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538f1952 WZ |
1 | /* |
2 | * Code for replacing ftrace calls with jumps. | |
3 | * | |
4 | * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> | |
5 | * Copyright (C) 2009 DSLab, Lanzhou University, China | |
f7a904df | 6 | * Author: Wu Zhangjin <wuzhangjin@gmail.com> |
538f1952 WZ |
7 | * |
8 | * Thanks goes to Steven Rostedt for writing the original x86 version. | |
9 | */ | |
10 | ||
11 | #include <linux/uaccess.h> | |
12 | #include <linux/init.h> | |
13 | #include <linux/ftrace.h> | |
14 | ||
15 | #include <asm/cacheflush.h> | |
29c5d346 WZ |
16 | #include <asm/asm.h> |
17 | #include <asm/asm-offsets.h> | |
538f1952 WZ |
18 | |
19 | #ifdef CONFIG_DYNAMIC_FTRACE | |
20 | ||
21 | #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ | |
22 | #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ | |
23 | #define jump_insn_encode(op_code, addr) \ | |
24 | ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK))) | |
25 | ||
4d6829f9 WZ |
26 | #define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */ |
27 | #define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */ | |
28 | #define INSN_NOP 0x00000000 /* nop */ | |
29 | #define INSN_JAL(addr) jump_insn_encode(JAL, addr) | |
538f1952 WZ |
30 | |
31 | static int ftrace_modify_code(unsigned long ip, unsigned int new_code) | |
32 | { | |
046199ca WZ |
33 | int faulted; |
34 | ||
35 | /* *(unsigned int *)ip = new_code; */ | |
36 | safe_store_code(new_code, ip, faulted); | |
37 | ||
38 | if (unlikely(faulted)) | |
39 | return -EFAULT; | |
538f1952 WZ |
40 | |
41 | flush_icache_range(ip, ip + 8); | |
42 | ||
43 | return 0; | |
44 | } | |
45 | ||
46 | static int lui_v1; | |
47 | static int jal_mcount; | |
48 | ||
49 | int ftrace_make_nop(struct module *mod, | |
50 | struct dyn_ftrace *rec, unsigned long addr) | |
51 | { | |
52 | unsigned int new; | |
046199ca | 53 | int faulted; |
538f1952 WZ |
54 | unsigned long ip = rec->ip; |
55 | ||
56 | /* We have compiled module with -mlong-calls, but compiled the kernel | |
57 | * without it, we need to cope with them respectively. */ | |
58 | if (ip & 0x40000000) { | |
59 | /* record it for ftrace_make_call */ | |
046199ca WZ |
60 | if (lui_v1 == 0) { |
61 | /* lui_v1 = *(unsigned int *)ip; */ | |
62 | safe_load_code(lui_v1, ip, faulted); | |
63 | ||
64 | if (unlikely(faulted)) | |
65 | return -EFAULT; | |
66 | } | |
538f1952 | 67 | |
3a2af2dc WZ |
68 | #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) |
69 | /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) | |
70 | * addiu v1, v1, low_16bit_of_mcount | |
71 | * move at, ra | |
72 | * move $12, ra_address | |
73 | * jalr v1 | |
74 | * sub sp, sp, 8 | |
75 | * 1: offset = 5 instructions | |
76 | */ | |
4d6829f9 | 77 | new = INSN_B_1F_5; |
3a2af2dc | 78 | #else |
538f1952 WZ |
79 | /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) |
80 | * addiu v1, v1, low_16bit_of_mcount | |
81 | * move at, ra | |
82 | * jalr v1 | |
3a2af2dc WZ |
83 | * nop | move $12, ra_address | sub sp, sp, 8 |
84 | * 1: offset = 4 instructions | |
538f1952 | 85 | */ |
4d6829f9 | 86 | new = INSN_B_1F_4; |
3a2af2dc | 87 | #endif |
538f1952 WZ |
88 | } else { |
89 | /* record/calculate it for ftrace_make_call */ | |
90 | if (jal_mcount == 0) { | |
91 | /* We can record it directly like this: | |
92 | * jal_mcount = *(unsigned int *)ip; | |
93 | * Herein, jump over the first two nop instructions */ | |
4d6829f9 | 94 | jal_mcount = INSN_JAL(MCOUNT_ADDR + 8); |
