Message ID | 5118FCC7.8020706@openwrt.org |
---|---|
State | Superseded |
Delegated to: | Daniel Schwierzeck |
Headers | show |
2013/2/11 Gabor Juhos <juhosg@openwrt.org>: >> that's weird. Actually I checked after each patch if the *_end symbols >> match the U-Boot binary size. Now I checked again with different >> toolchains (gcc-4.[5,6,7], binutils-2.[21.53,22] and I have again that >> binutils issue. >> >> But all toolchains have one in common (tested with qemu_mips): >> __rel_dyn_end - __rel_dyn_start = 0x1770 >> size from readelf = 0x15f8 >> >> Another problem is that your .deadcode workaround does not work >> anymore for me. It does not matter how I arrange or drop the unneeded >> sections, the size of .rel.dyn remains at 0x1770. I'll try to find >> another solution. > > Erm, the presence of the .deadcode section does not change the size of the > .rel.dyn section. > > The ELF headers shows that there is a gap between the .rel.dyn and the .deadcode > section: > > [ 6] .rel.dyn REL bfc30804 030864 0015f8 08 A 8 0 4 > [ 7] .deadcode PROGBITS bfc31f74 031fd4 000004 00 WA 0 0 1 > > However objcopy will copy the .deadcode section into the final binary because it > is placed after the .rel.dyn section, and the gap will be filled with 0xff bytes. > > As a result, the size of u-boot.bin will equal to (__rel_dyn_end - __start + 4), > and this ensures that it will contain the full .rel.dyn section. > ok. I guess I misunderstood the intention of your workaround. My goal was to minimize the increase of image size caused by PIE. I'll send a v2 of patch 6/7 with the .deadcode section.
From 07bbc17f35a78bbace7d91477643497f8b51cc0c Mon Sep 17 00:00:00 2001 From: Gabor Juhos <juhosg@openwrt.org> Date: Mon, 11 Feb 2013 15:06:17 +0100 Subject: [PATCH] MIPS: u-boot.lds: add back the .deadcode section --- arch/mips/cpu/u-boot.lds | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/mips/cpu/u-boot.lds b/arch/mips/cpu/u-boot.lds index cea9533..10513ab 100644 --- a/arch/mips/cpu/u-boot.lds +++ b/arch/mips/cpu/u-boot.lds @@ -76,6 +76,24 @@ SECTIONS __rel_dyn_end = .; } + .deadcode : { + /* + * Workaround for a binutils feature (or bug?). + * + * The GNU ld from binutils puts the dynamic relocation + * entries into the .rel.dyn section. Sometimes it + * allocates more dynamic relocation entries than it needs + * and the unused slots are set to R_MIPS_NONE entries. + * + * However the size of the .rel.dyn section in the ELF + * section header does not cover the unused entries, so + * objcopy removes those during stripping. + * + * Create a small section here to avoid that. + */ + LONG(0xffffffff); + } + .dynsym : { *(.dynsym) } -- 1.7.10