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Subject[PATCH 3.14 069/238] xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS
Date
3.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Max Filippov <jcmvbkbc@gmail.com>

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@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/xtensa/include/asm/uaccess.h | 5 +++++
arch/xtensa/kernel/entry.S | 12 ++++++++----
2 files changed, 13 insertions(+), 4 deletions(-)

--- 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

/*
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1820,7 +1820,6 @@ ENTRY(_switch_to)

entry a1, 16

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

l32i a4, a2, TASK_THREAD_INFO
@@ -1828,8 +1827,14 @@ 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. */

@@ -1870,7 +1875,6 @@ 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



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