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 #define RESET_PSW ((uint64_t)&jump_to_IPL_addr | RESET_PSW_MASK)
  16
  17 static uint64_t *reset_psw = 0, save_psw, ipl_continue;
  18
  19 void write_reset_psw(uint64_t psw)
  20 {
  21     *reset_psw = psw;
  22 }
  23
  24 static void jump_to_IPL_addr(void)
  25 {
  26     __attribute__((noreturn)) void (*ipl)(void) = (void *)ipl_continue;
  27
  28     /* Restore reset PSW */
  29     write_reset_psw(save_psw);
  30
  31     ipl();
  32     /* should not return */
  33 }
  34
  35 void jump_to_IPL_code(uint64_t address)
  36 {
  37     /* store the subsystem information _after_ the bootmap was loaded */
  38     write_subsystem_identification();
  39     write_iplb_location();
  40
  41     /* prevent unknown IPL types in the guest */
  42     if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
  43         iplb.pbt = S390_IPL_TYPE_CCW;
  44         set_iplb(&iplb);
  45     }
  46
  47     /*
  48      * The IPL PSW is at address 0. We also must not overwrite the
  49      * content of non-BIOS memory after we loaded the guest, so we
  50      * save the original content and restore it in jump_to_IPL_2.
  51      */
  52     if (address) {
  53         save_psw = *reset_psw;
  54         write_reset_psw(RESET_PSW);
  55         ipl_continue = address;
  56     }
  57     debug_print_int("set IPL addr to", address ?: *reset_psw & PSW_MASK_SHORT_ADDR);
  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 *)S390EP, "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         /*
  88          * Surely nobody will try running directly from lowcore, so
  89          * let's use 0 as an indication that we want to load the reset
  90          * psw at 0x0 and not jump to the entry.
  91          */
  92         jump_to_IPL_code(0);
  93     }
  94
  95     /* No other option left, so use the Linux kernel start address */
  96     jump_to_IPL_code(KERN_IMAGE_START);
  97 }