[PATCH 4.19 44/44] x86/build: Fix compiler support check for CONFIG_RETPOLINE

Greg Kroah-Hartman
2018-12-18T16:42:14Z

From: Masahiro Yamada <yamada.masahiro@socionext.com>

commit 25896d073d8a0403b07e6dec56f58e6c33678207 upstream.

It is troublesome to add a diagnostic like this to the Makefile
parse stage because the top-level Makefile could be parsed with
a stale include/config/auto.conf.

Once you are hit by the error about non-retpoline compiler, the
compilation still breaks even after disabling CONFIG_RETPOLINE.

The easiest fix is to move this check to the "archprepare" like
this commit did:

829fe4aa9ac1 ("x86: Allow generating user-space headers without a compiler")

Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler support")
Link: http://lkml.kernel.org/r/1543991239-18476-1-git-send-email-yamada.masahiro@socionext.com
Link: https://lkml.org/lkml/2018/12/4/206
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Cc: Gi-Oh Kim <gi-oh.kim@cloud.ionos.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/Makefile | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -223,9 +223,6 @@ KBUILD_CFLAGS += -fno-asynchronous-unwin

# Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE
-ifeq ($(RETPOLINE_CFLAGS),)
- $(error You are building kernel with non-retpoline compiler, please update your compiler.)
-endif
KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
endif

@@ -303,6 +300,13 @@ ifndef CC_HAVE_ASM_GOTO
@echo Compiler lacks asm-goto support.
@exit 1
endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(RETPOLINE_CFLAGS),)
+ @echo "You are building kernel with non-retpoline compiler." >&2
+ @echo "Please update your compiler." >&2
+ @false
+endif
+endif

archclean:
$(Q)rm -rf $(objtree)/arch/i386