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42 .Fn ktrace "const char *tracefile" "int ops" "int trpoints" "int pid"
46 system call enables or disables tracing of one or more processes.
47 Users may only trace their own processes.
48 Only the super-user can trace setuid or setgid programs.
53 gives the pathname of the file to be used for tracing.
54 The file must exist and be a regular file writable by the calling process.
55 All trace records are always appended to the file,
56 so the file must be truncated to zero length to discard
58 If tracing points are being disabled (see KTROP_CLEAR below),
64 argument specifies the requested ktrace operation.
65 The defined operations are:
66 .Bl -column KTRFLAG_DESCENDXXX -offset indent
67 .It KTROP_SET Ta "Enable trace points specified in"
69 .It KTROP_CLEAR Ta "Disable trace points specified in"
71 .It KTROP_CLEARFILE Ta "Stop all tracing."
72 .It KTRFLAG_DESCEND Ta "The tracing change should apply to the"
73 specified process and all its current children.
78 argument specifies the trace points of interest.
79 The defined trace points are:
80 .Bl -column KTRFAC_PROCCTORXXX -offset indent
81 .It KTRFAC_SYSCALL Ta "Trace system calls."
82 .It KTRFAC_SYSRET Ta "Trace return values from system calls."
83 .It KTRFAC_NAMEI Ta "Trace name lookup operations."
84 .It KTRFAC_GENIO Ta "Trace all I/O (note that this option can"
85 generate much output).
86 .It KTRFAC_PSIG Ta "Trace posted signals."
87 .It KTRFAC_CSW Ta "Trace context switch points."
88 .It KTRFAC_USER Ta "Trace application-specific events."
89 .It KTRFAC_STRUCT Ta "Trace certain data structures."
90 .It KTRFAC_SYSCTL Ta "Trace sysctls."
91 .It KTRFAC_PROCCTOR Ta "Trace process construction."
92 .It KTRFAC_PROCDTOR Ta "Trace process destruction."
93 .It KTRFAC_CAPFAIL Ta "Trace capability failures."
94 .It KTRFAC_FAULT Ta "Trace page faults."
95 .It KTRFAC_FAULTEND Ta "Trace the end of page faults."
96 .It KTRFAC_STRUCT_ARRAY Ta "Trace arrays of certain data structures."
97 .It KTRFAC_INHERIT Ta "Inherit tracing to future children."
100 Each tracing event outputs a record composed of a generic header
101 followed by a trace point specific structure.
102 The generic header is:
105 int ktr_len; /* length of buf */
106 short ktr_type; /* trace record type */
107 pid_t ktr_pid; /* process id */
108 char ktr_comm[MAXCOMLEN+1]; /* command name */
109 struct timeval ktr_time; /* timestamp */
110 long ktr_tid; /* thread id */
116 field specifies the length of the
118 data that follows this header.
123 fields specify the process and command generating the record.
126 field gives the time (with microsecond resolution)
127 that the record was generated.
130 field holds a thread id.
132 The generic header is followed by
137 The type specific records are defined in the
143 tunables influence the behaviour of
145 .Bl -tag -width indent
146 .It Va kern.ktrace.genio_size
147 bounds the amount of data a traced I/O request will log
149 .It Va kern.ktrace.request_pool
150 bounds the number of trace events being logged at a time.
153 Sysctl tunables that control process debuggability (as determined by
155 also affect the operation of
166 A component of the path prefix is not a directory.
167 .It Bq Er ENAMETOOLONG
168 A component of a pathname exceeded 255 characters,
169 or an entire path name exceeded 1023 characters.
171 The named tracefile does not exist.
173 Search permission is denied for a component of the path prefix.
175 Too many symbolic links were encountered in translating the pathname.
177 An I/O error occurred while reading from or writing to the file system.
179 Corrupted data was detected while reading from the file system.
181 The kernel was not compiled with
186 A thread may be unable to log one or more tracing events due to a
187 temporary shortage of resources.
188 This condition is remembered by the kernel, and the next tracing request
189 that succeeds will have the flag
203 system call first appeared in