1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/*
* Dynamic function tracing support.
*
* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
* Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
*
* For licencing details, see COPYING.
*
* Defines low-level handling of mcount calls when the kernel
* is compiled with the -pg flag. When using dynamic ftrace, the
* mcount call-sites get patched with NOP till they are enabled.
* All code mutation routines here are called under stop_machine().
*/
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <asm/cacheflush.h>
#include <asm/ftrace.h>
#ifdef CONFIG_THUMB2_KERNEL
#define NOP 0xeb04f85d /* pop.w {lr} */
#else
#define NOP 0xe8bd4000 /* pop {lr} */
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
#ifdef CONFIG_OLD_MCOUNT
#define OLD_MCOUNT_ADDR ((unsigned long) mcount)
#define OLD_FTRACE_ADDR ((unsigned long) ftrace_caller_old)
#define OLD_NOP 0xe1a00000 /* mov r0, r0 */
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return rec->arch.old_mcount ? OLD_NOP : NOP;
}
static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
{
if (!rec->arch.old_mcount)
return addr;
if (addr == MCOUNT_ADDR)
addr = OLD_MCOUNT_ADDR;
else if (addr == FTRACE_ADDR)
addr = OLD_FTRACE_ADDR;
return addr;
}
#else
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return NOP;
}
static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
{
return addr;
}
#endif
/* construct a branch (BL) instruction to addr */
#ifdef CONFIG_THUMB2_KERNEL
static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
{
unsigned long s, j1, j2, i1, i2, imm10, imm11;
unsigned long first, second;
long offset;
offset = (long)addr - (long)(pc + 4);
if (offset < -16777216 || offset > 16777214) {
WARN_ON_ONCE(1);
return 0;
}
s = (offset >> 24) & 0x1;
i1 = (offset >> 23) & 0x1;
i2 = (offset >> 22) & 0x1;
imm10 = (offset >> 12) & 0x3ff;
imm11 = (offset >> 1) & 0x7ff;
j1 = (!i1) ^ s;
j2 = (!i2) ^ s;
first = 0xf000 | (s << 10) | imm10;
second = 0xd000 | (j1 << 13) | (j2 << 11) | imm11;
return (second << 16) | first;
}
#else
static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
{
long offset;
offset = (long)addr - (long)(pc + 8);
if (unlikely(offset < -33554432 || offset > 33554428)) {
/* Can't generate branches that far (from ARM ARM). Ftrace
* doesn't generate branches outside of kernel text.
*/
WARN_ON_ONCE(1);
return 0;
}
offset = (offset >> 2) & 0x00ffffff;
return 0xeb000000 | offset;
}
#endif
static int ftrace_modify_code(unsigned long pc, unsigned long old,
unsigned long new)
{
unsigned long replaced;
if (probe_kernel_read(&replaced, (void *)pc, MCOUNT_INSN_SIZE))
return -EFAULT;
if (replaced != old)
return -EINVAL;
if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long pc, old;
unsigned long new;
int ret;
pc = (unsigned long)&ftrace_call;
memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, old, new);
#ifdef CONFIG_OLD_MCOUNT
if (!ret) {
pc = (unsigned long)&ftrace_call_old;
memcpy(&old, &ftrace_call_old, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(pc, (unsigned long)func);
ret = ftrace_modify_code(pc, old, new);
}
#endif
return ret;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long new, old;
unsigned long ip = rec->ip;
old = ftrace_nop_replace(rec);
new = ftrace_call_replace(ip, adjust_address(rec, addr));
return ftrace_modify_code(rec->ip, old, new);
}
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned long old;
unsigned long new;
int ret;
old = ftrace_call_replace(ip, adjust_address(rec, addr));
new = ftrace_nop_replace(rec);
ret = ftrace_modify_code(ip, old, new);
#ifdef CONFIG_OLD_MCOUNT
if (ret == -EINVAL && addr == MCOUNT_ADDR) {
rec->arch.old_mcount = true;
old = ftrace_call_replace(ip, adjust_address(rec, addr));
new = ftrace_nop_replace(rec);
ret = ftrace_modify_code(ip, old, new);
}
#endif
return ret;
}
int __init ftrace_dyn_arch_init(void *data)
{
*(unsigned long *)data = 0;
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long frame_pointer)
{
unsigned long return_hooker = (unsigned long) &return_to_handler;
struct ftrace_graph_ent trace;
unsigned long old;
int err;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
old = *parent;
*parent = return_hooker;
err = ftrace_push_return_trace(old, self_addr, &trace.depth,
frame_pointer);
if (err == -EBUSY) {
*parent = old;
return;
}
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
*parent = old;
}
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
