linux-kernel - Re: [PATCH v3 5/6] ptrace: introduce PTRACE_SET_SYSCALL

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Message-ID: <20250128155812.GB11869@strace.io>
Date: Tue, 28 Jan 2025 17:58:12 +0200
From: "Dmitry V. Levin" <ldv@...ace.io>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Oleg Nesterov <oleg@...hat.com>, Alexey Gladkov <legion@...nel.org>,
	Charlie Jenkins <charlie@...osinc.com>,
	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 v3 5/6] ptrace: introduce PTRACE_SET_SYSCALL_INFO request

On Tue, Jan 28, 2025 at 04:21:13PM +0100, Christophe Leroy wrote:
> Le 28/01/2025 à 10:16, Dmitry V. Levin a écrit :
> > PTRACE_SET_SYSCALL_INFO is a generic ptrace API that complements
> > PTRACE_GET_SYSCALL_INFO by letting the ptracer modify details of
> > system calls the tracee is blocked in.
> > 
> > This API allows ptracers to obtain and modify system call details
> > in a straightforward and architecture-agnostic way.
> > 
> > Current implementation supports changing only those bits of system call
> > information that are used by strace, namely, syscall number, syscall
> > arguments, and syscall return value.
> 
> How do you handle changes related to syscalls that call 
> force_successful_syscall_return() ?

I don't see why these syscalls would need any special treatment.
If a tracer wants to set an error status for a syscall that cannot return
an error, it's up to the tracer to face the consequences.
Tracers can do it now via PTRACE_SETREGS* anyway.


-- 
ldv