Messages in this thread | | | Date | Mon, 7 Oct 2019 16:44:23 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86/mm: determine whether the fault address is canonical |
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* Ingo Molnar <mingo@kernel.org> wrote:
> > All the other reasons would require a fairly egregious kernel bug, hence > > the speculation that the #GP is due to a non-canonical address. Something > > like the following would be more precise, though highly unlikely to ever > > be exercised, e.g. KVM had a fatal bug related to injecting a non-zero > > error code that went unnoticed for years. > > > > WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. %s?\n", > > (IS_ENABLED(CONFIG_X86_64) && !error_code) ? "Non-canonical address" : > > "Segmentation bug"); > > Instead of trying to guess the reason of the #GPF (which guess might be > wrong), please just state it as the reason if we are sure that the cause > is a non-canonical address - and provide a best-guess if it's not but > clearly signal that it's a guess. > > I.e. if I understood all the cases correctly we'd have three types of > messages generated: > > !error_code: > "General protection fault in user access, due to non-canonical address." > > error_code && !is_canonical_addr(fault_addr): > "General protection fault in user access. Non-canonical address?" > > error_code && is_canonical_addr(fault_addr): > "General protection fault in user access. Segmentation bug?"
Now that I've read the rest of the thread, since fault_addr is always 0 we can ignore most of this I suspect ...
Thanks,
Ingo
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