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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH 4.20 68/76] xtensa: fix get_wchan
Date:   Fri,  8 Mar 2019 13:50:20 +0100
Message-Id: <20190308124917.202790656@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

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

From: Max Filippov <jcmvbkbc@gmail.com>

commit d90b88fd3653f1fb66ecc6571b860d5a5749fa56 upstream.

Stack unwinding is implemented incorrectly in xtensa get_wchan: instead
of extracting a0 and a1 registers from the spill location under the
stack pointer it extracts a word pointed to by the stack pointer and
subtracts 4 or 3 from it.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/xtensa/kernel/process.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -320,8 +320,8 @@ unsigned long get_wchan(struct task_stru
 
 		/* Stack layout: sp-4: ra, sp-3: sp' */
 
-		pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
-		sp = *(unsigned long *)sp - 3;
+		pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
+		sp = SPILL_SLOT(sp, 1);
 	} while (count++ < 16);
 	return 0;
 }