On Friday, August 5, 2016 10:11:58 PM CEST Nicholas Piggin wrote: > Hello, > > I have 3 different things in this patchset. All arch specific, but all > involve kbuild changes, so I'd like to discuss them with kbuild > maintainers. The goal has been to improve long standing linking > difficulties with the powerpc kernel. > > * First, building kernel using thin archives rather than incremental > linking. This seems quite clean and is per-arch, so I hope it should > not be too controversial. > > * Second, building kernel using -ffunction-sections -fdata-sections, > --gc-sections. Yes, I'm spinning the wheel again. It was motivated > by tiny codesize regression in the first patch, but the results seem > too good to ignore. > > * Third, allowing architecture to run a tool over module after it has > been linked. Powerpc wants to use it in order to relocate "alternate > code" instructions that get don't get linked at their runtime > address. No idea if this is the right approach wrt kbuild, but it > seems to work. > > I have included the powerpc code for the first two as a reference. The > third is much bigger and mostly uninteresting for this cc list, but it > can be found here: > > https://patchwork.ozlabs.org/patch/651006/ > > Comments appreciated. > > I've started tested this a bit on ARM now. The first things I noticed are: 1. /home/arnd/cross-gcc/bin/arm-linux-gnueabi-ld: warning: drivers/xen/efi.o uses 2-byte wchar_t yet the output is to use 4-byte wchar_t; use of wchar_t values across objects may fail (actually this one has been present since the first version that stopped using recursive linking, I did 971a69db7dc0 ("Xen: don't warn about 2-byte wchar_t in efi") when I first saw the bug, but that fix no longer works and we have to do this differently 2. big-endian builds on ARM stopped working, I now get 22:53:02 CC init/do_mounts_md.o 22:53:02 LD init/mounts.o /home/arnd/cross-gcc/bin/arm-linux-gnueabi-ld: init/do_mounts.o: compiled for a big endian system and target is little endian /home/arnd/cross-gcc/bin/arm-linux-gnueabi-ld: failed to merge target specific data of file init/do_mounts.o The problem seems to be that we don't pass the correct linker flags any more, it should be using --be8 from arch/arm/Makefile:LDFLAGS_vmlinux += --be8 arch/arm/Makefile:LDFLAGS_MODULE += --be8 but that somehow is lost. 3. drivers/firmware/efi/libstub/lib.a: error adding symbols: Archive has no index; run ranlib to add one haven't investigated at all, turned off EFI for now. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
