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28 .\" @(#)ktrace.2 8.1 (Berkeley) 6/4/93
45 .Fn ktrace "const char *tracefile" "int ops" "int trpoints" "int pid"
49 system call enables or disables tracing of one or more processes.
50 Users may only trace their own processes.
51 Only the super-user can trace setuid or setgid programs.
56 gives the pathname of the file to be used for tracing.
57 The file must exist and be a regular file writable by the calling process.
58 All trace records are always appended to the file,
59 so the file must be truncated to zero length to discard
61 If tracing points are being disabled (see KTROP_CLEAR below),
67 argument specifies the requested ktrace operation.
68 The defined operations are:
69 .Bl -column KTRFLAG_DESCENDXXX -offset indent
70 .It "KTROP_SET Enable trace points specified in"
72 .It "KTROP_CLEAR Disable trace points specified in
74 .It "KTROP_CLEARFILE Stop all tracing."
75 .It "KTRFLAG_DESCEND The tracing change should apply to the"
76 specified process and all its current children.
81 argument specifies the trace points of interest.
82 The defined trace points are:
83 .Bl -column KTRFAC_PROCCTORXXX -offset indent
84 .It "KTRFAC_SYSCALL Trace system calls."
85 .It "KTRFAC_SYSRET Trace return values from system calls."
86 .It "KTRFAC_NAMEI Trace name lookup operations."
87 .It "KTRFAC_GENIO Trace all I/O (note that this option can"
88 generate much output).
89 .It "KTRFAC_PSIG Trace posted signals."
90 .It "KTRFAC_CSW Trace context switch points."
91 .It "KTRFAC_USER Trace application-specific events."
92 .It "KTRFAC_STRUCT Trace certain data structures."
93 .It "KTRFAC_SYSCTL Trace sysctls."
94 .It "KTRFAC_PROCCTOR Trace process construction."
95 .It "KTRFAC_PROCDTOR Trace process destruction."
96 .It "KTRFAC_INHERIT Inherit tracing to future children."
99 Each tracing event outputs a record composed of a generic header
100 followed by a trace point specific structure.
101 The generic header is:
104 int ktr_len; /* length of buf */
105 short ktr_type; /* trace record type */
106 pid_t ktr_pid; /* process id */
107 char ktr_comm[MAXCOMLEN+1]; /* command name */
108 struct timeval ktr_time; /* timestamp */
109 intptr_t ktr_tid; /* was ktr_buffer */
115 field specifies the length of the
117 data that follows this header.
122 fields specify the process and command generating the record.
125 field gives the time (with microsecond resolution)
126 that the record was generated.
129 field holds a thread id.
131 The generic header is followed by
136 The type specific records are defined in the
142 tunables influence the behaviour of
144 .Bl -tag -width indent
145 .It Va kern.ktrace.geniosize
146 bounds the amount of data a traced I/O request will log
148 .It Va kern.ktrace.request_pool
149 bounds the number of trace events being logged at a time.
152 Sysctl tunables that control process debuggability (as determined by
154 also affect the operation of
165 A component of the path prefix is not a directory.
166 .It Bq Er ENAMETOOLONG
167 A component of a pathname exceeded 255 characters,
168 or an entire path name exceeded 1023 characters.
170 The named tracefile does not exist.
172 Search permission is denied for a component of the path prefix.
174 Too many symbolic links were encountered in translating the pathname.
176 An I/O error occurred while reading from or writing to the file system.
178 The kernel was not compiled with
183 A thread may be unable to log one or more tracing events due to a
184 temporary shortage of resources.
185 This condition is remembered by the kernel, and the next tracing request
186 that succeeds will have the flag
200 system call first appeared in