Re: [tip:x86/core 1/1] vmlinux.o: warning: objtool: rcar_pcie_probe+0x13e: no-cfi indirect call!

[Nathan Chancellor]

On Mon, Oct 13, 2025 at 10:26:29AM +0200, Peter Zijlstra wrote:
> On Fri, Oct 10, 2025 at 03:30:12PM -0700, Nathan Chancellor wrote:
> > which does somewhat make sense because what's the point of setting up
> > the CFI call if you know nothing can actually make use of it since we
> > will crash when trying to indirectly call a NULL pointer?
> 
> As Sami says, it would be really nice if clang would at least WARN about
> emitting an unconditional NULL call like that. I mean, it *knows* its
> going to crash and burn at that point, right?

Yeah, I agree. It would have to happen after optimizations and the
infrastructure for reporting those instances back up to the frontend
is... not great IIRC but I will see if I can file something upstream.

Is there any way for objtool to detect these instances and emit a
slightly differently worded message? Figured it was worth asking ;)

> > Something like this would avoid this issue then.
> 
> Yes, this seems reasonable -- even if the driver should perhaps
> mandate/depend on CONFIG_OF, making sure to behave when NULL does get
> returned is definitely a good thing!.
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Thanks, I have sent this for review with your tag and Kees's:

https://lore.kernel.org/20251013-rcar_pcie_probe-avoid-nocfi-objtool-warning-v1-1-552876b94f04@xxxxxxxxxx/

Cheers,
Nathan