linux-kernel - Re: Compat 32-bit syscall entry from 64-bit task!?

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Date:	Thu, 26 Jan 2012 19:44:38 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Indan Zupancic <indan@....nu>,
	Andi Kleen <andi@...stfloor.org>,
	Jamie Lokier <jamie@...reable.org>,
	Andrew Lutomirski <luto@....edu>,
	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	keescook@...omium.org, john.johansen@...onical.com,
	serge.hallyn@...onical.com, coreyb@...ux.vnet.ibm.com,
	pmoore@...hat.com, eparis@...hat.com, djm@...drot.org,
	segoon@...nwall.com, rostedt@...dmis.org, jmorris@...ei.org,
	scarybeasts@...il.com, avi@...hat.com, penberg@...helsinki.fi,
	viro@...iv.linux.org.uk, mingo@...e.hu, akpm@...ux-foundation.org,
	khilman@...com, borislav.petkov@....com, amwang@...hat.com,
	ak@...ux.intel.com, eric.dumazet@...il.com, gregkh@...e.de,
	dhowells@...hat.com, daniel.lezcano@...e.fr,
	linux-fsdevel@...r.kernel.org,
	linux-security-module@...r.kernel.org, olofj@...omium.org,
	mhalcrow@...gle.com, dlaor@...hat.com,
	Roland McGrath <mcgrathr@...omium.org>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?

On 01/26, Denys Vlasenko wrote:
>
> On Wednesday 25 January 2012 20:36, Oleg Nesterov wrote:
> >
> > We can add the new events,
> >
> > 	PTRACE_EVENT_SYSCALL_ENTRY
> > 	PTRACE_EVENT_SYSCALL_COMPAT_ENTRY
> > 	PTRACE_EVENT_SYSCALL_EXIT
> > 	PTRACE_EVENT_SYSCALL_COMPAT_EXIT
>
> We can get away with just the first one.
> (1) It's unlikely people would want to get native sysentry events but not compat ones,
> thus first two options can be combined into one;

Confused... Sure, we need the single option, or we could even report
this unconditionally if PT_SEIZED.

I meant the different PTRACE_EVENT_* codes only.

> (2) syscall exit compat-ness is known from entry type - no need to indicate it; and
> (3) if we would flag syscall entry with an event value in wait status, then syscall
> exit will be already distinquisable.

Well, if we add _ENTRY then it looks more consistent to report _EXIT
as well even if it is not that useful.

Doesn't matter. Nobody seem to like this, and afaics Linus has the
good arguments against the arch-independent "consolidation".

Oleg.

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