3 files changed, 20 insertions, 7 deletions

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 450ee2cbfe17..a22a98c43ca5 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -26,12 +26,6 @@
 #include <asm/traps.h>
 #include <asm/cacheflush.h>
 
-/*
- * This undefined instruction must be unique and
- * reserved solely for kprobes' use.
- */
-#define KPROBE_BREAKPOINT_INSTRUCTION   0xe7f001f8
-
 #define MIN_STACK_SIZE(addr)                            \
         min((unsigned long)MAX_STACK_SIZE,              \
             (unsigned long)current_thread_info() + THREAD_START_SP - (addr))
@@ -206,7 +200,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs)
         }
 }
 
-static int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
+int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
 {
         kprobe_handler(regs);
         return 0;
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 65bb762b2d80..5595fdd75e82 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -19,6 +19,7 @@
 #include <linux/kallsyms.h>
 #include <linux/delay.h>
 #include <linux/init.h>
+#include <linux/kprobes.h>
 
 #include <asm/atomic.h>
 #include <asm/cacheflush.h>
@@ -313,6 +314,17 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
                 get_user(instr, (u32 __user *)pc);
         }
 
+#ifdef CONFIG_KPROBES
+        /*
+         * It is possible to have recursive kprobes, so we can't call
+         * the kprobe trap handler with the undef_lock held.
+         */
+        if (instr == KPROBE_BREAKPOINT_INSTRUCTION && !user_mode(regs)) {
+                kprobe_trap_handler(regs, instr);
+                return;
+        }
+#endif
+
         spin_lock_irqsave(&undef_lock, flags);
         list_for_each_entry(hook, &undef_hook, node) {
                 if ((instr & hook->instr_mask) == hook->instr_val &&
diff --git a/include/asm-arm/kprobes.h b/include/asm-arm/kprobes.h
index 273f37413ee6..4e7bd32288ae 100644
--- a/include/asm-arm/kprobes.h
+++ b/include/asm-arm/kprobes.h
@@ -25,6 +25,12 @@
 #define MAX_INSN_SIZE                   2
 #define MAX_STACK_SIZE                  64      /* 32 would probably be OK */
 
+/*
+ * This undefined instruction must be unique and
+ * reserved solely for kprobes' use.
+ */
+#define KPROBE_BREAKPOINT_INSTRUCTION   0xe7f001f8
+
 #define regs_return_value(regs)         ((regs)->ARM_r0)
 #define flush_insn_slot(p)              do { } while (0)
 #define kretprobe_blacklist_size        0
@@ -55,6 +61,7 @@ struct kprobe_ctlblk {
 
 void arch_remove_kprobe(struct kprobe *);
 
+int kprobe_trap_handler(struct pt_regs *regs, unsigned int instr);
 int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
 int kprobe_exceptions_notify(struct notifier_block *self,
                              unsigned long val, void *data);