[PATCH 3.16 009/212] MIPS: Fix is_jump_ins() handling of 16b microMIPS instructions

[Ben Hutchings]

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Paul Burton <paul.burton@xxxxxxxxxx>

commit 67c75057709a6d85c681c78b9b2f9b71191f01a2 upstream.

is_jump_ins() checks 16b instruction fields without verifying that the
instruction is indeed 16b, as is done by is_ra_save_ins() &
is_sp_move_ins(). Add the appropriate check.

Signed-off-by: Paul Burton <paul.burton@xxxxxxxxxx>
Fixes: 34c2f668d0f6 ("MIPS: microMIPS: Add unaligned access support.")
Cc: Leonid Yegoshin <leonid.yegoshin@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/14531/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/mips/kernel/process.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -269,9 +269,14 @@ static inline int is_jump_ins(union mips
 	 *
 	 * microMIPS is kind of more fun...
 	 */
-	if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
-	    (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
-	    ip->j_format.opcode == mm_jal32_op)
+	if (mm_insn_16bit(ip->halfword[1])) {
+		if ((ip->mm16_r5_format.opcode == mm_pool16c_op &&
+		    (ip->mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op))
+			return 1;
+		return 0;
+	}
+
+	if (ip->j_format.opcode == mm_jal32_op)
 		return 1;
 	if (ip->r_format.opcode != mm_pool32a_op ||
 			ip->r_format.func != mm_pool32axf_op)