linux-kernel - Re: [musl] Re: [PATCH V9 13/24] LoongArch: Add system call support

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Date:   Thu, 12 May 2022 09:21:13 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     musl@...ts.openwall.com
Cc:     Arnd Bergmann <arnd@...db.de>,
        Christian Brauner <brauner@...nel.org>,
        Huacai Chen <chenhuacai@...il.com>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Airlie <airlied@...ux.ie>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Linux API <linux-api@...r.kernel.org>,
        GNU C Library <libc-alpha@...rceware.org>
Subject: Re: [musl] Re: [PATCH V9 13/24] LoongArch: Add system call support

On Wed, May 11, 2022 at 11:12 PM Rich Felker <dalias@...c.org> wrote:
> On Wed, May 11, 2022 at 09:11:56AM +0200, Arnd Bergmann wrote:
> > On Mon, May 9, 2022 at 12:00 PM Christian Brauner <brauner@...nel.org> wrote:
> > .....
> > > I can try and move a poc for this up the todo list.
> > >
> > > Without an approach like this certain sandboxes will fallback to
> > > ENOSYSing system calls they can't filter. This is a generic problem
> > > though with clone3() being one promiment example.
> >
> > Thank you for the detailed reply. It sounds to me like this will eventually have
> > to get solved anyway, so we could move ahead without clone() on loongarch,
> > and just not have support for Chrome until this is fully solved.
> >
> > As both the glibc and musl ports are being proposed for inclusion right
> > now, we should try to come to a decision so the libc ports can adjust if
> > necessary. Adding both mailing lists to Cc here, the discussion is archived
> > at [1].
> >
> >          Arnd
> >
> > [1] https://lore.kernel.org/linux-arch/20220509100058.vmrgn5fkk3ayt63v@wittgenstein/
>
> Having read about the seccomp issue, I think it's a very strong
> argument that __NR_clone should be kept permanently for all future
> archs.

Ok, let's keep clone() around for all architectures then. We should probably
just remove the __ARCH_WANT_SYS_CLONE macro and build the
code into the kernel unconditionally, but at the moment there
are still private versions for ia64 and sparc with the same name as
the generic version. Both are also still lacking support for clone3() and
don't have anyone actively working on them.

In this case, we probably don't need to change clone3() to allow the
zero-length stack after all, and the wrapper that was added to the
musl port should get removed again.

For the other syscalls, I think the latest musl patches already dropped
the old-style stat() implementation, but the glibc patches still have those
and need to drop them as well to match what the kernel will get.

       Arnd