[PATCH] objtool: fix CONFIG_STACK_VALIDATION warning for out-of-tree modules

From: Josh Poimboeuf
Date: Wed Feb 15 2017 - 13:21:38 EST


When building a CONFIG_STACK_VALIDATION enabled kernel without the
libelf devel package installed, the Makefile prints a warning:

"Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel"

But when building an out-of-tree module, the warning doesn't show.
Instead it tries to use objtool, and the build fails with:

/bin/sh: ./tools/objtool/objtool: No such file or directory

Make sure the warning and the disabling of objtool occur in all cases,
by moving the CONFIG_STACK_VALIDATION checks outside the 'ifeq
($(KBUILD_EXTMOD),)' block in the Makefile.

Reported-by: Marc MERLIN <marc@xxxxxxxxxxx>
Suggested-by: Jessica Yu <jeyu@xxxxxxxxxx>
Fixes: 3b27a0c85d70 ("objtool: Detect and warn if libelf is missing and don't break the build")
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
Makefile | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/Makefile b/Makefile
index 8e223e0..bcf7036 100644
--- a/Makefile
+++ b/Makefile
@@ -908,6 +908,18 @@ mod_sign_cmd = true
endif
export mod_sign_cmd

+ifdef CONFIG_STACK_VALIDATION
+ has_libelf := $(call try-run,\
+ echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0)
+ ifeq ($(has_libelf),1)
+ objtool_target := tools/objtool FORCE
+ else
+ $(warning "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
+ SKIP_STACK_VALIDATION := 1
+ export SKIP_STACK_VALIDATION
+ endif
+endif
+

ifeq ($(KBUILD_EXTMOD),)
core-y += kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
@@ -1035,18 +1047,6 @@ prepare0: archprepare gcc-plugins
# All the preparing..
prepare: prepare0 prepare-objtool

-ifdef CONFIG_STACK_VALIDATION
- has_libelf := $(call try-run,\
- echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0)
- ifeq ($(has_libelf),1)
- objtool_target := tools/objtool FORCE
- else
- $(warning "Cannot use CONFIG_STACK_VALIDATION, please install libelf-dev, libelf-devel or elfutils-libelf-devel")
- SKIP_STACK_VALIDATION := 1
- export SKIP_STACK_VALIDATION
- endif
-endif
-
PHONY += prepare-objtool
prepare-objtool: $(objtool_target)

--
2.7.4