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 677bfcf4ee5ddab2207ed0e5f2885b4accd29f16..28f33a8b7f5f5b5b70d7d2f6cb6c0533bdc80a05 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 5e492aec7b47c5338bededc1ffc3b156fbf37d7d..3d9d221d2f0f774660426a1b1c412dc903d2bc38 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)