Date: Sat, 12 Mar 2016 18:16:48 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Tony Luck <tony.luck@gmail.com>
Cc: Mika =?iso-8859-1?Q?Penttil=E4?= <mika.penttila@nextfour.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>,
        "Williams, Dan J" <dan.j.williams@intel.com>
Subject: Re: [PATCH v14] x86, mce: Add memcpy_mcsafe()
Message-ID: <20160312171648.GA12167@gmail.com>
References: <a44e1055efc2d2a9473307b22c91caa437aa3f8b.1456439214.git.tony.luck@intel.com>
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* Tony Luck <tony.luck@gmail.com> wrote:

> On Thu, Mar 10, 2016 at 11:37 AM, Luck, Tony <tony.luck@intel.com> wrote:
> >> But you return 0 == false for success and 1 == true for failure.
> >
> > Aaargh!  -ETOOMUCHSHELLSCRIPTPROGRAMMING
> >
> > -Tony
> 
> Options to fix this:
> 1) Just change the comments in the code.
>      This seems like it would confuse people as I thing most people
>      would expect the "true" return to mean the copy succeeded.
> 2) Reverse the return values.
>      Better that option 1 - but doesn't leave scope to return a count
>      if some future user does want to know where the copy failed.
> 3) Change the return type back from "bool" to "int"
>      0 == success, non-zero == fail (with option to put the non-copied
> byte count in later).
> 4) Something else

Please use the copy_*_user() memory copying API semantics, which are: return 
negative code (-EFAULT) on error, 0 on success.

Don't return 1 and please don't use bools for any memory copy library 
functionality.

Thanks,

	Ingo