linux-kernel - Re: [PATCH 19/20] lto, module: Warn about modules that are not fully LTOed

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Message-ID: <20140218145039.GA5339@phenom.dumpdata.com>
Date:	Tue, 18 Feb 2014 09:50:39 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, sam@...nborg.org, x86@...nel.org,
	linux-kbuild@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
	rusty@...tcorp.com.au
Subject: Re: [PATCH 19/20] lto, module: Warn about modules that are not fully
 LTOed

On Tue, Feb 18, 2014 at 03:28:57PM +0100, Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> When __gnu_lto_* is present that means that the module hasn't run with
> LTO yet.

The title says 'warn' but this is not a warning just information.

Can you actually build modules against the kernel with different compiler
options? I thought it would complain when trying to load about some
form of mismatch?

> 
> Cc: rusty@...tcorp.com.au
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  kernel/module.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index b99e801..4f3eff7 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -1949,8 +1949,11 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
>  		switch (sym[i].st_shndx) {
>  		case SHN_COMMON:
>  			/* Ignore common symbols */
> -			if (!strncmp(name, "__gnu_lto", 9))
> +			if (!strncmp(name, "__gnu_lto", 9)) {
> +				pr_info("%s: module not link time optimized\n",
> +				       mod->name);
>  				break;
> +			}
>  
>  			/* We compiled with -fno-common.  These are not
>  			   supposed to happen.  */
> -- 
> 1.8.5.2
> 
> --
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