diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index ad6df8c..0710c11 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -85,6 +85,7 @@
 #define TIF_SECCOMP		8	/* secure computing */
 #define TIF_MCE_NOTIFY		10	/* notify userspace of an MCE */
 #define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */
+#define TIF_UPROBE		12	/* breakpointed or singlestepping */
 #define TIF_NOTSC		16	/* TSC is not accessible in userland */
 #define TIF_IA32		17	/* IA32 compatibility process */
 #define TIF_FORK		18	/* ret_from_fork */
@@ -109,6 +110,7 @@
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_MCE_NOTIFY		(1 << TIF_MCE_NOTIFY)
 #define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)
+#define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_NOTSC		(1 << TIF_NOTSC)
 #define _TIF_IA32		(1 << TIF_IA32)
 #define _TIF_FORK		(1 << TIF_FORK)
diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 0500391..1e9bed1 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -23,6 +23,8 @@
  *	Jim Keniston
  */
 
+#include <linux/notifier.h>
+
 typedef u8 uprobe_opcode_t;
 
 #define MAX_UINSN_BYTES			  16
@@ -39,5 +41,17 @@
 #endif
 };
 
-extern int arch_uprobes_analyze_insn(struct arch_uprobe *aup, struct mm_struct *mm);
+struct arch_uprobe_task {
+	unsigned long			saved_trap_nr;
+#ifdef CONFIG_X86_64
+	unsigned long			saved_scratch_register;
+#endif
+};
+
+extern int  arch_uprobe_analyze_insn(struct arch_uprobe *aup, struct mm_struct *mm);
+extern int  arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern int  arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
+extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
+extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
 #endif	/* _ASM_UPROBES_H */
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 9c73acc..b3cd691 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -18,6 +18,7 @@
 #include <linux/personality.h>
 #include <linux/uaccess.h>
 #include <linux/user-return-notifier.h>
+#include <linux/uprobes.h>
 
 #include <asm/processor.h>
 #include <asm/ucontext.h>
@@ -823,6 +824,11 @@
 		mce_notify_process();
 #endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
 
+	if (thread_info_flags & _TIF_UPROBE) {
+		clear_thread_flag(TIF_UPROBE);
+		uprobe_notify_resume(regs);
+	}
+
 	/* deal with pending signal delivery */
 	if (thread_info_flags & _TIF_SIGPENDING)
 		do_signal(regs);
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 851a11b..dc4e910 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -24,22 +24,28 @@
 #include <linux/sched.h>
 #include <linux/ptrace.h>
 #include <linux/uprobes.h>
+#include <linux/uaccess.h>
 
 #include <linux/kdebug.h>
+#include <asm/processor.h>
 #include <asm/insn.h>
 
 /* Post-execution fixups. */
 
 /* No fixup needed */
-#define UPROBE_FIX_NONE	0x0
+#define UPROBE_FIX_NONE		0x0
+
 /* Adjust IP back to vicinity of actual insn */
 #define UPROBE_FIX_IP		0x1
+
 /* Adjust the return address of a call insn */
 #define UPROBE_FIX_CALL	0x2
 
 #define UPROBE_FIX_RIP_AX	0x8000
 #define UPROBE_FIX_RIP_CX	0x4000
 
+#define	UPROBE_TRAP_NR		UINT_MAX
+
 /* Adaptations for mhiramat x86 decoder v14. */
 #define OPCODE1(insn)		((insn)->opcode.bytes[0])
 #define OPCODE2(insn)		((insn)->opcode.bytes[1])
@@ -221,10 +227,9 @@
 }
 
 /*
- * Figure out which fixups post_xol() will need to perform, and annotate
- * arch_uprobe->fixups accordingly.  To start with,
- * arch_uprobe->fixups is either zero or it reflects rip-related
- * fixups.
+ * Figure out which fixups arch_uprobe_post_xol() will need to perform, and
+ * annotate arch_uprobe->fixups accordingly.  To start with,
+ * arch_uprobe->fixups is either zero or it reflects rip-related fixups.
  */
 static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
 {
@@ -401,12 +406,12 @@
 #endif /* CONFIG_X86_64 */
 