538f1952 WZ |
95 | } |
96 | ||
97 | /* move at, ra | |
98 | * jalr v1 --> nop | |
99 | */ | |
4d6829f9 | 100 | new = INSN_NOP; |
538f1952 WZ |
101 | } |
102 | return ftrace_modify_code(ip, new); | |
103 | } | |
104 | ||
105 | static int modified; /* initialized as 0 by default */ | |
106 | ||
107 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) | |
108 | { | |
109 | unsigned int new; | |
110 | unsigned long ip = rec->ip; | |
111 | ||
112 | /* We just need to remove the "b ftrace_stub" at the fist time! */ | |
113 | if (modified == 0) { | |
114 | modified = 1; | |
4d6829f9 | 115 | ftrace_modify_code(addr, INSN_NOP); |
538f1952 WZ |
116 | } |
117 | /* ip, module: 0xc0000000, kernel: 0x80000000 */ | |
118 | new = (ip & 0x40000000) ? lui_v1 : jal_mcount; | |
119 | ||
120 | return ftrace_modify_code(ip, new); | |
121 | } | |
122 | ||
123 | #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) | |
124 | ||
125 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
126 | { | |
127 | unsigned int new; | |
128 | ||
4d6829f9 | 129 | new = INSN_JAL((unsigned long)func); |
538f1952 WZ |
130 | |
131 | return ftrace_modify_code(FTRACE_CALL_IP, new); | |
132 | } | |
133 | ||
134 | int __init ftrace_dyn_arch_init(void *data) | |
135 | { | |
136 | /* The return code is retured via data */ | |
137 | *(unsigned long *)data = 0; | |
138 | ||
139 | return 0; | |
140 | } | |
141 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
29c5d346 WZ |
142 | |
143 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
144 | ||
e17ff5fe WZ |
145 | #ifdef CONFIG_DYNAMIC_FTRACE |
146 | ||
147 | extern void ftrace_graph_call(void); | |
148 | #define JMP 0x08000000 /* jump to target directly */ | |
149 | #define CALL_FTRACE_GRAPH_CALLER \ | |
150 | jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller)) | |
151 | #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) | |
152 | ||
153 | int ftrace_enable_ftrace_graph_caller(void) | |
154 | { | |
155 | return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, | |
156 | CALL_FTRACE_GRAPH_CALLER); | |
157 | } | |
158 | ||
159 | int ftrace_disable_ftrace_graph_caller(void) | |
160 | { | |
4d6829f9 | 161 | return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); |
e17ff5fe WZ |
162 | } |
163 | ||
164 | #endif /* !CONFIG_DYNAMIC_FTRACE */ | |
165 | ||
7326c4e5 | 166 | #ifndef KBUILD_MCOUNT_RA_ADDRESS |
29c5d346 WZ |
167 | #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ |
168 | #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ | |
169 | #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ | |
170 | ||
171 | unsigned long ftrace_get_parent_addr(unsigned long self_addr, | |
172 | unsigned long parent, | |
173 | unsigned long parent_addr, | |
174 | unsigned long fp) | |
175 | { | |
176 | unsigned long sp, ip, ra; | |
177 | unsigned int code; | |
046199ca | 178 | int faulted; |
29c5d346 WZ |
179 | |
180 | /* in module or kernel? */ | |
181 | if (self_addr & 0x40000000) { | |
182 | /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */ | |
183 | ip = self_addr - 20; | |
184 | } else { | |
185 | /* kernel: move to the instruction "move ra, at" */ | |
186 | ip = self_addr - 12; | |
187 | } | |
188 | ||
189 | /* search the text until finding the non-store instruction or "s{d,w} | |
190 | * ra, offset(sp)" instruction */ | |
191 | do { | |
192 | ip -= 4; | |
193 | ||
046199ca WZ |
194 | /* get the code at "ip": code = *(unsigned int *)ip; */ |
195 | safe_load_code(code, ip, faulted); | |
196 | ||
197 | if (unlikely(faulted)) | |
