linux-kernel - Re: [PATCH 2/2] objtool: use host flags to detect if libelf is missing

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Date:   Fri, 23 Feb 2018 09:37:20 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Robin Jarry <robin.jarry@...nd.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 2/2] objtool: use host flags to detect if libelf is
 missing

On Fri, Feb 23, 2018 at 03:22:15PM +0100, Robin Jarry wrote:
> When libelf headers and libs are not found and CONFIG_UNWINDER_ORC is
> selected, there is a make error introduced by
> commit 3dd40cb320fe ("objtool: Upgrade libelf-devel warning to error for
> CONFIG_ORC_UNWINDER").
> 
> Host headers and libs may be in a non-standard location and the check is
> performed without host flags. Make sure to use host flags for the check
> (they will be used later when building objtool anyway).
> 
> Fixes: 3b27a0c85d70 ("objtool: Detect and warn if libelf is missing and don't break the build")
> Signed-off-by: Robin Jarry <robin.jarry@...nd.com>
> Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
>  Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index e9609319d2b8..4e8c667b9f3f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -955,7 +955,7 @@ export mod_sign_cmd
>  
>  ifdef CONFIG_STACK_VALIDATION
>    has_libelf := $(call try-run,\
> -		echo "int main() {}" | $(HOSTCC) -xc -o /dev/null -lelf -,1,0)
> +		echo "int main() {}" | $(HOSTCC) $(host_clfags) $(HOSTLDFLAGS) -xc -o /dev/null -lelf -,1,0)
>    ifeq ($(has_libelf),1)
>      objtool_target := tools/objtool FORCE
>    else
> -- 
> 2.11.0
> 

Hi Robin,

Did you test this?  I see some issues:

a) I don't see where the host_cflags variable comes from (and btw, it's
   misspelled...)

b) I don't see where objtool uses HOSTLDFLAGS.

-- 
Josh