x86, build: use objtool mcount

Select HAVE_OBJTOOL_MCOUNT if STACK_VALIDATION is selected to use
objtool to generate __mcount_loc sections for dynamic ftrace with
Clang and gcc <5 (later versions of gcc use -mrecord-mcount).

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7b6dd10b162ac71f4f7dd3ddbe3f8a9a5658fb16..9cd9bd6562e342199caadaf21fc7a3252dfc357b 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -167,6 +167,7 @@ config X86
        select HAVE_CONTEXT_TRACKING            if X86_64
        select HAVE_CONTEXT_TRACKING_OFFSTACK   if HAVE_CONTEXT_TRACKING
        select HAVE_C_RECORDMCOUNT
+       select HAVE_OBJTOOL_MCOUNT              if STACK_VALIDATION
        select HAVE_DEBUG_KMEMLEAK
        select HAVE_DMA_CONTIGUOUS
        select HAVE_DYNAMIC_FTRACE