tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
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
13static __always_inline bool arch_static_branch(struct static_key *key,
14 bool branch)
15{
16 asm 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;
24l_yes:
25 return true;
26}
27
28static __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 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;
52l_yes:
53 return true;
54}
55
56typedef u32 jump_label_t;
57
58struct jump_entry {
59 jump_label_t code;
60 jump_label_t target;
61 jump_label_t key;
62};
63
64#endif /* __ASSEMBLY__ */
65#endif