31.03.2020 23:23, Andrii Nakryiko пишет: > On Tue, Mar 31, 2020 at 12:58 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> >> On Tue, Mar 31, 2020 at 12:50:07PM -0700, Andrii Nakryiko wrote: >>> On Tue, Mar 31, 2020 at 11:12 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: >>>> >>>> On Tue, Mar 31, 2020 at 12:41:04AM +0200, Daniel Borkmann wrote: >>>>> On 3/30/20 7:20 PM, Kees Cook wrote: >>>>>> On Mon, Mar 30, 2020 at 06:17:32PM +0200, Jann Horn wrote: >>>>>>> On Mon, Mar 30, 2020 at 5:59 PM Alexei Starovoitov >>>>>>> <alexei.starovoitov@xxxxxxxxx> wrote: >>>>>>>> On Mon, Mar 30, 2020 at 8:14 AM Jann Horn <jannh@xxxxxxxxxx> wrote: >>>>>>>>> >>>>>>>>> I noticed that CONFIG_DEBUG_INFO_BTF seems to partly defeat the point >>>>>>>>> of CONFIG_GCC_PLUGIN_RANDSTRUCT. >>>>>>>> >>>>>>>> Is it a theoretical stmt or you have data? >>>>>>>> I think it's the other way around. >>>>>>>> gcc-plugin breaks dwarf and breaks btf. >>>>>>>> But I only looked at gcc patches without applying them. >>>>>>> >>>>>>> Ah, interesting - I haven't actually tested it, I just assumed >>>>>>> (perhaps incorrectly) that the GCC plugin would deal with DWARF info >>>>>>> properly. >>>>>> >>>>>> Yeah, GCC appears to create DWARF before the plugin does the >>>>>> randomization[1], so it's not an exposure, but yes, struct randomization >>>>>> is pretty completely incompatible with a bunch of things in the kernel >>>>>> (by design). I'm happy to add negative "depends" in the Kconfig if it >>>>>> helps clarify anything. >>>>> >>>>> Is this expected to get fixed at some point wrt DWARF? Perhaps would make >>>> >>>> No, gcc closed the issue as "won't fix". >>>> >>>>> sense then to add a negative "depends" for both DWARF and BTF if the option >>>>> GCC_PLUGIN_RANDSTRUCT is set given both would be incompatible/broken. >>>> >>>> I hadn't just to keep wider randconfig build test coverage. That said, I >>>> could make it be: depends COMPILE_TEST || !DWARF ... >>>> >>>> I can certainly do that. >>> >>> I've asked Slava in [0] to disable all three known configs that break >>> DWARF and subsequently BTF, I hope it's ok to just do it in one patch. >>> Currently all these appear to result in invalid BTF due to various >>> DWARF modifications: >>> >>> - DEBUG_INFO_REDUCED (see [1]) >>> - DEBUG_INFO_SPLIT (see [0] >>> - GCC_PLUGIN_RANDSTRUCT (this discussion). >>> >>> [0] https://lore.kernel.org/bpf/CAEf4BzadnfAwfa1D0jZb=01Ou783GpK_U7PAYeEJca-L9kdnVA@xxxxxxxxxxxxxx/ >>> [1] https://lore.kernel.org/bpf/CAEf4BzZri8KpwLcoPgjiVx_=QmJ2W9UzBkDqSO2rUWMzWogkKg@xxxxxxxxxxxxxx/ >> >> Sure! That'd by fine by me. I'd just like it to be a "|| COMPILE_TEST" >> for GCC_PLUGIN_RANDSTRUCT. Feel free to CC me for an Ack. :) >> > > +cc Slava > > I'm unsure what COMPILE_TEST dependency (or is it anti-dependency?) > has to do with BTF generation and reading description in Kconfig > didn't clarify it for me. Can you please elaborate just a bit? Thanks! > >> -Kees Hi, Regarding COMPILE_TEST, DEBUG_INFO has dependency on: DEBUG_KERNEL && !COMPILE_TEST And DEBUG_INFO_BTF depends on DEBUG_INFO, so enabling COMPILE_TEST would block DEBUG_INFO and so DEBUG_INFO_BTF as well. Unless I don't understand something and there is some other reason to add it. -- Slava >> >>> >>> >>>> >>>> -Kees >>>> >>>> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84052 >>>> >>>> -- >>>> Kees Cook >> >> -- >> Kees Cook
