1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* Copyright (C) 2018 Cadence Design Systems Inc. */
3 
4 #ifndef _ASM_XTENSA_JUMP_LABEL_H
5 #define _ASM_XTENSA_JUMP_LABEL_H
6 
7 #ifndef __ASSEMBLY__
8 
9 #include <linux/types.h>
10 
11 #define JUMP_LABEL_NOP_SIZE 3
12 
13 static __always_inline bool arch_static_branch(struct static_key *key,
14 					       bool branch)
15 {
16 	asm_volatile_goto("1:\n\t"
17 			  "_nop\n\t"
18 			  ".pushsection __jump_table,  \"aw\"\n\t"
19 			  ".word 1b, %l[l_yes], %c0\n\t"
20 			  ".popsection\n\t"
21 			  : :  "i" (&((char *)key)[branch]) :  : l_yes);
22 
23 	return false;
24 l_yes:
25 	return true;
26 }
27 
28 static __always_inline bool arch_static_branch_jump(struct static_key *key,
29 						    bool branch)
30 {
31 	/*
32 	 * Xtensa assembler will mark certain points in the code
33 	 * as unreachable, so that later assembler or linker relaxation
34 	 * passes could use them. A spot right after the J instruction
35 	 * is one such point. Assembler and/or linker may insert padding
36 	 * or literals here, breaking code flow in case the J instruction
37 	 * is later replaced with NOP. Put a label right after the J to
38 	 * make it reachable and wrap both into a no-transform block
39 	 * to avoid any assembler interference with this.
40 	 */
41 	asm_volatile_goto("1:\n\t"
42 			  ".begin no-transform\n\t"
43 			  "_j %l[l_yes]\n\t"
44 			  "2:\n\t"
45 			  ".end no-transform\n\t"
46 			  ".pushsection __jump_table,  \"aw\"\n\t"
47 			  ".word 1b, %l[l_yes], %c0\n\t"
48 			  ".popsection\n\t"
49 			  : :  "i" (&((char *)key)[branch]) :  : l_yes);
50 
51 	return false;
52 l_yes:
53 	return true;
54 }
55 
56 typedef u32 jump_label_t;
57 
58 struct jump_entry {
59 	jump_label_t code;
60 	jump_label_t target;
61 	jump_label_t key;
62 };
63 
64 #endif  /* __ASSEMBLY__ */
65 #endif
66