Re: [uml-devel] Re: [patch 1/1] SYSEMU: avoid intercepting syscall on return when using SYSCALL again.

[Bodo Stroesser <bstroesser@fujitsu-siemens.com>]

BlaisorBlade wrote:
> On Friday 22 October 2004 11:22, Bodo Stroesser wrote:
> 
>>blaisorblade_spam@yahoo.it wrote:
>>
>>>From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
>>>
>>>A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL
>>>crashes.
>>>
>>>The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch
>>>inhibits the syscall-handler to be called, but does not prevent
>>>do_syscall_trace to be called after this for syscall completion
>>>interception.
>>>
>>>The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to
>>>remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL",
>>>since the flag is unused in the depicted situation.
>>>
>>>The patch is tested, AFAICS, it works fine, i.e. sysemu can be switched
>>>on and off dynamically without crash.
>>>
>>>Bodo
>>>
>>>Signed-off-by: Paolo 'Blaisorblade' Giarrusso
>>><blaisorblade_spam@yahoo.it> ---
>>
>>Fine idea to move one part of the patch to sys_ptrace()!
>>But maybe you missed to reset TIF_SYSCALL_EMU while resuming with
>>PTRACE_CONT? Here is a revised patch.
> 
> Yes - I forgot it. Does the revised version work? My version did not - it 
> failed the startup test. In fact, PTRACE_CONT is called in the startup test 
> (which fails). I'm recompiling and testing.
Yes. My system works very fine with it.

Regards
> 
> Thanks again.



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