Loading...
1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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
11 * mcount call-sites get patched with NOP till they are enabled.
12 * All code mutation routines here are called under stop_machine().
13 */
14
15#include <linux/ftrace.h>
16#include <linux/uaccess.h>
17
18#include <asm/cacheflush.h>
19#include <asm/ftrace.h>
20
21#ifdef CONFIG_THUMB2_KERNEL
22#define NOP 0xeb04f85d /* pop.w {lr} */
23#else
24#define NOP 0xe8bd4000 /* pop {lr} */
25#endif
26
27#ifdef CONFIG_DYNAMIC_FTRACE
28#ifdef CONFIG_OLD_MCOUNT
29#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
30#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
31
32#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
33
34static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
35{
36 return rec->arch.old_mcount ? OLD_NOP : NOP;
37}
38
39static 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
52static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
53{
54 return NOP;
55}
56
57static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
58{
59 return addr;
60}
61#endif
62
63#ifdef CONFIG_THUMB2_KERNEL
64static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
65 bool link)
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;
87 second = 0x9000 | (j1 << 13) | (j2 << 11) | imm11;
88 if (link)
89 second |= 1 << 14;
90
91 return (second << 16) | first;
92}
93#else
94static unsigned long ftrace_gen_branch(unsigned long pc, unsigned long addr,
95 bool link)
96{
97 unsigned long opcode = 0xea000000;
98 long offset;
99
100 if (link)
101 opcode |= 1 << 24;
102
103 offset = (long)addr - (long)(pc + 8);
104 if (unlikely(offset < -33554432 || offset > 33554428)) {
105 /* Can't generate branches that far (from ARM ARM). Ftrace
106 * doesn't generate branches outside of kernel text.
107 */
108 WARN_ON_ONCE(1);
109 return 0;
110 }
111
112 offset = (offset >> 2) & 0x00ffffff;
113
114 return opcode | offset;
115}
116#endif
117
118static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
119{
120 return ftrace_gen_branch(pc, addr, true);
121}
122
123static int ftrace_modify_code(unsigned long pc, unsigned long old,
124 unsigned long new)
125{
126 unsigned long replaced;
127
128 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
129 return -EFAULT;
130
131 if (replaced != old)
132 return -EINVAL;
133
134 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
135 return -EPERM;
136
137 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
138
139 return 0;
140}
141
142int ftrace_update_ftrace_func(ftrace_func_t func)
143{
144 unsigned long pc, old;
145 unsigned long new;
146 int ret;
147
148 pc = (unsigned long)&ftrace_call;
149 memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
150 new = ftrace_call_replace(pc, (unsigned long)func);
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
167int 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
178int 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
200 return ret;
201}
202
203int __init ftrace_dyn_arch_init(void *data)
204{
205 *(unsigned long *)data = 0;
206
207 return 0;
208}
209#endif /* CONFIG_DYNAMIC_FTRACE */
210
211#ifdef CONFIG_FUNCTION_GRAPH_TRACER
212void 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}
241
242#ifdef CONFIG_DYNAMIC_FTRACE
243extern unsigned long ftrace_graph_call;
244extern unsigned long ftrace_graph_call_old;
245extern void ftrace_graph_caller_old(void);
246
247static 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
260static 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
278int ftrace_enable_ftrace_graph_caller(void)
279{
280 return ftrace_modify_graph_caller(true);
281}
282
283int ftrace_disable_ftrace_graph_caller(void)
284{
285 return ftrace_modify_graph_caller(false);
286}
287#endif /* CONFIG_DYNAMIC_FTRACE */
288#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
1/*
2 * Dynamic function tracing support.
3 *
4 * Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
5 * Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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
11 * mcount call-sites get patched with NOP till they are enabled.
12 * All code mutation routines here are called under stop_machine().
