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https://github.com/AsahiLinux/u-boot
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0ae7653128
Relocation code based on a patch by Scott Wood, which is: Signed-off-by: Scott Wood <scottwood@freescale.com> Signed-off-by: David Feng <fenghua@phytium.com.cn>
113 lines
3.5 KiB
ArmAsm
113 lines
3.5 KiB
ArmAsm
/*
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* crt0 - C-runtime startup Code for AArch64 U-Boot
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*
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* (C) Copyright 2013
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* David Feng <fenghua@phytium.com.cn>
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*
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* (C) Copyright 2012
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* Albert ARIBAUD <albert.u.boot@aribaud.net>
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*
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* SPDX-License-Identifier: GPL-2.0+
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*/
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#include <config.h>
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#include <asm-offsets.h>
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#include <asm/macro.h>
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#include <linux/linkage.h>
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/*
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* This file handles the target-independent stages of the U-Boot
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* start-up where a C runtime environment is needed. Its entry point
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* is _main and is branched into from the target's start.S file.
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*
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* _main execution sequence is:
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*
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* 1. Set up initial environment for calling board_init_f().
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* This environment only provides a stack and a place to store
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* the GD ('global data') structure, both located in some readily
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* available RAM (SRAM, locked cache...). In this context, VARIABLE
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* global data, initialized or not (BSS), are UNAVAILABLE; only
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* CONSTANT initialized data are available.
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*
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* 2. Call board_init_f(). This function prepares the hardware for
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* execution from system RAM (DRAM, DDR...) As system RAM may not
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* be available yet, , board_init_f() must use the current GD to
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* store any data which must be passed on to later stages. These
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* data include the relocation destination, the future stack, and
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* the future GD location.
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*
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* (the following applies only to non-SPL builds)
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*
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* 3. Set up intermediate environment where the stack and GD are the
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* ones allocated by board_init_f() in system RAM, but BSS and
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* initialized non-const data are still not available.
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*
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* 4. Call relocate_code(). This function relocates U-Boot from its
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* current location into the relocation destination computed by
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* board_init_f().
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*
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* 5. Set up final environment for calling board_init_r(). This
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* environment has BSS (initialized to 0), initialized non-const
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* data (initialized to their intended value), and stack in system
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* RAM. GD has retained values set by board_init_f(). Some CPUs
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* have some work left to do at this point regarding memory, so
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* call c_runtime_cpu_setup.
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*
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* 6. Branch to board_init_r().
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*/
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ENTRY(_main)
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/*
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* Set up initial C runtime environment and call board_init_f(0).
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*/
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ldr x0, =(CONFIG_SYS_INIT_SP_ADDR)
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sub x0, x0, #GD_SIZE /* allocate one GD above SP */
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bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */
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mov x18, sp /* GD is above SP */
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mov x0, #0
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bl board_init_f
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/*
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* Set up intermediate environment (new sp and gd) and call
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* relocate_code(addr_moni). Trick here is that we'll return
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* 'here' but relocated.
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*/
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ldr x0, [x18, #GD_START_ADDR_SP] /* x0 <- gd->start_addr_sp */
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bic sp, x0, #0xf /* 16-byte alignment for ABI compliance */
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ldr x18, [x18, #GD_BD] /* x18 <- gd->bd */
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sub x18, x18, #GD_SIZE /* new GD is below bd */
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adr lr, relocation_return
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ldr x9, [x18, #GD_RELOC_OFF] /* x9 <- gd->reloc_off */
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add lr, lr, x9 /* new return address after relocation */
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ldr x0, [x18, #GD_RELOCADDR] /* x0 <- gd->relocaddr */
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b relocate_code
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relocation_return:
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/*
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* Set up final (full) environment
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*/
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bl c_runtime_cpu_setup /* still call old routine */
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/*
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* Clear BSS section
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*/
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ldr x0, =__bss_start /* this is auto-relocated! */
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ldr x1, =__bss_end /* this is auto-relocated! */
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mov x2, #0
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clear_loop:
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str x2, [x0]
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add x0, x0, #8
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cmp x0, x1
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b.lo clear_loop
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/* call board_init_r(gd_t *id, ulong dest_addr) */
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mov x0, x18 /* gd_t */
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ldr x1, [x18, #GD_RELOCADDR] /* dest_addr */
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b board_init_r /* PC relative jump */
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/* NOTREACHED - board_init_r() does not return */
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ENDPROC(_main)
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