From: "Edgar E. Iglesias" edgar.iglesias@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.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com ---
arch/arm/cpu/armv8/start.S | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S index 002698b501c3..52cf1230c205 100644 --- 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 */