linux-kernel - Re: [PATCH] Make LIST

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Date:	Mon, 19 May 2008 16:18:35 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Make LIST_POISON less deadly

Ingo Molnar wrote:
>   
>> +/*
>> + * Define LIST_POISON[12] as pointers that cannot be dereferenced.
>> + */
>> +#ifdef CONFIG_X86_84
>> +#  undef LIST_POISON1
>> +#  undef LIST_POISON2
>> +#  define LIST_POISON1 ((void *)0x8001000100010001L)
>> +#  define LIST_POISON2 ((void *)0x8002000200020002L)
>> +#endif
>>     
>
> i'd suggest to add an ARCH_ILLEGAL_POINTER define instead, which 
> defaults to zero and gets added to pointer-ish poison values. That makes 
> it both simpler and also it does not need any include/asm changes 
> because ARCH_ILLEGAL_POINTER can be set from the Kconfig space.
>   

Right.

How much unmapped space do we have on i386 or other archs?  The deltas 
added to ARCH_ILLEGAL_POINTER will have to be limited to that.

Maybe have ARCH_ILLEGAL_POINTER_BASE and ARCH_ILLEGAL_POINTER_RANGE, 
defaulting to 0 and (say) 4MB, and use the range to mask the deltas to 
avoid overflows into legal pointer range.

-- 
error compiling committee.c: too many arguments to function

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