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Date: Sun, 6 Oct 2024 12:09:35 +0300
From: Konstantin Belousov <kostikbel@gmail.com>
To: Dag-Erling =?utf-8?B?U23DuHJncmF2?= <des@freebsd.org>
Cc: Mark Millard <marklmi@yahoo.com>,
        Current FreeBSD <freebsd-current@freebsd.org>,
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Subject: Re: git: 2c1963d46335 - main - procfs rlimit: handle pipebuf  [and
 related] :pipebuf . . . Invalid argument
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On Sun, Oct 06, 2024 at 10:57:23AM +0200, Dag-Erling Smørgrav wrote:
> Konstantin Belousov <kostikbel@gmail.com> writes:
> > We do not provide forward compatibility between kernel and userspace.
> > User binaries must be newer than kernel.
> 
> Uh, no.  The opposite, in fact.

Right, it is opposite.  It was a typo.

Anyway, __FreeBSD_version is not about compatibility between specific
snapshot of kernel and user sources.  It de-facto provides two technical
measures:
1. kernel refuses to load modules built against headers set with higher
   __FreeBSD_version than kernel
2. Some values of __FreeBSD_version are used by userspace to
   detect if specific change is present in kernel.  See sys/param.h
   P_OSREL_ list.