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819e50e2 AT |
1 | /* |
2 | * arch/arm64/kernel/ftrace.c | |
3 | * | |
4 | * Copyright (C) 2013 Linaro Limited | |
5 | * Author: AKASHI Takahiro <takahiro.akashi@linaro.org> | |
6 | * | |
7 | * This program is free software; you can redistribute it and/or modify | |
8 | * it under the terms of the GNU General Public License version 2 as | |
9 | * published by the Free Software Foundation. | |
10 | */ | |
11 | ||
12 | #include <linux/ftrace.h> | |
13 | #include <linux/swab.h> | |
14 | #include <linux/uaccess.h> | |
15 | ||
16 | #include <asm/cacheflush.h> | |
17 | #include <asm/ftrace.h> | |
18 | #include <asm/insn.h> | |
19 | ||
bd7d38db AT |
20 | #ifdef CONFIG_DYNAMIC_FTRACE |
21 | /* | |
22 | * Replace a single instruction, which may be a branch or NOP. | |
23 | * If @validate == true, a replaced instruction is checked against 'old'. | |
24 | */ | |
25 | static int ftrace_modify_code(unsigned long pc, u32 old, u32 new, | |
26 | bool validate) | |
27 | { | |
28 | u32 replaced; | |
29 | ||
30 | /* | |
31 | * Note: | |
004ab584 LB |
32 | * We are paranoid about modifying text, as if a bug were to happen, it |
33 | * could cause us to read or write to someplace that could cause harm. | |
34 | * Carefully read and modify the code with aarch64_insn_*() which uses | |
35 | * probe_kernel_*(), and make sure what we read is what we expected it | |
36 | * to be before modifying it. | |
bd7d38db AT |
37 | */ |
38 | if (validate) { | |
39 | if (aarch64_insn_read((void *)pc, &replaced)) | |
40 | return -EFAULT; | |
41 | ||
42 | if (replaced != old) | |
43 | return -EINVAL; | |
44 | } | |
45 | if (aarch64_insn_patch_text_nosync((void *)pc, new)) | |
46 | return -EPERM; | |
47 | ||
48 | return 0; | |
49 | } | |
50 | ||
51 | /* | |
52 | * Replace tracer function in ftrace_caller() | |
53 | */ | |
54 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
55 | { | |
56 | unsigned long pc; | |
57 | u32 new; | |
58 | ||
59 | pc = (unsigned long)&ftrace_call; | |
9f1ae759 CM |
60 | new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func, |
61 | AARCH64_INSN_BRANCH_LINK); | |
bd7d38db AT |
62 | |
63 | return ftrace_modify_code(pc, 0, new, false); | |
64 | } | |
65 | ||
66 | /* | |
67 | * Turn on the call to ftrace_caller() in instrumented function | |
68 | */ | |
69 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
70 | { | |
71 | unsigned long pc = rec->ip; | |
72 | u32 old, new; | |
73 | ||
74 | old = aarch64_insn_gen_nop(); | |
9f1ae759 | 75 | new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); |
bd7d38db AT |
76 | |
77 | return ftrace_modify_code(pc, old, new, true); | |
78 | } | |
79 | ||
80 | /* | |
81 | * Turn off the call to ftrace_caller() in instrumented function | |
82 | */ | |
83 | int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, | |
84 | unsigned long addr) | |
85 | { | |
86 | unsigned long pc = rec->ip; | |
87 | u32 old, new; | |
88 | ||
9f1ae759 | 89 | old = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK); |
bd7d38db AT |
90 | new = aarch64_insn_gen_nop(); |
91 | ||
92 | return ftrace_modify_code(pc, old, new, true); | |
93 | } | |
94 | ||
81a6a146 LB |
95 | void arch_ftrace_update_code(int command) |
96 | { | |
97 | ftrace_modify_all_code(command); | |
98 | } | |
99 | ||
bd7d38db AT |
100 | int __init ftrace_dyn_arch_init(void) |
101 | { | |
102 | return 0; | |
103 | } | |
104 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
105 | ||
819e50e2 AT |
106 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
107 | /* | |
108 | * function_graph tracer expects ftrace_return_to_handler() to be called | |
109 | * on the way back to parent. For this purpose, this function is called | |
110 | * in _mcount() or ftrace_caller() to replace return address (*parent) on | |
111 | * the call stack to return_to_handler. | |
112 | * | |
113 | * Note that @frame_pointer is used only for sanity check later. | |
114 | */ | |
115 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, | |
116 | unsigned long frame_pointer) | |
117 | { | |
118 | unsigned long return_hooker = (unsigned long)&return_to_handler; | |
119 | unsigned long old; | |
120 | struct ftrace_graph_ent trace; | |
121 | int err; | |
122 | ||
123 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) | |
124 | return; | |
125 | ||
126 | /* | |
127 | * Note: | |
128 | * No protection against faulting at *parent, which may be seen | |
129 | * on other archs. It's unlikely on AArch64. | |
130 | */ | |
131 | old = *parent; | |
132 | *parent = return_hooker; | |
133 | ||
134 | trace.func = self_addr; | |
135 | trace.depth = current->curr_ret_stack + 1; | |
136 | ||
137 | /* Only trace if the calling function expects to */ | |
138 | if (!ftrace_graph_entry(&trace)) { | |
139 | *parent = old; | |
140 | return; | |
141 | } | |
142 | ||
143 | err = ftrace_push_return_trace(old, self_addr, &trace.depth, | |
144 | frame_pointer); | |
145 | if (err == -EBUSY) { | |
146 | *parent = old; | |
147 | return; | |
148 | } | |
149 | } | |
bd7d38db AT |
150 | |
151 | #ifdef CONFIG_DYNAMIC_FTRACE | |
152 | /* | |
153 | * Turn on/off the call to ftrace_graph_caller() in ftrace_caller() | |
154 | * depending on @enable. | |
155 | */ | |
156 | static int ftrace_modify_graph_caller(bool enable) | |
157 | { | |
158 | unsigned long pc = (unsigned long)&ftrace_graph_call; | |
159 | u32 branch, nop; | |
160 | ||
161 | branch = aarch64_insn_gen_branch_imm(pc, | |
9f1ae759 | 162 | (unsigned long)ftrace_graph_caller, |
d0d62230 | 163 | AARCH64_INSN_BRANCH_NOLINK); |
bd7d38db AT |
164 | nop = aarch64_insn_gen_nop(); |
165 | ||
166 | if (enable) | |
167 | return ftrace_modify_code(pc, nop, branch, true); | |
168 | else | |
169 | return ftrace_modify_code(pc, branch, nop, true); | |
170 | } | |
171 | ||
172 | int ftrace_enable_ftrace_graph_caller(void) | |
173 | { | |
174 | return ftrace_modify_graph_caller(true); | |
175 | } | |
176 | ||
177 | int ftrace_disable_ftrace_graph_caller(void) | |
178 | { | |
179 | return ftrace_modify_graph_caller(false); | |
180 | } | |
181 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
819e50e2 | 182 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |