xtensa: fix kernel register spilling

commit 77d6273e79e3a86552fcf10cdd31a69b46ed2ce6 upstream.

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.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/arch/xtensa/include/asm/traps.h b/arch/xtensa/include/asm/traps.h
index f2faa58f9a43f3a591b41f9bf7f62b72bc8e6218..03d02df47b9a99dd7a62e196e1f87dd426d811c2 100644 (file)
--- a/arch/xtensa/include/asm/traps.h
+++ b/arch/xtensa/include/asm/traps.h
@@ -24,30 +24,39 @@ 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 900137e59b2024d8f0e5b9a4f7d1c071822e5adf..250c52b14edf703651653b084d1a5c457fd255bc 100644 (file)
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1828,7 +1828,7 @@ 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
@@ -1852,7 +1852,7 @@ ENDPROC(system_call)
 
 ENTRY(_switch_to)
 
-       entry   a1, 16
+       entry   a1, 48
 
        mov     a11, a3                 # and 'next' (a3)