linux-kernel - [ 38/42] sparc64: Like x86 we should check current->mm during perf backtrace generation.

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Date:	Thu, 25 Oct 2012 17:05:46 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, "David S. Miller" <davem@...emloft.net>
Subject: [ 38/42] sparc64: Like x86 we should check current->mm during perf backtrace generation.

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

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


From: "David S. Miller" <davem@...emloft.net>

[ Upstream commit 08280e6c4c2e8049ac61d9e8e3536ec1df629c0d ]

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@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/sparc/kernel/perf_event.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/arch/sparc/kernel/perf_event.c
+++ b/arch/sparc/kernel/perf_event.c
@@ -1428,8 +1428,6 @@ static void perf_callchain_user_64(struc
 {
 	unsigned long ufp;
 
-	perf_callchain_store(entry, regs->tpc);
-
 	ufp = regs->u_regs[UREG_I6] + STACK_BIAS;
 	do {
 		struct sparc_stackf *usf, sf;
@@ -1450,8 +1448,6 @@ static void perf_callchain_user_32(struc
 {
 	unsigned long ufp;
 
-	perf_callchain_store(entry, regs->tpc);
-
 	ufp = regs->u_regs[UREG_I6] & 0xffffffffUL;
 	do {
 		struct sparc_stackf32 *usf, sf;
@@ -1470,6 +1466,11 @@ static void perf_callchain_user_32(struc
 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);


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