Patch "MIPS: Clear ISA bit correctly in get_frame_info()" has been added to the 4.10-stable tree

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 4.10-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-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Paul Burton <[email protected]>
Date: Mon, 7 Nov 2016 15:07:02 +0000
Subject: MIPS: Clear ISA bit correctly in get_frame_info()

From: Paul Burton <[email protected]>

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.

Patchwork: https://patchwork.linux-mips.org/patch/14528/

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

@@ -303,17 +303,14 @@ 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 [email protected] are

queue-4.10/mips-calculate-micromips-ra-properly-when-unwinding-the-stack.patch queue-4.10/mips-fix-get_frame_info-handling-of-micromips-function-size.patch queue-4.10/mips-handle-micromips-jumps-in-the-same-way-as-mips32-mips64-jumps.patch queue-4.10/mips-fix-is_jump_ins-handling-of-16b-micromips-instructions.patch queue-4.10/mips-clear-isa-bit-correctly-in-get_frame_info.patch queue-4.10/mips-prevent-unaligned-accesses-during-stack-unwinding.patch