On Thu, Feb 25, 2021 at 12:20:56PM +0100, Arnd Bergmann wrote: > From: Arnd Bergmann <[email protected]> > > When looking at kernel size optimizations, I found that arm64 > does not currently support HAVE_LD_DEAD_CODE_DATA_ELIMINATION, > which enables the --gc-sections flag to the linker. > > I see that for a defconfig build with llvm, there are some > notable improvements from enabling this, in particular when > combined with the recently added CONFIG_LTO_CLANG_THIN > and CONFIG_TRIM_UNUSED_KSYMS: > > text data bss dec hex filename > 16570322 10998617 506468 28075407 1ac658f defconfig/vmlinux > 16318793 10569913 506468 27395174 1a20466 trim_defconfig/vmlinux > 16281234 10984848 504291 27770373 1a7be05 gc_defconfig/vmlinux > 16029705 10556880 504355 27090940 19d5ffc gc+trim_defconfig/vmlinux > 17040142 11102945 504196 28647283 1b51f73 thinlto_defconfig/vmlinux > 16788613 10663201 504196 27956010 1aa932a thinlto+trim_defconfig/vmlinux > 16347062 11043384 502499 27892945 1a99cd1 gc+thinlto_defconfig/vmlinux > 15759453 10532792 502395 26794640 198da90 gc+thinlto+trim_defconfig/vmlinux > > I needed a small change to the linker script to get clean randconfig > builds, but I have not done any meaningful boot testing on it to > see if it works. If there are no regressions, I wonder whether this > should be autmatically done for LTO builds, given that it improves > both kernel size and compile speed. > > Link: > https://lore.kernel.org/lkml/cak8p3a05vz9hskrzvtxtn+1nf9e+gqebjwtj6n23nfm+elh...@mail.gmail.com/ > Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Kees Cook <[email protected]> -- Kees Cook
