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
 9void __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}