powerpc: Document register clobbering in EXCEPTION_COMMON()

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
index 8f35cd7..066c15c 100644 (file)
--- a/arch/powerpc/include/asm/exception-64s.h
+++ b/arch/powerpc/include/asm/exception-64s.h
@@ -532,6 +532,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CTRL)
        .globl label##_common;                                  \
 label##_common:                                                        \
        EXCEPTION_PROLOG_COMMON(trap, PACA_EXGEN);              \
+       /* Volatile regs are potentially clobbered here */      \
        additions;                                              \
        addi    r3,r1,STACK_FRAME_OVERHEAD;                     \
        bl      hdlr;                                           \