Messages in this thread | | | Date | Wed, 23 Feb 2022 16:54:14 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 04/29] x86/livepatch: Validate __fentry__ location |
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On Wed, Feb 23, 2022 at 03:49:41PM +0100, Peter Zijlstra wrote:
> > Since we would want rec->ip if the pointer is before the ftrace > > instruction. But we would need to audit all use cases and make sure this is > > not called from any hot paths (in a callback). > > > > This will affect kprobes and BPF as they both use ftrace_location() as well. > > Yes, I already fixed kprobes, still trying to (re)discover how to run > the bpf-selftests, that stuff is too painful :-(
Ok, I think I managed... I'm obviously hitting the WARN_ON_ONCE() in is_ftrace_location(). Funnily, no dead kernel, so that's something I suppose.
Now, I'm trying to make sense of that code, but all that !ftrace_managed code scares me to death.
At the very least __bpf_arch_text_poke() needs a bunch of help. Let me go prod it with something sharp to see what falls out ...
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