[PATCH 169/241] sparc64: Like x86 we should check current->mm during perf backtrace generation.

[Herton Ronaldo Krzesinski]

3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: "David S. Miller" <davem at davemloft.net>

commit 08280e6c4c2e8049ac61d9e8e3536ec1df629c0d upstream.

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 at davemloft.net>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 arch/sparc/kernel/perf_event.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c
index 5713957..b0cce26 100644
--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -1426,8 +1426,6 @@ 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;
@@ -1448,8 +1446,6 @@ 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;
@@ -1468,6 +1464,11 @@ 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);
-- 
1.7.9.5