Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 13 Jul 2015 11:36:47 -0700 | Subject | Re: [PATCH 1/5] x86/vm86: Move userspace accesses to do_sys_vm86() |
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On Mon, Jul 13, 2015 at 9:45 AM, Brian Gerst <brgerst@gmail.com> wrote: > On Sat, Jul 11, 2015 at 12:37 PM, Andy Lutomirski <luto@amacapital.net> wrote: >> On Fri, Jul 10, 2015 at 10:09 PM, Brian Gerst <brgerst@gmail.com> wrote: >>> Move the userspace accesses down into the common function in >>> preparation for the next set of patches. >>> >> >> One thing I don't like about the current code that makes these patches >> harder to review is the bizarre approach to copying. If you changed >> this: >> >>> - tmp = copy_vm86_regs_from_user(&info.regs, &v86->regs, >>> - offsetof(struct kernel_vm86_struct, vm86plus) - >>> - sizeof(info.regs)); >> >> into a normal field-by-field get_user / copy_from_user (the latter for >> the big regs struct) then it would be clear what the ABI is and it >> would be much easier to read the patches and confirm that you aren't >> accidentally changing the ABI. >> >> You could also get rid of the constraint that certain fields in >> apparently kernel-internal structs had to be in a certain order. >> >> Other than that, patches 1-4 look good on cursory inspection. I'll >> look more carefully later. I need to think about patch 5 more. >> >> --Andy > > Any other comments before I start working on v2? >
Nothing major. I'm a bit nervous about leaving ds, es, fs, and gs in pt_regs more or less undefined until save_v86_state happens, but it's unlikely that there's any ABI to break there. The results from perf might be a bit odd with your patches applied. Of course, they're probably useless without your patch.
It might also be worth renaming save_v86_state in patch 5.
Do your patches pass my upgraded entry_from_vm86 test? You're changing handle_vm86_trap so it always returns, which may have unexpected side effects (or I missed something in your patch).
--Andy
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