On Tue, Apr 24, 2018 at 02:35:27PM +0100, Will Deacon wrote: > On Sun, Apr 15, 2018 at 06:20:11PM +0200, Jason A. Donenfeld wrote: > > Would you review/merge this when you have a chance? > > No real objection from me, but does the arm64 kernel actually build with > clang?
I belevie that currently it is not possible to use a released version of clang to build a working kernel without additional patches (at least 5.0.0, there don't seem to be any 6.0.0 binaries that can target AArch64). Issues include: * Released versions of clang don't support the 's' constraint used in some hyp code. * Released versions of clang don't support 'rX' as a register name, as is used by some workaround code shared between arm/arm64. * Additional flags need to be passed for hyp code to function correctly, since clang will convert switch statements into jump tables, meaning they aren't position-independent. I tried building a tip-of-tree clang recently (r330441 with llvm r330440) to see what was solved so far, but this blew up when bulding the kernel, and I was going to wait for the 7.0.0 release before trying again. Thanks, Mark.
