_slot(bp, false);
+
+	mutex_unlock(&nr_bp_mutex);
+}
+
+
+int __register_perf_hw_breakpoint(struct perf_event *bp)
+{
+	int ret;
+
+	ret = reserve_bp_slot(bp);
+	if (ret)
+		return ret;
+
+	if (!bp->attr.disabled)
+		ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+
+	return ret;
+}
+
+int register_perf_hw_breakpoint(struct perf_event *bp)
+{
+	bp->callback = perf_bp_event;
+
+	return __register_perf_hw_breakpoint(bp);
+}
+
+/*
+ * Register a breakpoint bound to a task and a given cpu.
+ * If cpu is -1, the breakpoint is active for the task in every cpu
+ * If the task is -1, the breakpoint is active for every tasks in the given
+ * cpu.
+ */
+static struct perf_event *
+register_user_hw_breakpoint_cpu(unsigned long addr,
+				int len,
+				int type,
+				perf_callback_t triggered,
+				pid_t pid,
+				int cpu,
+				bool active)
+{
+	struct perf_event_attr *attr;
+	struct perf_event *bp;
+
+	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+	if (!attr)
+		return ERR_PTR(-ENOMEM);
+
+	attr->type = PERF_TYPE_BREAKPOINT;
+	attr->size = sizeof(*attr);
+	attr->bp_addr = addr;
+	attr->bp_len = len;
+	attr->bp_type = type;
+	/*
+	 * Such breakpoints are used by debuggers to trigger signals when
+	 * we hit the excepted memory op. We can't miss such events, they
+	 * must be pinned.
+	 */
+	attr->pinned = 1;
+
+	if (!active)
+		attr->disabled = 1;
+
+	bp = perf_event_create_kernel_counter(attr, cpu, pid, triggered);
+	kfree(attr);
+
+	return bp;
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @addr: is the memory address that triggers the breakpoint
+ * @len: the length of the access to the memory (1 byte, 2 bytes etc...)
+ * @type: the type of the access to the memory (read/write/exec)
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ * @active: should we activate it while registering it
+ *
+ */
+struct perf_event *
+register_user_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    struct task_struct *tsk,
+			    bool active)
+{
+	return register_user_hw_breakpoint_cpu(addr, len, type, triggered,
+					       tsk->pid, -1, active);
+}
+EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
+
+/**
+ * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
+ * @bp: the breakpoint structure to modify
+ * @addr: is the memory address that triggers the breakpoint
+ * @len: the length of the access to the memory (1 byte, 2 bytes etc...)
+ * @type: the type of the access to the memory (read/write/exec)
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ * @active: should we activate it while registering it
+ */
+struct perf_event *
+modify_user_hw_breakpoint(struct perf_event *bp,
+			  unsigned long addr,
+			  int len,
+			  int type,
+			  perf_callback_t triggered,
+			  struct task_struct *tsk,
+			  bool active)
+{
+	/*
+	 * FIXME: do it without unregistering
+	 * - We don't want to lose our slot
+	 * - If the new bp is incorrect, don't lose the older one
+	 */
+	unregister_hw_breakpoint(bp);
+
+	return register_user_hw_breakpoint(addr, len, type, triggered,
+					   tsk, active);
+}
+EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
+
+/**
+ * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
+ * @bp: the breakpoint structure to unregister
+ */
+void unregister_hw_breakpoint(struct perf_event *bp)
+{
+	if (!bp)
+		return;
+	perf_event_release_kernel(bp);
+}
+EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
+
+static struct perf_event *
+register_kernel_hw_breakpoint_cpu(unsigned long addr,
+				  int len,
+				  int type,
+				  perf_callback_t triggered,
+				  int cpu,
+				  bool active)
+{
+	return register_user_hw_breakpoint_cpu(addr, len, type, triggered,
+					       -1, cpu, active);
+}
+
+/**
+ * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
+ * @addr: is the memory address that triggers the breakpoint
+ * @len: the length of the access to the memory (1 byte, 2 bytes etc...)
+ * @type: the type of the access to the memory (read/write/exec)
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @active: should we activate it while registering it
+ *
+ * @return a set of per_cpu pointers to perf events
+ */
+struct perf_event **
+register_wide_hw_breakpoint(unsigned long addr,
+			    int len,
+			    int type,
+			    perf_callback_t triggered,
+			    bool active)
+{
+	struct perf_event **cpu_events, **pevent, *bp;
+	long err;
+	int cpu;
+
+	cpu_events = alloc_percpu(typeof(*cpu_events));
+	if (!cpu_events)
+		return ERR_PTR(-ENOMEM);
+
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		bp = register_kernel_hw_breakpoint_cpu(addr, len, type,
+					triggered, cpu, active);
+
+		*pevent = bp;
+
+		if (IS_ERR(bp) || !bp) {
+			err = PTR_ERR(bp);
+			goto fail;
+		}
+	}
+
+	return cpu_events;
+
+fail:
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		if (IS_ERR(*pevent) || !*pevent)
+			break;
+		unregister_hw_breakpoint(*pevent);
+	}
+	free_percpu(cpu_events);
+	/* return the error if any */
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
+
+/**
+ * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
+ * @cpu_events: the per cpu set of events to unregister
+ */
+void unregister_wide_hw_breakpoint(struct perf_event **cpu_events)
+{
+	int cpu;
+	struct perf_event **pevent;
+
+	for_each_possible_cpu(cpu) {
+		pevent = per_cpu_ptr(cpu_events, cpu);
+		unregister_hw_breakpoint(*pevent);
+	}
+	free_percpu(cpu_events);
+}
+EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+	.notifier_call = hw_breakpoint_exceptions_notify,
+	/* we need to be notified first */
+	.priority = 0x7fffffff
+};
+
+static int __init init_hw_breakpoint(void)
+{
+	return register_die_notifier(&hw_breakpoint_exceptions_nb);
+}
+core_initcall(init_hw_breakpoint);
+
+
+struct pmu perf_ops_bp = {
+	.enable		= arch_install_hw_breakpoint,
+	.disable	= arch_uninstall_hw_breakpoint,
+	.read		= hw_breakpoint_pmu_read,
+	.unthrottle	= hw_breakpoint_pmu_unthrottle
+};
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 8b6b8b697c6..8e5288a8a35 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -181,6 +181,7 @@ unsigned long kallsyms_lookup_name(const char *name)
 	}
 	return module_kallsyms_lookup_name(name);
 }
+EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 
 int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
 				      unsigned long),
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3256e36ad25..3852e2656bb 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -29,6 +29,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/perf_event.h>
 #include <linux/ftrace_event.h>
+#include <linux/hw_breakpoint.h>
 
