linux-kernel - Re: [patch] crypto: sha256-mb - cleanup a || vs

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Message-ID: <1467285386.24287.143.camel@perches.com>
Date:	Thu, 30 Jun 2016 04:16:26 -0700
From:	Joe Perches <joe@...ches.com>
To:	Dan Carpenter <dan.carpenter@...cle.com>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Megha Dey <megha.dey@...el.com>,
	"Wang, Rui Y" <rui.y.wang@...el.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Xiaodong Liu <xiaodong.liu@...el.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [patch] crypto: sha256-mb - cleanup a || vs | typo

On Thu, 2016-06-30 at 10:50 +0300, Dan Carpenter wrote:
> On Wed, Jun 29, 2016 at 10:05:53AM -0700, H. Peter Anvin wrote:
> > On 06/29/16 07:42, Dan Carpenter wrote:
> > > > > and | behave basically the same here but || is intended.  It causes a
> > > static checker warning to mix up bitwise and logical operations.
> > > 
> > > Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> > > 
> > > diff --git a/arch/x86/crypto/sha256-mb/sha256_mb.c b/arch/x86/crypto/sha256-mb/sha256_mb.c
[]
> > > @@ -299,7 +299,7 @@ static struct sha256_hash_ctx *sha256_ctx_mgr_submit(struct sha256_ctx_mgr *mgr,
> > >  	 * Or if the user's buffer contains less than a whole block,
> > >  	 * append as much as possible to the extra block.
> > >  	 */
> > > -	if ((ctx->partial_block_buffer_length) | (len < SHA256_BLOCK_SIZE)) {
> > > +	if ((ctx->partial_block_buffer_length) || (len < SHA256_BLOCK_SIZE)) {
> > >  		/* Compute how many bytes to copy from user buffer into
> > >  		 * extra block
> > >  		 */
> > > 
> > As far as I know the | was an intentional optimization, so you may way
> > to look at the generated code.
> I know how the rules work.  I just thought it looked more like a typo
> than an optimization.  It's normally a typo.  It's hard to tell the
> intent.

The compiler could potentially emit the same code when
optimizing but at least gcc 5.3 doesn't.

It's probably useful to add a comment for the specific intent
here rather than change a potentially useful static checker.