xtensa: fix a6 and a7 handling in fast_syscall_xtensa

Remove restoring a6 on some return paths and instead modify and restore
it in a single place, using symbolic name.
Correctly restore a7 from PT_AREG7 in case of illegal a6 value.

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

1 files changed, 5 insertions, 7 deletions

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 21917e5fd53a..a06b7efaae82 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1001,9 +1001,8 @@ ENTRY(fast_syscall_xtensa)
         movi    a7, 4                   # sizeof(unsigned int)
         access_ok a3, a7, a0, a2, .Leac # a0: scratch reg, a2: sp
 
-        addi    a6, a6, -1              # assuming SYS_XTENSA_ATOMIC_SET = 1
-        _bgeui  a6, SYS_XTENSA_COUNT - 1, .Lill
-        _bnei   a6, SYS_XTENSA_ATOMIC_CMP_SWP - 1, .Lnswp
+        _bgeui  a6, SYS_XTENSA_COUNT, .Lill
+        _bnei   a6, SYS_XTENSA_ATOMIC_CMP_SWP, .Lnswp
 
         /* Fall through for ATOMIC_CMP_SWP. */
 
@@ -1015,27 +1014,26 @@ TRY	s32i	a5, a3, 0		# different, modify value
         l32i    a7, a2, PT_AREG7        # restore a7
         l32i    a0, a2, PT_AREG0        # restore a0
         movi    a2, 1                   # and return 1
-        addi    a6, a6, 1               # restore a6 (really necessary?)
         rfe
 
 1:      l32i    a7, a2, PT_AREG7        # restore a7
         l32i    a0, a2, PT_AREG0        # restore a0
         movi    a2, 0                   # return 0 (note that we cannot set
-        addi    a6, a6, 1               # restore a6 (really necessary?)
         rfe
 
 .Lnswp: /* Atomic set, add, and exg_add. */
 
 TRY     l32i    a7, a3, 0               # orig
+        addi    a6, a6, -SYS_XTENSA_ATOMIC_SET
         add     a0, a4, a7              # + arg
         moveqz  a0, a4, a6              # set
+        addi    a6, a6, SYS_XTENSA_ATOMIC_SET
 TRY     s32i    a0, a3, 0               # write new value
 
         mov     a0, a2
         mov     a2, a7
         l32i    a7, a0, PT_AREG7        # restore a7
         l32i    a0, a0, PT_AREG0        # restore a0
-        addi    a6, a6, 1               # restore a6 (really necessary?)
         rfe
 
 CATCH
@@ -1044,7 +1042,7 @@ CATCH
         movi    a2, -EFAULT
         rfe
 
-.Lill:  l32i    a7, a2, PT_AREG0        # restore a7
+.Lill:  l32i    a7, a2, PT_AREG7        # restore a7
         l32i    a0, a2, PT_AREG0        # restore a0
         movi    a2, -EINVAL
         rfe