1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/spinlock.h>
4 #include <linux/kprobes.h>
5 #include <linux/mm.h>
6 #include <linux/stop_machine.h>
7 
8 #include <asm/cacheflush.h>
9 #include <asm/fixmap.h>
10 #include <asm/smp_plat.h>
11 #include <asm/opcodes.h>
12 #include <asm/patch.h>
13 
14 struct patch {
15 	void *addr;
16 	unsigned int insn;
17 };
18 
19 #ifdef CONFIG_MMU
20 static DEFINE_RAW_SPINLOCK(patch_lock);
21 
patch_map(void * addr,int fixmap,unsigned long * flags)22 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
23 {
24 	unsigned int uintaddr = (uintptr_t) addr;
25 	bool module = !core_kernel_text(uintaddr);
26 	struct page *page;
27 
28 	if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
29 		page = vmalloc_to_page(addr);
30 	else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
31 		page = virt_to_page(addr);
32 	else
33 		return addr;
34 
35 	if (flags)
36 		raw_spin_lock_irqsave(&patch_lock, *flags);
37 
38 	set_fixmap(fixmap, page_to_phys(page));
39 
40 	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
41 }
42 
patch_unmap(int fixmap,unsigned long * flags)43 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
44 {
45 	clear_fixmap(fixmap);
46 
47 	if (flags)
48 		raw_spin_unlock_irqrestore(&patch_lock, *flags);
49 }
50 #else
patch_map(void * addr,int fixmap,unsigned long * flags)51 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
52 {
53 	return addr;
54 }
patch_unmap(int fixmap,unsigned long * flags)55 static void __kprobes patch_unmap(int fixmap, unsigned long *flags) { }
56 #endif
57 
__patch_text_real(void * addr,unsigned int insn,bool remap)58 void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
59 {
60 	bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
61 	unsigned int uintaddr = (uintptr_t) addr;
62 	bool twopage = false;
63 	unsigned long flags;
64 	void *waddr = addr;
65 	int size;
66 
67 	if (remap)
68 		waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
69 
70 	if (thumb2 && __opcode_is_thumb16(insn)) {
71 		*(u16 *)waddr = __opcode_to_mem_thumb16(insn);
72 		size = sizeof(u16);
73 	} else if (thumb2 && (uintaddr & 2)) {
74 		u16 first = __opcode_thumb32_first(insn);
75 		u16 second = __opcode_thumb32_second(insn);
76 		u16 *addrh0 = waddr;
77 		u16 *addrh1 = waddr + 2;
78 
79 		twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
80 		if (twopage && remap)
81 			addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);
82 
83 		*addrh0 = __opcode_to_mem_thumb16(first);
84 		*addrh1 = __opcode_to_mem_thumb16(second);
85 
86 		if (twopage && addrh1 != addr + 2) {
87 			flush_kernel_vmap_range(addrh1, 2);
88 			patch_unmap(FIX_TEXT_POKE1, NULL);
89 		}
90 
91 		size = sizeof(u32);
92 	} else {
93 		if (thumb2)
94 			insn = __opcode_to_mem_thumb32(insn);
95 		else
96 			insn = __opcode_to_mem_arm(insn);
97 
98 		*(u32 *)waddr = insn;
99 		size = sizeof(u32);
100 	}
101 
102 	if (waddr != addr) {
103 		flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
104 		patch_unmap(FIX_TEXT_POKE0, &flags);
105 	}
106 
107 	flush_icache_range((uintptr_t)(addr),
108 			   (uintptr_t)(addr) + size);
109 }
110 
patch_text_stop_machine(void * data)111 static int __kprobes patch_text_stop_machine(void *data)
112 {
113 	struct patch *patch = data;
114 
115 	__patch_text(patch->addr, patch->insn);
116 
117 	return 0;
118 }
119 
patch_text(void * addr,unsigned int insn)120 void __kprobes patch_text(void *addr, unsigned int insn)
121 {
122 	struct patch patch = {
123 		.addr = addr,
124 		.insn = insn,
125 	};
126 
127 	stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
128 }
129