198 | return 0; | |
29c5d346 WZ |
199 | |
200 | /* If we hit the non-store instruction before finding where the | |
201 | * ra is stored, then this is a leaf function and it does not | |
202 | * store the ra on the stack. */ | |
203 | if ((code & S_R_SP) != S_R_SP) | |
204 | return parent_addr; | |
205 | ||
206 | } while (((code & S_RA_SP) != S_RA_SP)); | |
207 | ||
208 | sp = fp + (code & OFFSET_MASK); | |
046199ca WZ |
209 | |
210 | /* ra = *(unsigned long *)sp; */ | |
211 | safe_load_stack(ra, sp, faulted); | |
212 | if (unlikely(faulted)) | |
213 | return 0; | |
29c5d346 WZ |
214 | |
215 | if (ra == parent) | |
216 | return sp; | |
29c5d346 WZ |
217 | return 0; |
218 | } | |
219 | ||
7326c4e5 WZ |
220 | #endif |
221 | ||
29c5d346 WZ |
222 | /* |
223 | * Hook the return address and push it in the stack of return addrs | |
224 | * in current thread info. | |
225 | */ | |
226 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, | |
227 | unsigned long fp) | |
228 | { | |
229 | unsigned long old; | |
230 | struct ftrace_graph_ent trace; | |
231 | unsigned long return_hooker = (unsigned long) | |
232 | &return_to_handler; | |
046199ca | 233 | int faulted; |
29c5d346 WZ |
234 | |
235 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) | |
236 | return; | |
237 | ||
238 | /* "parent" is the stack address saved the return address of the caller | |
7326c4e5 WZ |
239 | * of _mcount. |
240 | * | |
241 | * if the gcc < 4.5, a leaf function does not save the return address | |
242 | * in the stack address, so, we "emulate" one in _mcount's stack space, | |
243 | * and hijack it directly, but for a non-leaf function, it save the | |
244 | * return address to the its own stack space, we can not hijack it | |
245 | * directly, but need to find the real stack address, | |
29c5d346 | 246 | * ftrace_get_parent_addr() does it! |
7326c4e5 WZ |
247 | * |
248 | * if gcc>= 4.5, with the new -mmcount-ra-address option, for a | |
249 | * non-leaf function, the location of the return address will be saved | |
250 | * to $12 for us, and for a leaf function, only put a zero into $12. we | |
251 | * do it in ftrace_graph_caller of mcount.S. | |
29c5d346 WZ |
252 | */ |
253 | ||
046199ca WZ |
254 | /* old = *parent; */ |
255 | safe_load_stack(old, parent, faulted); | |
256 | if (unlikely(faulted)) | |
257 | goto out; | |
7326c4e5 | 258 | #ifndef KBUILD_MCOUNT_RA_ADDRESS |
29c5d346 WZ |
259 | parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old, |
260 | (unsigned long)parent, | |
261 | fp); | |
29c5d346 WZ |
262 | /* If fails when getting the stack address of the non-leaf function's |
263 | * ra, stop function graph tracer and return */ | |
046199ca WZ |
264 | if (parent == 0) |
265 | goto out; | |
7326c4e5 | 266 | #endif |
046199ca WZ |
267 | /* *parent = return_hooker; */ |
268 | safe_store_stack(return_hooker, parent, faulted); | |
269 | if (unlikely(faulted)) | |
270 | goto out; | |
29c5d346 WZ |
271 | |
272 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) == | |
273 | -EBUSY) { | |
274 | *parent = old; | |
275 | return; | |
276 | } | |
277 | ||
278 | trace.func = self_addr; | |
279 | ||
280 | /* Only trace if the calling function expects to */ | |
281 | if (!ftrace_graph_entry(&trace)) { | |
282 | current->curr_ret_stack--; | |
283 | *parent = old; | |
284 | } | |
046199ca WZ |
285 | return; |
286 | out: | |
287 | ftrace_graph_stop(); | |
288 | WARN_ON(1); | |
29c5d346 WZ |
289 | } |
290 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |