xtensa: fix access to THREAD_RA/THREAD_SP/THREAD_DS

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.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index ef7f4990722b..db96acb1362b 100644
--- 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