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
13static 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
21void 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