13 */
14
15#include <linux/ftrace.h>
16#include <linux/uaccess.h>
17#include <linux/module.h>
18#include <linux/stop_machine.h>
19
20#include <asm/cacheflush.h>
21#include <asm/opcodes.h>
22#include <asm/ftrace.h>
23#include <asm/insn.h>
24#include <asm/set_memory.h>
25
26#ifdef CONFIG_THUMB2_KERNEL
27#define NOP 0xf85deb04 /* pop.w {lr} */
28#else
29#define NOP 0xe8bd4000 /* pop {lr} */
30#endif
31
32#ifdef CONFIG_DYNAMIC_FTRACE
33
34static int __ftrace_modify_code(void *data)
35{
36 int *command = data;
37
38 set_kernel_text_rw();
39 ftrace_modify_all_code(*command);
40 set_kernel_text_ro();
41
42 return 0;
43}
44
45void arch_ftrace_update_code(int command)
46{
47 stop_machine(__ftrace_modify_code, &command, NULL);
48}
49
50#ifdef CONFIG_OLD_MCOUNT
51#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
52#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
53
54#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
55
56static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
57{
58 return rec->arch.old_mcount ? OLD_NOP : NOP;
59}
60
61static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
62{
63 if (!rec->arch.old_mcount)
64 return addr;
65
66 if (addr == MCOUNT_ADDR)
67 addr = OLD_MCOUNT_ADDR;
68 else if (addr == FTRACE_ADDR)
69 addr = OLD_FTRACE_ADDR;
70
71 return addr;
72}
73#else
74static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
75{
76 return NOP;
77}
78
79static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
80{
81 return addr;
82}
83#endif
84
85int ftrace_arch_code_modify_prepare(void)
86{
87 set_all_modules_text_rw();
88 return 0;
89}
90
91int ftrace_arch_code_modify_post_process(void)
92{
93 set_all_modules_text_ro();
94 /* Make sure any TLB misses during machine stop are cleared. */
95 flush_tlb_all();
96 return 0;
97}
98
99static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
100{
101 return arm_gen_branch_link(pc, addr);
102}
103
104static int ftrace_modify_code(unsigned long pc, unsigned long old,
105 unsigned long new, bool validate)
106{
107 unsigned long replaced;
108
109 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
110 old = __opcode_to_mem_thumb32(old);
111 new = __opcode_to_mem_thumb32(new);
112 } else {
113 old = __opcode_to_mem_arm(old);
114 new = __opcode_to_mem_arm(new);
115 }
116
117 if (validate) {
118 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
119 return -EFAULT;
120
121 if (replaced != old)
122 return -EINVAL;
123 }
124
125 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
126 return -EPERM;
127
128 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
129
130 return 0;
131}
132
133int ftrace_update_ftrace_func(ftrace_func_t func)
134{
135 unsigned long pc;
136 unsigned long new;
137 int ret;
138
139 pc = (unsigned long)&ftrace_call;
140 new = ftrace_call_replace(pc, (unsigned long)func);
141
142 ret = ftrace_modify_code(pc, 0, new, false);
143
144#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
145 if (!ret) {
146 pc = (unsigned long)&ftrace_regs_call;
147 new = ftrace_call_replace(pc, (unsigned long)func);
148
149 ret = ftrace_modify_code(pc, 0, new, false);
150 }
151#endif
152
153#ifdef CONFIG_OLD_MCOUNT
154 if (!ret) {
155 pc = (unsigned long)&ftrace_call_old;
156 new = ftrace_call_replace(pc, (unsigned long)func);
157
158 ret = ftrace_modify_code(pc, 0, new, false);
159 }
160#endif
161
162 return ret;
163}
164
165int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
166{
167 unsigned long new, old;
168 unsigned long ip = rec->ip;
169
170 old = ftrace_nop_replace(rec);
171
172 new = ftrace_call_replace(ip, adjust_address(rec, addr));
173
