arch/s390/kernel/early_nobss.c

// SPDX-License-Identifier: GPL-2.0
/*
 *    Copyright IBM Corp. 2007, 2018
 */

/*
 * Early setup functions which may not rely on an initialized bss
 * section. The last thing that is supposed to happen here is
 * initialization of the bss section.
 */

#include <linux/processor.h>
#include <linux/string.h>
#include <asm/sections.h>
#include <asm/lowcore.h>
#include <asm/setup.h>
#include <asm/timex.h>
#include "entry.h"

static void __init reset_tod_clock(void)
{
	u64 time;

	if (store_tod_clock(&time) == 0)
		return;
	/* TOD clock not running. Set the clock to Unix Epoch. */
	if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)
		disabled_wait(0);

	memset(tod_clock_base, 0, 16);
	*(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;
	S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;
}

static void __init rescue_initrd(void)
{
	unsigned long min_initrd_addr = (unsigned long) _end + (4UL << 20);

	/*
	 * Just like in case of IPL from VM reader we make sure there is a
	 * gap of 4MB between end of kernel and start of initrd.
	 * That way we can also be sure that saving an NSS will succeed,
	 * which however only requires different segments.
	 */
	if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD))
		return;
	if (!INITRD_START || !INITRD_SIZE)
		return;
	if (INITRD_START >= min_initrd_addr)
		return;
	memmove((void *) min_initrd_addr, (void *) INITRD_START, INITRD_SIZE);
	INITRD_START = min_initrd_addr;
}

static void __init clear_bss_section(void)
{
	memset(__bss_start, 0, __bss_stop - __bss_start);
}

void __init startup_init_nobss(void)
{
	reset_tod_clock();
	rescue_initrd();
	clear_bss_section();
}