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Date: Mon, 9 Sep 2013 10:49:33 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        x86@kernel.org, Jiri Slaby <jslaby@suse.cz>,
        David Woodhouse <David.Woodhouse@intel.com>
Subject: Re: [PATCH] x86, build: move build output statistics away from stderr
Message-ID: <20130909084933.GA20140@gmail.com>
References: <20130906181532.GA31260@www.outflux.net>
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* Kees Cook <keescook@chromium.org> wrote:

> When building on x86, the final image building step always emits stats
> to stderr, even though this information is neither a warning nor an error:
> 
>   BUILD   arch/x86/boot/bzImage
> Setup is 16188 bytes (padded to 16384 bytes).
> System is 6368 kB
> CRC cbe50c61
> 
> Validating automated builds would be cleaner if stderr did not have to 
> filter out these lines. Instead, change how tools/build is called, and 
> make the zoffset header unconditional, and write to a specified file 
> instead of to stdout, which can then be used for statistics, leaving 
> stderr open for legitimate warnings and errors, like the output from 
> die().

Nice, that output to stderr was always somewhat annoying.

> +	/* Catch any delayed write failures */
> +	if (fclose(dest))
> +		die("Writing image failed");
> +
>  	close(fd);

Looks like the new code is not just reporting errors better, but it's more 
robust by catching and reporting fclose()-time failures as well, avoiding 
a corrupt kernel image in certain corner cases - the most common being a 
file system full error I suspect.

Thanks,

	Ingo