Patch "MIPS: Fix bnezc/jialc return address calculation" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    MIPS: Fix bnezc/jialc return address calculation

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-fix-bnezc-jialc-return-address-calculation.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 Mon Sep 17 00:00:00 2001
From: Paul Burton <paul.burton@imgtec.com>
Date: Fri, 2 Jun 2017 11:35:01 -0700
Subject: MIPS: Fix bnezc/jialc return address calculation

From: Paul Burton <paul.burton@imgtec.com>

commit 1a73d9310e093fc3adffba4d0a67b9fab2ee3f63 upstream.

The code handling the pop76 opcode (ie. bnezc & jialc instructions) in
__compute_return_epc_for_insn() needs to set the value of $31 in the
jialc case, which is encoded with rs = 0. However its check to
differentiate bnezc (rs != 0) from jialc (rs = 0) was unfortunately
backwards, meaning that if we emulate a bnezc instruction we clobber $31
& if we emulate a jialc instruction it actually behaves like a jic
instruction.

Fix this by inverting the check of rs to match the way the instructions
are actually encoded.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 28d6f93d201d ("MIPS: Emulate the new MIPS R6 BNEZC and JIALC instructions")
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16178/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/branch.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/arch/mips/kernel/branch.c
+++ b/arch/mips/kernel/branch.c
@@ -804,8 +804,10 @@ int __compute_return_epc_for_insn(struct
 			break;
 		}
 		/* Compact branch: BNEZC || JIALC */
-		if (insn.i_format.rs)
+		if (!insn.i_format.rs) {
+			/* JIALC: set $31/ra */
 			regs->regs[31] = epc + 4;
+		}
 		regs->cp0_epc += 8;
 		break;
 #endif


Patches currently in stable-queue which might be from paul.burton@imgtec.com are

queue-4.9/mips-.its-targets-depend-on-vmlinux.patch
queue-4.9/mips-fix-bnezc-jialc-return-address-calculation.patch