 #include <asm/irq_regs.h>
 
@@ -1725,6 +1726,26 @@ static int perf_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+int perf_event_release_kernel(struct perf_event *event)
+{
+	struct perf_event_context *ctx = event->ctx;
+
+	WARN_ON_ONCE(ctx->parent_ctx);
+	mutex_lock(&ctx->mutex);
+	perf_event_remove_from_context(event);
+	mutex_unlock(&ctx->mutex);
+
+	mutex_lock(&event->owner->perf_event_mutex);
+	list_del_init(&event->owner_entry);
+	mutex_unlock(&event->owner->perf_event_mutex);
+	put_task_struct(event->owner);
+
+	free_event(event);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(perf_event_release_kernel);
+
 static int perf_event_read_size(struct perf_event *event)
 {
 	int entry = sizeof(u64); /* value */
@@ -1750,7 +1771,7 @@ static int perf_event_read_size(struct perf_event *event)
 	return size;
 }
 
-static u64 perf_event_read_value(struct perf_event *event)
+u64 perf_event_read_value(struct perf_event *event)
 {
 	struct perf_event *child;
 	u64 total = 0;
@@ -1761,6 +1782,7 @@ static u64 perf_event_read_value(struct perf_event *event)
 
 	return total;
 }
+EXPORT_SYMBOL_GPL(perf_event_read_value);
 
 static int perf_event_read_entry(struct perf_event *event,
 				   u64 read_format, char __user *buf)
@@ -4231,6 +4253,51 @@ static void perf_event_free_filter(struct perf_event *event)
 
 #endif /* CONFIG_EVENT_PROFILE */
 
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+static void bp_perf_event_destroy(struct perf_event *event)
+{
+	release_bp_slot(event);
+}
+
+static const struct pmu *bp_perf_event_init(struct perf_event *bp)
+{
+	int err;
+	/*
+	 * The breakpoint is already filled if we haven't created the counter
+	 * through perf syscall
+	 * FIXME: manage to get trigerred to NULL if it comes from syscalls
+	 */
+	if (!bp->callback)
+		err = register_perf_hw_breakpoint(bp);
+	else
+		err = __register_perf_hw_breakpoint(bp);
+	if (err)
+		return ERR_PTR(err);
+
+	bp->destroy = bp_perf_event_destroy;
+
+	return &perf_ops_bp;
+}
+
+void perf_bp_event(struct perf_event *bp, void *regs)
+{
+	/* TODO */
+}
+#else
+static void bp_perf_event_destroy(struct perf_event *event)
+{
+}
+
+static const struct pmu *bp_perf_event_init(struct perf_event *bp)
+{
+	return NULL;
+}
+
+void perf_bp_event(struct perf_event *bp, void *regs)
+{
+}
+#endif
+
 atomic_t perf_swevent_enabled[PERF_COUNT_SW_MAX];
 
 static void sw_perf_event_destroy(struct perf_event *event)
@@ -4297,6 +4364,7 @@ perf_event_alloc(struct perf_event_attr *attr,
 		   struct perf_event_context *ctx,
 		   struct perf_event *group_leader,
 		   struct perf_event *parent_event,
+		   perf_callback_t callback,
 		   gfp_t gfpflags)
 {
 	const struct pmu *pmu;
@@ -4339,6 +4407,11 @@ perf_event_alloc(struct perf_event_attr *attr,
 
 	event->state		= PERF_EVENT_STATE_INACTIVE;
 
