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
50static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
51{
52 return NOP;
53}
54
55static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
56{
57 return addr;
58}
59
60int ftrace_arch_code_modify_prepare(void)
61{
62 set_all_modules_text_rw();
63 return 0;
64}
65
66int ftrace_arch_code_modify_post_process(void)
67{
68 set_all_modules_text_ro();
69 /* Make sure any TLB misses during machine stop are cleared. */
70 flush_tlb_all();
71 return 0;
72}
73
74static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
75{
76 return arm_gen_branch_link(pc, addr);
77}
78
79static int ftrace_modify_code(unsigned long pc, unsigned long old,
80 unsigned long new, bool validate)
81{
82 unsigned long replaced;
83
84 if (IS_ENABLED(CONFIG_THUMB2_KERNEL)) {
85 old = __opcode_to_mem_thumb32(old);
86 new = __opcode_to_mem_thumb32(new);
87 } else {
88 old = __opcode_to_mem_arm(old);
89 new = __opcode_to_mem_arm(new);
90 }
91
92 if (validate) {
93 if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
94 return -EFAULT;
95
96 if (replaced != old)
97 return -EINVAL;
98 }
99
100 if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
101 return -EPERM;
102
103 flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
104
105 return 0;
106}
107
108int ftrace_update_ftrace_func(ftrace_func_t func)
109{
110 unsigned long pc;
111 unsigned long new;
112 int ret;
113
114 pc = (unsigned long)&ftrace_call;
115 new = ftrace_call_replace(pc, (unsigned long)func);
116
117 ret = ftrace_modify_code(pc, 0, new, false);
118
119#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
120 if (!ret) {
121 pc = (unsigned long)&ftrace_regs_call;
122 new = ftrace_call_replace(pc, (unsigned long)func);
123
124 ret = ftrace_modify_code(pc, 0, new, false);
125 }
126#endif
127
128 return ret;
129}
130
131int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
132{
133 unsigned long new, old;
134 unsigned long ip = rec->ip;
135
136 old = ftrace_nop_replace(rec);
137
138 new = ftrace_call_replace(ip, adjust_address(rec, addr));
139
140 return ftrace_modify_code(rec->ip, old, new, true);
141}
142
143#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
144
145int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
146 unsigned long addr)
147{
148 unsigned long new, old;
149 unsigned long ip = rec->ip;
150
151 old = ftrace_call_replace(ip, adjust_address(rec, old_addr));
152
153 new = ftrace_call_replace(ip, adjust_address(rec, addr));
154
155 return ftrace_modify_code(rec->ip, old, new, true);
156}
157
158#endif
159
160int ftrace_make_nop(struct module *mod,
161 struct dyn_ftrace *rec, unsigned long addr)
162{
163 unsigned long ip = rec->ip;
164 unsigned long old;
165 unsigned long new;
166 int ret;
167
168 old = ftrace_call_replace(ip, adjust_address(rec, addr));
169 new = ftrace_nop_replace(rec);
170 ret = ftrace_modify_code(ip, old, new, true);
171
172 return ret;
173}
174
175int __init ftrace_dyn_arch_init(void)
176{
177 return 0;
178}
179#endif /* CONFIG_DYNAMIC_FTRACE */
180
181#ifdef CONFIG_FUNCTION_GRAPH_TRACER
182void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
183 unsigned long frame_pointer)
184{
185 unsigned long return_hooker = (unsigned long) &return_to_handler;
186 unsigned long old;
187
188 if (unlikely(atomic_read(¤t->tracing_graph_pause)))
189 return;
190
191 old = *parent;
192 *parent = return_hooker;
193
194 if (function_graph_enter(old, self_addr, frame_pointer, NULL))
195 *parent = old;
196}
197
198#ifdef CONFIG_DYNAMIC_FTRACE
199extern unsigned long ftrace_graph_call;
200extern unsigned long ftrace_graph_call_old;
201extern void ftrace_graph_caller_old(void);
202extern unsigned long ftrace_graph_regs_call;
203extern void ftrace_graph_regs_caller(void);
204
205static int __ftrace_modify_caller(unsigned long *callsite,
206 void (*func) (void), bool enable)
207{
208 unsigned long caller_fn = (unsigned long) func;
209 unsigned long pc = (unsigned long) callsite;
210 unsigned long branch = arm_gen_branch(pc, caller_fn);
211 unsigned long nop = 0xe1a00000; /* mov r0, r0 */
212 unsigned long old = enable ? nop : branch;
213 unsigned long new = enable ? branch : nop;
214
215 return ftrace_modify_code(pc, old, new, true);
216}
217
218static int ftrace_modify_graph_caller(bool enable)
219{
220 int ret;
221
222 ret = __ftrace_modify_caller(&ftrace_graph_call,
223 ftrace_graph_caller,
224 enable);
225
226#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
227 if (!ret)
228 ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
229 ftrace_graph_regs_caller,
230 enable);
231#endif
232
233
234 return ret;
235}
236
237int ftrace_enable_ftrace_graph_caller(void)
238{
239 return ftrace_modify_graph_caller(true);
240}
241
242int ftrace_disable_ftrace_graph_caller(void)
243{
244 return ftrace_modify_graph_caller(false);
245}
246#endif /* CONFIG_DYNAMIC_FTRACE */
247#endif /* CONFIG_FUNCTION_GRAPH_TRACER */