Re: [MirageOS-devel] Mirage on Xen/ARM status

[Thomas Leonard <talex5@xxxxxxxxx>]

An update on the Mirage/ARM port:

I have mirage-platform upgraded to the new Mini-OS (plus openlibm and
no libc). Networking is working again on x86_64 (I can telnet to the
mirage-skeleton/network service and send it a message), but not on ARM
yet.

This required some changes to Mini-OS to expose the grant table
details and to stop Mini-OS's xenbus from stealing the event
notifications. I need this clean this up.

OCaml's Random currently tries to open /dev/urandom, which fails.
Looks like it falls back to using gettimeofday in that case. It logs a
message to the console ("Attempt to open(/dev/urandom)!"), so
hopefully we'll remember to fix it eventually.

Networking doesn't work on ARM as the code wants to use start_info,
which doesn't exist. I might try making a fake start_info page on ARM
rather than modifying everything else.


My current plan is:

- Upstream Karim's initial ARM support to Xen. I split the original
patch into three smaller ones and submitted them, but they want it
broken up further, which is fair enough.

- Upstream my patches to build a libminios.a library, plus some other
fixes to the build system.

- Make some changes to Mini-OS to work unmodified with Mirage
(specifically: expose grant table details, disable interrupt-based
event handlers, and allow linking only the features we need).

- Add a proper string library to mirage-platform to replace Mini-OS's
limited sprintf.

- Upstream my patches to mirage-platform and mirage to build using the
new libminios and openlibm (these are on github in my forks).

- Upstream my Mini-OS ARM patches to Xen.

- Add a start_info structure on ARM, or find some other way to expose
those details to Mirage.


There are various other bits that would be nice to have:

- Use a proper virtual memory mapping on ARM, including a stack guard
page and a non-mapped page zero. I should probably find out what it
does on x86 and make them consistent too.

- Allow running C code in Mirage in a restricted sandbox (non-privileged mode).

- Use ctypes to replace current stubs.

- Replace all the unimplemented stubs (lseek, etc) to check nothing is
relying on them.

- Import the FreeBSD hardware float support code so we can use
hardware floating point. Currently, everything is soft-float.


On 16 May 2014 17:41, Thomas Leonard <talex5@xxxxxxxxx> wrote:
> Good news for Mirage on Xen/ARM: mirage-skeleton/console is now working!
>
> It needs tidying up, but currently to run you need:
>
> 1. mirage-platform/arm-hacks3:
> https://github.com/talex5/mirage-platform/tree/arm-hacks3
>
> This has been updated for the new Mini-OS. dietlibc is gone (we no
> longer need a C library). libm is also gone, but you'll need to
> replace it with something else (see below). There's a new libxencaml
> with the separated-out Mini-OS OCaml bindings.
>
> I had to make some changes to the Mirage API, because on ARM Xen
> doesn't provide start_info. Also, I switched the timer stuff to use
> mini-os's block_domain call, which handles ARM correctly.
>
> 2. mirage-console/master (modified to avoid using start_page)
> https://github.com/talex5/mirage-console/commits/master
>
> 3. openlibm/arm-hacks (disables all long double support, which ARM
> doesn't have and OCaml doesn't need)
> https://github.com/talex5/openlibm/tree/arm-hacks
>
> 4. Mini-OS/devel (can now be installed as a library, libminios.a - use
> "make install-ocamlfind")
> https://github.com/talex5/xen/tree/devel
>
>
> You'll also need a *soft-float* ARM build machine. Hard-float would
> require extra support from Mini-OS. You can cross-compile the C code
> easily enough, but OCaml can't cross compile, even from armhf to armel
> (the -ffpu option just gives a silly error message). I got mine with:
>
>   debootstrap --arch armel testing /mnt
>
> Finally, you'll also need to modify mir-console's Makefile, because I
> didn't update mirage to generate it properly. This worked for me:
>
> KERNEL_DIR = $(shell ocamlfind query minios-kernel)
> PLATFORM_DIR = $(shell ocamlfind query mirage-xen)
>
> build: main.native.o
>         ld -d -static -nostdlib -T $(KERNEL_DIR)/link.lds \
>                 --start-group  \
>                 /usr/lib/gcc/arm-linux-gnueabi/4.8/libgcc.a \
>                   $(PLATFORM_DIR)/libocaml.a \
>                   $(PLATFORM_DIR)/libxencaml.a \
>                   ~/lib/libopenlibm.a \
>                   $(KERNEL_DIR)/libminios.a -o mir-console.elf \
>                   _build/main.native.o \
>           --end-group
>         objcopy -O binary mir-console.elf mir-console.xen
>
> The next steps are to make this all a bit easier to install and clean
> up the branches so they can be merged. Also, some things are broken
> (printf doesn't accept %f, for example, because we're just using
> Mini-OS's version).
>
>
> --
> Dr Thomas Leonard        http://0install.net/
> GPG: 9242 9807 C985 3C07 44A6  8B9A AE07 8280 59A5 3CC1
> GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA



-- 
Dr Thomas Leonard        http://0install.net/
GPG: 9242 9807 C985 3C07 44A6  8B9A AE07 8280 59A5 3CC1
GPG: DA98 25AE CAD0 8975 7CDA  BD8E 0713 3F96 CA74 D8BA

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