+	if (!callback && parent_event)
+		callback = parent_event->callback;
+	
+	event->callback	= callback;
+
 	if (attr->disabled)
 		event->state = PERF_EVENT_STATE_OFF;
 
@@ -4373,6 +4446,11 @@ perf_event_alloc(struct perf_event_attr *attr,
 		pmu = tp_perf_event_init(event);
 		break;
 
+	case PERF_TYPE_BREAKPOINT:
+		pmu = bp_perf_event_init(event);
+		break;
+
+
 	default:
 		break;
 	}
@@ -4615,7 +4693,7 @@ SYSCALL_DEFINE5(perf_event_open,
 	}
 
 	event = perf_event_alloc(&attr, cpu, ctx, group_leader,
-				     NULL, GFP_KERNEL);
+				     NULL, NULL, GFP_KERNEL);
 	err = PTR_ERR(event);
 	if (IS_ERR(event))
 		goto err_put_context;
@@ -4663,6 +4741,58 @@ err_put_context:
 	return err;
 }
 
+/**
+ * perf_event_create_kernel_counter
+ *
+ * @attr: attributes of the counter to create
+ * @cpu: cpu in which the counter is bound
+ * @pid: task to profile
+ */
+struct perf_event *
+perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
+				 pid_t pid, perf_callback_t callback)
+{
+	struct perf_event *event;
+	struct perf_event_context *ctx;
+	int err;
+
+	/*
+	 * Get the target context (task or percpu):
+	 */
+
+	ctx = find_get_context(pid, cpu);
+	if (IS_ERR(ctx))
+		return NULL;
+
+	event = perf_event_alloc(attr, cpu, ctx, NULL,
+				     NULL, callback, GFP_KERNEL);
+	err = PTR_ERR(event);
+	if (IS_ERR(event))
+		goto err_put_context;
+
+	event->filp = NULL;
+	WARN_ON_ONCE(ctx->parent_ctx);
+	mutex_lock(&ctx->mutex);
+	perf_install_in_context(ctx, event, cpu);
+	++ctx->generation;
+	mutex_unlock(&ctx->mutex);
+
+	event->owner = current;
+	get_task_struct(current);
+	mutex_lock(&current->perf_event_mutex);
+	list_add_tail(&event->owner_entry, &current->perf_event_list);
+	mutex_unlock(&current->perf_event_mutex);
+
+	return event;
+
+err_put_context:
+	if (err < 0)
+		put_ctx(ctx);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(perf_event_create_kernel_counter);
+
 /*
  * inherit a event from parent task to child task:
  */
@@ -4688,7 +4818,7 @@ inherit_event(struct perf_event *parent_event,
 	child_event = perf_event_alloc(&parent_event->attr,
 					   parent_event->cpu, child_ctx,
 					   group_leader, parent_event,
-					   GFP_KERNEL);
+					   NULL, GFP_KERNEL);
 	if (IS_ERR(child_event))
 		return child_event;
 	get_ctx(child_ctx);
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f05671609a8..d006554888d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -339,6 +339,27 @@ config POWER_TRACER
 	  power management decisions, specifically the C-state and P-state
 	  behavior.
 
+config KSYM_TRACER
+	bool "Trace read and write access on kernel memory locations"
+	depends on HAVE_HW_BREAKPOINT
+	select TRACING
+	help
+	  This tracer helps find read and write operations on any given kernel
+	  symbol i.e. /proc/kallsyms.
+
+config PROFILE_KSYM_TRACER
+	bool "Profile all kernel memory accesses on 'watched' variables"
+	depends on KSYM_TRACER
+	help
+	  This tracer profiles kernel accesses on variables watched through the
+	  ksym tracer ftrace plugin. Depending upon the hardware, all read
+	  and write operations on kernel variables can be monitored for
+	  accesses.
+
+	  The results will be displayed in:
+	  /debugfs/tracing/profile_ksym
+
+	  Say N if unsure.
 
 config STACK_TRACER
 	bool "Trace max stack"
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index edc3a3cca1a..cd9ecd89ec7 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_FTRACE_SYSCALLS) += trace_syscalls.o
 obj-$(CONFIG_EVENT_PROFILE) += trace_event_profile.o
 obj-$(CONFIG_EVENT_TRACING) += trace_events_filter.o
 obj-$(CONFIG_KPROBE_EVENT) += trace_kprobe.o
+obj-$(CONFIG_KSYM_TRACER) += trace_ksym.o
 obj-$(CONFIG_EVENT_TRACING) += power-traces.o
 
 libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index b4e4212e66d..4da6ede7440 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -11,6 +11,7 @@
 #include <linux/ftrace.h>
 #include <trace/boot.h>
 #include <linux/kmemtrace.h>
+#include <linux/hw_breakpoint.h>
 
 #include <linux/trace_seq.h>
 #include <linux/ftrace_event.h>
@@ -37,6 +38,7 @@ enum trace_type {
 	TRACE_KMEM_ALLOC,
 	TRACE_KMEM_FREE,
 	TRACE_BLK,
+	TRACE_KSYM,
 
