Commit | Line | Data |
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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> | |
e4240540 | 5 | * Copyright (C) 2009, 2010 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 | ||
29c5d346 WZ |
15 | #include <asm/asm.h> |
16 | #include <asm/asm-offsets.h> | |
e4240540 WZ |
17 | #include <asm/cacheflush.h> |
18 | #include <asm/uasm.h> | |
538f1952 WZ |
19 | |
20 | #ifdef CONFIG_DYNAMIC_FTRACE | |
21 | ||
22 | #define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */ | |
23 | #define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */ | |
538f1952 | 24 | |
4d6829f9 WZ |
25 | #define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */ |
26 | #define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */ | |
27 | #define INSN_NOP 0x00000000 /* nop */ | |
e4240540 WZ |
28 | #define INSN_JAL(addr) \ |
29 | ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK))) | |
30 | ||
31 | static unsigned int insn_jal_ftrace_caller __read_mostly; | |
32 | static unsigned int insn_lui_v1_hi16_mcount __read_mostly; | |
33 | static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly; | |
34 | ||
35 | static inline void ftrace_dyn_arch_init_insns(void) | |
36 | { | |
37 | u32 *buf; | |
38 | unsigned int v1; | |
39 | ||
40 | /* lui v1, hi16_mcount */ | |
41 | v1 = 3; | |
42 | buf = (u32 *)&insn_lui_v1_hi16_mcount; | |
43 | UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR); | |
44 | ||
45 | /* jal (ftrace_caller + 8), jump over the first two instruction */ | |
46 | buf = (u32 *)&insn_jal_ftrace_caller; | |
47 | uasm_i_jal(&buf, (FTRACE_ADDR + 8)); | |
48 | ||
49 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
50 | /* j ftrace_graph_caller */ | |
51 | buf = (u32 *)&insn_j_ftrace_graph_caller; | |
52 | uasm_i_j(&buf, (unsigned long)ftrace_graph_caller); | |
53 | #endif | |
54 | } | |
538f1952 WZ |
55 | |
56 | static int ftrace_modify_code(unsigned long ip, unsigned int new_code) | |
57 | { | |
046199ca WZ |
58 | int faulted; |
59 | ||
60 | /* *(unsigned int *)ip = new_code; */ | |
61 | safe_store_code(new_code, ip, faulted); | |
62 | ||
63 | if (unlikely(faulted)) | |
64 | return -EFAULT; | |
538f1952 WZ |
65 | |
66 | flush_icache_range(ip, ip + 8); | |
67 | ||
68 | return 0; | |
69 | } | |
70 | ||
538f1952 WZ |
71 | int ftrace_make_nop(struct module *mod, |
72 | struct dyn_ftrace *rec, unsigned long addr) | |
73 | { | |
74 | unsigned int new; | |
75 | unsigned long ip = rec->ip; | |
76 | ||
e4240540 WZ |
77 | /* |
78 | * We have compiled module with -mlong-calls, but compiled the kernel | |
79 | * without it, we need to cope with them respectively. | |
80 | */ | |
538f1952 | 81 | if (ip & 0x40000000) { |
3a2af2dc | 82 | #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT) |
e4240540 WZ |
83 | /* |
84 | * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005) | |
3a2af2dc WZ |
85 | * addiu v1, v1, low_16bit_of_mcount |
86 | * move at, ra | |
87 | * move $12, ra_address | |
88 | * jalr v1 | |
89 | * sub sp, sp, 8 | |
90 | * 1: offset = 5 instructions | |
91 | */ | |
4d6829f9 | 92 | new = INSN_B_1F_5; |
3a2af2dc | 93 | #else |
e4240540 WZ |
94 | /* |
95 | * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004) | |
538f1952 WZ |
96 | * addiu v1, v1, low_16bit_of_mcount |
97 | * move at, ra | |
98 | * jalr v1 | |
3a2af2dc WZ |
99 | * nop | move $12, ra_address | sub sp, sp, 8 |
100 | * 1: offset = 4 instructions | |
538f1952 | 101 | */ |
4d6829f9 | 102 | new = INSN_B_1F_4; |
