From: Elvira Khabirova <lineprinter@altlinux.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: rostedt@goodmis.org, mingo@redhat.com,
linux-kernel@vger.kernel.org, ldv@altlinux.org, esyr@redhat.com,
luto@kernel.org, strace-devel@lists.strace.io,
linux-api@vger.kernel.org
Subject: Re: [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message
Date: Tue, 27 Nov 2018 03:53:57 +0100 [thread overview]
Message-ID: <20181127035357.0b381323@akathisia> (raw)
In-Reply-To: <20181126145643.GD1660@redhat.com>
On Mon, 26 Nov 2018 15:56:43 +0100
Oleg Nesterov <oleg@redhat.com> wrote:
> On 11/25, Elvira Khabirova wrote:
> >
> > + * These values are stored in task->ptrace_message by tracehook_report_syscall_*
> > + * to describe current syscall-stop.
> > + *
> > + * Values for these constants are chosen so that they do not appear
> > + * in task->ptrace_message by other means.
> > + */
> > +#define PTRACE_EVENTMSG_SYSCALL_ENTRY 0x80000000U
> > +#define PTRACE_EVENTMSG_SYSCALL_EXIT 0x90000000U
>
> Stupid question, why not
>
> #define PTRACE_EVENT_SYSCALL_ENTRY 8
> #define PTRACE_EVENT_SYSCALL_EXIT 9
>
> right after other PTRACE_EVENT_* constants?
I thought about adding new events for syscall {entry,exit}.
For tracers, using new events means setting new options and checking
for new values after waitpid(). They will also have to switch from using
PTRACE_SYSCALL to PTRACE_CONT.
Right now (with this version of the patch) tracers can use
PTRACE_GETEVENTMSG without doing any additional configuration.
More importantly, adding these events would require much more complex
modifications of kernel code than this patch does.
The only benefit I see from adding these events instead of letting
syscall-stops put a value in ptrace_message is an ability to subscribe
to syscall entries, but not to exits, and vice-versa, and I don't think
it is worth it.
next prev parent reply other threads:[~2018-11-27 2:54 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-25 1:21 [PATCH RESEND v3 0/3] ptrace: add PTRACE_GET_SYSCALL_INFO request Elvira Khabirova
2018-11-25 1:22 ` [PATCH RESEND v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message Elvira Khabirova
2018-11-25 1:54 ` Joey Pabalinas
2018-11-25 2:10 ` Dmitry V. Levin
2018-11-25 6:17 ` Joey Pabalinas
2018-11-26 14:56 ` Oleg Nesterov
2018-11-27 2:53 ` Elvira Khabirova [this message]
2018-11-27 3:48 ` Dmitry V. Levin
2018-11-25 1:23 ` [PATCH RESEND v3 2/3] ptrace: add PTRACE_GET_SYSCALL_INFO request Elvira Khabirova
2018-11-25 1:23 ` [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO Elvira Khabirova
2018-11-26 14:35 ` Oleg Nesterov
2018-11-27 3:07 ` Elvira Khabirova
2018-11-27 3:21 ` Dmitry V. Levin
2018-11-27 12:31 ` Oleg Nesterov
2018-11-27 23:27 ` Dmitry V. Levin
2018-11-28 12:35 ` Oleg Nesterov
2018-11-28 12:44 ` Dmitry V. Levin
2018-11-28 13:13 ` Oleg Nesterov
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