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.
