1// SPDX-License-Identifier: GPL-2.0-only
2/* Copyright (C) 2020 SiFive
3 * Copyright (C) 2025 Chen Miao
4 */
5
6#include <linux/mm.h>
7#include <linux/kernel.h>
8#include <linux/spinlock.h>
9#include <linux/uaccess.h>
10
11#include <asm/insn-def.h>
12#include <asm/cacheflush.h>
13#include <asm/page.h>
14#include <asm/fixmap.h>
15#include <asm/text-patching.h>
16#include <asm/sections.h>
17
18static DEFINE_RAW_SPINLOCK(patch_lock);
19
20static __always_inline void *patch_map(void *addr, int fixmap)
21{
22 uintptr_t uaddr = (uintptr_t) addr;
23 phys_addr_t phys;
24
25 if (core_kernel_text(addr: uaddr)) {
26 phys = __pa_symbol(addr);
27 } else {
28 struct page *page = vmalloc_to_page(addr);
29 BUG_ON(!page);
30 phys = page_to_phys(page) + offset_in_page(addr);
31 }
32
33 return (void *)set_fixmap_offset(fixmap, phys);
34}
35
36static void patch_unmap(int fixmap)
37{
38 clear_fixmap(fixmap);
39}
40
41static int __patch_insn_write(void *addr, u32 insn)
42{
43 void *waddr = addr;
44 unsigned long flags = 0;
45 int ret;
46
47 raw_spin_lock_irqsave(&patch_lock, flags);
48
49 waddr = patch_map(addr, fixmap: FIX_TEXT_POKE0);
50
51 ret = copy_to_kernel_nofault(dst: waddr, src: &insn, size: OPENRISC_INSN_SIZE);
52 local_icache_range_inv((unsigned long)waddr,
53 (unsigned long)waddr + OPENRISC_INSN_SIZE);
54
55 patch_unmap(fixmap: FIX_TEXT_POKE0);
56
57 raw_spin_unlock_irqrestore(&patch_lock, flags);
58
59 return ret;
60}
61
62/*
63 * patch_insn_write - Write a single instruction to a specified memory location
64 * This API provides a single-instruction patching, primarily used for runtime
65 * code modification.
66 * By the way, the insn size must be 4 bytes.
67 */
68int patch_insn_write(void *addr, u32 insn)
69{
70 u32 *tp = addr;
71 int ret;
72
73 if ((uintptr_t) tp & 0x3)
74 return -EINVAL;
75
76 ret = __patch_insn_write(addr: tp, insn);
77
78 return ret;
79}
80

source code of linux/arch/openrisc/kernel/patching.c