3a2af2dc | 103 | #endif |
538f1952 | 104 | } else { |
e4240540 WZ |
105 | /* |
106 | * move at, ra | |
107 | * jal _mcount --> nop | |
538f1952 | 108 | */ |
4d6829f9 | 109 | new = INSN_NOP; |
538f1952 WZ |
110 | } |
111 | return ftrace_modify_code(ip, new); | |
112 | } | |
113 | ||
538f1952 WZ |
114 | int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) |
115 | { | |
116 | unsigned int new; | |
117 | unsigned long ip = rec->ip; | |
118 | ||
538f1952 | 119 | /* ip, module: 0xc0000000, kernel: 0x80000000 */ |
e4240540 | 120 | new = (ip & 0x40000000) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller; |
538f1952 WZ |
121 | |
122 | return ftrace_modify_code(ip, new); | |
123 | } | |
124 | ||
125 | #define FTRACE_CALL_IP ((unsigned long)(&ftrace_call)) | |
126 | ||
127 | int ftrace_update_ftrace_func(ftrace_func_t func) | |
128 | { | |
129 | unsigned int new; | |
130 | ||
4d6829f9 | 131 | new = INSN_JAL((unsigned long)func); |
538f1952 WZ |
132 | |
133 | return ftrace_modify_code(FTRACE_CALL_IP, new); | |
134 | } | |
135 | ||
136 | int __init ftrace_dyn_arch_init(void *data) | |
137 | { | |
e4240540 WZ |
138 | /* Encode the instructions when booting */ |
139 | ftrace_dyn_arch_init_insns(); | |
140 | ||
141 | /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */ | |
142 | ftrace_modify_code(MCOUNT_ADDR, INSN_NOP); | |
143 | ||
538f1952 WZ |
144 | /* The return code is retured via data */ |
145 | *(unsigned long *)data = 0; | |
146 | ||
147 | return 0; | |
148 | } | |
149 | #endif /* CONFIG_DYNAMIC_FTRACE */ | |
29c5d346 WZ |
150 | |
151 | #ifdef CONFIG_FUNCTION_GRAPH_TRACER | |
152 | ||
e17ff5fe WZ |
153 | #ifdef CONFIG_DYNAMIC_FTRACE |
154 | ||
155 | extern void ftrace_graph_call(void); | |
e17ff5fe WZ |
156 | #define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call)) |
157 | ||
158 | int ftrace_enable_ftrace_graph_caller(void) | |
159 | { | |
160 | return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, | |
e4240540 | 161 | insn_j_ftrace_graph_caller); |
e17ff5fe WZ |
162 | } |
163 | ||
164 | int ftrace_disable_ftrace_graph_caller(void) | |
165 | { | |
4d6829f9 | 166 | return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP); |
e17ff5fe WZ |
167 | } |
168 | ||
169 | #endif /* !CONFIG_DYNAMIC_FTRACE */ | |
170 | ||
7326c4e5 | 171 | #ifndef KBUILD_MCOUNT_RA_ADDRESS |
29c5d346 WZ |
172 | #define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */ |
173 | #define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */ | |
174 | #define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */ | |
175 | ||
176 | unsigned long ftrace_get_parent_addr(unsigned long self_addr, | |
177 | unsigned long parent, | |
178 | unsigned long parent_addr, | |
179 | unsigned long fp) | |
180 | { | |
181 | unsigned long sp, ip, ra; | |
182 | unsigned int code; | |
046199ca | 183 | int faulted; |
29c5d346 WZ |
184 | |
185 | /* in module or kernel? */ | |
186 | if (self_addr & 0x40000000) { | |
187 | /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */ | |
188 | ip = self_addr - 20; | |
189 | } else { | |
190 | /* kernel: move to the instruction "move ra, at" */ | |
191 | ip = self_addr - 12; | |
192 | } | |
193 | ||
194 | /* search the text until finding the non-store instruction or "s{d,w} | |
195 | * ra, offset(sp)" instruction */ | |
196 | do { | |
197 | ip -= 4; | |
198 | ||
046199ca WZ |
199 | /* get the code at "ip": code = *(unsigned int *)ip; */ |
200 | safe_load_code(code, ip, faulted); | |
201 | ||
202 | if (unlikely(faulted)) | |
