Commit | Line | Data |
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014c257c AS |
1 | /* |
2 | * Dynamic function tracing support. | |
3 | * | |
4 | * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com> | |
3b6c223b | 5 | * Copyright (C) 2010 Rabin Vincent <rabin@rab.in> |
014c257c AS |
6 | * |
7 | * For licencing details, see COPYING. | |
8 | * | |
9 | * Defines low-level handling of mcount calls when the kernel | |
10 | * is compiled with the -pg flag. When using dynamic ftrace, the | |
3b6c223b RV |
11 | * mcount call-sites get patched with NOP till they are enabled. |
12 | * All code mutation routines here are called under stop_machine(). | |
014c257c AS |
13 | */ |
14 | ||
15 | #include <linux/ftrace.h> | |
3b6c223b | 16 | #include <linux/uaccess.h> |
395a59d0 | 17 | |
014c257c | 18 | #include <asm/cacheflush.h> |
395a59d0 | 19 | #include <asm/ftrace.h> |
014c257c | 20 | |
72dc43a9 RV |
21 | #ifdef CONFIG_THUMB2_KERNEL |
22 | #define NOP 0xeb04f85d /* pop.w {lr} */ | |
23 | #else | |
3b6c223b | 24 | #define NOP 0xe8bd4000 /* pop {lr} */ |
72dc43a9 | 25 | #endif |
014c257c | 26 | |
376cfa87 | 27 | #ifdef CONFIG_DYNAMIC_FTRACE |
3b6c223b RV |
28 | #ifdef CONFIG_OLD_MCOUNT |
29 | #define OLD_MCOUNT_ADDR ((unsigned long) mcount) | |
30 | #define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old) | |
014c257c | 31 | |
3b6c223b RV |
32 | #define OLD_NOP 0xe1a00000 /* mov r0, r0 */ |
33 | ||
34 | static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) | |
35 | { | |
36 | return rec->arch.old_mcount ? OLD_NOP : NOP; | |
37 | } | |
38 | ||
39 | static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) | |
40 | { | |
41 | if (!rec->arch.old_mcount) | |
42 | return addr; | |
43 | ||
44 | if (addr == MCOUNT_ADDR) | |
45 | addr = OLD_MCOUNT_ADDR; | |
46 | else if (addr == FTRACE_ADDR) | |
47 | addr = OLD_FTRACE_ADDR; | |
48 | ||
49 | return addr; | |
50 | } | |
51 | #else | |
52 | static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec) | |
53 | { | |
54 | return NOP; | |
55 | } | |
56 | ||
57 | static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr) | |
014c257c | 58 | { |
3b6c223b | 59 | return addr; |
014c257c | 60 | } |
3b6c223b | 61 | #endif |
014c257c | 62 | |
72dc43a9 | 63 | #ifdef CONFIG_THUMB2_KERNEL |
dd686eb1 RV |
64 | static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr, |
65 | bool link) | |
72dc43a9 RV |
66 | { |
67 | unsigned long s, j1, j2, i1, i2, imm10, imm11; | |
68 | unsigned long first, second; | |
69 | long offset; | |
70 | ||
71 | offset = (long)addr - (long)(pc + 4); | |
72 | if (offset < -16777216 || offset > 16777214) { | |
73 | WARN_ON_ONCE(1); | |
74 | return 0; | |
75 | } | |
76 | ||
77 | s = (offset >> 24) & 0x1; | |
78 | i1 = (offset >> 23) & 0x1; | |
79 | i2 = (offset >> 22) & 0x1; | |
80 | imm10 = (offset >> 12) & 0x3ff; | |
81 | imm11 = (offset >> 1) & 0x7ff; | |
82 | ||
83 | j1 = (!i1) ^ s; | |
84 | j2 = (!i2) ^ s; | |
85 | ||
86 | first = 0xf000 | (s << 10) | imm10; | |
dd686eb1 RV |
87 | second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11; |
88 | if (link) | |
89 | second |= 1 << 14; | |
72dc43a9 RV |
90 | |
91 | return (second << 16) | first; | |
92 | } | |
93 | #else | |
dd686eb1 RV |
94 | static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr, |
95 | bool link) | |
014c257c | 96 | { |
dd686eb1 | 97 | unsigned long opcode = 0xea000000; |
014c257c AS |
98 | long offset; |
99 | ||
dd686eb1 RV |
100 | if (link) |
101 | opcode |= 1 << 24; | |
102 | ||
3b6c223b | 103 | offset = (long)addr - (long)(pc + 8); |
014c257c AS |
104 | if (unlikely(offset < -33554432 || offset > 33554428)) { |
105 | /* Can't generate branches that far (from ARM ARM). Ftrace | |
395a59d0 | 106 | * doesn't generate branches outside of kernel text. |
014c257c AS |
107 | */ |
108 | WARN_ON_ONCE(1); | |
3b6c223b | 109 | return 0; |
014c257c | 110 | } |
014c257c | 111 | |
3b6c223b | 112 | offset = (offset >> 2) & 0x00ffffff; |
014c257c | 113 | |
dd686eb1 | 114 | return opcode | offset; |
3b6c223b | 115 | } |
72dc43a9 | 116 | #endif |
014c257c | 117 | |
dd686eb1 RV |
118 | static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr) |
119 | { | |
120 | return ftrace_gen_branch(pc, addr, true); | |
121 | } | |
122 | ||
3b6c223b RV |
123 | static int ftrace_modify_code(unsigned long pc, unsigned long old, |
124 | unsigned long new) | |
125 | { | |
126 | unsigned long replaced; | |
014c257c | 127 | |
3b6c223b RV |
128 | if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE)) |
129 | return -EFAULT; | |
014c257c | 130 | |
3b6c223b RV |
131 | if (replaced != old) |
132 | return -EINVAL; | |
014c257c | 133 | |
3b6c223b RV |
134 | if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE)) |
135 | return -EPERM; | |
014c257c | 136 | |
3b6c223b | 137 | flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); |
014c257c | 138 | |
3b6c223b | 139 | return 0; |
014c257c AS |
140 | } |
141 | ||
142 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
143 | { | |
014c257c | 144 | unsigned long pc, old; |
3b6c223b RV |
145 | unsigned long new; |
146 | int ret; | |
014c257c AS |
147 | |
148 | pc = (unsigned long)&ftrace_call; | |
395a59d0 | 149 | memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE); |
014c257c | 150 | new = ftrace_call_replace(pc, (unsigned long)func); |
3b6c223b RV |
151 | |
152 | ret = ftrace_modify_code(pc, old, new); | |
153 | ||
154 | #ifdef CONFIG_OLD_MCOUNT | |
155 | if (!ret) { | |
156 | pc = (unsigned long)&ftrace_call_old; | |
157 | memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE); | |
158 | new = ftrace_call_replace(pc, (unsigned long)func); | |
159 | ||
160 | ret = ftrace_modify_code(pc, old, new); | |
161 | } | |
162 | #endif | |
163 | ||
164 | return ret; | |
165 | } | |
166 | ||
167 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
168 | { | |
169 | unsigned long new, old; | |
170 | unsigned long ip = rec->ip; | |
171 | ||
172 | old = ftrace_nop_replace(rec); | |
173 | new = ftrace_call_replace(ip, adjust_address(rec, addr)); | |
174 | ||
175 | return ftrace_modify_code(rec->ip, old, new); | |
176 | } | |
177 | ||
178 | int ftrace_make_nop(struct module *mod, | |
179 | struct dyn_ftrace *rec, unsigned long addr) | |
180 | { | |
181 | unsigned long ip = rec->ip; | |
182 | unsigned long old; | |
183 | unsigned long new; | |
184 | int ret; | |
185 | ||
186 | old = ftrace_call_replace(ip, adjust_address(rec, addr)); | |
187 | new = ftrace_nop_replace(rec); | |
