From: David S. Miller <davem@davemloft.net>
Date: Mon, 15 Oct 2012 00:59:40 +0000 (-0700)
Subject: sparc64: Like x86 we should check current->mm during perf backtrace generation.
X-Git-Tag: v3.7-rc2~34^2~2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=08280e6c4c2e8049ac61d9e8e3536ec1df629c0d;p=platform%2Fkernel%2Flinux-3.10.git

sparc64: Like x86 we should check current->mm during perf backtrace generation.

If the MM is not active, only report the top-level PC.  Do not try to
access the address space.

Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c
index e48651d..9e96f84 100644
--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -1738,8 +1738,6 @@ static void perf_callchain_user_64(struct perf_callchain_entry *entry,
 {
 	unsigned long ufp;
 
-	perf_callchain_store(entry, regs->tpc);
-
 	ufp = regs->u_regs[UREG_I6] + STACK_BIAS;
 	do {
 		struct sparc_stackf *usf, sf;
@@ -1760,8 +1758,6 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 {
 	unsigned long ufp;
 
-	perf_callchain_store(entry, regs->tpc);
-
 	ufp = regs->u_regs[UREG_I6] & 0xffffffffUL;
 	do {
 		struct sparc_stackf32 *usf, sf;
@@ -1780,6 +1776,11 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry,
 void
 perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
 {
+	perf_callchain_store(entry, regs->tpc);
+
+	if (!current->mm)
+		return;
+
 	flushw_user();
 	if (test_thread_flag(TIF_32BIT))
 		perf_callchain_user_32(entry, regs);