1 // SPDX-License-Identifier: GPL-2.0
2
3 #ifndef pr_fmt
4 #define pr_fmt(fmt) "alt: " fmt
5 #endif
6
7 #include <linux/uaccess.h>
8 #include <linux/printk.h>
9 #include <asm/nospec-branch.h>
10 #include <asm/abs_lowcore.h>
11 #include <asm/alternative.h>
12 #include <asm/facility.h>
13 #include <asm/sections.h>
14 #include <asm/machine.h>
15
16 #ifndef a_debug
17 #define a_debug pr_debug
18 #endif
19
20 #ifndef __kernel_va
21 #define __kernel_va(x) (void *)(x)
22 #endif
23
24 unsigned long __bootdata_preserved(machine_features[1]);
25
26 struct alt_debug {
27 unsigned long facilities[MAX_FACILITY_BIT / BITS_PER_LONG];
28 unsigned long mfeatures[MAX_MFEATURE_BIT / BITS_PER_LONG];
29 int spec;
30 };
31
32 static struct alt_debug __bootdata_preserved(alt_debug);
33
alternative_dump(u8 * old,u8 * new,unsigned int len,unsigned int type,unsigned int data)34 static void alternative_dump(u8 *old, u8 *new, unsigned int len, unsigned int type, unsigned int data)
35 {
36 char oinsn[33], ninsn[33];
37 unsigned long kptr;
38 unsigned int pos;
39
40 for (pos = 0; pos < len && 2 * pos < sizeof(oinsn) - 3; pos++)
41 hex_byte_pack(&oinsn[2 * pos], old[pos]);
42 oinsn[2 * pos] = 0;
43 for (pos = 0; pos < len && 2 * pos < sizeof(ninsn) - 3; pos++)
44 hex_byte_pack(&ninsn[2 * pos], new[pos]);
45 ninsn[2 * pos] = 0;
46 kptr = (unsigned long)__kernel_va(old);
47 a_debug("[%d/%3d] %016lx: %s -> %s\n", type, data, kptr, oinsn, ninsn);
48 }
49
__apply_alternatives(struct alt_instr * start,struct alt_instr * end,unsigned int ctx)50 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
51 {
52 struct alt_debug *d;
53 struct alt_instr *a;
54 bool debug, replace;
55 u8 *old, *new;
56
57 /*
58 * The scan order should be from start to end. A later scanned
59 * alternative code can overwrite previously scanned alternative code.
60 */
61 d = &alt_debug;
62 for (a = start; a < end; a++) {
63 if (!(a->ctx & ctx))
64 continue;
65 switch (a->type) {
66 case ALT_TYPE_FACILITY:
67 replace = test_facility(a->data);
68 debug = __test_facility(a->data, d->facilities);
69 break;
70 case ALT_TYPE_FEATURE:
71 replace = test_machine_feature(a->data);
72 debug = __test_machine_feature(a->data, d->mfeatures);
73 break;
74 case ALT_TYPE_SPEC:
75 replace = nobp_enabled();
76 debug = d->spec;
77 break;
78 default:
79 replace = false;
80 debug = false;
81 }
82 if (!replace)
83 continue;
84 old = (u8 *)&a->instr_offset + a->instr_offset;
85 new = (u8 *)&a->repl_offset + a->repl_offset;
86 if (debug)
87 alternative_dump(old, new, a->instrlen, a->type, a->data);
88 s390_kernel_write(old, new, a->instrlen);
89 }
90 }
91