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Date: Fri, 19 Nov 2004 21:41:44 +0100
From: Eric Pouech <pouech-eric@wanadoo.fr>
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To: Linus Torvalds <torvalds@osdl.org>
Cc: Roland McGrath <roland@redhat.com>, Mike Hearn <mh@codeweavers.com>,
       linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
       wine-devel <wine-devel@winehq.com>
Subject: Re: ptrace single-stepping change breaks Wine
References: <200411152253.iAFMr8JL030601@magilla.sf.frob.com> <419E42B3.8070901@wanadoo.fr> <Pine.LNX.4.58.0411191119320.2222@ppc970.osdl.org> <419E4A76.8020909@wanadoo.fr> <Pine.LNX.4.58.0411191148480.2222@ppc970.osdl.org>
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> Btw, does wine ever _use_ PTRACE_SINGLESTEP for any of the things it does?
> 
> If it does, then that woulc certainly explain why my "fix" made no 
> difference: my fix _only_ handles the case where the ptracer never 
> actually asks for single-stepping, and single-stepping was started 
> entirely by the program being run (ie by setting TF in eflags from within 
> the program itself).
> 
> But if wine ends up using PTRACE_SINGESTEP because wine actually wants to 
> single-step over some instructions, then the kernel will set the PT_DTRACE 
> bit, and start tracing through signal handlers too. The way Wine doesn't 
> want..

wine mixes both approches, we have (to control what's generated inside the 
various exception) to ptrace from our NT-kernel-like process (the ptracer) to 
get the context of the exception. Restart from the ptracer is done with 
PTRACE_SINGLESTEP.

(BTW: I also CC:ed wine-devel ML, that might be of interest to them too)

A+