 	__TRACE_LAST_TYPE,
 };
@@ -232,6 +234,7 @@ extern void __ftrace_bad_type(void);
 			  TRACE_KMEM_ALLOC);	\
 		IF_ASSIGN(var, ent, struct kmemtrace_free_entry,	\
 			  TRACE_KMEM_FREE);	\
+		IF_ASSIGN(var, ent, struct ksym_trace_entry, TRACE_KSYM);\
 		__ftrace_bad_type();					\
 	} while (0)
 
@@ -387,6 +390,8 @@ int register_tracer(struct tracer *type);
 void unregister_tracer(struct tracer *type);
 int is_tracing_stopped(void);
 
+extern int process_new_ksym_entry(char *ksymname, int op, unsigned long addr);
+
 extern unsigned long nsecs_to_usecs(unsigned long nsecs);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
@@ -461,6 +466,8 @@ extern int trace_selftest_startup_branch(struct tracer *trace,
 					 struct trace_array *tr);
 extern int trace_selftest_startup_hw_branches(struct tracer *trace,
 					      struct trace_array *tr);
+extern int trace_selftest_startup_ksym(struct tracer *trace,
+					 struct trace_array *tr);
 #endif /* CONFIG_FTRACE_STARTUP_TEST */
 
 extern void *head_page(struct trace_array_cpu *data);
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index ead3d724599..c16a08f399d 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -364,3 +364,19 @@ FTRACE_ENTRY(kmem_free, kmemtrace_free_entry,
 	F_printk("type:%u call_site:%lx ptr:%p",
 		 __entry->type_id, __entry->call_site, __entry->ptr)
 );
+
+FTRACE_ENTRY(ksym_trace, ksym_trace_entry,
+
+	TRACE_KSYM,
+
+	F_STRUCT(
+		__field(	unsigned long,	ip			  )
+		__field(	unsigned char,	type			  )
+		__array(	char	     ,	cmd,	   TASK_COMM_LEN  )
+		__field(	unsigned long,  addr			  )
+	),
+
+	F_printk("ip: %pF type: %d ksym_name: %pS cmd: %s",
+		(void *)__entry->ip, (unsigned int)__entry->type,
+		(void *)__entry->addr,  __entry->cmd)
+);
diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
new file mode 100644
index 00000000000..11935b53a6c
--- /dev/null
+++ b/kernel/trace/trace_ksym.c
@@ -0,0 +1,554 @@
+/*
+ * trace_ksym.c - Kernel Symbol Tracer
+ *
+ * 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, 2009
+ */
+
+#include <linux/kallsyms.h>
+#include <linux/uaccess.h>
+#include <linux/debugfs.h>
+#include <linux/ftrace.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+
+#include "trace_output.h"
+#include "trace_stat.h"
+#include "trace.h"
+
+#include <linux/hw_breakpoint.h>
+#include <asm/hw_breakpoint.h>
+
+/*
+ * For now, let us restrict the no. of symbols traced simultaneously to number
+ * of available hardware breakpoint registers.
+ */
+#define KSYM_TRACER_MAX HBP_NUM
+
+#define KSYM_TRACER_OP_LEN 3 /* rw- */
+
+struct trace_ksym {
+	struct perf_event	**ksym_hbp;
+	unsigned long		ksym_addr;
+	int			type;
+	int			len;
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+	unsigned long		counter;
+#endif
+	struct hlist_node	ksym_hlist;
+};
+
+static struct trace_array *ksym_trace_array;
+
+static unsigned int ksym_filter_entry_count;
+static unsigned int ksym_tracing_enabled;
+
+static HLIST_HEAD(ksym_filter_head);
+
+static DEFINE_MUTEX(ksym_tracer_mutex);
+
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+
+#define MAX_UL_INT 0xffffffff
+
+void ksym_collect_stats(unsigned long hbp_hit_addr)
+{
+	struct hlist_node *node;
+	struct trace_ksym *entry;
+
+	rcu_read_lock();
+	hlist_for_each_entry_rcu(entry, node, &ksym_filter_head, ksym_hlist) {
+		if ((entry->ksym_addr == hbp_hit_addr) &&
+		    (entry->counter <= MAX_UL_INT)) {
+			entry->counter++;
+			break;
+		}
+	}
+	rcu_read_unlock();
+}
+#endif /* CONFIG_PROFILE_KSYM_TRACER */
+
+void ksym_hbp_handler(struct perf_event *hbp, void *data)
+{
+	struct ring_buffer_event *event;
+	struct ksym_trace_entry *entry;
+	struct pt_regs *regs = data;
+	struct ring_buffer *buffer;
+	int pc;
+
+	if (!ksym_tracing_enabled)
+		return;
+
+	buffer = ksym_trace_array->buffer;
+
+	pc = preempt_count();
+
+	event = trace_buffer_lock_reserve(buffer, TRACE_KSYM,
+							sizeof(*entry), 0, pc);
+	if (!event)
+		return;
+
+	entry		= ring_buffer_event_data(event);
+	entry->ip	= instruction_pointer(regs);
+	entry->type	= hw_breakpoint_type(hbp);
+	entry->addr	= hw_breakpoint_addr(hbp);
+	strlcpy(entry->cmd, current->comm, TASK_COMM_LEN);
+
