Re: RFC: executable archive

From: Måns Rullgård
Date: Tue Apr 20 2004 - 07:29:29 EST

Terje Eggestad <terje.eggestad@xxxxxxxxx> writes:

> Hello everybody
> I wanted to share and idea (and I'm sure I going to get booh'ed of the
> list but...) with you all.
> One thing have annoyed me for a long time while writing perl progs, and
> that it not possible to "link" it, in that programs must span multiple
> files to be manageable as they grow. I'm sure we all agree that only
> trivial programs can be coded in a single source file.
> The annoyment stems from the fact that a single "executable" must be
> distributed as multiple files.
> A problem with perl, that Larry Wall should have though of right?
> Same problem with python (i'm just learning), and a collection of .class
> files for java.
> The problem is compounded that all decent scripting languages allow
> compiled modules in the shaped of a shared object, which make it really
> hard on the developers of the scripting engine to make single exec.
> What would solve it is have an executable archive, in where you put the
> top level script, subscripts, shared objects, and any other file it may
> need.
> It would be nice to have a general solution to the problem.
> My first though would be to make a stub, and put the ar file in the data
> area of the process, something akind to self extracting zip files on
> dos/windoze.
> A couple of problems:
> a) you can't "mount" the ar file to make it visible to the process as a
> part of it's file system view. ( Atleast not without intercepting a
> whole lot of libc calls)
> b) unpacking it somewhere would clobber up your fs as it would not be
> cleaned up after a program crash or machine crash.
> Ideally I'd like to see the files in the ar as in the cwd, but that
> would make a namespace collision possible.
> The second though would be to do it in the kernel, which would go
> something like this:
> - let the exec() handler in the kernel recognize the exec-ar, just like
> it recognizes the #! magic.
> - use the loopback mount device to mount the ar (read only) under
> /proc/self/archive
> (- it would be nice to do something to the env's like adding
> /proc/self/archive to PATH, LD:LIBRARY_PATH, of honor a file like
> /proc/self/env to modify the envs)
> - now exec the file /proc/self/archive/main

Apart from the /proc manipulations, all of the above could be
accomplished using binfmt_misc and a suitable wrapper program.

Måns Rullgård

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