Messages in this thread | | | From | Andy Lutomirski <> | Date | Wed, 20 May 2020 08:36:57 -0700 | Subject | Re: [patch V6 07/37] x86/entry: Provide helpers for execute on irqstack |
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On Wed, May 20, 2020 at 8:27 AM Thomas Gleixner <tglx@linutronix.de> wrote: > > 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. >
Meh, this is all fine I think. I think it would be slightly nicer if objtool were to warn if noinstr code called run_on_stack(), but I'm not sure it matters much.
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