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Message-ID: <9f8280540bbc6f3c857ac5749eeafcd145577da3.camel@sipsolutions.net>
Subject: Re: [PATCH 0/4 POC] Allow executing code and syscalls in another
 address space
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Andrei Vagin <avagin@gmail.com>, linux-kernel@vger.kernel.org,
        linux-api@vger.kernel.org,
        Benjamin Berg <benjamin@sipsolutions.net>
Cc:     linux-um@lists.infradead.org, criu@openvz.org, avagin@google.com,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Richard Weinberger <richard@nod.at>,
        Thomas Gleixner <tglx@linutronix.de>
Date:   Wed, 14 Apr 2021 09:34:40 +0200
In-Reply-To: <78cdee11-1923-595f-90d2-e236efbafa6a@cambridgegreys.com>
References: <20210414055217.543246-1-avagin@gmail.com>
         <78cdee11-1923-595f-90d2-e236efbafa6a@cambridgegreys.com>
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On Wed, 2021-04-14 at 08:22 +0100, Anton Ivanov wrote:
> On 14/04/2021 06:52, Andrei Vagin wrote:
> > We already have process_vm_readv and process_vm_writev to read and write
> > to a process memory faster than we can do this with ptrace. And now it
> > is time for process_vm_exec that allows executing code in an address
> > space of another process. We can do this with ptrace but it is much
> > slower.
> > 
> > = Use-cases =
> > 
> > Here are two known use-cases. The first one is “application kernel”
> > sandboxes like User-mode Linux and gVisor. In this case, we have a
> > process that runs the sandbox kernel and a set of stub processes that
> > are used to manage guest address spaces. Guest code is executed in the
> > context of stub processes but all system calls are intercepted and
> > handled in the sandbox kernel. Right now, these sort of sandboxes use
> > PTRACE_SYSEMU to trap system calls, but the process_vm_exec can
> > significantly speed them up.
> 
> Certainly interesting, but will require um to rework most of its memory 
> management and we will most likely need extra mm support to make use of 
> it in UML. We are not likely to get away just with one syscall there.

Might help the seccomp mode though:

https://patchwork.ozlabs.org/project/linux-um/list/?series=231980

johannes