xref: /openbmc/qemu/pc-bios/s390-ccw/jump2ipl.c (revision be3fc97a)
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 <string.h>
10 #include <stdio.h>
11 #include "s390-ccw.h"
12 #include "s390-arch.h"
13 
14 #define KERN_IMAGE_START 0x010000UL
15 #define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
16 #define RESET_PSW ((uint64_t)&jump_to_IPL_addr | RESET_PSW_MASK)
17 
18 static uint64_t *reset_psw = 0, save_psw, ipl_continue;
19 
20 void write_reset_psw(uint64_t psw)
21 {
22     *reset_psw = psw;
23 }
24 
25 static void jump_to_IPL_addr(void)
26 {
27     __attribute__((noreturn)) void (*ipl)(void) = (void *)ipl_continue;
28 
29     /* Restore reset PSW */
30     write_reset_psw(save_psw);
31 
32     ipl();
33     /* should not return */
34 }
35 
36 int jump_to_IPL_code(uint64_t address)
37 {
38     /* store the subsystem information _after_ the bootmap was loaded */
39     write_subsystem_identification();
40     write_iplb_location();
41 
42     /*
43      * The IPLB for QEMU SCSI type devices must be rebuilt during re-ipl. The
44      * iplb.devno is set to the boot position of the target SCSI device.
45      */
46     if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
47         iplb.devno = qipl.index;
48     }
49 
50     if (have_iplb && !set_iplb(&iplb)) {
51         panic("Failed to set IPLB");
52     }
53 
54     /*
55      * The IPL PSW is at address 0. We also must not overwrite the
56      * content of non-BIOS memory after we loaded the guest, so we
57      * save the original content and restore it in jump_to_IPL_2.
58      */
59     if (address) {
60         save_psw = *reset_psw;
61         write_reset_psw(RESET_PSW);
62         ipl_continue = address;
63     }
64     debug_print_int("set IPL addr to", address ?: *reset_psw & PSW_MASK_SHORT_ADDR);
65 
66     /* Ensure the guest output starts fresh */
67     printf("\n");
68 
69     /*
70      * HACK ALERT.
71      * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
72      * can then use r15 as its stack pointer.
73      */
74     asm volatile("lghi %%r1,1\n\t"
75                  "diag %%r1,%%r1,0x308\n\t"
76                  : : : "1", "memory");
77     puts("IPL code jump failed");
78     return -1;
79 }
80 
81 void jump_to_low_kernel(void)
82 {
83     /*
84      * If it looks like a Linux binary, i.e. there is the "S390EP" magic from
85      * arch/s390/kernel/head.S here, then let's jump to the well-known Linux
86      * kernel start address (when jumping to the PSW-at-zero address instead,
87      * the kernel startup code fails when we booted from a network device).
88      */
89     if (!memcmp((char *)S390EP, "S390EP", 6)) {
90         jump_to_IPL_code(KERN_IMAGE_START);
91     }
92 
93     /* Trying to get PSW at zero address (pointed to by reset_psw) */
94     if (*reset_psw & RESET_PSW_MASK) {
95         /*
96          * Surely nobody will try running directly from lowcore, so
97          * let's use 0 as an indication that we want to load the reset
98          * psw at 0x0 and not jump to the entry.
99          */
100         jump_to_IPL_code(0);
101     }
102 
103     /* No other option left, so use the Linux kernel start address */
104     jump_to_IPL_code(KERN_IMAGE_START);
105 }
106