 /**
- * arch_uprobes_analyze_insn - instruction analysis including validity and fixups.
+ * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
  * @mm: the probed address space.
  * @arch_uprobe: the probepoint information.
  * Return 0 on success or a -ve number on error.
  */
-int arch_uprobes_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm)
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm)
 {
 	int ret;
 	struct insn insn;
@@ -421,3 +426,249 @@
 
 	return 0;
 }
+
+#ifdef CONFIG_X86_64
+/*
+ * If we're emulating a rip-relative instruction, save the contents
+ * of the scratch register and store the target address in that register.
+ */
+static void
+pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs,
+				struct arch_uprobe_task *autask)
+{
+	if (auprobe->fixups & UPROBE_FIX_RIP_AX) {
+		autask->saved_scratch_register = regs->ax;
+		regs->ax = current->utask->vaddr;
+		regs->ax += auprobe->rip_rela_target_address;
+	} else if (auprobe->fixups & UPROBE_FIX_RIP_CX) {
+		autask->saved_scratch_register = regs->cx;
+		regs->cx = current->utask->vaddr;
+		regs->cx += auprobe->rip_rela_target_address;
+	}
+}
+#else
+static void
+pre_xol_rip_insn(struct arch_uprobe *auprobe, struct pt_regs *regs,
+				struct arch_uprobe_task *autask)
+{
+	/* No RIP-relative addressing on 32-bit */
+}
+#endif
+
+/*
+ * arch_uprobe_pre_xol - prepare to execute out of line.
+ * @auprobe: the probepoint information.
+ * @regs: reflects the saved user state of current task.
+ */
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct arch_uprobe_task *autask;
+
+	autask = &current->utask->autask;
+	autask->saved_trap_nr = current->thread.trap_nr;
+	current->thread.trap_nr = UPROBE_TRAP_NR;
+	regs->ip = current->utask->xol_vaddr;
+	pre_xol_rip_insn(auprobe, regs, autask);
+
+	return 0;
+}
+
+/*
+ * This function is called by arch_uprobe_post_xol() to adjust the return
+ * address pushed by a call instruction executed out of line.
+ */
+static int adjust_ret_addr(unsigned long sp, long correction)
+{
+	int rasize, ncopied;
+	long ra = 0;
+
+	if (is_ia32_task())
+		rasize = 4;
+	else
+		rasize = 8;
+
+	ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
+	if (unlikely(ncopied))
+		return -EFAULT;
+
+	ra += correction;
+	ncopied = copy_to_user((void __user *)sp, &ra, rasize);
+	if (unlikely(ncopied))
+		return -EFAULT;
+
+	return 0;
+}
+
+#ifdef CONFIG_X86_64
+static bool is_riprel_insn(struct arch_uprobe *auprobe)
+{
+	return ((auprobe->fixups & (UPROBE_FIX_RIP_AX | UPROBE_FIX_RIP_CX)) != 0);
+}
+
+static void
+handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction)
+{
+	if (is_riprel_insn(auprobe)) {
+		struct arch_uprobe_task *autask;
+
+		autask = &current->utask->autask;
+		if (auprobe->fixups & UPROBE_FIX_RIP_AX)
+			regs->ax = autask->saved_scratch_register;
+		else
+			regs->cx = autask->saved_scratch_register;
+
+		/*
+		 * The original instruction includes a displacement, and so
+		 * is 4 bytes longer than what we've just single-stepped.
+		 * Fall through to handle stuff like "jmpq *...(%rip)" and
+		 * "callq *...(%rip)".
+		 */
+		if (correction)
+			*correction += 4;
+	}
+}
+#else
+static void
+handle_riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs, long *correction)
+{
+	/* No RIP-relative addressing on 32-bit */
+}
+#endif
+
+/*
+ * If xol insn itself traps and generates a signal(Say,
+ * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
+ * instruction jumps back to its own address. It is assumed that anything
+ * like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
+ *
+ * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
+ * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
+ * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
+ */
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+	if (t->thread.trap_nr != UPROBE_TRAP_NR)
+		return true;
+
+	return false;
+}
+
+/*
+ * Called after single-stepping. To avoid the SMP problems that can
+ * occur when we temporarily put back the original opcode to
+ * single-step, we single-stepped a copy of the instruction.
+ *
+ * This function prepares to resume execution after the single-step.
+ * We have to fix things up as follows:
+ *
+ * Typically, the new ip is relative to the copied instruction.  We need
+ * to make it relative to the original instruction (FIX_IP).  Exceptions
+ * are return instructions and absolute or indirect jump or call instructions.
+ *
+ * If the single-stepped instruction was a call, the return address that
+ * is atop the stack is the address following the copied instruction.  We
+ * need to make it the address following the original instruction (FIX_CALL).
+ *
+ * If the original instruction was a rip-relative instruction such as
+ * "movl %edx,0xnnnn(%rip)", we have instead executed an equivalent
+ * instruction using a scratch register -- e.g., "movl %edx,(%rax)".
+ * We need to restore the contents of the scratch register and adjust
+ * the ip, keeping in mind that the instruction we executed is 4 bytes
+ * shorter than the original instruction (since we squeezed out the offset
+ * field).  (FIX_RIP_AX or FIX_RIP_CX)
+ */
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask;
+	long correction;
+	int result = 0;
+
+	WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
+
+	utask = current->utask;
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+	correction = (long)(utask->vaddr - utask->xol_vaddr);
+	handle_riprel_post_xol(auprobe, regs, &correction);
+	if (auprobe->fixups & UPROBE_FIX_IP)
+		regs->ip += correction;
+
+	if (auprobe->fixups & UPROBE_FIX_CALL)
+		result = adjust_ret_addr(regs->sp, correction);
+
+	return result;
+}
+
+/* callback routine for handling exceptions. */
+int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+	struct die_args *args = data;
+	struct pt_regs *regs = args->regs;
+	int ret = NOTIFY_DONE;
+
+	/* We are only interested in userspace traps */
+	if (regs && !user_mode_vm(regs))
+		return NOTIFY_DONE;
+
+	switch (val) {
+	case DIE_INT3:
+		if (uprobe_pre_sstep_notifier(regs))
+			ret = NOTIFY_STOP;
+
+		break;
+
+	case DIE_DEBUG:
+		if (uprobe_post_sstep_notifier(regs))
+			ret = NOTIFY_STOP;
+
+	default:
+		break;
+	}
+
+	return ret;
+}
+
+/*
+ * This function gets called when XOL instruction either gets trapped or
+ * the thread has a fatal signal, so reset the instruction pointer to its
+ * probed address.
+ */
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
+	handle_riprel_post_xol(auprobe, regs, NULL);
+	instruction_pointer_set(regs, utask->vaddr);
+}
+
+/*
+ * Skip these instructions as per the currently known x86 ISA.
+ * 0x66* { 0x90 | 0x0f 0x1f | 0x0f 0x19 | 0x87 0xc0 }
+ */
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+	int i;
+
+	for (i = 0; i < MAX_UINSN_BYTES; i++) {
+		if ((auprobe->insn[i] == 0x66))
+			continue;
+
+		if (auprobe->insn[i] == 0x90)
+			return true;
+
+		if (i == (MAX_UINSN_BYTES - 1))
+			break;
+
+		if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x1f))
+			return true;
+
+		if ((auprobe->insn[i] == 0x0f) && (auprobe->insn[i+1] == 0x19))
+			return true;
+
+		if ((auprobe->insn[i] == 0x87) && (auprobe->insn[i+1] == 0xc0))
+			return true;
+
+		break;
+	}
+	return false;
+}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7d379a6..8379e377 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1590,6 +1590,10 @@
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
 	atomic_t ptrace_bp_refcnt;
 #endif
+#ifdef CONFIG_UPROBES
+	struct uprobe_task *utask;
+	int uprobe_srcu_id;
+#endif
 };
 
