xref: /qemu/pc-bios/s390-ccw/jump2ipl.c (revision 5b76dd13)
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 
12 #define KERN_IMAGE_START 0x010000UL
13 #define PSW_MASK_64 0x0000000100000000ULL
14 #define PSW_MASK_32 0x0000000080000000ULL
15 #define IPL_PSW_MASK (PSW_MASK_32 | PSW_MASK_64)
16 
17 typedef struct ResetInfo {
18     uint32_t ipl_mask;
19     uint32_t ipl_addr;
20     uint32_t ipl_continue;
21 } ResetInfo;
22 
23 static ResetInfo save;
24 
25 static void jump_to_IPL_2(void)
26 {
27     ResetInfo *current = 0;
28 
29     void (*ipl)(void) = (void *) (uint64_t) current->ipl_continue;
30     *current = save;
31     ipl(); /* should not return */
32 }
33 
34 void jump_to_IPL_code(uint64_t address)
35 {
36     /* store the subsystem information _after_ the bootmap was loaded */
37     write_subsystem_identification();
38 
39     /* prevent unknown IPL types in the guest */
40     if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
41         iplb.pbt = S390_IPL_TYPE_CCW;
42         set_iplb(&iplb);
43     }
44 
45     /*
46      * The IPL PSW is at address 0. We also must not overwrite the
47      * content of non-BIOS memory after we loaded the guest, so we
48      * save the original content and restore it in jump_to_IPL_2.
49      */
50     ResetInfo *current = 0;
51 
52     save = *current;
53     current->ipl_addr = (uint32_t) (uint64_t) &jump_to_IPL_2;
54     current->ipl_continue = address & 0x7fffffff;
55 
56     debug_print_int("set IPL addr to", current->ipl_continue);
57 
58     /* Ensure the guest output starts fresh */
59     sclp_print("\n");
60 
61     /*
62      * HACK ALERT.
63      * We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
64      * can then use r15 as its stack pointer.
65      */
66     asm volatile("lghi 1,1\n\t"
67                  "diag 1,1,0x308\n\t"
68                  : : : "1", "memory");
69     panic("\n! IPL returns !\n");
70 }
71 
72 void jump_to_low_kernel(void)
73 {
74     /*
75      * If it looks like a Linux binary, i.e. there is the "S390EP" magic from
76      * arch/s390/kernel/head.S here, then let's jump to the well-known Linux
77      * kernel start address (when jumping to the PSW-at-zero address instead,
78      * the kernel startup code fails when we booted from a network device).
79      */
80     if (!memcmp((char *)0x10008, "S390EP", 6)) {
81         jump_to_IPL_code(KERN_IMAGE_START);
82     }
83 
84     /* Trying to get PSW at zero address */
85     if (*((uint64_t *)0) & IPL_PSW_MASK) {
86         jump_to_IPL_code((*((uint64_t *)0)) & 0x7fffffff);
87     }
88 
89     /* No other option left, so use the Linux kernel start address */
90     jump_to_IPL_code(KERN_IMAGE_START);
91 }
92