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  
__apply_alternatives(struct alt_instr * start,struct alt_instr * end,unsigned int ctx)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