 /* Future-safe accessor for struct task_struct's cpus_allowed. */
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index eac525f..5ec778f 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -28,8 +28,9 @@
 #include <linux/rbtree.h>
 
 struct vm_area_struct;
+
 #ifdef CONFIG_ARCH_SUPPORTS_UPROBES
-#include <asm/uprobes.h>
+# include <asm/uprobes.h>
 #endif
 
 /* flags that denote/change uprobes behaviour */
@@ -39,6 +40,8 @@
 
 /* Dont run handlers when first register/ last unregister in progress*/
 #define UPROBE_RUN_HANDLER	0x2
+/* Can skip singlestep */
+#define UPROBE_SKIP_SSTEP	0x4
 
 struct uprobe_consumer {
 	int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
@@ -52,13 +55,42 @@
 };
 
 #ifdef CONFIG_UPROBES
+enum uprobe_task_state {
+	UTASK_RUNNING,
+	UTASK_BP_HIT,
+	UTASK_SSTEP,
+	UTASK_SSTEP_ACK,
+	UTASK_SSTEP_TRAPPED,
+};
+
+/*
+ * uprobe_task: Metadata of a task while it singlesteps.
+ */
+struct uprobe_task {
+	enum uprobe_task_state		state;
+	struct arch_uprobe_task		autask;
+
+	struct uprobe			*active_uprobe;
+
+	unsigned long			xol_vaddr;
+	unsigned long			vaddr;
+};
+
 extern int __weak set_swbp(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long vaddr);
 extern int __weak set_orig_insn(struct arch_uprobe *aup, struct mm_struct *mm,  unsigned long vaddr, bool verify);
 extern bool __weak is_swbp_insn(uprobe_opcode_t *insn);
 extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
 extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
 extern int uprobe_mmap(struct vm_area_struct *vma);
-#else /* CONFIG_UPROBES is not defined */
+extern void uprobe_free_utask(struct task_struct *t);
+extern void uprobe_copy_process(struct task_struct *t);
+extern unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs);
+extern int uprobe_post_sstep_notifier(struct pt_regs *regs);
+extern int uprobe_pre_sstep_notifier(struct pt_regs *regs);
+extern void uprobe_notify_resume(struct pt_regs *regs);
+extern bool uprobe_deny_signal(void);
+extern bool __weak arch_uprobe_skip_sstep(struct arch_uprobe *aup, struct pt_regs *regs);
+#else /* !CONFIG_UPROBES */
 static inline int
 uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
 {
@@ -72,5 +104,22 @@
 {
 	return 0;
 }
-#endif /* CONFIG_UPROBES */
+static inline void uprobe_notify_resume(struct pt_regs *regs)
+{
+}
+static inline bool uprobe_deny_signal(void)
+{
+	return false;
+}
+static inline unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+	return 0;
+}
+static inline void uprobe_free_utask(struct task_struct *t)
+{
+}
+static inline void uprobe_copy_process(struct task_struct *t)
+{
+}
+#endif /* !CONFIG_UPROBES */
 #endif	/* _LINUX_UPROBES_H */
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index e56e56a..b807d15 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -30,9 +30,12 @@
 #include <linux/rmap.h>		/* anon_vma_prepare */
 #include <linux/mmu_notifier.h>	/* set_pte_at_notify */
 #include <linux/swap.h>		/* try_to_free_swap */
+#include <linux/ptrace.h>	/* user_enable_single_step */
+#include <linux/kdebug.h>	/* notifier mechanism */
 
 #include <linux/uprobes.h>
 
+static struct srcu_struct uprobes_srcu;
 static struct rb_root uprobes_tree = RB_ROOT;
 
 static DEFINE_SPINLOCK(uprobes_treelock);	/* serialize rbtree access */
@@ -486,6 +489,9 @@
 	u = __insert_uprobe(uprobe);
 	spin_unlock_irqrestore(&uprobes_treelock, flags);
 
+	/* For now assume that the instruction need not be single-stepped */
+	uprobe->flags |= UPROBE_SKIP_SSTEP;
+
 	return u;
 }
 
@@ -523,6 +529,21 @@
 	return uprobe;
 }
 
+static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
+{
+	struct uprobe_consumer *uc;
+
+	if (!(uprobe->flags & UPROBE_RUN_HANDLER))
+		return;
+
+	down_read(&uprobe->consumer_rwsem);
+	for (uc = uprobe->consumers; uc; uc = uc->next) {
+		if (!uc->filter || uc->filter(uc, current))
+			uc->handler(uc, regs);
+	}
+	up_read(&uprobe->consumer_rwsem);
+}
+
 /* Returns the previous consumer */
 static struct uprobe_consumer *
 consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
@@ -645,7 +666,7 @@
 		if (is_swbp_insn((uprobe_opcode_t *)uprobe->arch.insn))
 			return -EEXIST;
 
