arch/s390/kernel/early_nobss.c

   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
  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
  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
  55 static void __init clear_bss_section(void)
  56 {
  57         memset(__bss_start, 0, __bss_stop - __bss_start);
  58 }
  59
  60 void __init startup_init_nobss(void)
  61 {
  62         reset_tod_clock();
  63         rescue_initrd();
  64         clear_bss_section();
  65 }