ktrace(2) - NetBSD Manual Pages

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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 9.4                      March 19, 2016                      NetBSD 9.4