linux-kernel - Re: [PATCH] x86,boot: standardize strcmp()

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Date:	Tue, 17 Mar 2015 08:46:08 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Arjun Sreedharan <arjun024@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86,boot: standardize strcmp()


* Arjun Sreedharan <arjun024@...il.com> wrote:

> strcmp() is always expected to return 0 when args are
> same, <0 when arg1 is lesser and >0 otherwise.
> Previously strcmp("a","b") returned 1. Now it gives -1.

I'd also add the following to the changelog:

Until now this bug never triggered, because all uses for strcmp() in 
the boot code tested for nonzero:

 triton:~/tip> git grep strcmp arch/x86/boot/
 arch/x86/boot/boot.h:int strcmp(const char *str1, const char *str2);
 arch/x86/boot/edd.c:            if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
 arch/x86/boot/edd.c:            else if (!strcmp(eddarg, "off"))
 arch/x86/boot/edd.c:            else if (!strcmp(eddarg, "on"))

should in the future strcmp() be used in a comparative way in the boot 
code, it might have led to (not so subtle) bugs.

Thanks,

	Ingo
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