1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *    Copyright IBM Corp. 2007, 2018
4  */
5 
6 /*
7  * Early setup functions which may not rely on an initialized bss
8  * section. The last thing that is supposed to happen here is
9  * initialization of the bss section.
10  */
11 
12 #include <linux/processor.h>
13 #include <linux/string.h>
14 #include <asm/sections.h>
15 #include <asm/lowcore.h>
16 #include <asm/setup.h>
17 #include <asm/timex.h>
18 #include "entry.h"
19 
reset_tod_clock(void)20 static void __init reset_tod_clock(void)
21 {
22 	u64 time;
23 
24 	if (store_tod_clock(&time) == 0)
25 		return;
26 	/* TOD clock not running. Set the clock to Unix Epoch. */
27 	if (set_tod_clock(TOD_UNIX_EPOCH) != 0 || store_tod_clock(&time) != 0)
28 		disabled_wait(0);
29 
30 	memset(tod_clock_base, 0, 16);
31 	*(__u64 *) &tod_clock_base[1] = TOD_UNIX_EPOCH;
32 	S390_lowcore.last_update_clock = TOD_UNIX_EPOCH;
33 }
34 
rescue_initrd(void)35 static void __init rescue_initrd(void)
36 {
37 	unsigned long min_initrd_addr = (unsigned long) _end + (4UL << 20);
38 
39 	/*
40 	 * Just like in case of IPL from VM reader we make sure there is a
41 	 * gap of 4MB between end of kernel and start of initrd.
42 	 * That way we can also be sure that saving an NSS will succeed,
43 	 * which however only requires different segments.
44 	 */
45 	if (!IS_ENABLED(CONFIG_BLK_DEV_INITRD))
46 		return;
47 	if (!INITRD_START || !INITRD_SIZE)
48 		return;
49 	if (INITRD_START >= min_initrd_addr)
50 		return;
51 	memmove((void *) min_initrd_addr, (void *) INITRD_START, INITRD_SIZE);
52 	INITRD_START = min_initrd_addr;
53 }
54 
clear_bss_section(void)55 static void __init clear_bss_section(void)
56 {
57 	memset(__bss_start, 0, __bss_stop - __bss_start);
58 }
59 
startup_init_nobss(void)60 void __init startup_init_nobss(void)
61 {
62 	reset_tod_clock();
63 	rescue_initrd();
64 	clear_bss_section();
65 }
66