x86/speculation/mds: Fix documentation typo
[linux/fpc-iii.git] / arch / s390 / kernel / alternative.c
blobb57b293998dc8442fc233c9ead5651004296aef1
1 #include <linux/module.h>
2 #include <asm/alternative.h>
3 #include <asm/facility.h>
4 #include <asm/nospec-branch.h>
6 #define MAX_PATCH_LEN (255 - 1)
8 static int __initdata_or_module alt_instr_disabled;
10 static int __init disable_alternative_instructions(char *str)
12 alt_instr_disabled = 1;
13 return 0;
16 early_param("noaltinstr", disable_alternative_instructions);
18 struct brcl_insn {
19 u16 opc;
20 s32 disp;
21 } __packed;
23 static u16 __initdata_or_module nop16 = 0x0700;
24 static u32 __initdata_or_module nop32 = 0x47000000;
25 static struct brcl_insn __initdata_or_module nop48 = {
26 0xc004, 0
29 static const void *nops[] __initdata_or_module = {
30 &nop16,
31 &nop32,
32 &nop48
35 static void __init_or_module add_jump_padding(void *insns, unsigned int len)
37 struct brcl_insn brcl = {
38 0xc0f4,
39 len / 2
42 memcpy(insns, &brcl, sizeof(brcl));
43 insns += sizeof(brcl);
44 len -= sizeof(brcl);
46 while (len > 0) {
47 memcpy(insns, &nop16, 2);
48 insns += 2;
49 len -= 2;
53 static void __init_or_module add_padding(void *insns, unsigned int len)
55 if (len > 6)
56 add_jump_padding(insns, len);
57 else if (len >= 2)
58 memcpy(insns, nops[len / 2 - 1], len);
61 static void __init_or_module __apply_alternatives(struct alt_instr *start,
62 struct alt_instr *end)
64 struct alt_instr *a;
65 u8 *instr, *replacement;
66 u8 insnbuf[MAX_PATCH_LEN];
69 * The scan order should be from start to end. A later scanned
70 * alternative code can overwrite previously scanned alternative code.
72 for (a = start; a < end; a++) {
73 int insnbuf_sz = 0;
75 instr = (u8 *)&a->instr_offset + a->instr_offset;
76 replacement = (u8 *)&a->repl_offset + a->repl_offset;
78 if (!__test_facility(a->facility,
79 S390_lowcore.alt_stfle_fac_list))
80 continue;
82 if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
83 WARN_ONCE(1, "cpu alternatives instructions length is "
84 "odd, skipping patching\n");
85 continue;
88 memcpy(insnbuf, replacement, a->replacementlen);
89 insnbuf_sz = a->replacementlen;
91 if (a->instrlen > a->replacementlen) {
92 add_padding(insnbuf + a->replacementlen,
93 a->instrlen - a->replacementlen);
94 insnbuf_sz += a->instrlen - a->replacementlen;
97 s390_kernel_write(instr, insnbuf, insnbuf_sz);
101 void __init_or_module apply_alternatives(struct alt_instr *start,
102 struct alt_instr *end)
104 if (!alt_instr_disabled)
105 __apply_alternatives(start, end);
108 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
109 void __init apply_alternative_instructions(void)
111 apply_alternatives(__alt_instructions, __alt_instructions_end);