203 | return 0; | |
29c5d346 WZ |
204 | |
205 | /* If we hit the non-store instruction before finding where the | |
206 | * ra is stored, then this is a leaf function and it does not | |
207 | * store the ra on the stack. */ | |
208 | if ((code & S_R_SP) != S_R_SP) | |
209 | return parent_addr; | |
210 | ||
211 | } while (((code & S_RA_SP) != S_RA_SP)); | |
212 | ||
213 | sp = fp + (code & OFFSET_MASK); | |
046199ca WZ |
214 | |
215 | /* ra = *(unsigned long *)sp; */ | |
216 | safe_load_stack(ra, sp, faulted); | |
217 | if (unlikely(faulted)) | |
218 | return 0; | |
29c5d346 WZ |
219 | |
220 | if (ra == parent) | |
221 | return sp; | |
29c5d346 WZ |
222 | return 0; |
223 | } | |
224 | ||
7326c4e5 WZ |
225 | #endif |
226 | ||
29c5d346 WZ |
227 | /* |
228 | * Hook the return address and push it in the stack of return addrs | |
229 | * in current thread info. | |
230 | */ | |
231 | void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, | |
232 | unsigned long fp) | |
233 | { | |
234 | unsigned long old; | |
235 | struct ftrace_graph_ent trace; | |
236 | unsigned long return_hooker = (unsigned long) | |
237 | &return_to_handler; | |
046199ca | 238 | int faulted; |
29c5d346 WZ |
239 | |
240 | if (unlikely(atomic_read(¤t->tracing_graph_pause))) | |
241 | return; | |
242 | ||
243 | /* "parent" is the stack address saved the return address of the caller | |
7326c4e5 WZ |
244 | * of _mcount. |
245 | * | |
246 | * if the gcc < 4.5, a leaf function does not save the return address | |
247 | * in the stack address, so, we "emulate" one in _mcount's stack space, | |
248 | * and hijack it directly, but for a non-leaf function, it save the | |
249 | * return address to the its own stack space, we can not hijack it | |
250 | * directly, but need to find the real stack address, | |
29c5d346 | 251 | * ftrace_get_parent_addr() does it! |
7326c4e5 WZ |
252 | * |
253 | * if gcc>= 4.5, with the new -mmcount-ra-address option, for a | |
254 | * non-leaf function, the location of the return address will be saved | |
255 | * to $12 for us, and for a leaf function, only put a zero into $12. we | |
256 | * do it in ftrace_graph_caller of mcount.S. | |
29c5d346 WZ |
257 | */ |
258 | ||
046199ca WZ |
259 | /* old = *parent; */ |
260 | safe_load_stack(old, parent, faulted); | |
261 | if (unlikely(faulted)) | |
262 | goto out; | |
7326c4e5 | 263 | #ifndef KBUILD_MCOUNT_RA_ADDRESS |
29c5d346 WZ |
264 | parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old, |
265 | (unsigned long)parent, | |
266 | fp); | |
29c5d346 WZ |
267 | /* If fails when getting the stack address of the non-leaf function's |
268 | * ra, stop function graph tracer and return */ | |
046199ca WZ |
269 | if (parent == 0) |
270 | goto out; | |
7326c4e5 | 271 | #endif |
046199ca WZ |
272 | /* *parent = return_hooker; */ |
273 | safe_store_stack(return_hooker, parent, faulted); | |
274 | if (unlikely(faulted)) | |
275 | goto out; | |
29c5d346 WZ |
276 | |
277 | if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) == | |
278 | -EBUSY) { | |
279 | *parent = old; | |
280 | return; | |
281 | } | |
282 | ||
283 | trace.func = self_addr; | |
284 | ||
285 | /* Only trace if the calling function expects to */ | |
286 | if (!ftrace_graph_entry(&trace)) { | |
287 | current->curr_ret_stack--; | |
288 | *parent = old; | |
289 | } | |
046199ca WZ |
290 | return; |
291 | out: | |
292 | ftrace_graph_stop(); | |
293 | WARN_ON(1); | |
29c5d346 WZ |
294 | } |
295 | #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |