Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 18 Jun 2020 11:36:53 -0700 | Subject | Re: [PATCH 1/7] x86/entry: Fix #UD vs WARN more |
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On Thu, Jun 18, 2020 at 8:50 AM Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Jun 18, 2020 at 07:57:35AM -0700, Andy Lutomirski wrote: > > > > > > > On Jun 18, 2020, at 7:50 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > > > > > vmlinux.o: warning: objtool: exc_invalid_op()+0x47: call to probe_kernel_read() leaves .noinstr.text section > > > > > > Since we use UD2 as a short-cut for 'CALL __WARN', treat it as such. > > > Have the bare exception handler do the report_bug() thing. > > > > I think you should consider inlining or noinstr-ifying report_bug() > > too if you want to make this more bulletproof. I admit the scenario > > where someone instruments it and it goes wrong is farfetched. > > How far down that rabbit hole do we go? Because then we need to noinstr > printk, the console drivers, those will very quickly pull in lovely bits > like PCI, USB, DRM :/ > > At some point we have to just give up.
I wasn't imagining going far down the rabbit hole at all -- I think that, at most, we should cover the path for when the fault wasn't a BUG/WARN in the first place. I admit that, for #UD in particular, this isn't a big deal, but if it were a different vector, this could matter.
I suppose report_bug() could be split into lookup_bug() and handle_bug(), and just lookup_bug() could be noinstr.
--Andy
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