qemu

FORK: QEMU emulator
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jump2ipl.c (2844B)

      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 %%r1,1\n\t"
     68                  "diag %%r1,%%r1,0x308\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 (pointed to by reset_psw) */
     86     if (*reset_psw & 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 }