174 return ftrace_modify_code(rec->ip, old, new, true);
175}
176
177#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
178
179int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
180 unsigned long addr)
181{
182 unsigned long new, old;
183 unsigned long ip = rec->ip;
184
185 old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
186
187 new = ftrace_call_replace(ip, adjust_address(rec, addr));
188
189 return ftrace_modify_code(rec->ip, old, new, true);
190}
191
192#endif
193
194int ftrace_make_nop(struct module *mod,
195 struct dyn_ftrace *rec, unsigned long addr)
196{
197 unsigned long ip = rec->ip;
198 unsigned long old;
199 unsigned long new;
200 int ret;
201
202 old = ftrace_call_replace(ip, adjust_address(rec, addr));
203 new = ftrace_nop_replace(rec);
204 ret = ftrace_modify_code(ip, old, new, true);
205
206#ifdef CONFIG_OLD_MCOUNT
207 if (ret == -EINVAL && addr == MCOUNT_ADDR) {
208 rec->arch.old_mcount = true;
209
210 old = ftrace_call_replace(ip, adjust_address(rec, addr));
211 new = ftrace_nop_replace(rec);
212 ret = ftrace_modify_code(ip, old, new, true);
213 }
214#endif
215
216 return ret;
217}
218
219int __init ftrace_dyn_arch_init(void)
220{
221 return 0;
222}
223#endif /* CONFIG_DYNAMIC_FTRACE */
224
225#ifdef CONFIG_FUNCTION_GRAPH_TRACER
226void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
227 unsigned long frame_pointer)
228{
229 unsigned long return_hooker = (unsigned long) &return_to_handler;
230 struct ftrace_graph_ent trace;
231 unsigned long old;
232 int err;
233
234 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
235 return;
236
237 old = *parent;
238 *parent = return_hooker;
239
240 trace.func = self_addr;
241 trace.depth = current->curr_ret_stack + 1;
242
243 /* Only trace if the calling function expects to */
244 if (!ftrace_graph_entry(&trace)) {
245 *parent = old;
246 return;
247 }
248
249 err = ftrace_push_return_trace(old, self_addr, &trace.depth,
250 frame_pointer, NULL);
251 if (err == -EBUSY) {
252 *parent = old;
253 return;
254 }
255}
256
257#ifdef CONFIG_DYNAMIC_FTRACE
258extern unsigned long ftrace_graph_call;
259extern unsigned long ftrace_graph_call_old;
260extern void ftrace_graph_caller_old(void);
261extern unsigned long ftrace_graph_regs_call;
262extern void ftrace_graph_regs_caller(void);
263
264static int __ftrace_modify_caller(unsigned long *callsite,
265 void (*func) (void), bool enable)
266{
267 unsigned long caller_fn = (unsigned long) func;
268 unsigned long pc = (unsigned long) callsite;
269 unsigned long branch = arm_gen_branch(pc, caller_fn);
270 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
271 unsigned long old = enable ? nop : branch;
272 unsigned long new = enable ? branch : nop;
273
274 return ftrace_modify_code(pc, old, new, true);
275}
276
277static int ftrace_modify_graph_caller(bool enable)
278{
279 int ret;
280
281 ret = __ftrace_modify_caller(&ftrace_graph_call,
282 ftrace_graph_caller,
283 enable);
284
285#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
286 if (!ret)
287 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
288 ftrace_graph_regs_caller,
289 enable);
290#endif
291
292
293#ifdef CONFIG_OLD_MCOUNT
294 if (!ret)
295 ret = __ftrace_modify_caller(&ftrace_graph_call_old,
296 ftrace_graph_caller_old,
297 enable);
298#endif
299
300 return ret;
301}
302
303int ftrace_enable_ftrace_graph_caller(void)
304{
305 return ftrace_modify_graph_caller(true);
306}
307
308int ftrace_disable_ftrace_graph_caller(void)
309{
310 return ftrace_modify_graph_caller(false);
311}
312#endif /* CONFIG_DYNAMIC_FTRACE */
313#endif /* CONFIG_FUNCTION_GRAPH_TRACER */