arm/lib/crt0_64.S

1 /* SPDX-License-Identifier: GPL-2.0+ */
3  * crt0 - C-runtime startup Code for AArch64 U-Boot
9  * Albert ARIBAUD <albert.u.boot@aribaud.net>
13 #include <asm-offsets.h>
18  * This file handles the target-independent stages of the U-Boot
19  * start-up where a C runtime environment is needed. Its entry point
24  * 1. Set up initial environment for calling board_init_f().
39  * 3. Set up intermediate environment where the stack and GD are the
41  *    initialized non-const data are still not available.
43  * 4a.For U-Boot proper (not SPL), call relocate_code(). This function
44  *    relocates U-Boot from its current location into the relocation
50  * 5. Set up final environment for calling board_init_r(). This
51  *    environment has BSS (initialized to 0), initialized non-const
53  *    RAM (for SPL moving the stack and GD into RAM is optional - see
58  * 6. For U-Boot proper (not SPL), some CPUs have some work left to do
69  * Set up initial C runtime environment and call board_init_f(0).
81 	bic	sp, x0, #0xf	/* 16-byte alignment for ABI compliance */
85 	/* set up gd here, outside any C code */
94  * Set up intermediate environment (new sp and gd) and call
98 	ldr	x0, [x18, #GD_START_ADDR_SP]	/* x0 <- gd->start_addr_sp */
99 	bic	sp, x0, #0xf	/* 16-byte alignment for ABI compliance */
100 	ldr	x18, [x18, #GD_NEW_GD]		/* x18 <- gd->new_gd */
104 	/* Add in link-vs-runtime offset */
105 	adr	x0, _start		/* x0 <- Runtime value of _start */
106 	ldr	x9, _TEXT_BASE		/* x9 <- Linked value of _start */
107 	sub	x9, x9, x0		/* x9 <- Run-vs-link offset */
110 	/* Add in link-vs-relocation offset */
111 	ldr	x9, [x18, #GD_RELOC_OFF]	/* x9 <- gd->reloc_off */
113 	ldr	x0, [x18, #GD_RELOCADDR]	/* x0 <- gd->relocaddr */
119  * Set up final (full) environment
125 	/* set up gd here, outside any C code, if new stack is returned */
142 	ldr	x0, =__bss_start		/* this is auto-relocated! */
143 	ldr	x1, =__bss_end			/* this is auto-relocated! */
154 	/* NOTREACHED - board_init_r() does not return */