linux-kernel - Re: [PATCH V10 07/10] efi: print unrecognized CPER section

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Date:   Wed, 22 Feb 2017 10:13:28 +0000
From:   James Morse <james.morse@....com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
CC:     Tyler Baicar <tbaicar@...eaurora.org>, christoffer.dall@...aro.org,
        marc.zyngier@....com, pbonzini@...hat.com, rkrcmar@...hat.com,
        catalin.marinas@....com, will.deacon@....com, rjw@...ysocki.net,
        lenb@...nel.org, matt@...eblueprint.co.uk, robert.moore@...el.com,
        lv.zheng@...el.com, nkaje@...eaurora.org, zjzhang@...eaurora.org,
        mark.rutland@....com, akpm@...ux-foundation.org,
        eun.taik.lee@...sung.com, sandeepa.s.prabhu@...il.com,
        labbott@...hat.com, shijie.huang@....com, rruigrok@...eaurora.org,
        paul.gortmaker@...driver.com, tn@...ihalf.com, fu.wei@...aro.org,
        rostedt@...dmis.org, bristot@...hat.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-efi@...r.kernel.org,
        devel@...ica.org, Suzuki.Poulose@....com, punit.agrawal@....com,
        astone@...hat.com, harba@...eaurora.org, hanjun.guo@...aro.org,
        john.garry@...wei.com, shiju.jose@...wei.com
Subject: Re: [PATCH V10 07/10] efi: print unrecognized CPER section

On 22/02/17 01:12, Russell King - ARM Linux wrote:
> On Tue, Feb 21, 2017 at 07:10:11PM +0000, James Morse wrote:
>> Hi Tyler,
>>
>> On 15/02/17 19:51, Tyler Baicar wrote:
>>> +	} else {
>>> +		const void *unknown_err;
>>> +
>>> +		unknown_err = acpi_hest_generic_data_payload(gdata);
>>> +		printk("%ssection type: %pUl\n", newpfx, sec_type);
>>> +		printk("%ssection length: %d\n", newpfx,
>>
>> Nit: please use the "%s""section... that this file consistently uses. This means
>> this code will still work as expected when someone adds '%ss' support to printk!
> 
> No.  That is wrong:
> 
> "%s""section" is stored in memory as bytes containing:
> 
> '%' 's' 's' 'e' 'c' 't' 'i' 'o' 'n'
> 
> whereas "%ssection" is stored in memory as bytes containing:
> 
> '%' 's' 's' 'e' 'c' 't' 'i' 'o' 'n'
> 
> They're exactly the same, so when printk() comes to parse the string, it
> sees exactly the same byte sequence.  So, the only thing that's happening
> is code obfuscation for no good reason what so ever.
> 
> If you don't believe me, run some build tests and look at the resulting
> strings... also look at the C standard.  "Adjacent string literal tokens
> are concatenated."
> 
> Please get rid of this obfuscation.

Sure, I was always told not do this, clearly I didn't think about it for very long!

This file otherwise consistently uses the now-weird "%s""otherstring" pattern.



Thanks,

James