[MirageOS-devel] TLS packaging status update

[Thomas Leonard <talex5@xxxxxxxxx>]

This is taking a bit longer than expected... here's the current status.

I have ocaml-tls working on Xen/ARM (and demoed by Anil at #osio), by
compiling in an OPAM switch with the right CFLAGS for Mini-OS.
However, we don't want to do it this way because dealing with OPAM
switches is annoying.

Instead, I'm adding an ocamlfind variable which packages can use to
indicate the C stubs to link against under Xen. e.g. tcpip would put
this in its META file:

xen_linkopts = "-ltcpip_xen_stubs"

No libraries will be linked without this option, so we won't
accidentally link Unix libraries. This is important on x86_64, where
linking Unix libraries creates subtle race conditions due to the "red
zone" not being available in kernel mode.

When testing this, I realised we compile openlibm for Unix, so I
updated that to get the CFLAGS from Mini-OS, but it turned out that
didn't work because Mini-OS doesn't provide sys/types.h (just
types.h), and also openlibm used some legacy type names that Mini-OS
doesn't provide. sys/types.h is currently provided by mirage-platform.

Options:

1. Make openlibm depend on mirage-platform to get sys/types.h.
2. Rename Mini-OS's types.h to sys/types.h and put everything there.
3. Modify openlibm to use only stdint.h.

I'm leaning towards option (3) at the moment (assuming it's possible),
but shout if you have a better idea!

After that, I'll update mirage-profile and tcpip to the new linking
system and make a pull request for the updated mirage tool. You'll
probably need to update several things at once when this happens.

Then we'll be in a position to add the tls libraries. That might
require a little
extra work if we want to add Xen C stubs to 3rd-party packages (e.g.
zarith). Anil has suggested using OPAM depexts for this.

Finally, we could really use some pkg-config support in OASIS.
Otherwise, getting the necessary CFLAGS is unreasonably difficult...


-- 
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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