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+	ksym_collect_stats(hw_breakpoint_addr(hbp));
+#endif /* CONFIG_PROFILE_KSYM_TRACER */
+
+	trace_buffer_unlock_commit(buffer, event, 0, pc);
+}
+
+/* Valid access types are represented as
+ *
+ * rw- : Set Read/Write Access Breakpoint
+ * -w- : Set Write Access Breakpoint
+ * --- : Clear Breakpoints
+ * --x : Set Execution Break points (Not available yet)
+ *
+ */
+static int ksym_trace_get_access_type(char *str)
+{
+	int access = 0;
+
+	if (str[0] == 'r')
+		access |= HW_BREAKPOINT_R;
+
+	if (str[1] == 'w')
+		access |= HW_BREAKPOINT_W;
+
+	if (str[2] == 'x')
+		access |= HW_BREAKPOINT_X;
+
+	switch (access) {
+	case HW_BREAKPOINT_R:
+	case HW_BREAKPOINT_W:
+	case HW_BREAKPOINT_W | HW_BREAKPOINT_R:
+		return access;
+	default:
+		return -EINVAL;
+	}
+}
+
+/*
+ * There can be several possible malformed requests and we attempt to capture
+ * all of them. We enumerate some of the rules
+ * 1. We will not allow kernel symbols with ':' since it is used as a delimiter.
+ *    i.e. multiple ':' symbols disallowed. Possible uses are of the form
+ *    <module>:<ksym_name>:<op>.
+ * 2. No delimiter symbol ':' in the input string
+ * 3. Spurious operator symbols or symbols not in their respective positions
+ * 4. <ksym_name>:--- i.e. clear breakpoint request when ksym_name not in file
+ * 5. Kernel symbol not a part of /proc/kallsyms
+ * 6. Duplicate requests
+ */
+static int parse_ksym_trace_str(char *input_string, char **ksymname,
+							unsigned long *addr)
+{
+	int ret;
+
+	*ksymname = strsep(&input_string, ":");
+	*addr = kallsyms_lookup_name(*ksymname);
+
+	/* Check for malformed request: (2), (1) and (5) */
+	if ((!input_string) ||
+	    (strlen(input_string) != KSYM_TRACER_OP_LEN) ||
+	    (*addr == 0))
+		return -EINVAL;;
+
+	ret = ksym_trace_get_access_type(input_string);
+
+	return ret;
+}
+
+int process_new_ksym_entry(char *ksymname, int op, unsigned long addr)
+{
+	struct trace_ksym *entry;
+	int ret = -ENOMEM;
+
+	if (ksym_filter_entry_count >= KSYM_TRACER_MAX) {
+		printk(KERN_ERR "ksym_tracer: Maximum limit:(%d) reached. No"
+		" new requests for tracing can be accepted now.\n",
+			KSYM_TRACER_MAX);
+		return -ENOSPC;
+	}
+
+	entry = kzalloc(sizeof(struct trace_ksym), GFP_KERNEL);
+	if (!entry)
+		return -ENOMEM;
+
+	entry->type = op;
+	entry->ksym_addr = addr;
+	entry->len = HW_BREAKPOINT_LEN_4;
+
+	ret = -EAGAIN;
+	entry->ksym_hbp = register_wide_hw_breakpoint(entry->ksym_addr,
+					entry->len, entry->type,
+					ksym_hbp_handler, true);
+	if (IS_ERR(entry->ksym_hbp)) {
+		entry->ksym_hbp = NULL;
+		ret = PTR_ERR(entry->ksym_hbp);
+	}
+
+	if (!entry->ksym_hbp) {
+		printk(KERN_INFO "ksym_tracer request failed. Try again"
+					" later!!\n");
+		goto err;
+	}
+
+	hlist_add_head_rcu(&(entry->ksym_hlist), &ksym_filter_head);
+	ksym_filter_entry_count++;
+
+	return 0;
+
+err:
+	kfree(entry);
+
+	return ret;
+}
+
+static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
+						size_t count, loff_t *ppos)
+{
+	struct trace_ksym *entry;
+	struct hlist_node *node;
+	struct trace_seq *s;
+	ssize_t cnt = 0;
+	int ret;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (!s)
+		return -ENOMEM;
+	trace_seq_init(s);
+
+	mutex_lock(&ksym_tracer_mutex);
+
+	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
+		ret = trace_seq_printf(s, "%pS:", (void *)entry->ksym_addr);
+		if (entry->type == HW_BREAKPOINT_R)
+			ret = trace_seq_puts(s, "r--\n");
+		else if (entry->type == HW_BREAKPOINT_W)
+			ret = trace_seq_puts(s, "-w-\n");
+		else if (entry->type == (HW_BREAKPOINT_W | HW_BREAKPOINT_R))
+			ret = trace_seq_puts(s, "rw-\n");
+		WARN_ON_ONCE(!ret);
+	}
+
+	cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
+
+	mutex_unlock(&ksym_tracer_mutex);
+
+	kfree(s);
+
+	return cnt;
+}
+
+static void __ksym_trace_reset(void)
+{
+	struct trace_ksym *entry;
+	struct hlist_node *node, *node1;
+
+	mutex_lock(&ksym_tracer_mutex);
+	hlist_for_each_entry_safe(entry, node, node1, &ksym_filter_head,
+								ksym_hlist) {
+		unregister_wide_hw_breakpoint(entry->ksym_hbp);
+		ksym_filter_entry_count--;
+		hlist_del_rcu(&(entry->ksym_hlist));
+		synchronize_rcu();
+		kfree(entry);
+	}
+	mutex_unlock(&ksym_tracer_mutex);
+}
+
