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

[Jessica Yu]

+++ Josh Poimboeuf [15/02/17 12:21 -0600]:
> 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>

With this patch the warning now prints for OOT modules, and more
importantly, the build no longer breaks for them, so:

Reviewed-by: Jessica Yu <jeyu@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