xref: /openbmc/linux/arch/xtensa/kernel/jump_label.c (revision 91335ca9)
1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (C) 2018 Cadence Design Systems Inc.
3 
4 #include <linux/cpu.h>
5 #include <linux/jump_label.h>
6 #include <linux/kernel.h>
7 #include <linux/memory.h>
8 #include <linux/stop_machine.h>
9 #include <linux/types.h>
10 
11 #include <asm/cacheflush.h>
12 
13 #define J_OFFSET_MASK 0x0003ffff
14 #define J_SIGN_MASK (~(J_OFFSET_MASK >> 1))
15 
16 #if defined(__XTENSA_EL__)
17 #define J_INSN 0x6
18 #define NOP_INSN 0x0020f0
19 #elif defined(__XTENSA_EB__)
20 #define J_INSN 0x60000000
21 #define NOP_INSN 0x0f020000
22 #else
23 #error Unsupported endianness.
24 #endif
25 
26 struct patch {
27 	atomic_t cpu_count;
28 	unsigned long addr;
29 	size_t sz;
30 	const void *data;
31 };
32 
local_patch_text(unsigned long addr,const void * data,size_t sz)33 static void local_patch_text(unsigned long addr, const void *data, size_t sz)
34 {
35 	memcpy((void *)addr, data, sz);
36 	local_flush_icache_range(addr, addr + sz);
37 }
38 
patch_text_stop_machine(void * data)39 static int patch_text_stop_machine(void *data)
40 {
41 	struct patch *patch = data;
42 
43 	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
44 		local_patch_text(patch->addr, patch->data, patch->sz);
45 		atomic_inc(&patch->cpu_count);
46 	} else {
47 		while (atomic_read(&patch->cpu_count) <= num_online_cpus())
48 			cpu_relax();
49 		__invalidate_icache_range(patch->addr, patch->sz);
50 	}
51 	return 0;
52 }
53 
patch_text(unsigned long addr,const void * data,size_t sz)54 static void patch_text(unsigned long addr, const void *data, size_t sz)
55 {
56 	if (IS_ENABLED(CONFIG_SMP)) {
57 		struct patch patch = {
58 			.cpu_count = ATOMIC_INIT(0),
59 			.addr = addr,
60 			.sz = sz,
61 			.data = data,
62 		};
63 		stop_machine_cpuslocked(patch_text_stop_machine,
64 					&patch, cpu_online_mask);
65 	} else {
66 		unsigned long flags;
67 
68 		local_irq_save(flags);
69 		local_patch_text(addr, data, sz);
70 		local_irq_restore(flags);
71 	}
72 }
73 
arch_jump_label_transform(struct jump_entry * e,enum jump_label_type type)74 void arch_jump_label_transform(struct jump_entry *e,
75 			       enum jump_label_type type)
76 {
77 	u32 d = (jump_entry_target(e) - (jump_entry_code(e) + 4));
78 	u32 insn;
79 
80 	/* Jump only works within 128K of the J instruction. */
81 	BUG_ON(!((d & J_SIGN_MASK) == 0 ||
82 		 (d & J_SIGN_MASK) == J_SIGN_MASK));
83 
84 	if (type == JUMP_LABEL_JMP) {
85 #if defined(__XTENSA_EL__)
86 		insn = ((d & J_OFFSET_MASK) << 6) | J_INSN;
87 #elif defined(__XTENSA_EB__)
88 		insn = ((d & J_OFFSET_MASK) << 8) | J_INSN;
89 #endif
90 	} else {
91 		insn = NOP_INSN;
92 	}
93 
94 	patch_text(jump_entry_code(e), &insn, JUMP_LABEL_NOP_SIZE);
95 }
96