From: Rich Felker <dalias@libc.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: musl@lists.openwall.com, Christian Brauner <brauner@kernel.org>,
Huacai Chen <chenhuacai@gmail.com>,
Huacai Chen <chenhuacai@loongson.cn>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Airlie <airlied@linux.ie>, Jonathan Corbet <corbet@lwn.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch <linux-arch@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Xuefeng Li <lixuefeng@loongson.cn>,
Yanteng Si <siyanteng@loongson.cn>, Guo Ren <guoren@kernel.org>,
Xuerui Wang <kernel@xen0n.name>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
Linux API <linux-api@vger.kernel.org>,
GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [musl] Re: [PATCH V9 13/24] LoongArch: Add system call support
Date: Thu, 12 May 2022 08:11:31 -0400 [thread overview]
Message-ID: <20220512121131.GH7074@brightrain.aerifal.cx> (raw)
In-Reply-To: <CAK8P3a05wSVu7M9kVMw5cSqx84YUCk1394Yfd_5tweEOc2P69g@mail.gmail.com>
On Thu, May 12, 2022 at 09:21:13AM +0200, Arnd Bergmann wrote:
> On Wed, May 11, 2022 at 11:12 PM Rich Felker <dalias@libc.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@kernel.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.
I still think disallowing a zero length (unknown length with caller
providing the start address only) stack is a gratuitous limitation on
the clone3 interface, and would welcome leaving the change to allow
zero-length in place. There does not seem to be any good justification
for forbidding it, and it does pose other real-world obstruction to
use. For example if your main thread had exited (or if you're forking
from a non-main thread) and you wanted to create a new process using
the old main thread stack as your stack, you would not know a
size/lowest-address, only a starting address from which it extends
some long (and possibly expanding) amount.
Rich
prev parent reply other threads:[~2022-05-12 12:11 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220430090518.3127980-1-chenhuacai@loongson.cn>
[not found] ` <20220430090518.3127980-14-chenhuacai@loongson.cn>
[not found] ` <CAK8P3a0A9dW4mwJ6JHDiJxizL7vWfr4r4c5KhbjtAY0sWbZJVA@mail.gmail.com>
[not found] ` <CAAhV-H4te_+AS69viO4eBz=abBUm5oQ6AfoY1Cb+nOCZyyeMdA@mail.gmail.com>
[not found] ` <CAK8P3a0DqQcApv8aa2dgBS5At=tEkN7cnaskoUeXDi2-Bu9Rnw@mail.gmail.com>
[not found] ` <20220507121104.7soocpgoqkvwv3gc@wittgenstein>
[not found] ` <20220509100058.vmrgn5fkk3ayt63v@wittgenstein>
2022-05-11 7:11 ` Arnd Bergmann
2022-05-11 21:12 ` Rich Felker
2022-05-12 7:21 ` Arnd Bergmann
2022-05-12 12:11 ` Rich Felker [this message]
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