On 29.07.2019 00:06, Kamil Rytarowski wrote: > On 28.07.2019 16:09, Maxime Villard wrote: >> Le 27/07/2019 à 14:14, Kamil Rytarowski a écrit : >>> On 25.07.2019 06:39, Masanobu SAITOH wrote: >>>> Hi. >>>> >>>> I have two UEFI based machines. I noticed both of them didn't boot >>>> with KUBSAN. After loading kernel, the video console is cleared, >>>> the cursol went upper left and then hang. I couldn't see the >>>> NetBSD's copyright message. >>>> >>>> Is this known problem? >>>> >>> >>> I have got a local problem that I'm not successfully booting my amd64 >>> desktop with enabled i915 DRM KMS Framebuffer driver. >> >> This could be that the KMS driver itself is generating a KUBSAN message. >> So printf() gets called, it lands back in the KMS driver to print the >> actual thing, which triggers again a KUBSAN message, so printf() gets >> called again, and so on. It likely dies in a deadlock on whatever mutex >> we take along the way. >> >> In Masanobu's case, it is probably that the UEFI boot path triggers a >> KUBSAN message, printf() gets called, but the console hasn't yet been >> initialized, so it faults and dies there. >> > > What are the best workarounds for these problems? > Actually one option to go once is to reuse debugcon_printf, whenever we can reproduce it in qemu: http://pkgsrc.se/devel/debugcon_printf https://github.com/krytarowski/debugcon_printf In my case I'm booting on a real hardware. >>> There is also a similar problem with Kernel UBSan + Kernel ASan. >>> Something breaks during early boot and needs investigation. >> >> You should not use two kernel sanitizers at the same time. > > > This is what we want to do now with syzbot, run one setup with kUBSan > and another one with kASan. > > Siddharth will work on this after Monday and it was accepted by the > syzbot maintainer. Hopefully kMSan will be third sanitizer. >
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