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

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Message-ID: <20170308234154.GA2352@altlinux.org>
Date:   Thu, 9 Mar 2017 02:41:54 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Denys Vlasenko <vda.linux@...glemail.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Indan Zupancic <indan@....nu>, Oleg Nesterov <oleg@...hat.com>,
        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!?

Hi,

On Thu, Jan 26, 2012 at 07:03:43PM +0100, Denys Vlasenko wrote:
> Hi Linus,
> 
> On Thu, Jan 26, 2012 at 4:47 AM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >> Please look at strace source, get_scno() function, where
> >> it reads syscall no and parameters. Let's see....
> >> - POWERPC: has 32-bit and 64-bit mode
> >> - X86_64: has 32-bit and 64-bit mode
> >> - IA64: has i386-compat mode
> >> - ARM: has more than one ABI
> >> - SPARC: has 32-bit and 64-bit mode
> >>
> >> Do you want to re-invent a different arch-specific way to report
> >> syscall type for each of these arches?
> >
> > I think an arch-specific one is better than trying to make some
> > generic one that is messy.
> >
> > As you say, many architectures have multiple system call ABIs.
> >
> > But they tend to be very *different* issues. They can be about
> > multiple ABI's, as you mention, and even when they *look* similar
> > (32-bit vs 64-bit ABI's) they are actually totally different issues.
> > [skip]
> 
> I don't have a particular attachment to my solution,
> and I think we already talk about this problem for
> far too long.
> 
> Looks like nobody is _strongly_ opposed to your patch
> which uses a few bits in eflags to report bitness
> of the x86 syscall.
> 
> Lets just do that already. If you commit it to kernel git,
> I will immediately change strace accordingly.

Is there any progress with this (or any alternative) solution?

I see the kernel side has changed a bit, and the strace part
is in a better shape than 5 years ago (although I'm biased of course),
but I don't see any kernel interface that would allow strace to reliably
recognize this 0x80 case.


-- 
ldv

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