linux-kernel - Re: [PATCH 1/5] x86/alternative: simplify DUMP

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Message-ID: <793b7cd9b229bc9427539c683524572259f2893b.camel@perches.com>
Date:   Sun, 13 Mar 2022 20:21:15 -0700
From:   Joe Perches <joe@...ches.com>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     x86@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] x86/alternative: simplify DUMP_BYTES macro

On Sun, 2022-03-13 at 21:09 +0300, Alexey Dobriyan wrote:
> On Sat, Mar 12, 2022 at 08:36:11AM -0800, Joe Perches wrote:
> > On Fri, 2022-03-11 at 17:43 +0300, Alexey Dobriyan wrote:
> > > Avoid zero length check with clever whitespace placement in the format
> > > string.
> > []
> > > diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> > []
> > > @@ -66,13 +66,10 @@ do {									\
> > >  	if (unlikely(debug_alternative)) {				\
> > >  		int j;							\
> > >  									\
> > > -		if (!(len))						\
> > > -			break;						\
> > > -									\
> > >  		printk(KERN_DEBUG pr_fmt(fmt), ##args);			\
> > > -		for (j = 0; j < (len) - 1; j++)				\
> > > -			printk(KERN_CONT "%02hhx ", buf[j]);		\
> > > -		printk(KERN_CONT "%02hhx\n", buf[j]);			\
> > > +		for (j = 0; j < (len); j++)				\
> > > +			printk(KERN_CONT " %02hhx", buf[j]);		\
> > > +		printk(KERN_CONT "\n");					\
> > >  	}								\
> > 
> > This could also use %02x and not %02hhx
> 
> I doubt as there is funky stuff possible with 255 and such values.

'"%02hhx", u8' and '"%02x", u8' have the same output as the
u8 is converted anyway given the integer promotions.

https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/

> Format specifiers aren't the purpose of the patch anyway.

IMO: If you are already touching the lines,
     you might as well fix it at the same time.

cheers, Joe