xref: /openbmc/linux/arch/arm/kernel/patch.c (revision 82e6fdd6)
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 static DEFINE_SPINLOCK(patch_lock);
20 
21 static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
22 	__acquires(&patch_lock)
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 		spin_lock_irqsave(&patch_lock, *flags);
37 	else
38 		__acquire(&patch_lock);
39 
40 	set_fixmap(fixmap, page_to_phys(page));
41 
42 	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
43 }
44 
45 static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
46 	__releases(&patch_lock)
47 {
48 	clear_fixmap(fixmap);
49 
50 	if (flags)
51 		spin_unlock_irqrestore(&patch_lock, *flags);
52 	else
53 		__release(&patch_lock);
54 }
55 
56 void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
57 {
58 	bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
59 	unsigned int uintaddr = (uintptr_t) addr;
60 	bool twopage = false;
61 	unsigned long flags;
62 	void *waddr = addr;
63 	int size;
64 
65 	if (remap)
66 		waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);
67 	else
68 		__acquire(&patch_lock);
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 	} else
106 		__release(&patch_lock);
107 
108 	flush_icache_range((uintptr_t)(addr),
109 			   (uintptr_t)(addr) + size);
110 }
111 
112 static int __kprobes patch_text_stop_machine(void *data)
113 {
114 	struct patch *patch = data;
115 
116 	__patch_text(patch->addr, patch->insn);
117 
118 	return 0;
119 }
120 
121 void __kprobes patch_text(void *addr, unsigned int insn)
122 {
123 	struct patch patch = {
124 		.addr = addr,
125 		.insn = insn,
126 	};
127 
128 	stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
129 }
130