On Thu, Nov 16, 2017 at 08:41:01AM -0800, Sami Tolvanen wrote: > On Thu, Nov 16, 2017 at 11:50:12AM +0000, Will Deacon wrote: > > Why don't we just not do LTO if the toolchain is busted? > > Because LTO can not only potentially improve performance, especially > when combined with PGO (Profile Guided Optimization), but it also > makes it possible to enable features like Control Flow Integrity that > can make kernel vulnerabilities more difficult to exploit: > > https://clang.llvm.org/docs/ControlFlowIntegrity.html > > > This feels like it will end up being a game of whack-a-mole as code > > could be introduced that tickles known bugs on older toolchains. > > I'm not sure this is much different from dealing with older versions > of the existing toolchain. Otherwise, we wouldn't need cc-version or > other similar macros, for example.
I think the big difference is that we have no compelling need to support older versions of clang or gold. Will
