AArch64 Relocations

9.1.3.3 Relocations

Relocations for ‘MOVZ’ and ‘MOVK’ instructions can be generated by prefixing the label with ‘#:abs_g2:’ etc. For example to load the 48-bit absolute address of foo into x0:

   movz x0, #:abs_g2:foo         // bits 32-47, overflow check
        movk x0, #:abs_g1_nc:foo        // bits 16-31, no overflow check
        movk x0, #:abs_g0_nc:foo        // bits  0-15, no overflow check

Relocations for ‘ADRP’, and ‘ADD’, ‘LDR’ or ‘STR’ instructions can be generated by prefixing the label with ‘:pg_hi21:’ and ‘#:lo12:’ respectively.

For example to use 33-bit (+/-4GB) pc-relative addressing to load the address of foo into x0:

        adrp x0, :pg_hi21:foo
        add  x0, x0, #:lo12:foo

Or to load the value of foo into x0:

        adrp x0, :pg_hi21:foo
        ldr  x0, [x0, #:lo12:foo]

Note that ‘:pg_hi21:’ is optional.

        adrp x0, foo

is equivalent to

        adrp x0, :pg_hi21:foo

from:

https://www.rowleydownload.co.uk/arm/documentation/gnu/as/AArch64_002dRelocations.html

reference:

https://developer.arm.com/documentation/100067/0612/armclang-Integrated-Assembler/Assembly-expressions