| /* |
| * Copyright 2019, Data61, CSIRO (ABN 41 687 119 230) |
| * |
| * SPDX-License-Identifier: BSD-2-Clause |
| */ |
| .section .text |
| .global _start |
| _start: |
| |
| /* |
| * RISC-V uses the gp (global pointer) to provide a link-time |
| * optimisation. It is kept in a location near the most-used symbols in |
| * the text segments for any particular section of code. |
| * |
| * This means that a single instruction can be used to jump to a small |
| * offset from the gp rather than 2 or more instructions to do a far |
| * jump to an absolute address. |
| * |
| * The initial location for this is only known at the final link stage |
| * before assembly of the static image. This code below uses a |
| * replacement from the linker to set the value of the gp. |
| * |
| * Relaxation must be disabled when this value is set, otherwise parts |
| * of this code may be optimised away. |
| * |
| * https://web.archive.org/web/20170828212605/https://www.sifive.com/blog/2017/08/28/all-aboard-part-3-linker-relaxation-in-riscv-toolchain/ |
| */ |
| .option push |
| .option norelax |
| 1:auipc gp, %pcrel_hi(__global_pointer$) |
| addi gp, gp, %pcrel_lo(1b) |
| .option pop |
| |
| li s0, 0 |
| |
| addi a0, sp, 0 |
| la x5, __sel4_start_c |
| jalr ra, x5, 0 |
| |
| /* should not return */ |
| 1: |
| j 1b |
