1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2020 Emil Renner Berthing
4 *
5 * Based on arch/arm64/kernel/jump_label.c
6 */
7 #include <linux/jump_label.h>
8 #include <linux/kernel.h>
9 #include <linux/memory.h>
10 #include <linux/mutex.h>
11 #include <asm/bug.h>
12 #include <asm/patch.h>
13
14 #define RISCV_INSN_NOP 0x00000013U
15 #define RISCV_INSN_JAL 0x0000006fU
16
arch_jump_label_transform(struct jump_entry * entry,enum jump_label_type type)17 void arch_jump_label_transform(struct jump_entry *entry,
18 enum jump_label_type type)
19 {
20 void *addr = (void *)jump_entry_code(entry);
21 u32 insn;
22
23 if (type == JUMP_LABEL_JMP) {
24 long offset = jump_entry_target(entry) - jump_entry_code(entry);
25
26 if (WARN_ON(offset & 1 || offset < -524288 || offset >= 524288))
27 return;
28
29 insn = RISCV_INSN_JAL |
30 (((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
31 (((u32)offset & GENMASK(11, 11)) << (20 - 11)) |
32 (((u32)offset & GENMASK(10, 1)) << (21 - 1)) |
33 (((u32)offset & GENMASK(20, 20)) << (31 - 20));
34 } else {
35 insn = RISCV_INSN_NOP;
36 }
37
38 mutex_lock(&text_mutex);
39 patch_text_nosync(addr, &insn, sizeof(insn));
40 mutex_unlock(&text_mutex);
41 }
42
arch_jump_label_transform_static(struct jump_entry * entry,enum jump_label_type type)43 void arch_jump_label_transform_static(struct jump_entry *entry,
44 enum jump_label_type type)
45 {
46 /*
47 * We use the same instructions in the arch_static_branch and
48 * arch_static_branch_jump inline functions, so there's no
49 * need to patch them up here.
50 * The core will call arch_jump_label_transform when those
51 * instructions need to be replaced.
52 */
53 }
54