-		ret = arch_uprobes_analyze_insn(&uprobe->arch, mm);
+		ret = arch_uprobe_analyze_insn(&uprobe->arch, mm);
 		if (ret)
 			return ret;
 
@@ -662,10 +683,21 @@
 	set_orig_insn(&uprobe->arch, mm, (unsigned long)vaddr, true);
 }
 
+/*
+ * There could be threads that have hit the breakpoint and are entering the
+ * notifier code and trying to acquire the uprobes_treelock. The thread
+ * calling delete_uprobe() that is removing the uprobe from the rb_tree can
+ * race with these threads and might acquire the uprobes_treelock compared
+ * to some of the breakpoint hit threads. In such a case, the breakpoint
+ * hit threads will not find the uprobe. The current unregistering thread
+ * waits till all other threads have hit a breakpoint, to acquire the
+ * uprobes_treelock before the uprobe is removed from the rbtree.
+ */
 static void delete_uprobe(struct uprobe *uprobe)
 {
 	unsigned long flags;
 
+	synchronize_srcu(&uprobes_srcu);
 	spin_lock_irqsave(&uprobes_treelock, flags);
 	rb_erase(&uprobe->rb_node, &uprobes_tree);
 	spin_unlock_irqrestore(&uprobes_treelock, flags);
@@ -1010,6 +1042,288 @@
 	return ret;
 }
 