+static ssize_t ksym_trace_filter_write(struct file *file,
+					const char __user *buffer,
+						size_t count, loff_t *ppos)
+{
+	struct trace_ksym *entry;
+	struct hlist_node *node;
+	char *input_string, *ksymname = NULL;
+	unsigned long ksym_addr = 0;
+	int ret, op, changed = 0;
+
+	input_string = kzalloc(count + 1, GFP_KERNEL);
+	if (!input_string)
+		return -ENOMEM;
+
+	if (copy_from_user(input_string, buffer, count)) {
+		kfree(input_string);
+		return -EFAULT;
+	}
+	input_string[count] = '\0';
+
+	strstrip(input_string);
+
+	/*
+	 * Clear all breakpoints if:
+	 * 1: echo > ksym_trace_filter
+	 * 2: echo 0 > ksym_trace_filter
+	 * 3: echo "*:---" > ksym_trace_filter
+	 */
+	if (!input_string[0] || !strcmp(input_string, "0") ||
+	    !strcmp(input_string, "*:---")) {
+		__ksym_trace_reset();
+		kfree(input_string);
+		return count;
+	}
+
+	ret = op = parse_ksym_trace_str(input_string, &ksymname, &ksym_addr);
+	if (ret < 0) {
+		kfree(input_string);
+		return ret;
+	}
+
+	mutex_lock(&ksym_tracer_mutex);
+
+	ret = -EINVAL;
+	hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
+		if (entry->ksym_addr == ksym_addr) {
+			/* Check for malformed request: (6) */
+			if (entry->type != op)
+				changed = 1;
+			else
+				goto out;
+			break;
+		}
+	}
+	if (changed) {
+		unregister_wide_hw_breakpoint(entry->ksym_hbp);
+		entry->type = op;
+		if (op > 0) {
+			entry->ksym_hbp =
+				register_wide_hw_breakpoint(entry->ksym_addr,
+					entry->len, entry->type,
+					ksym_hbp_handler, true);
+			if (IS_ERR(entry->ksym_hbp))
+				entry->ksym_hbp = NULL;
+			if (!entry->ksym_hbp)
+				goto out;
+		}
+		ksym_filter_entry_count--;
+		hlist_del_rcu(&(entry->ksym_hlist));
+		synchronize_rcu();
+		kfree(entry);
+		ret = 0;
+		goto out;
+	} else {
+		/* Check for malformed request: (4) */
+		if (op == 0)
+			goto out;
+		ret = process_new_ksym_entry(ksymname, op, ksym_addr);
+	}
+out:
+	mutex_unlock(&ksym_tracer_mutex);
+
+	kfree(input_string);
+
+	if (!ret)
+		ret = count;
+	return ret;
+}
+
+static const struct file_operations ksym_tracing_fops = {
+	.open		= tracing_open_generic,
+	.read		= ksym_trace_filter_read,
+	.write		= ksym_trace_filter_write,
+};
+
+static void ksym_trace_reset(struct trace_array *tr)
+{
+	ksym_tracing_enabled = 0;
+	__ksym_trace_reset();
+}
+
+static int ksym_trace_init(struct trace_array *tr)
+{
+	int cpu, ret = 0;
+
+	for_each_online_cpu(cpu)
+		tracing_reset(tr, cpu);
+	ksym_tracing_enabled = 1;
+	ksym_trace_array = tr;
+
+	return ret;
+}
+
+static void ksym_trace_print_header(struct seq_file *m)
+{
+	seq_puts(m,
+		 "#       TASK-PID   CPU#      Symbol                    "
+		 "Type    Function\n");
+	seq_puts(m,
+		 "#          |        |          |                       "
+		 " |         |\n");
+}
+
+static enum print_line_t ksym_trace_output(struct trace_iterator *iter)
+{
+	struct trace_entry *entry = iter->ent;
+	struct trace_seq *s = &iter->seq;
+	struct ksym_trace_entry *field;
+	char str[KSYM_SYMBOL_LEN];
+	int ret;
+
+	if (entry->type != TRACE_KSYM)
+		return TRACE_TYPE_UNHANDLED;
+
+	trace_assign_type(field, entry);
+
+	ret = trace_seq_printf(s, "%11s-%-5d [%03d] %pS", field->cmd,
+				entry->pid, iter->cpu, (char *)field->addr);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	switch (field->type) {
+	case HW_BREAKPOINT_R:
+		ret = trace_seq_printf(s, " R  ");
+		break;
+	case HW_BREAKPOINT_W:
+		ret = trace_seq_printf(s, " W  ");
+		break;
+	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
+		ret = trace_seq_printf(s, " RW ");
+		break;
+	default:
+		return TRACE_TYPE_PARTIAL_LINE;
+	}
+
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	sprint_symbol(str, field->ip);
+	ret = trace_seq_printf(s, "%s\n", str);
+	if (!ret)
+		return TRACE_TYPE_PARTIAL_LINE;
+
+	return TRACE_TYPE_HANDLED;
+}
+
+struct tracer ksym_tracer __read_mostly =
+{
+	.name		= "ksym_tracer",
+	.init		= ksym_trace_init,
+	.reset		= ksym_trace_reset,
+#ifdef CONFIG_FTRACE_SELFTEST
+	.selftest	= trace_selftest_startup_ksym,
+#endif
+	.print_header   = ksym_trace_print_header,
+	.print_line	= ksym_trace_output
+};
+
+__init static int init_ksym_trace(void)
+{
+	struct dentry *d_tracer;
+	struct dentry *entry;
