From mboxrd@z Thu Jan  1 00:00:00 1970
From: Florian Weimer <fweimer@redhat.com>
Subject: Re: For review: documentation of clone3() system call
Date: Mon, 11 Nov 2019 16:03:11 +0100
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        (Michael Kerrisk's message of "Fri, 25 Oct 2019 18:59:31 +0200")
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* Michael Kerrisk:

>        Another  difference  for  the  raw clone() system call is that the
>        stack argument may be NULL, in which case the child uses a  dupli=
=E2=80=90
>        cate  of the parent's stack.  (Copy-on-write semantics ensure that
>        the child gets separate copies of stack pages when either  process
>        modifies  the  stack.)   In  this case, for correct operation, the
>        CLONE_VM option should not be specified.  (If the child shares the
>        parent's  memory  because of the use of the CLONE_VM flag, then no
>        copy-on-write duplication occurs and chaos is likely to result.)

I think sharing the stack also works with CLONE_VFORK with CLONE_VM, as
long as measures are taken to preserve the return address in a register.

Thanks,
Florian