ktrace(2)
- NetBSD Manual Pages
KTRACE(2) NetBSD System Calls Manual KTRACE(2)
NAME
ktrace, fktrace -- process tracing
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/param.h>
#include <sys/ktrace.h>
int
ktrace(const char *tracefile, int ops, int trpoints, pid_t pid);
int
fktrace(int fd, int ops, int trpoints, pid_t pid);
DESCRIPTION
The ktrace() function enables or disables tracing of one or more pro-
cesses. Users may only trace their own processes. Only the super-user
can trace setuid or setgid programs.
The tracefile gives the pathname of the file to be used for tracing. The
file must exist and be writable by the calling process. All trace
records are always appended to the file, so the file must be truncated to
zero length to discard previous trace data. If tracing points are being
disabled (see KTROP_CLEAR below), tracefile may be NULL. If using
fktrace() then instead of passing a filename as tracefile, a file
descriptor is passed as fd and behaviour is otherwise the same.
The ops parameter specifies the requested ktrace operation. The defined
operations are:
KTROP_SET Enable trace points specified in trpoints.
KTROP_CLEAR Disable trace points specified in trpoints.
KTROP_CLEARFILE Stop all tracing.
KTRFLAG_DESCEND The tracing change should apply to the speci-
fied process and all its current children.
The trpoints parameter specifies the trace points of interest. The
defined trace points are:
KTRFAC_SYSCALL Trace system calls.
KTRFAC_SYSRET Trace return values from system calls.
KTRFAC_NAMEI Trace name lookup operations.
KTRFAC_GENIO Trace all I/O (note that this option can gen-
erate much output).
KTRFAC_PSIG Trace posted signals.
KTRFAC_CSW Trace context switch points.
KTRFAC_EMUL Trace emulation changes.
KTRFAC_INHERIT Inherit tracing to future children.
Each tracing event outputs a record composed of a generic header followed
by a trace point specific structure. The generic header is:
struct ktr_header {
int ktr_len; /* length of buf */
short ktr_type; /* trace record type */
short ktr_version; /* trace record version */
pid_t ktr_pid; /* process id */
char ktr_comm[MAXCOMLEN+1]; /* command name */
struct timespec ktr_time; /* timestamp */
lwpid_t ktr_lid;
};
The ktr_len field specifies the length of the data that follows this
header. The ktr_type and ktr_version fields (whose ordering in the
structure depends on byte order) specify the format of this data. The
ktr_pid, ktr_lid, and ktr_comm fields specify the process and command
generating the record. The ktr_time field gives the time (with nanosec-
ond resolution) that the record was generated.
The generic header is followed by ktr_len bytes of a ktr_type record of
version ktr_version. The type specific records are defined in the
<sys/ktrace.h> include file.
RETURN VALUES
On successful completion a value of 0 is returned. Otherwise, a value of
-1 is returned and errno is set to show the error.
ERRORS
ktrace() will fail if:
[EACCES] Search permission is denied for a component of the path
prefix.
[EINVAL] The pathname contains a character with the high-order bit
set.
[EIO] An I/O error occurred while reading from or writing to
the file system.
[ELOOP] Too many symbolic links were encountered in translating
the pathname.
[ENAMETOOLONG] A component of a pathname exceeded {NAME_MAX} characters,
or an entire path name exceeded {PATH_MAX} characters.
[ENOENT] The named tracefile does not exist.
[ENOTDIR] A component of the path prefix is not a directory.
SEE ALSO
kdump(1), ktrace(1)
HISTORY
A ktrace function call first appeared in 4.4BSD.
NetBSD 9.2 March 19, 2016 NetBSD 9.2
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