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
|
'\" t
.\" Manual page created with latex2man on Thu Aug 16 09:44:44 MDT 2007
.\" NOTE: This file is generated, DO NOT EDIT.
.de Vb
.ft CW
.nf
..
.de Ve
.ft R
.fi
..
.TH "LIBUNWIND\-PTRACE" "3" "16 August 2007" "Programming Library " "Programming Library "
.SH NAME
libunwind\-ptrace
\-\- ptrace() support in libunwind
.PP
.SH SYNOPSIS
.PP
#include <libunwind\-ptrace.h>
.br
.PP
unw_accessors_t
_UPT_accessors;
.br
.PP
void *_UPT_create(pid_t);
.br
void
_UPT_destroy(void *);
.br
.PP
int
_UPT_find_proc_info(unw_addr_space_t,
unw_word_t,
unw_proc_info_t *,
int,
void *);
.br
void
_UPT_put_unwind_info(unw_addr_space_t,
unw_proc_info_t *,
void *);
.br
int
_UPT_get_dyn_info_list_addr(unw_addr_space_t,
unw_word_t *,
void *);
.br
int
_UPT_access_mem(unw_addr_space_t,
unw_word_t,
unw_word_t *,
int,
void *);
.br
int
_UPT_access_reg(unw_addr_space_t,
unw_regnum_t,
unw_word_t *,
int,
void *);
.br
int
_UPT_access_fpreg(unw_addr_space_t,
unw_regnum_t,
unw_fpreg_t *,
int,
void *);
.br
int
_UPT_get_proc_name(unw_addr_space_t,
unw_word_t,
char *,
size_t,
unw_word_t *,
void *);
.br
int
_UPT_resume(unw_addr_space_t,
unw_cursor_t *,
void *);
.br
.PP
.SH DESCRIPTION
.PP
The ptrace(2)
system\-call makes it possible for a process to
gain access to the machine\-state and virtual memory of \fIanother\fP
process. With the right set of call\-back routines, it is therefore
possible to hook up libunwind
to another process via
ptrace(2).
While it\&'s not very difficult to do so directly,
libunwind
further facilitates this task by providing
ready\-to\-use callbacks for this purpose. The routines and variables
implementing this facility use a name\-prefix of _UPT,
which is
stands for ``unwind\-via\-ptrace\&''\&.
.PP
An application that wants to use the _UPT\-facility
first needs
to create a new libunwind
address\-space that represents the
target process. This is done by calling
unw_create_addr_space().
In many cases, the application
will simply want to pass the address of _UPT_accessors
as the
first argument to this routine. Doing so will ensure that
libunwind
will be able to properly unwind the target process.
However, in special circumstances, an application may prefer to use
only portions of the _UPT\-facility.
For this reason, the
individual callback routines (_UPT_find_proc_info(),
_UPT_put_unwind_info(),
etc.) are also available for direct
use. Of course, the addresses of these routines could also be picked
up from _UPT_accessors,
but doing so would prevent static
initialization. Also, when using _UPT_accessors,
\fIall\fP
the callback routines will be linked into the application, even if
they are never actually called.
.PP
Next, the application can turn on ptrace\-mode on the target process,
either by forking a new process, invoking PTRACE_TRACEME,
and
then starting the target program (via execve(2)),
or by
directly attaching to an already running process (via
PTRACE_ATTACH).
Either way, once the process\-ID (pid) of the
target process is known, a _UPT\-info\-structure
can be created
by calling _UPT_create(),
passing the pid of the target process
as the only argument. The returned void\-pointer then needs to be
passed as the ``argument\&'' pointer (third argument) to
unw_init_remote().
.PP
The _UPT_resume()
routine can be used to resume execution of
the target process. It simply invokes ptrace(2)
with a command
value of PTRACE_CONT\&.
.PP
When the application is done using libunwind
on the target
process, _UPT_destroy()
needs to be called, passing it the
void\-pointer that was returned by the corresponding call to
_UPT_create().
This ensures that all memory and other
resources are freed up.
.PP
.SH AVAILABILITY
.PP
Since ptrace(2)
works within a single machine only, the
_UPT\-facility
by definition is not available in
libunwind\-versions
configured for cross\-unwinding.
.PP
.SH THREAD SAFETY
.PP
The _UPT\-facility
assumes that a single _UPT\-info
structure is never shared between threads. Because of this, no
explicit locking is used. As long as only one thread uses
a _UPT\-info
structure at any given time, this facility
is thread\-safe.
.PP
.SH RETURN VALUE
.PP
_UPT_create()
may return a NULL
pointer if it fails
to create the _UPT\-info\-structure
for any reason. For the
current implementation, the only reason this call may fail is when the
system is out of memory.
.PP
.SH FILES
.PP
.TP
libunwind\-ptrace.h
Headerfile to include when using the
interface defined by this library.
.TP
\fB\-l\fPunwind\-ptrace \fB\-l\fPunwind\-generic
Linker\-switches to add when building a program that uses the
functions defined by this library.
.PP
.SH SEE ALSO
.PP
execve(2),
libunwind(3),
ptrace(2)
.PP
.SH AUTHOR
.PP
David Mosberger\-Tang
.br
Email: \fBdmosberger@gmail.com\fP
.br
WWW: \fBhttp://www.nongnu.org/libunwind/\fP\&.
.\" NOTE: This file is generated, DO NOT EDIT.
|
