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 _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
