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
|
/*
* arch/arm64/kernel/entry-ftrace.S
*
* Copyright (C) 2013 Linaro Limited
* Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
/*
* Gcc with -pg will put the following code in the beginning of each function:
* mov x0, x30
* bl _mcount
* [function's body ...]
* "bl _mcount" may be replaced to "bl ftrace_caller" or NOP if dynamic
* ftrace is enabled.
*
* Please note that x0 as an argument will not be used here because we can
* get lr(x30) of instrumented function at any time by winding up call stack
* as long as the kernel is compiled without -fomit-frame-pointer.
* (or CONFIG_FRAME_POINTER, this is forced on arm64)
*
* stack layout after mcount_enter in _mcount():
*
* current sp/fp => 0:+-----+
* in _mcount() | x29 | -> instrumented function's fp
* +-----+
* | x30 | -> _mcount()'s lr (= instrumented function's pc)
* old sp => +16:+-----+
* when instrumented | |
* function calls | ... |
* _mcount() | |
* | |
* instrumented => +xx:+-----+
* function's fp | x29 | -> parent's fp
* +-----+
* | x30 | -> instrumented function's lr (= parent's pc)
* +-----+
* | ... |
*/
.macro mcount_enter
stp x29, x30, [sp, #-16]!
mov x29, sp
.endm
.macro mcount_exit
ldp x29, x30, [sp], #16
ret
.endm
.macro mcount_adjust_addr rd, rn
sub \rd, \rn, #AARCH64_INSN_SIZE
.endm
/* for instrumented function's parent */
.macro mcount_get_parent_fp reg
ldr \reg, [x29]
ldr \reg, [\reg]
.endm
/* for instrumented function */
.macro mcount_get_pc0 reg
mcount_adjust_addr \reg, x30
.endm
.macro mcount_get_pc reg
ldr \reg, [x29, #8]
mcount_adjust_addr \reg, \reg
.endm
.macro mcount_get_lr reg
ldr \reg, [x29]
ldr \reg, [\reg, #8]
mcount_adjust_addr \reg, \reg
.endm
.macro mcount_get_lr_addr reg
ldr \reg, [x29]
add \reg, \reg, #8
.endm
#ifndef CONFIG_DYNAMIC_FTRACE
/*
* void _mcount(unsigned long return_address)
* @return_address: return address to instrumented function
*
* This function makes calls, if enabled, to:
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
ENTRY(_mcount)
mcount_enter
adrp x0, ftrace_trace_function
ldr x2, [x0, #:lo12:ftrace_trace_function]
adr x0, ftrace_stub
cmp x0, x2 // if (ftrace_trace_function
b.eq skip_ftrace_call // != ftrace_stub) {
mcount_get_pc x0 // function's pc
mcount_get_lr x1 // function's lr (= parent's pc)
blr x2 // (*ftrace_trace_function)(pc, lr);
#ifndef CONFIG_FUNCTION_GRAPH_TRACER
skip_ftrace_call: // return;
mcount_exit // }
#else
mcount_exit // return;
// }
skip_ftrace_call:
adrp x1, ftrace_graph_return
ldr x2, [x1, #:lo12:ftrace_graph_return]
cmp x0, x2 // if ((ftrace_graph_return
b.ne ftrace_graph_caller // != ftrace_stub)
adrp x1, ftrace_graph_entry // || (ftrace_graph_entry
adrp x0, ftrace_graph_entry_stub // != ftrace_graph_entry_stub))
ldr x2, [x1, #:lo12:ftrace_graph_entry]
add x0, x0, #:lo12:ftrace_graph_entry_stub
cmp x0, x2
b.ne ftrace_graph_caller // ftrace_graph_caller();
mcount_exit
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
ENDPROC(_mcount)
#else /* CONFIG_DYNAMIC_FTRACE */
/*
* _mcount() is used to build the kernel with -pg option, but all the branch
* instructions to _mcount() are replaced to NOP initially at kernel start up,
* and later on, NOP to branch to ftrace_caller() when enabled or branch to
* NOP when disabled per-function base.
*/
ENTRY(_mcount)
ret
ENDPROC(_mcount)
/*
* void ftrace_caller(unsigned long return_address)
* @return_address: return address to instrumented function
*
* This function is a counterpart of _mcount() in 'static' ftrace, and
* makes calls to:
* - tracer function to probe instrumented function's entry,
* - ftrace_graph_caller to set up an exit hook
*/
ENTRY(ftrace_caller)
mcount_enter
mcount_get_pc0 x0 // function's pc
mcount_get_lr x1 // function's lr
.global ftrace_call
ftrace_call: // tracer(pc, lr);
nop // This will be replaced with "bl xxx"
// where xxx can be any kind of tracer.
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
.global ftrace_graph_call
ftrace_graph_call: // ftrace_graph_caller();
nop // If enabled, this will be replaced
// "b ftrace_graph_caller"
#endif
mcount_exit
ENDPROC(ftrace_caller)
#endif /* CONFIG_DYNAMIC_FTRACE */
ENTRY(ftrace_stub)
ret
ENDPROC(ftrace_stub)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* void ftrace_graph_caller(void)
*
* Called from _mcount() or ftrace_caller() when function_graph tracer is
* selected.
* This function w/ prepare_ftrace_return() fakes link register's value on
* the call stack in order to intercept instrumented function's return path
* and run return_to_handler() later on its exit.
*/
ENTRY(ftrace_graph_caller)
mcount_get_lr_addr x0 // pointer to function's saved lr
mcount_get_pc x1 // function's pc
mcount_get_parent_fp x2 // parent's fp
bl prepare_ftrace_return // prepare_ftrace_return(&lr, pc, fp)
mcount_exit
ENDPROC(ftrace_graph_caller)
/*
* void return_to_handler(void)
*
* Run ftrace_return_to_handler() before going back to parent.
* @fp is checked against the value passed by ftrace_graph_caller()
* only when CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
*/
ENTRY(return_to_handler)
str x0, [sp, #-16]!
mov x0, x29 // parent's fp
bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
mov x30, x0 // restore the original return address
ldr x0, [sp], #16
ret
END(return_to_handler)
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
