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>

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 21917e5fd53a64a19a39fbd7ca868f3914b57e55..a06b7efaae82454af75f5c44b943492275059cc6 100644 (file)
--- 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