From: Renzo Davoli <renzo@cs.unibo.it>
To: Oleg Nesterov <oleg@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Shuah Khan <shuah@kernel.org>, Alexey Gladkov <legion@kernel.org>,
Eugene Syromyatnikov <evgsyr@gmail.com>,
Mike Frysinger <vapier@gentoo.org>,
Davide Berardi <berardi.dav@gmail.com>,
strace-devel@lists.strace.io, Dmitry Levin <ldv@strace.io>
Subject: Re: [PATCH 1/5] ptrace: add PTRACE_SYSCALL_INFO_SECCOMP_SKIP
Date: Thu, 2 Jul 2026 11:09:03 +0200 [thread overview]
Message-ID: <akYoiowicHKWB3_J@cs.unibo.it> (raw)
In-Reply-To: <akYksXzCP4ioczEU@redhat.com>
Hi Oleg,
> Rather than add the new PTRACE_SYSCALL_INFO_SECCOMP_SKIP, can't we teach
> ptrace_set_syscall_info_seccomp() to treat info->entry.nr == -1 as "skip" ?
it already does
> Note that ptrace_set_syscall_info_seccomp() -> ptrace_set_syscall_info_entry()
> already does syscall_set_nr().
Syscall skipping is useless if there is not a way to set the return value/errno.
As I explain in the cover letter
+ The tracer can skip the system call by setting the system call number
+ to -1. However, the current PTRACE_SET_SYSCALL_INFO interface does not
+ provide a way to specify the return value or error code that should be
+ reported to the tracee after skipping the call.
currently retvalue/errno can be set only at PTRACE_SYSCALL_INFO_EXIT
renzo
next prev parent reply other threads:[~2026-07-02 9:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 15:05 [PATCH 0/5] ptrace_set_syscall_info: add support for seccomp syscall skipping and instruction pointer modification Renzo Davoli
2026-07-01 15:05 ` [PATCH 1/5] ptrace: add PTRACE_SYSCALL_INFO_SECCOMP_SKIP Renzo Davoli
2026-07-02 8:43 ` Oleg Nesterov
2026-07-02 9:09 ` Renzo Davoli [this message]
2026-07-02 9:58 ` Oleg Nesterov
2026-07-02 11:07 ` Dmitry V. Levin
2026-07-02 11:31 ` Oleg Nesterov
2026-07-02 11:39 ` Oleg Nesterov
2026-07-02 14:47 ` Oleg Nesterov
2026-07-02 16:10 ` Renzo Davoli
2026-07-03 9:58 ` Oleg Nesterov
2026-07-06 14:16 ` Dmitry V. Levin
2026-07-01 15:05 ` [PATCH 2/5] selftests/ptrace: add a test case for PTRACE_SYSCALL_INFO_SECCOMP_SKIP Renzo Davoli
2026-07-01 15:05 ` [PATCH 3/5] asm/ptrace.h: add instruction_pointer_set Renzo Davoli
2026-07-01 15:05 ` [PATCH 4/5] ptrace: add PTRACE_SYSCALL_INFO_FLAG_SET_IP Renzo Davoli
2026-07-01 15:05 ` [PATCH 5/5] selftests/ptrace: add a test case for PTRACE_SYSCALL_INFO_FLAG_SET_IP Renzo Davoli
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