linux-kernel - Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for fsl

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Message-ID: <046ebac6-9cab-cc3e-e535-9a50051dc25f@c-s.fr>
Date:   Wed, 26 Feb 2020 06:08:13 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Jason Yan <yanaijie@...wei.com>, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
        benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        keescook@...omium.org, kernel-hardening@...ts.openwall.com,
        oss@...error.net
Cc:     linux-kernel@...r.kernel.org, zhaohongjiang@...wei.com
Subject: Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for
 fsl_booke64



Le 26/02/2020 à 03:40, Jason Yan a écrit :
> 
> 
> 在 2020/2/20 21:48, Christophe Leroy 写道:
>>
>>
>> Le 06/02/2020 à 03:58, Jason Yan a écrit :
>>>       /*
>>>        * Decide which 64M we want to start
>>>        * Only use the low 8 bits of the random seed
>>>        */
>>> -    index = random & 0xFF;
>>> +    unsigned long index = random & 0xFF;
>>
>> That's not good in terms of readability, index declaration should 
>> remain at the top of the function, should be possible if using 
>> IS_ENABLED() instead
> 
> I'm wondering how to declare a variable inside a code block such as if 
> (IS_ENABLED(CONFIG_PPC32)) at the top of the function and use the 
> variable in another if (IS_ENABLED(CONFIG_PPC32)). Is there any good idea?

You declare it outside the block as usual:

	unsigned long some_var;

	if (condition) {
		some_var = something;
	}
	do_many_things();
	do_other_things();

	if (condition)
		return some_var;
	else
		return 0;


Christophe