1 files changed, 60 insertions, 9 deletions

diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 8b866a8572c..accbff3fec4 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -37,10 +37,12 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/preempt.h>
+#include <linux/module.h>
 
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 #include <asm/kdebug.h>
+#include <asm/uaccess.h>
 
 void jprobe_return_end(void);
 static void __kprobes arch_copy_kprobe(struct kprobe *p);
@@ -222,9 +224,9 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p)
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)
 {
-	down(&kprobe_mutex);
+	mutex_lock(&kprobe_mutex);
 	free_insn_slot(p->ainsn.insn);
-	up(&kprobe_mutex);
+	mutex_unlock(&kprobe_mutex);
 }
 
 static inline void save_previous_kprobe(struct kprobe_ctlblk *kcb)
@@ -578,16 +580,62 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 {
 	struct kprobe *cur = kprobe_running();
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
+	const struct exception_table_entry *fixup;
 
-	if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
-		return 1;
-
-	if (kcb->kprobe_status & KPROBE_HIT_SS) {
-		resume_execution(cur, regs, kcb);
+	switch(kcb->kprobe_status) {
+	case KPROBE_HIT_SS:
+	case KPROBE_REENTER:
+		/*
+		 * We are here because the instruction being single
+		 * stepped caused a page fault. We reset the current
+		 * kprobe and the rip points back to the probe address
+		 * and allow the page fault handler to continue as a
+		 * normal page fault.
+		 */
+		regs->rip = (unsigned long)cur->addr;
 		regs->eflags |= kcb->kprobe_old_rflags;
-
-		reset_current_kprobe();
+		if (kcb->kprobe_status == KPROBE_REENTER)
+			restore_previous_kprobe(kcb);
+		else
+			reset_current_kprobe();
 		preempt_enable_no_resched();
+		break;
+	case KPROBE_HIT_ACTIVE:
+	case KPROBE_HIT_SSDONE:
+		/*
+		 * We increment the nmissed count for accounting,
+		 * we can also use npre/npostfault count for accouting
+		 * these specific fault cases.
+		 */
+		kprobes_inc_nmissed_count(cur);
+
+		/*
+		 * We come here because instructions in the pre/post
+		 * handler caused the page_fault, this could happen
+		 * if handler tries to access user space by
+		 * copy_from_user(), get_user() etc. Let the
+		 * user-specified handler try to fix it first.
+		 */
+		if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr))
+			return 1;
+
+		/*
+		 * In case the user-specified fault handler returned
+		 * zero, try to fix up.
+		 */
+		fixup = search_exception_tables(regs->rip);
+		if (fixup) {
+			regs->rip = fixup->fixup;
+			return 1;
+		}
+
+		/*
+		 * fixup() could not handle it,
+		 * Let do_page_fault() fix it.
+		 */
+		break;
+	default:
+		break;
 	}
 	return 0;
 }
@@ -601,6 +649,9 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
 	struct die_args *args = (struct die_args *)data;
 	int ret = NOTIFY_DONE;
 
+	if (args->regs && user_mode(args->regs))
+		return ret;
+
 	switch (val) {
 	case DIE_INT3:
 		if (kprobe_handler(args->regs))