Patch "ARC: use correct offset in pt_regs for saving/restoring user mode r25" has been added to the 4.4-stable tree

Patch "ARC: use correct offset in pt_regs for saving/restoring user mode r25" has been added to the 4.4-stable tree

[gregkh]

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

    ARC: use correct offset in pt_regs for saving/restoring user mode r25

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:
     arc-use-correct-offset-in-pt_regs-for-saving-restoring-user-mode-r25.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 86147e3cfa5e118b61e78f4f0bf29e920dcbd477 Mon Sep 17 00:00:00 2001
From: Liav Rehana <liavr@mellanox.com>
Date: Tue, 16 Aug 2016 10:55:35 +0300
Subject: ARC: use correct offset in pt_regs for saving/restoring user mode r25

From: Liav Rehana <liavr@mellanox.com>

commit 86147e3cfa5e118b61e78f4f0bf29e920dcbd477 upstream.

User mode callee regs are explicitly collected before signal delivery or
breakpoint trap. r25 is special for kernel as it serves as task pointer,
so user mode value is clobbered very early. It is saved in pt_regs where
generally only scratch (aka caller saved) regs are saved.

The code to access the corresponding pt_regs location had a subtle bug as
it was using load/store with scaling of offset, whereas the offset was already
byte wise correct. So fix this by replacing LD.AS with a standard LD

Signed-off-by: Liav Rehana <liavr@mellanox.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
[vgupta: rewrote title and commit log]
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arc/include/asm/entry.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -142,7 +142,7 @@
 
 #ifdef CONFIG_ARC_CURR_IN_REG
 	; Retrieve orig r25 and save it with rest of callee_regs
-	ld.as   r12, [r12, PT_user_r25]
+	ld	r12, [r12, PT_user_r25]
 	PUSH	r12
 #else
 	PUSH	r25
@@ -198,7 +198,7 @@
 
 	; SP is back to start of pt_regs
 #ifdef CONFIG_ARC_CURR_IN_REG
-	st.as   r12, [sp, PT_user_r25]
+	st	r12, [sp, PT_user_r25]
 #endif
 .endm
 


Patches currently in stable-queue which might be from liavr@mellanox.com are

queue-4.4/arc-use-correct-offset-in-pt_regs-for-saving-restoring-user-mode-r25.patch