Messages in this thread | | | From | Nadav Amit <> | Subject | Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() | Date | Mon, 16 Oct 2023 20:35:24 +0000 |
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> On Oct 16, 2023, at 10:24 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote: > > So there's some serious corruption there, but from the oops itself I > can't tell the source. I guess if we get 'current' wrong anywhere, all > bets are off.
I don’t think it means that it the aliasing does not work; I think it all means that it actually works *too well*.
I have encountered several such issues before [1], and while some have been fixed, some have not (I looked at switch_fpu_finish()), and might under the right/wrong circumstances use the wrongly-“cached” current. Moreover, perhaps new problems have been added since my old patch.
Perhaps the whack-a-mole approach that I took in [1] is wrong. Instead, perhaps it is better to use an uncached version of current when compiling arch/x86/kernel/process_64.c and arch/x86/kernel/process_32.c , so they would not use the const alias, but instead use the original (non-const) one. Some macro magic and an additional "-D” build flag can do that.
But first, there is a need to confirm that’s actually the problem. I’ll try to do it tomorrow.
Regards, Nadav
[1] https://lore.kernel.org/all/20190823224424.15296-5-namit@vmware.com/
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