Re: LLVM build warnings

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Sun, Apr 26, 2020 at 02:31:08PM +0200, Maxime Villard wrote:
> Le 13/04/2020 à 08:12, Maxime Villard a écrit :
> > Le 13/04/2020 à 00:39, Joerg Sonnenberger a écrit :
> >> On Sat, Apr 11, 2020 at 01:05:07PM +0200, Maxime Villard wrote:
> >>> When testing CFLAGS with LLVM, I often hit warnings like this one:
> >>
> >> OK, let's take a step back. What *exactly* are you trying to do?
> > 
> > Well, it's rather simple. Try to build aarch64 with PAC, you get:
> > 
> > 	--- libkern.o ---
> > 	building standard kern library
> > 	aarch64--netbsd-clang: error: argument unused during compilation: '-mbranch-protection=pac-ret' [-Werror,-Wunused-command-line-argument]
> > 
> > The Makefile is here:
> > 
> > 	https://nxr.netbsd.org/xref/src/sys/arch/aarch64/conf/Makefile.aarch64?r=1.19#46
> > 
> > I want to compile each kernel object with '-mbranch-protection=pac-ret'.
> > 
> > Same warning with BTI enabled. And I've basically had this warning
> > many times on amd64 when testing new flags.
> > 
> > Thanks,
> > Maxime
> 
> Now you also get the warning when building KASAN on LLVM.
> 
> So, would you have a better flag to suggest? Because if not, I will disable
> the warning.

We are discussing this upstream, it's a bug in the target-specific CPU
flag handling. Please also add a note to the hack file, please.

Joerg