linux-kernel - Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND

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Message-ID: <5665CF5A.1090207@android.com>
Date:	Mon, 7 Dec 2015 10:26:34 -0800
From:	Daniel Cashman <dcashman@...roid.com>
To:	Arnd Bergmann <arnd@...db.de>, Jon Hunter <jonathanh@...dia.com>
Cc:	linux-kernel@...r.kernel.org, dcashman@...gle.com,
	linux-doc@...r.kernel.org, catalin.marinas@....com,
	will.deacon@....com, linux-mm@...ck.org, hpa@...or.com,
	mingo@...nel.org, aarcange@...hat.com, linux@....linux.org.uk,
	corbet@....net, xypron.glpk@....de, x86@...nel.org,
	hecmargi@....es, mgorman@...e.de, rientjes@...gle.com, bp@...e.de,
	nnk@...gle.com, dzickus@...hat.com, keescook@...omium.org,
	jpoimboe@...hat.com, tglx@...utronix.de, n-horiguchi@...jp.nec.com,
	linux-arm-kernel@...ts.infradead.org, salyzyn@...roid.com,
	ebiederm@...ssion.com, jeffv@...gle.com, akpm@...ux-foundation.org,
	kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v5 3/4] arm64: mm: support ARCH_MMAP_RND_BITS.

On 12/07/2015 03:13 AM, Arnd Bergmann wrote:
> On Monday 07 December 2015 10:26:16 Jon Hunter wrote:
>>
>> diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
>> index af461b935137..e59a75a308bc 100644
>> --- a/arch/arm64/mm/mmap.c
>> +++ b/arch/arm64/mm/mmap.c
>> @@ -51,7 +51,7 @@ unsigned long arch_mmap_rnd(void)
>>  {
>>         unsigned long rnd;
>>  
>> -ifdef CONFIG_COMPAT
>> +#ifdef CONFIG_COMPAT

Thank you Jon.  This ought to persuade me to do a final build against
the final patch, rather than the ugly porting I had been doing.  I'll
include this in v6. (how embarassing =/)

>>         if (test_thread_flag(TIF_32BIT))
>>                 rnd = (unsigned long)get_random_int() % (1 << mmap_rnd_compat_bits);
>>         else
>>
>> Cheers
>>
> 
> Ideally we'd remove the #ifdef around the mmap_rnd_compat_bits declaration
> and change this code to use
> 
> 	if (IS_ENABLED(CONFIG_COMPAT) && test_thread_flag(TIF_32BIT))
> 
> 	Arnd

That would result in "undefined reference to mmap_rnd_compat_bits" in
the not-defined case, no?

Thank You,
Dan
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