188 | ret = ftrace_modify_code(ip, old, new); | |
189 | ||
190 | #ifdef CONFIG_OLD_MCOUNT | |
191 | if (ret == -EINVAL && addr == MCOUNT_ADDR) { | |
192 | rec->arch.old_mcount = true; | |
193 | ||
194 | old = ftrace_call_replace(ip, adjust_address(rec, addr)); | |
195 | new = ftrace_nop_replace(rec); | |
196 | ret = ftrace_modify_code(ip, old, new); | |
197 | } | |
198 | #endif | |
199 | ||
014c257c AS |
200 | return ret; |
201 | } | |
202 | ||
014c257c AS |
203 | int __init ftrace_dyn_arch_init(void *data) |
204 | { | |
3b6c223b RV |
205 | *(unsigned long *)data = 0; |
206 | ||
014c257c AS |
207 | return 0; |
208 | } | |
376cfa87 TB |
209 | #endif /* CONFIG_DYNAMIC_FTRACE */ |
210 | ||
211 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
212 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, | |
213 | unsigned long frame_pointer) | |
214 | { | |
215 | unsigned long return_hooker = (unsigned long) &return_to_handler; | |
216 | struct ftrace_graph_ent trace; | |
217 | unsigned long old; | |
218 | int err; | |
219 | ||
220 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) | |
221 | return; | |
222 | ||
223 | old = *parent; | |
224 | *parent = return_hooker; | |
225 | ||
226 | err = ftrace_push_return_trace(old, self_addr, &trace.depth, | |
227 | frame_pointer); | |
228 | if (err == -EBUSY) { | |
229 | *parent = old; | |
230 | return; | |
231 | } | |
232 | ||
233 | trace.func = self_addr; | |
234 | ||
235 | /* Only trace if the calling function expects to */ | |
236 | if (!ftrace_graph_entry(&trace)) { | |
237 | current->curr_ret_stack--; | |
238 | *parent = old; | |
239 | } | |
240 | } | |
dd686eb1 RV |
241 | |
242 | #ifdef CONFIG_DYNAMIC_FTRACE | |
243 | extern unsigned long ftrace_graph_call; | |
244 | extern unsigned long ftrace_graph_call_old; | |
245 | extern void ftrace_graph_caller_old(void); | |
246 | ||
247 | static int __ftrace_modify_caller(unsigned long *callsite, | |
248 | void (*func) (void), bool enable) | |
249 | { | |
250 | unsigned long caller_fn = (unsigned long) func; | |
251 | unsigned long pc = (unsigned long) callsite; | |
252 | unsigned long branch = ftrace_gen_branch(pc, caller_fn, false); | |
253 | unsigned long nop = 0xe1a00000; /* mov r0, r0 */ | |
254 | unsigned long old = enable ? nop : branch; | |
255 | unsigned long new = enable ? branch : nop; | |
256 | ||
257 | return ftrace_modify_code(pc, old, new); | |
258 | } | |
259 | ||
260 | static int ftrace_modify_graph_caller(bool enable) | |
261 | { | |
262 | int ret; | |
263 | ||
264 | ret = __ftrace_modify_caller(&ftrace_graph_call, | |
265 | ftrace_graph_caller, | |
266 | enable); | |
267 | ||
268 | #ifdef CONFIG_OLD_MCOUNT | |
269 | if (!ret) | |
270 | ret = __ftrace_modify_caller(&ftrace_graph_call_old, | |
271 | ftrace_graph_caller_old, | |
272 | enable); | |
273 | #endif | |
274 | ||
275 | return ret; | |
276 | } | |
277 | ||
278 | int ftrace_enable_ftrace_graph_caller(void) | |
279 | { | |
280 | return ftrace_modify_graph_caller(true); | |
281 | } | |
282 | ||
283 | int ftrace_disable_ftrace_graph_caller(void) | |
284 | { | |
285 | return ftrace_modify_graph_caller(false); | |
286 | } | |
287 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
376cfa87 | 288 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |