Linux compat / changing compat path

[Konstantin Belousov]

On Wed, Mar 21, 2018 at 01:57:37PM +0200, Andriy Gapon wrote:
> On 21/03/2018 10:39, Stefan Esser wrote:
> > And you want to change occurances of /compat/linux in the kernel (and possibly
> > some libraries and user programs), e.g. in /sys/amd64/linux/linux_sysvec.c ...
> > 
> > There is some magic that makes an exec of /bin/sh look up /compat/linux/bin/sh
> > first, if performed from within a program running under Linux emulation, and
> > if you need that behavior, you have to adjust at least the kernel sources.
> > 
> > Maybe the hard-coded "/compat/linux" should be replaced by a macro, to allow
> > easy modification without loss of functionality ...
> 
> I am not sure what would actually happen in the following case.
> Create a jail and make it "pure Linux".  That is, install only Linux binaries
> there, no FreeBSD at all.  And install them under the root of the jail, that is,
> no /compat/linux within the jail.
> Would that work?
> Would I be able to start such a jail (processes in it) ?
> Would they be able to correctly find their libraries and other executables they
> might want to exec?
> 
> If this works or could be made to work, then I am sure that some people would it
> useful.
> 
This already works. /compat/linux prefix is first try, and if not found,
code falls back to normal lookup.

People did used 'native linux' jails, in particular, to do builds.