[3.13.y.z extended stable] Patch "xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6a763ff6e45044f3b7f9ebe0cfc34a80fb7953dc Mon Sep 17 00:00:00 2001
From: Max Filippov <jcmvbkbc at gmail.com>
Date: Sun, 27 Jul 2014 07:23:41 +0400
Subject: xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS

commit 52247123749cc3cbc30168b33ad8c69515c96d23 upstream.

With SMP and a lot of debug options enabled task_struct::thread gets out
of reach of s32i/l32i instructions with base pointing at task_struct,
breaking build with the following messages:

  arch/xtensa/kernel/entry.S: Assembler messages:
  arch/xtensa/kernel/entry.S:1002: Error: operand 3 of 'l32i.n' has invalid value '1048'
  arch/xtensa/kernel/entry.S:1831: Error: operand 3 of 's32i.n' has invalid value '1040'
  arch/xtensa/kernel/entry.S:1832: Error: operand 3 of 's32i.n' has invalid value '1044'

Change base to point to task_struct::thread in such cases.
Don't use a10 in _switch_to to save/restore prev pointer as a2 is not
clobbered.

Signed-off-by: Max Filippov <jcmvbkbc at gmail.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/xtensa/include/asm/uaccess.h |  5 +++++
 arch/xtensa/kernel/entry.S        | 12 ++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/xtensa/include/asm/uaccess.h b/arch/xtensa/include/asm/uaccess.h
index fd686dc..c7211e7 100644
--- a/arch/xtensa/include/asm/uaccess.h
+++ b/arch/xtensa/include/asm/uaccess.h
@@ -52,7 +52,12 @@
  */
 	.macro	get_fs	ad, sp
 	GET_CURRENT(\ad,\sp)
+#if THREAD_CURRENT_DS > 1020
+	addi	\ad, \ad, TASK_THREAD
+	l32i	\ad, \ad, THREAD_CURRENT_DS - TASK_THREAD
+#else
 	l32i	\ad, \ad, THREAD_CURRENT_DS
+#endif
 	.endm

 /*
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index b61e251..b1444f9 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1855,7 +1855,6 @@ ENTRY(_switch_to)

 	entry	a1, 16

-	mov	a10, a2			# preserve 'prev' (a2)
 	mov	a11, a3			# and 'next' (a3)

 	l32i	a4, a2, TASK_THREAD_INFO
@@ -1863,8 +1862,14 @@ ENTRY(_switch_to)

 	save_xtregs_user a4 a6 a8 a9 a12 a13 THREAD_XTREGS_USER

-	s32i	a0, a10, THREAD_RA	# save return address
-	s32i	a1, a10, THREAD_SP	# save stack pointer
+#if THREAD_RA > 1020 || THREAD_SP > 1020
+	addi	a10, a2, TASK_THREAD
+	s32i	a0, a10, THREAD_RA - TASK_THREAD	# save return address
+	s32i	a1, a10, THREAD_SP - TASK_THREAD	# save stack pointer
+#else
+	s32i	a0, a2, THREAD_RA	# save return address
+	s32i	a1, a2, THREAD_SP	# save stack pointer
+#endif

 	/* Disable ints while we manipulate the stack pointer. */

@@ -1905,7 +1910,6 @@ ENTRY(_switch_to)
 	load_xtregs_user a5 a6 a8 a9 a12 a13 THREAD_XTREGS_USER

 	wsr	a14, ps
-	mov	a2, a10			# return 'prev'
 	rsync

 	retw
--
1.9.1