From: Florian Weimer <fweimer@redhat.com>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: "Michael Kerrisk \(man-pages\)" <mtk.manpages@gmail.com>,
Christian Brauner <christian@brauner.io>,
lkml <linux-kernel@vger.kernel.org>,
linux-man <linux-man@vger.kernel.org>,
Kees Cook <keescook@chromium.org>,
Oleg Nesterov <oleg@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
David Howells <dhowells@redhat.com>,
Pavel Emelyanov <xemul@virtuozzo.com>,
Andrew Morton <akpm@linux-foundation.org>,
Adrian Reber <adrian@lisas.de>, Andrei Vagin <avagin@gmail.com>,
Linux API <linux-api@vger.kernel.org>,
Jann Horn <jannh@google.com>
Subject: Re: For review: documentation of clone3() system call
Date: Thu, 07 Nov 2019 17:10:51 +0100 [thread overview]
Message-ID: <87y2wrbras.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <20191107151941.dw4gtul5lrtax4se@wittgenstein> (Christian Brauner's message of "Thu, 7 Nov 2019 16:19:43 +0100")
* Christian Brauner:
> I've always been confused by the "..." for the glibc wrapper. The glibc
> prototype in bits/sched.h also looks like this:
>
> extern int clone (int (*__fn) (void *__arg), void *__child_stack, int __flags, void *__arg, ...) __THROW;
>
> The additionl args parent_tid, tls, and child_tid are present in _all_
> clone version in the same order. In fact the glibc wrapper here give the
> illusion that it's parent_tid, tls, child_tid. The underlying syscall
> has a different order parent_tidptr, child_tidptr, tls.
>
> Florian, can you advise what prototype we should mention for the glibc
> clone() wrapper here. I'd like it to be as simple as possible and get
> rid of the ...
> Architectural differences are explained in detail below anyway.
Our header has:
/* Clone current process. */
extern int clone (int (*__fn) (void *__arg), void *__child_stack,
int __flags, void *__arg, ...) __THROW;
I have not checked all assembler implementations. In theory there could
be one that relies on the different calling convention for variadic
functions (e.g., the existence of a parameter save area on POWER). Or
that swaps arguments in some architecure-specific way. 8-(
I don't have much guidance on this matter, sorry. I expect that for
clone3, we'll provide a same-stack variant as well (for fork/vfork-like
usage), which will be much closer to the kernel interface. clone/clone2
doesn't seem very fixable to me at this point.
Thanks,
Florian
next prev parent reply other threads:[~2019-11-07 16:11 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-25 16:59 For review: documentation of clone3() system call Michael Kerrisk (man-pages)
2019-10-25 17:07 ` Christian Brauner
2019-11-07 12:26 ` Michael Kerrisk (man-pages)
2019-10-26 2:28 ` G. Branden Robinson
2019-10-31 6:06 ` Michael Kerrisk (man-pages)
2019-10-28 15:12 ` Jann Horn
2019-10-28 17:21 ` Christian Brauner
2019-10-28 19:09 ` Jann Horn
2019-10-29 11:27 ` Christian Brauner
2019-10-29 14:26 ` Christian Brauner
2019-10-29 14:36 ` Florian Weimer
2019-10-29 16:04 ` Christian Brauner
2019-10-29 15:20 ` Jann Horn
2019-10-29 16:05 ` Christian Brauner
2019-11-07 15:19 ` Christian Brauner
2019-11-07 16:10 ` Florian Weimer [this message]
2019-11-09 8:09 ` Michael Kerrisk (man-pages)
2019-11-09 16:53 ` Christian Brauner
2019-11-11 9:02 ` Michael Kerrisk (man-pages)
2019-11-11 11:36 ` Christian Brauner
2019-11-11 19:56 ` Michael Kerrisk (man-pages)
2019-11-11 14:55 ` Jann Horn
2019-11-11 16:58 ` Theodore Y. Ts'o
2019-11-11 20:24 ` Jann Horn
2019-11-12 23:03 ` Kees Cook
2019-11-14 12:15 ` Michael Kerrisk (man-pages)
2019-11-14 12:29 ` Christian Brauner
2019-11-11 15:03 ` Florian Weimer
2019-11-11 15:15 ` Jann Horn
2019-11-11 15:20 ` Florian Weimer
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