On Sat, Feb 15, 2014 at 10:24:43PM +0100, Sam Ravnborg wrote: > Hi Andi. > > On Sat, Feb 15, 2014 at 06:44:24PM +0100, Andi Kleen wrote: > > On Sat, Feb 15, 2014 at 02:38:14PM +0100, Markus Trippelsdorf wrote: > > > On 2014.02.14 at 22:21 +0100, Andi Kleen wrote: > > > > This is the updated LTO patchkit for 3.14-rc2. LTO allows > > > > the compiler to do global optimization over the whole kernel. > > > > > > It is mildly annoying that one couldn't use vanilla binutils. Have you > > > already opened bugs on sourceware.org/bugzilla/ to get this fixed for > > > gold and ld.bfd? > > > > The problem is supporting "pass through" of both pure (.S) assembler code and > > LTO through ld -r, because the kernel makefiles use ld -r heavily. > > Standard binutils would throw all the assembler away when in plugin LTO > > mode. > > Long time ago I looked at eliminating the use of -r in the kernel build. > I lost the patch - but the attached patch managed to build > a "make defconfig; make" kernel. > > I have not event tried boot with this - it only managed to build! > > What the patch does is for each directory visited a built-in.link file is created > which is really a linker script. > It uses INPUT (file file file) to specify all the object files. > And in the final link the files are all read and the link is performed. > > This limit the depth to 10 levels due to a restriction in ld. > The binutils people have suggested some other methods that I did not look into. > > Half of the patch is fixes to the security makefiles which I > will submit anyway as this needs to be cleaned up indendent on > this patch. > > The patch drops $(cmd_secanalysis) because I did not look into this. > > If this could make it easier to enable LTO then this would be > a nice win. I gave it a quick try and it failed like below with LTO Right now using the Linux binutils is ok for me. -Andi + ld -m elf_x86_64 -r -o vmlinux.o arch/x86/kernel/head_64.o arch/x86/kernel/head64.o arch/x86/kernel/head.o init/built-in.link --start-group usr/built-in.link arch/x86/built-in.link kernel/built-in.link mm/built-in.link fs/built-in.link ipc/built-in.link security/built-in.link crypto/built-in.link block/built-in.link lib/lib.a arch/x86/lib/lib.a lib/built-in.link arch/x86/lib/built-in.link drivers/built-in.link sound/built-in.link firmware/built-in.link arch/x86/pci/built-in.link arch/x86/oprofile/built-in.link arch/x86/power/built-in.link arch/x86/video/built-in.link net/built-in.link --end-group lib/lib.a: could not read symbols: Bad value -- 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
