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