arm64: PIE: Skip fixups if distance is zero

When the actual offset between link and runtime address is zero, there
is no need for patching up U-Boot early when running with
CONFIG_POSITION_INDEPENDENT.

Skip the whole routine when the distance is 0.

This helps when U-Boot is loaded into ROM, or in otherwise sensitive
memory locations.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Stephen Warren <swarren@nvidia.com>

diff --git a/arch/arm/cpu/armv8/start.S b/arch/arm/cpu/armv8/start.S
index e5c2856..6624491 100644 (file)
--- a/arch/arm/cpu/armv8/start.S
+++ b/arch/arm/cpu/armv8/start.S
@@ -83,7 +83,8 @@ save_boot_params_ret:
 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 */
+       subs    x9, x0, x1              /* x9 <- Run-vs-link offset */
+       beq     pie_fixup_done
        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 */