Messages in this thread |  | | From | Andy Lutomirski <> | Date | Wed, 16 Aug 2017 09:14:41 -0700 | Subject | Re: [PATCH 3/3] x86/efi: Use efi_switch_mm() rather than manually twiddling with cr3 |
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On Wed, Aug 16, 2017 at 5:57 AM, Matt Fleming <matt@codeblueprint.co.uk> wrote: > On Wed, 16 Aug, at 12:03:22PM, Mark Rutland wrote: >> >> I'd expect we'd abort at a higher level, not taking any sample. i.e. >> we'd have the core overflow handler check in_funny_mm(), and if so, skip >> the sample, as with the skid case. > > FYI, this is my preferred solution for x86 too.
One option for the "funny mm" flag would be literally the condition current->mm != current->active_mm. I *think* this gets all the cases right as long as efi_switch_mm is careful with its ordering and that the arch switch_mm() code can handle the resulting ordering. (x86's can now, I think, or at least will be able to in 4.14 -- not sure about other arches).
That being said, there's a totally different solution: run EFI callbacks in a kernel thread. This has other benefits: we could run those callbacks in user mode some day, and doing *that* in a user thread seems like a mistake.
--Andy
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