Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch V6 07/37] x86/entry: Provide helpers for execute on irqstack | Date | Wed, 20 May 2020 17:27:12 +0200 |
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Andy Lutomirski <luto@kernel.org> writes: > On Wed, May 20, 2020 at 5:35 AM Thomas Gleixner <tglx@linutronix.de> wrote: >> >> Andy Lutomirski <luto@kernel.org> writes: >> > On Mon, May 18, 2020 at 4:53 PM Thomas Gleixner <tglx@linutronix.de> wrote: >> >> >> >> Andy Lutomirski <luto@kernel.org> writes: >> >> > Actually, I revoke my ack. Can you make one of two changes: >> >> > >> >> > Option A: Add an assertion to run_on_irqstack to verify that irq_count >> >> > was -1 at the beginning? I suppose this also means you could just >> >> > explicitly write 0 instead of adding and subtracting. >> >> > >> >> > Option B: Make run_on_irqstack() just call the function on the current >> >> > stack if we're already on the irq stack. >> >> > >> >> > Right now, it's too easy to mess up and not verify the right >> >> > precondition before calling run_on_irqstack(). >> >> > >> >> > If you choose A, perhaps add a helper to do the if(irq_needs_irqstack) >> >> > dance so that users can just do: >> >> > >> >> > run_on_irqstack_if_needed(...); >> >> > >> >> > instead of checking everything themselves. >> >> >> >> I'll have a look tomorrow morning with brain awake. >> > >> > Also, reading more of the series, I suspect that asm_call_on_stack is >> > logically in the wrong section or that the noinstr stuff is otherwise >> > not quite right. I think that objtool should not accept >> > run_on_irqstack() from noinstr code. See followups on patch 10. >> >> It's in entry.text which is non-instrumentable as well. > > Hmm. I suppose we can chalk this up to the noinstr checking not being > entirely perfect.
objtool considers both entry.text and noinstr.text. We just can't stick everything into entry.text for these !%@#45@# reasons.
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