xtensa: fix kernel register spilling

call12 can't be safely used as the first call in the inline function,
because the compiler does not extend the stack frame of the bounding
function accordingly, which may result in corruption of local variables.

If a call needs to be done, do call8 first followed by call12.

For pure assembly code in _switch_to increase stack frame size of the
bounding function.

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

diff --git a/arch/xtensa/include/asm/traps.h b/arch/xtensa/include/asm/traps.h
index 677bfcf..28f33a8 100644 (file)
--- a/arch/xtensa/include/asm/traps.h
+++ b/arch/xtensa/include/asm/traps.h
@@ -25,30 +25,39 @@ static inline void spill_registers(void)
 {
 #if XCHAL_NUM_AREGS > 16
        __asm__ __volatile__ (
-               "       call12  1f\n"
+               "       call8   1f\n"
                "       _j      2f\n"
                "       retw\n"
                "       .align  4\n"
                "1:\n"
+#if XCHAL_NUM_AREGS == 32
+               "       _entry  a1, 32\n"
+               "       addi    a8, a0, 3\n"
+               "       _entry  a1, 16\n"
+               "       mov     a12, a12\n"
+               "       retw\n"
+#else
                "       _entry  a1, 48\n"
-               "       addi    a12, a0, 3\n"
-#if XCHAL_NUM_AREGS > 32
-               "       .rept   (" __stringify(XCHAL_NUM_AREGS) " - 32) / 12\n"
+               "       call12  1f\n"
+               "       retw\n"
+               "       .align  4\n"
+               "1:\n"
+               "       .rept   (" __stringify(XCHAL_NUM_AREGS) " - 16) / 12\n"
                "       _entry  a1, 48\n"
                "       mov     a12, a0\n"
                "       .endr\n"
-#endif
-               "       _entry  a1, 48\n"
+               "       _entry  a1, 16\n"
 #if XCHAL_NUM_AREGS % 12 == 0
-               "       mov     a8, a8\n"
-#elif XCHAL_NUM_AREGS % 12 == 4
                "       mov     a12, a12\n"
-#elif XCHAL_NUM_AREGS % 12 == 8
+#elif XCHAL_NUM_AREGS % 12 == 4
                "       mov     a4, a4\n"
+#elif XCHAL_NUM_AREGS % 12 == 8
+               "       mov     a8, a8\n"
 #endif
                "       retw\n"
+#endif
                "2:\n"
-               : : : "a12", "a13", "memory");
+               : : : "a8", "a9", "memory");
 #else
        __asm__ __volatile__ (
                "       mov     a12, a12\n"

diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 5e492ae..3d9d221 100644 (file)
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1823,7 +1823,7 @@ ENDPROC(system_call)
        mov     a12, a0
        .endr
 #endif
-       _entry  a1, 48
+       _entry  a1, 16
 #if XCHAL_NUM_AREGS % 12 == 0
        mov     a8, a8
 #elif XCHAL_NUM_AREGS % 12 == 4
@@ -1847,7 +1847,7 @@ ENDPROC(system_call)
 
 ENTRY(_switch_to)
 
-       entry   a1, 16
+       entry   a1, 48
 
        mov     a11, a3                 # and 'next' (a3)