linux-kernel - Re: [PATCH v2 6/7] ptrace: introduce PTRACE_SET_SYSCALL

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Message-ID: <20250115191002.GC21801@redhat.com>
Date: Wed, 15 Jan 2025 20:10:03 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: "Dmitry V. Levin" <ldv@...ace.io>
Cc: Alexey Gladkov <legion@...nel.org>,
	Eugene Syromyatnikov <evgsyr@...il.com>,
	Mike Frysinger <vapier@...too.org>,
	Renzo Davoli <renzo@...unibo.it>,
	Davide Berardi <berardi.dav@...il.com>,
	strace-devel@...ts.strace.io, linux-kernel@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v2 6/7] ptrace: introduce PTRACE_SET_SYSCALL_INFO request

On 01/15, Dmitry V. Levin wrote:
>
> On Wed, Jan 15, 2025 at 05:38:09PM +0100, Oleg Nesterov wrote:
> >
> > But may be
> >
> > 	if (syscall_get_nr() != -1)
> > 		syscall_set_arguments(...);
> >
> > will look a bit more consistent?
>
> I'm sorry, but I didn't follow.  As we've just set the syscall number with
> syscall_set_nr(), why would we want to call syscall_get_nr() right after
> that to obtain the syscall number?

Mostly for grep. We have more syscall_get_nr() != -1 checks. Even right after
syscall_set_nr-like code, see putreg32().

I think this needs another helper (which can have more users) and some cleanups.

But this is another issue, so please forget. I agree that syscall_get_nr() in
this code will probably just add the unnecessary confusion.

Oleg.