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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 Ta "Enable trace points specified in"
72 .It KTROP_CLEAR Ta "Disable trace points specified in"
74 .It KTROP_CLEARFILE Ta "Stop all tracing."
75 .It KTRFLAG_DESCEND Ta "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 Ta "Trace system calls."
85 .It KTRFAC_SYSRET Ta "Trace return values from system calls."
86 .It KTRFAC_NAMEI Ta "Trace name lookup operations."
87 .It KTRFAC_GENIO Ta "Trace all I/O (note that this option can"
88 generate much output).
89 .It KTRFAC_PSIG Ta "Trace posted signals."
90 .It KTRFAC_CSW Ta "Trace context switch points."
91 .It KTRFAC_USER Ta "Trace application-specific events."
92 .It KTRFAC_STRUCT Ta "Trace certain data structures."
93 .It KTRFAC_SYSCTL Ta "Trace sysctls."
94 .It KTRFAC_PROCCTOR Ta "Trace process construction."
95 .It KTRFAC_PROCDTOR Ta "Trace process destruction."
96 .It KTRFAC_CAPFAIL Ta "Trace capability failures."
97 .It KTRFAC_FAULT Ta "Trace page faults."
98 .It KTRFAC_FAULTEND Ta "Trace the end of page faults."
99 .It KTRFAC_STRUCT_ARRAY Ta "Trace arrays of certain data structures."
100 .It KTRFAC_INHERIT Ta "Inherit tracing to future children."
103 Each tracing event outputs a record composed of a generic header
104 followed by a trace point specific structure.
105 The generic header is:
108 int ktr_len; /* length of buf */
109 short ktr_type; /* trace record type */
110 pid_t ktr_pid; /* process id */
111 char ktr_comm[MAXCOMLEN+1]; /* command name */
112 struct timeval ktr_time; /* timestamp */
113 long ktr_tid; /* thread id */
119 field specifies the length of the
121 data that follows this header.
126 fields specify the process and command generating the record.
129 field gives the time (with microsecond resolution)
130 that the record was generated.
133 field holds a thread id.
135 The generic header is followed by
140 The type specific records are defined in the
146 tunables influence the behaviour of
148 .Bl -tag -width indent
149 .It Va kern.ktrace.geniosize
150 bounds the amount of data a traced I/O request will log
152 .It Va kern.ktrace.request_pool
153 bounds the number of trace events being logged at a time.
156 Sysctl tunables that control process debuggability (as determined by
158 also affect the operation of
169 A component of the path prefix is not a directory.
170 .It Bq Er ENAMETOOLONG
171 A component of a pathname exceeded 255 characters,
172 or an entire path name exceeded 1023 characters.
174 The named tracefile does not exist.
176 Search permission is denied for a component of the path prefix.
178 Too many symbolic links were encountered in translating the pathname.
180 An I/O error occurred while reading from or writing to the file system.
182 Corrupted data was detected while reading from the file system.
184 The kernel was not compiled with
189 A thread may be unable to log one or more tracing events due to a
190 temporary shortage of resources.
191 This condition is remembered by the kernel, and the next tracing request
192 that succeeds will have the flag
206 system call first appeared in