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Date: Fri, 10 Jul 2026 18:49:11 +0200
From: Renzo Davoli <renzo@cs.unibo.it>
To: Michal =?iso-8859-1?Q?Such=E1nek?= <msuchanek@suse.de>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
	Oleg Nesterov <oleg@redhat.com>, Shuah Khan <shuah@kernel.org>,
	Alexey Gladkov <legion@kernel.org>,
	Eugene Syromyatnikov <evgsyr@gmail.com>,
	Davide Berardi <berardi.dav@gmail.com>,
	strace-devel@lists.strace.io, "Dmitry V . Levin" <ldv@strace.io>
Subject: Re: [PATCH v5 0/2] PTRACE_SET_SYSCALL_INFO: add support for seccomp
 syscall skipping
Message-ID: <alEih9lMnDnpP64F@cs.unibo.it>
References: <20260709100949.94345-1-renzo@cs.unibo.it>
 <alER-CLAgNdLQjRU@kunlun.suse.cz>
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In-Reply-To: <alER-CLAgNdLQjRU@kunlun.suse.cz>

Hi Michal,
	 I am not an expert of the powerpc architecture.

On Fri, Jul 10, 2026 at 05:38:32PM +0200, Michal Suchánek wrote:
> On these architectures the syscall number and the syscall return value
> share the same register.

Reading the file arch/powerpc/include/asm/syscall.h
the functions
 	syscall_get_nr()
	syscall_set_nr()
read and write regs->gpr[0]

while
	syscall_get_return_value()
	syscall_set_return_value()
read and write regs->gpr[3] (and one bit in regs->ccr as an error flag).

Am I missing another part of the entry/exit path where the two overlap?

Thank you.

	renzo