1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2019 Helge Deller <deller@gmx.de>
4 *
5 * Based on arch/arm64/kernel/jump_label.c
6 */
7 #include <linux/kernel.h>
8 #include <linux/jump_label.h>
9 #include <linux/bug.h>
10 #include <asm/alternative.h>
11 #include <asm/patch.h>
12
13 static inline int reassemble_17(int as17)
14 {
15 return (((as17 & 0x10000) >> 16) |
16 ((as17 & 0x0f800) << 5) |
17 ((as17 & 0x00400) >> 8) |
18 ((as17 & 0x003ff) << 3));
19 }
20
21 void arch_jump_label_transform(struct jump_entry *entry,
22 enum jump_label_type type)
23 {
24 void *addr = (void *)jump_entry_code(entry);
25 u32 insn;
26
27 if (type == JUMP_LABEL_JMP) {
28 void *target = (void *)jump_entry_target(entry);
29 int distance = target - addr;
30 /*
31 * Encode the PA1.1 "b,n" instruction with a 17-bit
32 * displacement. In case we hit the BUG(), we could use
33 * another branch instruction with a 22-bit displacement on
34 * 64-bit CPUs instead. But this seems sufficient for now.
35 */
36 distance -= 8;
37 BUG_ON(distance > 262143 || distance < -262144);
38 insn = 0xe8000002 | reassemble_17(distance >> 2);
39 } else {
40 insn = INSN_NOP;
41 }
42
43 patch_text(addr, insn);
44 }
45
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