acpi: RSDP is not found when on Ubuntu 18.04

[dlrobertson]

Summary

When running make qemu from a Ubuntu 18.04 host we fail to find the RSDP.

  [   0.000000] MYTHRIL-INFO: tsc calibrate diff=5493740 (khz=3200699)
  [   0.000001] MYTHRIL-INFO: Allocating from 0x3320ecd-3ffe0000
  [   0.000528] MYTHRIL-ERROR: Panic in mythril_multiboot2/src/main.rs at (241, 16):
  [   0.001074] MYTHRIL-ERROR: Failed to find the RSDP: NotFound

CC: @barkera @ntegan @sruffell

[ntegan]

Is found, however, via the multiboot crate BootInformation as in

https://github.com/mythril-hypervisor/mythril/pull/56

[ALSchwalm]

Bizarrely I can't reproduce this under docker at all. Using the 18.04 container (grub-mkrescue (GRUB) 2.02-2ubuntu8.15 and QEMU emulator version 2.11.1(Debian 1:2.11+dfsg-1ubuntu7.26)), things seem to work as expected. I suppose that pretty much narrows it down to a kvm issue in whatever kernel ubuntu 18.04 uses.

[ALSchwalm]

Anybody have a 18.10 ubuntu box to test on? This isn't that shocking now that I think about it. Nested virtualization was probably not super functional back then.

[dlrobertson]

Bizarrely I can't reproduce this under docker at all.

Sanity check: was this pre https://github.com/mythril-hypervisor/mythril/commit/36bb1e165b257e70ae5ae4ddf5d7b24e33a09f07 ?

Anybody have a 18.10 ubuntu box to test on?

Installing it on an old laptop now.

[ALSchwalm]

Correct, this was before the multiboot stuff

[dlrobertson]

I suppose that pretty much narrows it down to a kvm issue in whatever kernel ubuntu 18.04 uses.

Can confirm. We find the RSDP when we disable kvm on a Ubuntu 18.04 box. When dumping memory in gdb, it seems that the main bios area is zeroed out.

[ALSchwalm]

Ah, we can test that because we don't need kvm for the nested virt until we actually go vtx-on. Clever. Well I guess now we just need to determine when they fixed that and document the earliest supported kernel version for testing.

[ntegan]

I could do some brute force searching of which kernels work, once I finish the other issue i'm working on.

unless you guys get to it first

[ALSchwalm]

Honestly I really just want to know if it works in 18.10. That would be sufficient for a minimum viable platform kind of thing.

I'd really like to spin up a test platform at some point, though I'm not sure how we would actually integrate it in to the current CI approach. Moving the project to gitlab might make sense.

[dlrobertson]

Honestly I really just want to know if it works in 18.10. That would be sufficient for a minimum viable platform kind of thing.

Would the work to use the multiboot info satisfy this?

[dlrobertson]

I don't hit this issue when I force the RSDP search on ubuntu 20.04.

[dlrobertson]

Is this issue still hit? I don't think we should hit this any more now that we also look in the multiboot info