Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 8 Nov 2018 15:33:43 +0100
From:   Oleg Nesterov <oleg@redhat.com>
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Elvira Khabirova <lineprinter@altlinux.org>, 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
Subject: Re: [RFC PATCH] ptrace: add PTRACE_GET_SYSCALL_INFO request
Message-ID: <20181108143342.GC9939@redhat.com>
References: <20181107042751.3b519062@akathisia>
 <20181107112100.GA20419@redhat.com>
 <3BDB914D-12F3-4703-A033-EBE02226EC45@amacapital.net>
 <20181107164443.GA8726@redhat.com>
 <35B601B0-4D56-4706-B7A1-C9A522AB2D6F@amacapital.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <35B601B0-4D56-4706-B7A1-C9A522AB2D6F@amacapital.net>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 11/07, Andy Lutomirski wrote:
>
> > On Nov 7, 2018, at 8:44 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Not sure I understand you... I do not like "compat" too, but this patch uses
> > is_compat/etc and I agree with any naming.
>
> My point is: returning a value to user code that is:
>
> 0 if the kernel and tracee are 32-bit
> 0 if the kernel and tracer are 64-but
> 1 if the kernel is 64-bit and the tracer is 32-bit
> ? If the tracer is arm64 ILP32
>
> Is not a good design.  And 32-bit builds of strace will not appreciate it.

Sure, I agree.

> While oddly named, audit_arch fits the bill nicely, and we already
> require it to have the right semantics for seccomp support.

Again, I agree, and I even mentioned PTRACE_EVENT_SECCOMP.


This reminds me about in_ia32_syscall/TS_COMPAT problems... The 1st one is
get_nr_restart_syscall, I'll try to re-send the fix tomorrow.

Another problem is in_compat_syscall() in get_unmapped_area() paths, it can
return the addr > TASK_SIZE for uprobed 32-bit task.

There was something else but I forgot...

Oleg.