+/**
+ * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
+ * @regs: Reflects the saved state of the task after it has hit a breakpoint
+ * instruction.
+ * Return the address of the breakpoint instruction.
+ */
+unsigned long __weak uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+	return instruction_pointer(regs) - UPROBE_SWBP_INSN_SIZE;
+}
+
+/*
+ * Called with no locks held.
+ * Called in context of a exiting or a exec-ing thread.
+ */
+void uprobe_free_utask(struct task_struct *t)
+{
+	struct uprobe_task *utask = t->utask;
+
+	if (t->uprobe_srcu_id != -1)
+		srcu_read_unlock_raw(&uprobes_srcu, t->uprobe_srcu_id);
+
+	if (!utask)
+		return;
+
+	if (utask->active_uprobe)
+		put_uprobe(utask->active_uprobe);
+
+	kfree(utask);
+	t->utask = NULL;
+}
+
+/*
+ * Called in context of a new clone/fork from copy_process.
+ */
+void uprobe_copy_process(struct task_struct *t)
+{
+	t->utask = NULL;
+	t->uprobe_srcu_id = -1;
+}
+
+/*
+ * Allocate a uprobe_task object for the task.
+ * Called when the thread hits a breakpoint for the first time.
+ *
+ * Returns:
+ * - pointer to new uprobe_task on success
+ * - NULL otherwise
+ */
+static struct uprobe_task *add_utask(void)
+{
+	struct uprobe_task *utask;
+
+	utask = kzalloc(sizeof *utask, GFP_KERNEL);
+	if (unlikely(!utask))
+		return NULL;
+
+	utask->active_uprobe = NULL;
+	current->utask = utask;
+	return utask;
+}
+
+/* Prepare to single-step probed instruction out of line. */
+static int
+pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
+{
+	return -EFAULT;
+}
+
+/*
+ * If we are singlestepping, then ensure this thread is not connected to
+ * non-fatal signals until completion of singlestep.  When xol insn itself
+ * triggers the signal,  restart the original insn even if the task is
+ * already SIGKILL'ed (since coredump should report the correct ip).  This
+ * is even more important if the task has a handler for SIGSEGV/etc, The
+ * _same_ instruction should be repeated again after return from the signal
+ * handler, and SSTEP can never finish in this case.
+ */
+bool uprobe_deny_signal(void)
+{
+	struct task_struct *t = current;
+	struct uprobe_task *utask = t->utask;
+
+	if (likely(!utask || !utask->active_uprobe))
+		return false;
+
+	WARN_ON_ONCE(utask->state != UTASK_SSTEP);
+
+	if (signal_pending(t)) {
+		spin_lock_irq(&t->sighand->siglock);
+		clear_tsk_thread_flag(t, TIF_SIGPENDING);
+		spin_unlock_irq(&t->sighand->siglock);
+
+		if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
+			utask->state = UTASK_SSTEP_TRAPPED;
+			set_tsk_thread_flag(t, TIF_UPROBE);
+			set_tsk_thread_flag(t, TIF_NOTIFY_RESUME);
+		}
+	}
+
+	return true;
+}
+
+/*
+ * Avoid singlestepping the original instruction if the original instruction
+ * is a NOP or can be emulated.
+ */
+static bool can_skip_sstep(struct uprobe *uprobe, struct pt_regs *regs)
+{
+	if (arch_uprobe_skip_sstep(&uprobe->arch, regs))
+		return true;
+
+	uprobe->flags &= ~UPROBE_SKIP_SSTEP;
+	return false;
+}
+
+/*
+ * Run handler and ask thread to singlestep.
+ * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
+ */
+static void handle_swbp(struct pt_regs *regs)
+{
+	struct vm_area_struct *vma;
+	struct uprobe_task *utask;
+	struct uprobe *uprobe;
+	struct mm_struct *mm;
+	unsigned long bp_vaddr;
+
+	uprobe = NULL;
+	bp_vaddr = uprobe_get_swbp_addr(regs);
+	mm = current->mm;
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, bp_vaddr);
+
+	if (vma && vma->vm_start <= bp_vaddr && valid_vma(vma, false)) {
+		struct inode *inode;
+		loff_t offset;
+
+		inode = vma->vm_file->f_mapping->host;
+		offset = bp_vaddr - vma->vm_start;
+		offset += (vma->vm_pgoff << PAGE_SHIFT);
+		uprobe = find_uprobe(inode, offset);
+	}
+
+	srcu_read_unlock_raw(&uprobes_srcu, current->uprobe_srcu_id);
