linux-kernel - Re: [PATCH] x86: make PTRACE_GETREGSET return 32-bit regs if 64-bit process entered kernel with int 80

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Message-ID: <20130215151602.GF8193@moon>
Date:	Fri, 15 Feb 2013 19:16:02 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [PATCH] x86: make PTRACE_GETREGSET return 32-bit regs if 64-bit
 process entered kernel with int 80

On Fri, Feb 15, 2013 at 04:09:40PM +0100, Oleg Nesterov wrote:
> On 02/15, Cyrill Gorcunov wrote:
> >
> > > strace needs to get that data on every syscall entry in the traced process.
> > > Doing open/read/close on every syscall entry is going to slow it down a lot.
> >
> > Don't you need to read it only once when strace is attached? Compat flag can't
> > be arbitrary dropped when program executes, no?
> 
> TS_COMPAT is set/cleared every time a 64bit task does int80.
> 
> I guess you need TIF_IA32, not TS_COMPAT, for c/r.

Yeah, indeed. Still if there will be a metadata in registers set, this
will be even better I think.
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