Re: x86: get rid of the insane TIF_ABI_PENDING bit

From: H. Peter Anvin
Date: Mon Feb 15 2010 - 13:07:41 EST


On 02/15/2010 08:50 AM, Oleg Nesterov wrote:
>
> Could you please point me where do we check TS_COMPAT during return
> to user-mode?
>

Sorry, I was thinking about TIF_IA32, which is examined on line 415 of
entry_64.S.

>>> If a 64bit task execs a 32bit app, can't this TS_COMPAT break, say,
>>> syscall_get_arguments() ?
>>
>> At that point (this is after the exec!) we don't get arguments anyway.
>
> I meant /proc/pid/syscall, but even if I am right this probably
> doesn't matter.

What does getting the arguments from a process which has never done a
system call yet even mean? Presumably we get some kind of "null answer"
which depends on the default register set; in that case the compat null
answer is the correct one.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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