+	current->uprobe_srcu_id = -1;
+	up_read(&mm->mmap_sem);
+
+	if (!uprobe) {
+		/* No matching uprobe; signal SIGTRAP. */
+		send_sig(SIGTRAP, current, 0);
+		return;
+	}
+
+	utask = current->utask;
+	if (!utask) {
+		utask = add_utask();
+		/* Cannot allocate; re-execute the instruction. */
+		if (!utask)
+			goto cleanup_ret;
+	}
+	utask->active_uprobe = uprobe;
+	handler_chain(uprobe, regs);
+	if (uprobe->flags & UPROBE_SKIP_SSTEP && can_skip_sstep(uprobe, regs))
+		goto cleanup_ret;
+
+	utask->state = UTASK_SSTEP;
+	if (!pre_ssout(uprobe, regs, bp_vaddr)) {
+		user_enable_single_step(current);
+		return;
+	}
+
+cleanup_ret:
+	if (utask) {
+		utask->active_uprobe = NULL;
+		utask->state = UTASK_RUNNING;
+	}
+	if (uprobe) {
+		if (!(uprobe->flags & UPROBE_SKIP_SSTEP))
+
+			/*
+			 * cannot singlestep; cannot skip instruction;
+			 * re-execute the instruction.
+			 */
+			instruction_pointer_set(regs, bp_vaddr);
+
+		put_uprobe(uprobe);
+	}
+}
+
+/*
+ * Perform required fix-ups and disable singlestep.
+ * Allow pending signals to take effect.
+ */
+static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
+{
+	struct uprobe *uprobe;
+
+	uprobe = utask->active_uprobe;
+	if (utask->state == UTASK_SSTEP_ACK)
+		arch_uprobe_post_xol(&uprobe->arch, regs);
+	else if (utask->state == UTASK_SSTEP_TRAPPED)
+		arch_uprobe_abort_xol(&uprobe->arch, regs);
+	else
+		WARN_ON_ONCE(1);
+
+	put_uprobe(uprobe);
+	utask->active_uprobe = NULL;
+	utask->state = UTASK_RUNNING;
+	user_disable_single_step(current);
+
+	spin_lock_irq(&current->sighand->siglock);
+	recalc_sigpending(); /* see uprobe_deny_signal() */
+	spin_unlock_irq(&current->sighand->siglock);
+}
+
+/*
+ * On breakpoint hit, breakpoint notifier sets the TIF_UPROBE flag.  (and on
+ * subsequent probe hits on the thread sets the state to UTASK_BP_HIT) and
+ * allows the thread to return from interrupt.
+ *
+ * On singlestep exception, singlestep notifier sets the TIF_UPROBE flag and
+ * also sets the state to UTASK_SSTEP_ACK and allows the thread to return from
+ * interrupt.
+ *
+ * While returning to userspace, thread notices the TIF_UPROBE flag and calls
+ * uprobe_notify_resume().
+ */
+void uprobe_notify_resume(struct pt_regs *regs)
+{
+	struct uprobe_task *utask;
+
+	utask = current->utask;
+	if (!utask || utask->state == UTASK_BP_HIT)
+		handle_swbp(regs);
+	else
+		handle_singlestep(utask, regs);
+}
+
+/*
+ * uprobe_pre_sstep_notifier gets called from interrupt context as part of
+ * notifier mechanism. Set TIF_UPROBE flag and indicate breakpoint hit.
+ */
+int uprobe_pre_sstep_notifier(struct pt_regs *regs)
+{
+	struct uprobe_task *utask;
+
+	if (!current->mm)
+		return 0;
+
+	utask = current->utask;
+	if (utask)
+		utask->state = UTASK_BP_HIT;
+
+	set_thread_flag(TIF_UPROBE);
+	current->uprobe_srcu_id = srcu_read_lock_raw(&uprobes_srcu);
+
+	return 1;
+}
+
+/*
+ * uprobe_post_sstep_notifier gets called in interrupt context as part of notifier
+ * mechanism. Set TIF_UPROBE flag and indicate completion of singlestep.
+ */
+int uprobe_post_sstep_notifier(struct pt_regs *regs)
+{
+	struct uprobe_task *utask = current->utask;
+
+	if (!current->mm || !utask || !utask->active_uprobe)
+		/* task is currently not uprobed */
+		return 0;
+
+	utask->state = UTASK_SSTEP_ACK;
+	set_thread_flag(TIF_UPROBE);
+	return 1;
+}
+
+static struct notifier_block uprobe_exception_nb = {
+	.notifier_call		= arch_uprobe_exception_notify,
+	.priority		= INT_MAX-1,	/* notified after kprobes, kgdb */
+};
+
 static int __init init_uprobes(void)
 {
 	int i;
@@ -1018,12 +1332,13 @@
 		mutex_init(&uprobes_mutex[i]);
 		mutex_init(&uprobes_mmap_mutex[i]);
 	}
-	return 0;
+	init_srcu_struct(&uprobes_srcu);
+
+	return register_die_notifier(&uprobe_exception_nb);
 }
+module_init(init_uprobes);
 
