Re: Segfault on the i386 enter instruction

[linux-os (Dick Johnson)]

On Mon, 15 May 2006, Bart Hartgers wrote:

> Tomasz Malesinski wrote:
>> On Fri, May 12, 2006 at 03:50:20PM +0200, Andi Kleen wrote:
>>> Handling it like you expect would require to disassemble
>>> the function in the page fault handler and it's probably not
>>> worth doing that for this weird case.
>>
>> Does it mean that the ENTER instruction should not be used to create
>> stack frames in Linux programs?
>>
>
> Basically, yes. Here is a link to a relevant discussion in the 2.2.7 era:
>
> http://groups.google.co.nz/groups?selm=7i86ni%24b7n%241%40palladium.transmeta.com
>
> And perhaps x86-64 is handled different because of the red zone (some
> memory below the stack-pointer that can be accessed legally)?
>
> Groeten,
> Bart

The enter instruction works perfectly fine. The processors were
designed to use both enter and leave. There are no prohibitions
against their use. It's just that if you play games with assembly
so you create a stack-pointer wrap situation, you can get a
bounds error.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.16.4 on an i686 machine (5592.89 BogoMips).
New book: http://www.lymanschool.com
_


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