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1 .\" $NetBSD: ktrace.2,v 1.17 2004/05/13 10:20:58 wiz Exp $
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30 .\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93
31 .\"
32 .Dd June 4, 1993
33 .Dt KTRACE 2
34 .Os
35 .Sh NAME
36 .Nm ktrace
37 .Nd process tracing
38 .Sh LIBRARY
39 .Lb libc
40 .Sh SYNOPSIS
41 .In sys/types.h
42 .In sys/uio.h
43 .In sys/ktrace.h
44 .Ft int
45 .Fn ktrace "const char *tracefile" "int ops" "int trpoints" "pid_t pid"
46 .Ft int
47 .Fn fktrace "int fd" "int ops" "int trpoints" "pid_t pid"
48 .Sh DESCRIPTION
49 The
50 .Fn ktrace
51 function enables or disables tracing of one or more processes.
52 Users may only trace their own processes.
53 Only the super-user can trace setuid or setgid programs.
54 .Pp
55 The
56 .Ar tracefile
57 gives the pathname of the file to be used for tracing.
58 The file must exist and be writable by the calling process.
59 All trace records are always appended to the file,
60 so the file must be truncated to zero length to discard
61 previous trace data.
62 If tracing points are being disabled (see KTROP_CLEAR below),
63 .Ar tracefile
64 may be NULL.
65 If using
66 .Fn fktrace
67 then instead of passing a filename as
68 .Ar tracefile ,
69 a file descriptor is passed as
70 .Ar fd
71 and behaviour is otherwise the same.
72 .Pp
73 The
74 .Nm ops
75 parameter specifies the requested ktrace operation.
76 The defined operations are:
77 .Bl -column KTRFLAG_DESCENDXXX -offset indent
78 .It KTROP_SET Enable trace points specified in Ar trpoints .
79 .It KTROP_CLEAR Disable trace points specified in Ar trpoints .
80 .It KTROP_CLEARFILE Stop all tracing.
81 .It KTRFLAG_DESCEND The tracing change should apply to the
82 specified process and all its current children.
83 .El
84 .Pp
85 The
86 .Nm trpoints
87 parameter specifies the trace points of interest.
88 The defined trace points are:
89 .Bl -column KTRFAC_SYSCALLXXX -offset indent
90 .It KTRFAC_SYSCALL Trace system calls.
91 .It KTRFAC_SYSRET Trace return values from system calls.
92 .It KTRFAC_NAMEI Trace name lookup operations.
93 .It KTRFAC_GENIO Trace all I/O (note that this option can
94 generate much output).
95 .It KTRFAC_PSIG Trace posted signals.
96 .It KTRFAC_CSW Trace context switch points.
97 .It KTRFAC_EMUL Trace emulation changes.
98 .It KTRFAC_INHERIT Inherit tracing to future children.
99 .El
100 .Pp
101 Each tracing event outputs a record composed of a generic header
102 followed by a trace point specific structure.
103 The generic header is:
104 .Bd -literal
105 struct ktr_header {
106 int ktr_len; /* length of buf */
107 short ktr_type; /* trace record type */
108 pid_t ktr_pid; /* process id */
109 char ktr_comm[MAXCOMLEN+1]; /* command name */
110 struct timeval ktr_time; /* timestamp */
111 caddr_t ktr_buf;
112 };
113 .Ed
114 .Pp
115 The
116 .Nm ktr_len
117 field specifies the length of the
118 .Nm ktr_type
119 data that follows this header.
120 The
121 .Nm ktr_pid
122 and
123 .Nm ktr_comm
124 fields specify the process and command generating the record.
125 The
126 .Nm ktr_time
127 field gives the time (with microsecond resolution)
128 that the record was generated.
129 The
130 .Nm ktr_buf
131 is an internal kernel pointer and is not useful.
132 .Pp
133 The generic header is followed by
134 .Nm ktr_len
135 bytes of a
136 .Nm ktr_type
137 record.
138 The type specific records are defined in the
139 .Pa \*[Lt]sys/ktrace.h\*[Gt]
140 include file.
141 .Sh RETURN VALUES
142 On successful completion a value of 0 is returned.
143 Otherwise, a value of \-1 is returned and
144 .Va errno
145 is set to show the error.
146 .Sh ERRORS
147 .Fn ktrace
148 will fail if:
149 .Bl -tag -width ENAMETOOLONGAA
150 .It Bq Er ENOTDIR
151 A component of the path prefix is not a directory.
152 .It Bq Er EINVAL
153 The pathname contains a character with the high-order bit set.
154 .It Bq Er ENAMETOOLONG
155 A component of a pathname exceeded 255 characters,
156 or an entire path name exceeded 1023 characters.
157 .It Bq Er ENOENT
158 The named tracefile does not exist.
159 .It Bq Er EACCES
160 Search permission is denied for a component of the path prefix.
161 .It Bq Er ELOOP
162 Too many symbolic links were encountered in translating the pathname.
163 .It Bq Er EIO
164 An I/O error occurred while reading from or writing to the file system.
165 .El
166 .Sh SEE ALSO
167 .Xr kdump 1 ,
168 .Xr ktrace 1
169 .Sh HISTORY
170 A
171 .Nm ktrace
172 function call first appeared in
173 .Bx 4.4 .