Merge commit 'v3.17' into next

1 files changed, 12 insertions, 6 deletions

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 4238bcba9d6..266cba46db3 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -560,11 +560,16 @@ user_backtrace(struct frame_tail __user *tail,
 	       struct perf_callchain_entry *entry)
 {
 	struct frame_tail buftail;
+	unsigned long err;
 
-	/* Also check accessibility of one struct frame_tail beyond */
 	if (!access_ok(VERIFY_READ, tail, sizeof(buftail)))
 		return NULL;
-	if (__copy_from_user_inatomic(&buftail, tail, sizeof(buftail)))
+
+	pagefault_disable();
+	err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
+	pagefault_enable();
+
+	if (err)
 		return NULL;
 
 	perf_callchain_store(entry, buftail.lr);
@@ -590,6 +595,10 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 	}
 
 	perf_callchain_store(entry, regs->ARM_pc);
+
+	if (!current->mm)
+		return;
+
 	tail = (struct frame_tail __user *)regs->ARM_fp - 1;
 
 	while ((entry->nr < PERF_MAX_STACK_DEPTH) &&
@@ -621,10 +630,7 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
 		return;
 	}
 
-	fr.fp = regs->ARM_fp;
-	fr.sp = regs->ARM_sp;
-	fr.lr = regs->ARM_lr;
-	fr.pc = regs->ARM_pc;
+	arm_get_current_stackframe(regs, &fr);
 	walk_stackframe(&fr, callchain_trace, entry);
 }