xref: /linux/arch/riscv/kernel/jump_label.c (revision 8e1bb4a41aa78d6105e59186af3dcd545fc66e70)
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/cacheflush.h>
13 #include <asm/patch.h>
14 
15 #define RISCV_INSN_NOP 0x00000013U
16 #define RISCV_INSN_JAL 0x0000006fU
17 
18 bool arch_jump_label_transform_queue(struct jump_entry *entry,
19 				     enum jump_label_type type)
20 {
21 	void *addr = (void *)jump_entry_code(entry);
22 	u32 insn;
23 
24 	if (type == JUMP_LABEL_JMP) {
25 		long offset = jump_entry_target(entry) - jump_entry_code(entry);
26 
27 		if (WARN_ON(offset & 1 || offset < -524288 || offset >= 524288))
28 			return true;
29 
30 		insn = RISCV_INSN_JAL |
31 			(((u32)offset & GENMASK(19, 12)) << (12 - 12)) |
32 			(((u32)offset & GENMASK(11, 11)) << (20 - 11)) |
33 			(((u32)offset & GENMASK(10,  1)) << (21 -  1)) |
34 			(((u32)offset & GENMASK(20, 20)) << (31 - 20));
35 	} else {
36 		insn = RISCV_INSN_NOP;
37 	}
38 
39 	mutex_lock(&text_mutex);
40 	patch_insn_write(addr, &insn, sizeof(insn));
41 	mutex_unlock(&text_mutex);
42 
43 	return true;
44 }
45 
46 void arch_jump_label_transform_apply(void)
47 {
48 	flush_icache_all();
49 }
50