 static void __exit exit_uprobes(void)
 {
 }
-
-module_init(init_uprobes);
 module_exit(exit_uprobes);
diff --git a/kernel/fork.c b/kernel/fork.c
index e2cd3e2..eb7b633 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -67,6 +67,7 @@
 #include <linux/oom.h>
 #include <linux/khugepaged.h>
 #include <linux/signalfd.h>
+#include <linux/uprobes.h>
 
 #include <asm/pgtable.h>
 #include <asm/pgalloc.h>
@@ -701,6 +702,8 @@
 		exit_pi_state_list(tsk);
 #endif
 
+	uprobe_free_utask(tsk);
+
 	/* Get rid of any cached register state */
 	deactivate_mm(tsk, mm);
 
@@ -1295,6 +1298,7 @@
 	INIT_LIST_HEAD(&p->pi_state_list);
 	p->pi_state_cache = NULL;
 #endif
+	uprobe_copy_process(p);
 	/*
 	 * sigaltstack should be cleared when sharing the same VM
 	 */
diff --git a/kernel/signal.c b/kernel/signal.c
index 8511e39..e93ff0a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -29,6 +29,7 @@
 #include <linux/pid_namespace.h>
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
+#include <linux/uprobes.h>
 #define CREATE_TRACE_POINTS
 #include <trace/events/signal.h>
 
@@ -2192,6 +2193,9 @@
 	struct signal_struct *signal = current->signal;
 	int signr;
 
+	if (unlikely(uprobe_deny_signal()))
+		return 0;
+
 relock:
 	/*
 	 * We'll jump back here after any time we were stopped in TASK_STOPPED.