On Thu, Sep 03, 2020 at 09:45:39AM -0600, Stephen Warren wrote: > On 9/3/20 7:40 AM, André Przywara wrote: > > On 03/09/2020 14:35, Michal Simek wrote: > >> > >> > >> On 02. 09. 20 18:34, Stephen Warren wrote: > >>> On 9/2/20 5:15 AM, Michal Simek wrote: > >>>> From: "Edgar E. Iglesias" <edgar.igles...@xilinx.com> > >>>> > >>>> When U-Boot binary exceeds 1MB with CONFIG_POSITION_INDEPENDENT=y > >>>> compilation error is shown: > >>>> /mnt/disk/u-boot/arch/arm/cpu/armv8/start.S:71:(.text+0x3c): relocation > >>>> truncated to fit: R_AARCH64_ADR_PREL_LO21 against symbol `__rel_dyn_end' > >>>> defined in .bss_start section in u-boot. > >>>> > >>>> It is caused by adr instruction which permits the calculation of any byte > >>>> address within +- 1MB of the current PC. > >>>> Because U-Boot is bigger then 1MB calculation is failing. > >>>> > >>>> The patch is using adrp/add instructions where adrp shifts a signed, > >>>> 21-bit > >>>> immediate left by 12 bits (4k page), adds it to the value of the program > >>>> counter with the bottom 12 bits cleared to zero. Then add instruction > >>>> provides the lower 12 bits which is offset within 4k page. > >>>> These two instructions together compose full 32bit offset which should be > >>>> more then enough to cover the whole u-boot size. > >>> > >>>> diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S > >>> > >>>> @@ -67,8 +67,10 @@ pie_fixup: > >>>> adr x0, _start /* x0 <- Runtime value of > >>>> _start */ > >>>> ldr x1, _TEXT_BASE /* x1 <- Linked value of _start > >>>> */ > >>>> sub x9, x0, x1 /* x9 <- Run-vs-link offset */ > >>>> - adr x2, __rel_dyn_start /* x2 <- Runtime > >>>> &__rel_dyn_start */ > >>>> - adr x3, __rel_dyn_end /* x3 <- Runtime &__rel_dyn_end > >>>> */ > >>>> + adrp x2, __rel_dyn_start /* x2 <- Runtime > >>>> &__rel_dyn_start */ > >>>> + add x2, x2, #:lo12:__rel_dyn_start > >>>> + adrp x3, __rel_dyn_end /* x3 <- Runtime &__rel_dyn_end > >>>> */ > >>>> + add x3, x3, #:lo12:__rel_dyn_end > >>>> pie_fix_loop: > >>>> ldp x0, x1, [x2], #16 /* (x0, x1) <- (Link location, > >>>> fixup) */ > >>>> ldr x4, [x2], #8 /* x4 <- addend */ > >>> > >>> There are likely a bunch of other places in the code that need updating > >>> too; take a look at commit 49e93875a62f "arm64: support running at addr > >>> other than linked to" (which introduced the code above) to find other > >>> places with similar instruction sequences that almost certainly need > >>> updating. > >>> > >> > >> I didn't hit any issue to have a need to update them. Definitely worth > >> to check that locations too. > > > > So I thought the same, so I checked at least this file. And while there > > are other "adr" instructions, they only go to nearby labels, so don't > > need to be pumped up. > > But I will try to grep for more cases as well. > > > So in the patch I linked to, what about the added ard instructions in > arch/arm/lib/crt0_64.S and arch/arm/lib/relocate_64.S? > > Perhaps that code gets linked more towards the middle of U-Boot than the > code you're fixing in start.S, so the max 1M offset just happens to > reach all the relevant symbols and relocations that are in your current > binary, but if your binary gets a little larger (e.g. goes from 1.05M to > 2M say) that code will fail in the same way?
Yes, those were apparently already corrected by Ibai: https://github.com/u-boot/u-boot/commit/98ffbb78e12646a1d06236ad6a1893217f255aae#diff-4f864f65dc6b6f2535a5d252b7c9fcc7 Cheers, Edgar
