Re: [Qemu-devel] Bug#632192: [PATCH] add QEMU_LD_PREFIX environment variable

[Johannes Schauer <j.schauer@email.de>]

On Fri, Jul 29, 2011 at 05:52:50AM -0700, Vagrant Cascadian wrote:
> setting up a wrapper makes trivial cross-architecture chroots harder
> as you'll have to copy two binaries into the chroot, and i'm not sure
> if it would work at all, as the wrapper will need to somehow emulate
> it's own interpreter...

Agreed - this makes a wrapper not an option. I didnt think of that.

> > Alternatively we should have a generic setup for mapping enviroment
> > variables to command line options. Now we get special per-option
> > code every time someone needs to setup a command line option from
> > binfmt.
> 
> this would seem a bit better alternative to me...

So if we agree on using environment variables to pass options to
qemu-user we next need to agree on how to name the options.

The following commandline arguments exist (in order as they are checked
in linux-user/main.c) and I shortly described and proposed a name for
the environment variable in the same line.

-d (activate log)             - QEMU_LOG
-D (logfile)                  - QEMU_LOGFILE
-E (set target env variabe)   - QEMU_SET_ENV
-U (unset target env variabe) - QEMU_UNSET_ENV
-0 (set target argv[0])       - QEMU_ARGV0
-s (stack size)               - QEMU_STACK_SIZE
-L (elf interpreter prefix)   - QEMU_LD_PREFIX
-p (page size)                - QEMU_PAGESIZE
-g (listen for gdb on port)   - QEMU_GDB
-r (uname)                    - QEMU_UNAME
-cpu (cpu model)              - QEMU_CPU
-B (guest base)               - QEMU_GUEST_BASE
-R (reserved virtual address) - QEMU_RESERVED_VA
-drop-ld-preload              - QEMU_DROP_LD_PRELOAD
-singlestep                   - QEMU_SINGLESTEP
-strace                       - QEMU_STRACE

also, there already is the QEMU_STRACE environment variable which could
be incorporated into the solution?

the -E and -U options can be specified several times so the environment
variables should be able to receive a list - maybe in the getsubopt(3)
style?

So what do you think?

cheers, josch