U-Boot

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2013-2014 Synopsys, Inc. All rights reserved.
 */

#include <common.h>
#include <bootstage.h>
#include <env.h>
#include <image.h>
#include <irq_func.h>
#include <lmb.h>
#include <log.h>
#include <asm/cache.h>

DECLARE_GLOBAL_DATA_PTR;

static ulong get_sp(void)
{
	ulong ret;

	asm("mov %0, sp" : "=r"(ret) : );
	return ret;
}

void arch_lmb_reserve(struct lmb *lmb)
{
	ulong sp;

	/*
	 * Booting a (Linux) kernel image
	 *
	 * Allocate space for command line and board info - the
	 * address should be as high as possible within the reach of
	 * the kernel (see CONFIG_SYS_BOOTMAPSZ settings), but in unused
	 * memory, which means far enough below the current stack
	 * pointer.
	 */
	sp = get_sp();
	debug("## Current stack ends at 0x%08lx ", sp);

	/* adjust sp by 4K to be safe */
	sp -= 4096;
	lmb_reserve(lmb, sp, (CONFIG_SYS_SDRAM_BASE + gd->ram_size - sp));
}

static int cleanup_before_linux(void)
{
	disable_interrupts();
	sync_n_cleanup_cache_all();

	return 0;
}

__weak int board_prep_linux(bootm_headers_t *images) { return 0; }

/* Subcommand: PREP */
static int boot_prep_linux(bootm_headers_t *images)
{
	int ret;

	ret = image_setup_linux(images);
	if (ret)
		return ret;

	return board_prep_linux(images);
}

/* Generic implementation for single core CPU */
__weak void board_jump_and_run(ulong entry, int zero, int arch, uint params)
{
	void (*kernel_entry)(int zero, int arch, uint params);

	kernel_entry = (void (*)(int, int, uint))entry;

	kernel_entry(zero, arch, params);
}

/* Subcommand: GO */
static void boot_jump_linux(bootm_headers_t *images, int flag)
{
	ulong kernel_entry;
	unsigned int r0, r2;
	int fake = (flag & BOOTM_STATE_OS_FAKE_GO);

	kernel_entry = images->ep;

	debug("## Transferring control to Linux (at address %08lx)...\n",
	      kernel_entry);
	bootstage_mark(BOOTSTAGE_ID_RUN_OS);

	printf("\nStarting kernel ...%s\n\n", fake ?
	       "(fake run for tracing)" : "");
	bootstage_mark_name(BOOTSTAGE_ID_BOOTM_HANDOFF, "start_kernel");

	if (IMAGE_ENABLE_OF_LIBFDT && images->ft_len) {
		r0 = 2;
		r2 = (unsigned int)images->ft_addr;
	} else {
		r0 = 1;
		r2 = (unsigned int)env_get("bootargs");
	}

	cleanup_before_linux();

	if (!fake)
		board_jump_and_run(kernel_entry, r0, 0, r2);
}

int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
{
	/* No need for those on ARC */
	if ((flag & BOOTM_STATE_OS_BD_T) || (flag & BOOTM_STATE_OS_CMDLINE))
		return -1;

	if (flag & BOOTM_STATE_OS_PREP)
		return boot_prep_linux(images);

	if (flag & (BOOTM_STATE_OS_GO | BOOTM_STATE_OS_FAKE_GO)) {
		boot_jump_linux(images, flag);
		return 0;
	}

	return -1;
}