From: Alex LIU <alex.liu@st.com>
To: "'Andries Brouwer'" <aebr@win.tue.nl>, "'Pavel Machek'" <pavel@ucw.cz>
Cc: <linux-kernel@vger.kernel.org>
Subject: RE: The purpose of PT_TRACESYSGOOD
Date: Tue, 11 Jan 2005 14:28:33 +0800
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Then I think the tracing thread should call the ptrace_request to set
PTRACE_O_TRACESYSGOOD flag of the traced thread first before
ptrace(PTRACE_SYSCALL...) ,right?
Thanks a lot! 

Alex

Andries Brouwer wrote:

>> What's the effect of PT_TRACESYSGOOD flag? I found it's used only set 
>> in ptrace_setoptions, which is called in the function ptrace_request. 
>> And the PT_TRACESYSGOOD flag will be requested in do_syscall_trace. 
>> What's the purpose of that flag?

>/*
> * A child stopped at a syscall has status as if it received SIGTRAP.
> * In order to distinguish between SIGTRAP and syscall, some kernel
> * versions have the PTRACE_O_TRACESYSGOOD option, that sets an extra
> * bit 0x80 in the syscall case.
> */

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