linux-kernel - [PATCH 4.2.y-ckt 268/273] s390/oprofile: fix address range for asynchronous stack

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Message-Id: <1457391064-6660-269-git-send-email-kamal@canonical.com>
Date:	Mon,  7 Mar 2016 14:50:59 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 268/273] s390/oprofile: fix address range for asynchronous stack

4.2.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Heiko Carstens <heiko.carstens@...ibm.com>

commit 232f5dd78586a684a7364a486b934e19384189dc upstream.

git commit dc7ee00d4771 ("s390: lowcore stack pointer offsets")
introduced a regression in regard to s390_backtrace(). The stack
pointer for the asynchronous stack in the lowcore now has an
additional offset applied. This offset needs to be taken into account
in the calculation for the low and high address for the stack.

This bug was already partially fixed with commit 9cc5c206d9b4
("s390/dumpstack: fix address ranges for asynchronous and panic
stack"). This patch fixes it also for the oprofile code.

Fixes: dc7ee00d4771 ("s390: lowcore stack pointer offsets")
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/s390/oprofile/backtrace.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/arch/s390/oprofile/backtrace.c b/arch/s390/oprofile/backtrace.c
index 8a6811b..71164df 100644
--- a/arch/s390/oprofile/backtrace.c
+++ b/arch/s390/oprofile/backtrace.c
@@ -55,12 +55,13 @@ __show_trace(unsigned int *depth, unsigned long sp,
 
 void s390_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
-	unsigned long head;
+	unsigned long head, frame_size;
 	struct stack_frame* head_sf;
 
 	if (user_mode(regs))
 		return;
 
+	frame_size = STACK_FRAME_OVERHEAD + sizeof(struct pt_regs);
 	head = regs->gprs[15];
 	head_sf = (struct stack_frame*)head;
 
@@ -69,8 +70,9 @@ void s390_backtrace(struct pt_regs * const regs, unsigned int depth)
 
 	head = head_sf->back_chain;
 
-	head = __show_trace(&depth, head, S390_lowcore.async_stack - ASYNC_SIZE,
-			    S390_lowcore.async_stack);
+	head = __show_trace(&depth, head,
+			    S390_lowcore.async_stack + frame_size - ASYNC_SIZE,
+			    S390_lowcore.async_stack + frame_size);
 
 	__show_trace(&depth, head, S390_lowcore.thread_info,
 		     S390_lowcore.thread_info + THREAD_SIZE);
-- 
2.7.0