On Fri, 20 Apr 2018 19:46:08 -0400 John David Anglin <dave.anglin@xxxxxxxx> wrote: > On 2018-04-20 9:20 AM, James Bottomley wrote: > > On Fri, 2018-04-20 at 23:07 +1000, Nicholas Piggin wrote: > >> Does parisc still need to use -ffunction-sections flag, now that we > >> build with thin archives and don't use `ld -r`? I think it should not > >> be required anymore. > > I think we may have some modules that are too big. The original > > problem is that without -ffunction-sections, the linker doesn't have > > any way of inserting trampolines in the middle of the text code, and > > our relative jumps are comparatively short distance, so to get from the > > code to the PLT is sometimes to far for a single relative jump. > Correct. This is not just an issue with `ld -r`. > > The -ffunction-sections flag is only helpful for 32-bit PA 1.x builds. > PA 2.0 `b,l` branches > are 32 times longer and it's unlikely the maximum module size is > exceeded in a 32-bit build. > > The 64-bit linker doesn't support adding long branch stubs. This limits > the maximum kernel > size to about 8 MB using without using long calls. They are slow. > > I would keep this option for PA 1.x builds. Well I'm interested. Would you really have a single .c/.S file that benefits from it? It's possible. gnu ld has a --stats option, for powerpc it gives you an output like: powerpc64le-linux-gnu-ld: linker stubs in 0 groups powerpc64le-linux-gnu-ld: branch 0 powerpc64le-linux-gnu-ld: toc adjust 0 powerpc64le-linux-gnu-ld: long branch 0 powerpc64le-linux-gnu-ld: long toc adj 0 powerpc64le-linux-gnu-ld: plt call 0 powerpc64le-linux-gnu-ld: plt call toc 0 powerpc64le-linux-gnu-ld: global entry 0 powerpc64le-linux-gnu-ld: total time in link: 0.242010 Not sure if parisc has the same output, but if it does, add --stats to LDFLAGS_vmlinux, and you could see what happens with/without -ffunction-sections. Thanks, Nick -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
