Re: [RFC PATCH 00/11] an introduction of library operating system for Linux (LibOS)

At Tue, 24 Mar 2015 15:32:05 +0100,
Richard Weinberger wrote:

Am 24.03.2015 um 15:25 schrieb Hajime Tazaki:

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At Tue, 24 Mar 2015 14:21:49 +0100,
Richard Weinberger wrote:

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Am 24.03.2015 um 14:10 schrieb Hajime Tazaki:
 > == More information ==

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The crucial difference between UML (user-mode linux) and this approach
is that we allow multiple network stack instances to co-exist within a
single process with dlmopen(3) like linking for easy debugging.

Is this the only difference?
We already have arch/um, why do you need arch/lib/ then?
My point is, can't you merge your arch/lib into the existing arch/um stuff?
From a very rough look your arch/lib seems like a micro UML.

I understand your point.
but ptrace(2) based system call interception used by UML
makes it depend on the host OS (i.e., linux kernel), while
LibOS uses symbol hijacking with weak alias and LD_PRELOAD.

we're really thinking to run this library on other
POSIX-like hosts (e.g., osx) though it's not coming yet.

Yeah, but this does not mean that arch/um and arch/lib can't coexist in arch/um.
Maybe you can add a "library operation mode" to UML.
I'll happily help you in that area.

I was thinking that such 'architectural' differences in core
idea (like system call handling, execution model, process
context design, etc) is better to have a different architecture
even if some part of the code is similar.

Isn't it also the same to the other 'hardware-dependent'
architectures' case like between arm and arm64 ?

of course I'm also happy to share the code between us,
especially _pure_ userspace part like (virtual) NIC with
tap or pcap because we also need that part, but we kept such
code at an external codebase (i.e., linux-libos-tools).

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BTW: There was already an idea for having UML as regular library.
See: http://user-mode-linux.sourceforge.net/old/projects.html
"UML as a normal userspace library"

thanks, it's new information for me.
were there any trial on this idea ?

IIRC Jeff (the original author of UML) wanted to create a special linker script
such that you can build UML as shared object.

okay.

thanks.
-- Hajime