On Sat, Oct 10, 2009 at 8:27 PM, Joakim Tjernlund <joakim.tjernl...@transmode.se> wrote: > > > Graeme Russ <graeme.r...@gmail.com> wrote on 10/10/2009 10:46:52: >> >> On Sat, Oct 10, 2009 at 7:07 PM, Joakim Tjernlund >> <joakim.tjernl...@transmode.se> wrote: >> > Graeme Russ <graeme.r...@gmail.com> wrote on 10/10/2009 06:43:52: >> >> >> >> On Fri, Oct 9, 2009 at 10:12 AM, Joakim Tjernlund >> >> <joakim.tjernl...@transmode.se> wrote: >> >> >> >> >> >> On Fri, Oct 9, 2009 at 9:27 AM, J. William Campbell >> >> >> <jwilliamcampb...@comcast.net> wrote: >> >> >> > Graeme Russ wrote: >> >> >> >> >> >> >> >> On Fri, Oct 9, 2009 at 2:58 AM, J. William Campbell >> >> >> >> <jwilliamcampb...@comcast.net> wrote: >> >> >> >> >> >> >> >>> >> >> >> >>> Graeme Russ wrote: >> >> >> >>> >> >> >> >>>> >> >> >> >>>> Out of curiosity, I wanted to see just how much of a size penalty >> >> >> >>>> I am >> >> >> >>>> incurring by using gcc -fpic / ld -pic on my x86 u-boot build. >> >> >> >>>> Here are >> >> >> >>>> the results (fixed width font will help - its space, not tab, >> >> >> >>>> formatted): >> >> >> >>>> >> >> >> >>>> Section non-reloc reloc >> >> >> >>>> --------------------------------------- >> >> >> >>>> .text 000118c4 000137fc <- 0x1f38 bytes (~8kB) >> >> >> >>>> bigger >> >> >> >>>> .rodata 00005bad 000059d0 >> >> >> >>>> .interp n/a 00000013 >> >> >> >>>> .dynstr n/a 00000648 >> >> >> >>>> .hash n/a 00000428 >> >> >> >>>> .eh_frame 00003268 000034fc >> >> >> >>>> .data 00000a6c 000001dc >> >> >> >>>> .data.rel n/a 00000098 >> >> >> >>>> .data.rel.ro.local n/a 00000178 >> >> >> >>>> .data.rel.local n/a 000007e4 >> >> >> >>>> .got 00000000 000001f0 >> >> >> >>>> .got.plt n/a 0000000c >> >> >> >>>> .rel.got n/a 000003e0 >> >> >> >>>> .rel.dyn n/a 00001228 >> >> >> >>>> .dynsym n/a 00000850 >> >> >> >>>> .dynamic n/a 00000080 >> >> >> >>>> .u_boot_cmd 000003c0 000003c0 >> >> >> >>>> .bss 00001a34 00001a34 >> >> >> >>>> .realmode 00000166 00000166 >> >> >> >>>> .bios 0000053e 0000053e >> >> >> >>>> ======================================= >> >> >> >>>> Total 0001d5dd 00022287 <- 0x4caa bytes (~19kB) >> >> >> >>>> bigger >> >> >> >>>> >> >> >> >>>> Its more than a 16% increase in size!!! >> >> >> >>>> >> >> >> >>>> .text accounts for a little under half of the total bloat, and of >> >> >> >>>> that, >> >> >> >>>> the crude dynamic loader accounts for only 341 bytes >> >> >> >>>> >> >> >> >>>> >> >> >> >>> >> >> >> >>> Hi Graeme, >> >> >> >>> I would be interested in a third option (column), the x86 >> >> >> >>> build with >> >> >> >>> just -mrelocateable but NOT -fpic. It will not be definitive >> >> >> >>> because >> >> >> >>> there >> >> >> >>> will be extra code that references the GOT and missing code to do >> >> >> >>> some of >> >> >> >>> the relocation, but it would still be interesting. >> >> >> >>> >> >> >> >> >> >> >> >> x86 does not have -mrelocatable. This is a PPC only option :( >> >> >> >> >> >> >> > >> >> >> > Hi Graeme, >> >> >> > You are unfortunately correct. However, I wonder if we can >> >> >> > get >> >> >> > essentially the same result by executing the final ld step with the >> >> >> > --emit-relocs switch included. This may also include some "extra" >> >> >> > sections >> >> >> > that we would want to strip out, but if it works, it could give all >> >> >> > ELF-based systems a way to a relocatable u-boot. >> >> >> > >> >> >> >> >> >> I don't think --emit-relocs is necessary with -pic. I haven't gone >> >> >> through >> >> >> all the permutations to see if there is a smaller option, but gcc >> >> >> -fpic and >> >> >> ld -pie creates enough information to perform relocation on the x86 >> >> >> platform >> >> > >> >> > Try -fvisibility=hidden >> >> >> >> Thanks - Shaved another 2539 bytes off the binary >> >> >> >> Also found out how to get rid of .eh_frame (crept in when I upgraded to >> >> gcc 4.4.1) with -fno-dwarf2-cfi-asm, so that shaves another 13452 bytes >> >> >> >> Total saving of 15.6k >> > >> > Great, so now you are back at just a few percent added I guess? >> > >> > >> >> Not really - The .eh_frame saving applies to both relocated and non >> relocated builds > > OK, so you didn't use PIC before at all? > > Anyway I think you can do more. Using -Bsymbolic you should get > away with RELATIVE relocs only and be able to skip a lot of segments above. > Have a look at uClibc ldso/ldso/dl-startup.c > >
My build options thus far are: PLATFORM_RELFLAGS += -fpie -fvisibility=hidden PLATFORM_CPPFLAGS += -fno-dwarf2-cfi-asm PLATFORM_LDFLAGS += -pie -fpic / -pic make no difference Interestingly, -Bsymbolic adds exactly 8 bytes to .dynamic, but doesn't change the size of any other section Pulling apart the relocation sections, it seems that all relocations are already RELATIVE even without -Bsymbolic _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