+
+	d_tracer = tracing_init_dentry();
+	ksym_filter_entry_count = 0;
+
+	entry = debugfs_create_file("ksym_trace_filter", 0644, d_tracer,
+				    NULL, &ksym_tracing_fops);
+	if (!entry)
+		pr_warning("Could not create debugfs "
+			   "'ksym_trace_filter' file\n");
+
+	return register_tracer(&ksym_tracer);
+}
+device_initcall(init_ksym_trace);
+
+
+#ifdef CONFIG_PROFILE_KSYM_TRACER
+static int ksym_tracer_stat_headers(struct seq_file *m)
+{
+	seq_puts(m, "  Access Type ");
+	seq_puts(m, "  Symbol                                       Counter\n");
+	seq_puts(m, "  ----------- ");
+	seq_puts(m, "  ------                                       -------\n");
+	return 0;
+}
+
+static int ksym_tracer_stat_show(struct seq_file *m, void *v)
+{
+	struct hlist_node *stat = v;
+	struct trace_ksym *entry;
+	int access_type = 0;
+	char fn_name[KSYM_NAME_LEN];
+
+	entry = hlist_entry(stat, struct trace_ksym, ksym_hlist);
+
+	access_type = entry->type;
+
+	switch (access_type) {
+	case HW_BREAKPOINT_R:
+		seq_puts(m, "  R           ");
+		break;
+	case HW_BREAKPOINT_W:
+		seq_puts(m, "  W           ");
+		break;
+	case HW_BREAKPOINT_R | HW_BREAKPOINT_W:
+		seq_puts(m, "  RW          ");
+		break;
+	default:
+		seq_puts(m, "  NA          ");
+	}
+
+	if (lookup_symbol_name(entry->ksym_addr, fn_name) >= 0)
+		seq_printf(m, "  %-36s", fn_name);
+	else
+		seq_printf(m, "  %-36s", "<NA>");
+	seq_printf(m, " %15lu\n", entry->counter);
+
+	return 0;
+}
+
+static void *ksym_tracer_stat_start(struct tracer_stat *trace)
+{
+	return ksym_filter_head.first;
+}
+
+static void *
+ksym_tracer_stat_next(void *v, int idx)
+{
+	struct hlist_node *stat = v;
+
+	return stat->next;
+}
+
+static struct tracer_stat ksym_tracer_stats = {
+	.name = "ksym_tracer",
+	.stat_start = ksym_tracer_stat_start,
+	.stat_next = ksym_tracer_stat_next,
+	.stat_headers = ksym_tracer_stat_headers,
+	.stat_show = ksym_tracer_stat_show
+};
+
+__init static int ksym_tracer_stat_init(void)
+{
+	int ret;
+
+	ret = register_stat_tracer(&ksym_tracer_stats);
+	if (ret) {
+		printk(KERN_WARNING "Warning: could not register "
+				    "ksym tracer stats\n");
+		return 1;
+	}
+
+	return 0;
+}
+fs_initcall(ksym_tracer_stat_init);
+#endif /* CONFIG_PROFILE_KSYM_TRACER */
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index d2cdbabb4ea..dc98309e839 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -17,6 +17,7 @@ static inline int trace_valid_entry(struct trace_entry *entry)
 	case TRACE_GRAPH_ENT:
 	case TRACE_GRAPH_RET:
 	case TRACE_HW_BRANCHES:
+	case TRACE_KSYM:
 		return 1;
 	}
 	return 0;
@@ -808,3 +809,57 @@ trace_selftest_startup_hw_branches(struct tracer *trace,
 	return ret;
 }
 #endif /* CONFIG_HW_BRANCH_TRACER */
+
+#ifdef CONFIG_KSYM_TRACER
+static int ksym_selftest_dummy;
+
+int
+trace_selftest_startup_ksym(struct tracer *trace, struct trace_array *tr)
+{
+	unsigned long count;
+	int ret;
+
+	/* start the tracing */
+	ret = tracer_init(trace, tr);
+	if (ret) {
+		warn_failed_init_tracer(trace, ret);
+		return ret;
+	}
+
+	ksym_selftest_dummy = 0;
+	/* Register the read-write tracing request */
+
+	ret = process_new_ksym_entry("ksym_selftest_dummy",
+				     HW_BREAKPOINT_R | HW_BREAKPOINT_W,
+					(unsigned long)(&ksym_selftest_dummy));
+
+	if (ret < 0) {
+		printk(KERN_CONT "ksym_trace read-write startup test failed\n");
+		goto ret_path;
+	}
+	/* Perform a read and a write operation over the dummy variable to
+	 * trigger the tracer
+	 */
+	if (ksym_selftest_dummy == 0)
+		ksym_selftest_dummy++;
+
+	/* stop the tracing. */
+	tracing_stop();
+	/* check the trace buffer */
+	ret = trace_test_buffer(tr, &count);
+	trace->reset(tr);
+	tracing_start();
+
+	/* read & write operations - one each is performed on the dummy variable
+	 * triggering two entries in the trace buffer
+	 */
+	if (!ret && count != 2) {
+		printk(KERN_CONT "Ksym tracer startup test failed");
+		ret = -1;
+	}
+
+ret_path:
+	return ret;
+}
+#endif /* CONFIG_KSYM_TRACER */
+
diff --git a/samples/Kconfig b/samples/Kconfig
index b92bde3c6a8..e4be84ac3d3 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -40,5 +40,11 @@ config SAMPLE_KRETPROBES
 	default m
 	depends on SAMPLE_KPROBES && KRETPROBES
 
