On 2018/12/5 11:00, Masahiro Yamada wrote:
It is wrong to add CONFIG option diagnostic to the Makefile parse
stage.
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 commit
829fe4aa9ac1 ("x86: Allow generating user-space headers without a
compiler") did.
Link: https://lkml.org/lkml/2018/12/4/206
Reported-by: Meelis Roos <mr...@linux.ee>
Fixes: 4cd24de3a098 ("x86/retpoline: Make CONFIG_RETPOLINE depend on compiler
support")
Signed-off-by: Masahiro Yamada <yamada.masah...@socionext.com>
---
arch/x86/Makefile | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index f5d7f41..ae0148b 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -219,12 +219,7 @@ KBUILD_CFLAGS += -Wno-sign-compare
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
# 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
+KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
Is it better to also move "# Avoid indirect branches in kernel to deal
with Spectre"
and "KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)"?
Seems unconditionaly using "KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)" will
have compiler
using "__x86_indirect_thunk_\reg" call even ifCONFIG_RETPOLINE is
disabled. I guess
link process will fail?
Thanks
Zhenzhong
archscripts: scripts_basic
$(Q)$(MAKE) $(build)=arch/x86/tools relocs
@@ -307,6 +302,13 @@ ifndef CC_HAVE_ASM_GOTO
@echo Compiler lacks asm-goto support.
@exit 1
endif
+ifdef CONFIG_RETPOLINE
+ifeq ($(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
