1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/module.h>
3 #include <linux/cpu.h>
4 #include <linux/smp.h>
5 #include <asm/text-patching.h>
6 #include <asm/alternative.h>
7 #include <asm/facility.h>
8 #include <asm/nospec-branch.h>
9
10 #define MAX_PATCH_LEN (255 - 1)
11
12 static int __initdata_or_module alt_instr_disabled;
13
disable_alternative_instructions(char * str)14 static int __init disable_alternative_instructions(char *str)
15 {
16 alt_instr_disabled = 1;
17 return 0;
18 }
19
20 early_param("noaltinstr", disable_alternative_instructions);
21
22 struct brcl_insn {
23 u16 opc;
24 s32 disp;
25 } __packed;
26
27 static u16 __initdata_or_module nop16 = 0x0700;
28 static u32 __initdata_or_module nop32 = 0x47000000;
29 static struct brcl_insn __initdata_or_module nop48 = {
30 0xc004, 0
31 };
32
33 static const void *nops[] __initdata_or_module = {
34 &nop16,
35 &nop32,
36 &nop48
37 };
38
add_jump_padding(void * insns,unsigned int len)39 static void __init_or_module add_jump_padding(void *insns, unsigned int len)
40 {
41 struct brcl_insn brcl = {
42 0xc0f4,
43 len / 2
44 };
45
46 memcpy(insns, &brcl, sizeof(brcl));
47 insns += sizeof(brcl);
48 len -= sizeof(brcl);
49
50 while (len > 0) {
51 memcpy(insns, &nop16, 2);
52 insns += 2;
53 len -= 2;
54 }
55 }
56
add_padding(void * insns,unsigned int len)57 static void __init_or_module add_padding(void *insns, unsigned int len)
58 {
59 if (len > 6)
60 add_jump_padding(insns, len);
61 else if (len >= 2)
62 memcpy(insns, nops[len / 2 - 1], len);
63 }
64
__apply_alternatives(struct alt_instr * start,struct alt_instr * end)65 static void __init_or_module __apply_alternatives(struct alt_instr *start,
66 struct alt_instr *end)
67 {
68 struct alt_instr *a;
69 u8 *instr, *replacement;
70 u8 insnbuf[MAX_PATCH_LEN];
71
72 /*
73 * The scan order should be from start to end. A later scanned
74 * alternative code can overwrite previously scanned alternative code.
75 */
76 for (a = start; a < end; a++) {
77 int insnbuf_sz = 0;
78
79 instr = (u8 *)&a->instr_offset + a->instr_offset;
80 replacement = (u8 *)&a->repl_offset + a->repl_offset;
81
82 if (!__test_facility(a->facility, alt_stfle_fac_list))
83 continue;
84
85 if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
86 WARN_ONCE(1, "cpu alternatives instructions length is "
87 "odd, skipping patching\n");
88 continue;
89 }
90
91 memcpy(insnbuf, replacement, a->replacementlen);
92 insnbuf_sz = a->replacementlen;
93
94 if (a->instrlen > a->replacementlen) {
95 add_padding(insnbuf + a->replacementlen,
96 a->instrlen - a->replacementlen);
97 insnbuf_sz += a->instrlen - a->replacementlen;
98 }
99
100 s390_kernel_write(instr, insnbuf, insnbuf_sz);
101 }
102 }
103
apply_alternatives(struct alt_instr * start,struct alt_instr * end)104 void __init_or_module apply_alternatives(struct alt_instr *start,
105 struct alt_instr *end)
106 {
107 if (!alt_instr_disabled)
108 __apply_alternatives(start, end);
109 }
110
111 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
apply_alternative_instructions(void)112 void __init apply_alternative_instructions(void)
113 {
114 apply_alternatives(__alt_instructions, __alt_instructions_end);
115 }
116
do_sync_core(void * info)117 static void do_sync_core(void *info)
118 {
119 sync_core();
120 }
121
text_poke_sync(void)122 void text_poke_sync(void)
123 {
124 on_each_cpu(do_sync_core, NULL, 1);
125 }
126
text_poke_sync_lock(void)127 void text_poke_sync_lock(void)
128 {
129 cpus_read_lock();
130 text_poke_sync();
131 cpus_read_unlock();
132 }
133