Patch "MIPS: Clear ISA bit correctly in get_frame_info()" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    MIPS: Clear ISA bit correctly in get_frame_info()

to the 4.4-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-clear-isa-bit-correctly-in-get_frame_info.patch
and it can be found in the queue-4.4 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 ccaf7caf2c73c6db920772bf08bf1d47b2170634 Mon Sep 17 00:00:00 2001
From: Paul Burton <paul.burton@imgtec.com>
Date: Mon, 7 Nov 2016 15:07:02 +0000
Subject: MIPS: Clear ISA bit correctly in get_frame_info()

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

commit ccaf7caf2c73c6db920772bf08bf1d47b2170634 upstream.

get_frame_info() can be called in microMIPS kernels with the ISA bit
already clear. For example this happens when unwind_stack_by_address()
is called because we begin with a PC that has the ISA bit set & subtract
the (odd) offset from the preceding symbol (which does not have the ISA
bit set). Since get_frame_info() unconditionally subtracts 1 from the PC
in microMIPS kernels it incorrectly misaligns the address it then
attempts to access code at, leading to an address error exception.

Fix this by using msk_isa16_mode() to clear the ISA bit, which allows
get_frame_info() to function regardless of whether it is provided with a
PC that has the ISA bit set or not.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Fixes: 34c2f668d0f6 ("MIPS: microMIPS: Add unaligned access support.")
Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14528/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/process.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -299,17 +299,14 @@ static inline int is_sp_move_ins(union m
 
 static int get_frame_info(struct mips_frame_info *info)
 {
-#ifdef CONFIG_CPU_MICROMIPS
-	union mips_instruction *ip = (void *) (((char *) info->func) - 1);
-#else
-	union mips_instruction *ip = info->func;
-#endif
+	union mips_instruction *ip;
 	unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 	unsigned i;
 
 	info->pc_offset = -1;
 	info->frame_size = 0;
 
+	ip = (void *)msk_isa16_mode((ulong)info->func);
 	if (!ip)
 		goto err;
 


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

queue-4.4/mips-calculate-micromips-ra-properly-when-unwinding-the-stack.patch
queue-4.4/mips-fix-get_frame_info-handling-of-micromips-function-size.patch
queue-4.4/mips-handle-micromips-jumps-in-the-same-way-as-mips32-mips64-jumps.patch
queue-4.4/mips-fix-is_jump_ins-handling-of-16b-micromips-instructions.patch
queue-4.4/mips-clear-isa-bit-correctly-in-get_frame_info.patch
queue-4.4/mips-prevent-unaligned-accesses-during-stack-unwinding.patch