1 // SPDX-License-Identifier: GPL-2.0
2
3 #include <linux/uaccess.h>
4 #include <asm/nospec-branch.h>
5 #include <asm/abs_lowcore.h>
6 #include <asm/alternative.h>
7 #include <asm/facility.h>
8
9 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
10 {
11 u8 *instr, *replacement;
12 struct alt_instr *a;
13 bool replace;
14
15 /*
16 * The scan order should be from start to end. A later scanned
17 * alternative code can overwrite previously scanned alternative code.
18 */
19 for (a = start; a < end; a++) {
20 if (!(a->ctx & ctx))
21 continue;
22 switch (a->type) {
23 case ALT_TYPE_FACILITY:
24 replace = test_facility(a->data);
25 break;
26 case ALT_TYPE_SPEC:
27 replace = nobp_enabled();
28 break;
29 case ALT_TYPE_LOWCORE:
30 replace = have_relocated_lowcore();
31 break;
32 default:
33 replace = false;
34 }
35 if (!replace)
36 continue;
37 instr = (u8 *)&a->instr_offset + a->instr_offset;
38 replacement = (u8 *)&a->repl_offset + a->repl_offset;
39 s390_kernel_write(instr, replacement, a->instrlen);
40 }
41 }
42
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