pc-bios/s390-ccw/jump2ipl.c

   1 /*
   2  * QEMU s390-ccw firmware - jump to IPL code
   3  *
   4  * This work is licensed under the terms of the GNU GPL, version 2 or (at
   5  * your option) any later version. See the COPYING file in the top-level
   6  * directory.
   7  */
   8
   9 #include "libc.h"
  10 #include "s390-ccw.h"
  11 #include "s390-arch.h"
  12
  13 #define KERN_IMAGE_START 0x010000UL
  14 #define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
  15
  16 typedef struct ResetInfo {
  17     uint64_t ipl_psw;
  18     uint32_t ipl_continue;
  19 } ResetInfo;
  20
  21 static ResetInfo save;
  22
  23 static void jump_to_IPL_2(void)
  24 {
  25     ResetInfo *current = 0;
  26
  27     void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
  28     *current = save;
  29     ipl(); /* should not return */
  30 }
  31
  32 void jump_to_IPL_code(uint64_t address)
  33 {
  34     /* store the subsystem information _after_ the bootmap was loaded */
  35     write_subsystem_identification();
  36     write_iplb_location();
  37
  38     /* prevent unknown IPL types in the guest */
  39     if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
  40         iplb.pbt = S390_IPL_TYPE_CCW;
  41         set_iplb(&iplb);
  42     }
  43
  44     /*
  45      * The IPL PSW is at address 0. We also must not overwrite the
  46      * content of non-BIOS memory after we loaded the guest, so we
  47      * save the original content and restore it in jump_to_IPL_2.
  48      */
  49     ResetInfo *current = 0;
  50
  51     save = *current;
  52
  53     current->ipl_psw = (uint64_t) &jump_to_IPL_2;
  54     current->ipl_psw |= RESET_PSW_MASK;
  55     current->ipl_continue = address & PSW_MASK_SHORT_ADDR;
  56
  57     debug_print_int("set IPL addr to", current->ipl_continue);
  58
  59     /* Ensure the guest output starts fresh */
  60     sclp_print("\n");
  61
  62     /*
  63      * HACK ALERT.
  64      * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
  65      * can then use r15 as its stack pointer.
  66      */
  67     asm volatile("lghi 1,1\n\t"
  68                  "diag 1,1,0x308\n\t"
  69                  : : : "1", "memory");
  70     panic("\n! IPL returns !\n");
  71 }
  72
  73 void jump_to_low_kernel(void)
  74 {
  75     /*
  76      * If it looks like a Linux binary, i.e. there is the "S390EP" magic from
  77      * arch/s390/kernel/head.S here, then let's jump to the well-known Linux
  78      * kernel start address (when jumping to the PSW-at-zero address instead,
  79      * the kernel startup code fails when we booted from a network device).
  80      */
  81     if (!memcmp((char *)0x10008, "S390EP", 6)) {
  82         jump_to_IPL_code(KERN_IMAGE_START);
  83     }
  84
  85     /* Trying to get PSW at zero address */
  86     if (*((uint64_t *)0) & RESET_PSW_MASK) {
  87         jump_to_IPL_code((*((uint64_t *)0)) & PSW_MASK_SHORT_ADDR);
  88     }
  89
  90     /* No other option left, so use the Linux kernel start address */
  91     jump_to_IPL_code(KERN_IMAGE_START);
  92 }