+config SAMPLE_HW_BREAKPOINT
+	tristate "Build kernel hardware breakpoint examples -- loadable module only"
+	depends on HAVE_HW_BREAKPOINT && m
+	help
+	  This builds kernel hardware breakpoint example modules.
+
 endif # SAMPLES
 
diff --git a/samples/Makefile b/samples/Makefile
index 43343a03b1f..0f15e6d77fd 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,3 +1,4 @@
 # Makefile for Linux samples code
 
-obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/
+obj-$(CONFIG_SAMPLES)	+= kobject/ kprobes/ tracepoints/ trace_events/ \
+			   hw_breakpoint/
diff --git a/samples/hw_breakpoint/Makefile b/samples/hw_breakpoint/Makefile
new file mode 100644
index 00000000000..0f5c31c2fc4
--- /dev/null
+++ b/samples/hw_breakpoint/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o
diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
new file mode 100644
index 00000000000..5bc9819a819
--- /dev/null
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -0,0 +1,88 @@
+/*
+ * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
+ *
+ * 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.
+ *
+ * usage: insmod data_breakpoint.ko ksym=<ksym_name>
+ *
+ * This file is a kernel module that places a breakpoint over ksym_name kernel
+ * variable using Hardware Breakpoint register. The corresponding handler which
+ * prints a backtrace is invoked everytime a write operation is performed on
+ * that variable.
+ *
+ * Copyright (C) IBM Corporation, 2009
+ */
+#include <linux/module.h>	/* Needed by all modules */
+#include <linux/kernel.h>	/* Needed for KERN_INFO */
+#include <linux/init.h>		/* Needed for the macros */
+#include <linux/kallsyms.h>
+
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+
+struct perf_event **sample_hbp;
+
+static char ksym_name[KSYM_NAME_LEN] = "pid_max";
+module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
+MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
+			" write operations on the kernel symbol");
+
+static void sample_hbp_handler(struct perf_event *temp, void *data)
+{
+	printk(KERN_INFO "%s value is changed\n", ksym_name);
+	dump_stack();
+	printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
+}
+
+static int __init hw_break_module_init(void)
+{
+	int ret;
+	unsigned long addr;
+
+	addr = kallsyms_lookup_name(ksym_name);
+
+	sample_hbp = register_wide_hw_breakpoint(addr, HW_BREAKPOINT_LEN_4,
+						 HW_BREAKPOINT_W | HW_BREAKPOINT_R,
+						 sample_hbp_handler, true);
+	if (IS_ERR(sample_hbp)) {
+		ret = PTR_ERR(sample_hbp);
+		goto fail;
+	} else if (!sample_hbp) {
+		ret = -EINVAL;
+		goto fail;
+	}
+
+	printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);
+
+	return 0;
+
+fail:
+	printk(KERN_INFO "Breakpoint registration failed\n");
+
+	return ret;
+}
+
+static void __exit hw_break_module_exit(void)
+{
+	unregister_wide_hw_breakpoint(sample_hbp);
+	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
+}
+
+module_init(hw_break_module_init);
+module_exit(hw_break_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("K.Prasad");
+MODULE_DESCRIPTION("ksym breakpoint");