KTRACE(9)		     OpenBSD Kernel Manual		     KTRACE(9)

NAME
     ktrcsw, ktremul, ktrgenio, ktrnamei, ktrpsig, ktrsyscall, ktrsysret,
     KTRPOINT - process tracing kernel interface

SYNOPSIS
     #include <sys/param.h>
     #include <sys/proc.h>
     #include <sys/ktrace.h>

     KTRPOINT(struct proc *p, int type);

     void
     ktrcsw(struct proc *p, int out, int user);

     void
     ktremul(struct proc *p, char *emul);

     void
     ktrgenio(struct proc *p, int fd, enum uio_rw rw, struct iovec *iov, int
     len, int error);

     void
     ktrnamei(struct proc *p, char *path);

     void
     ktrpsig(struct proc *p, int sig, sig_t action, int mask, int
     code, siginfo_t *si);

     void
     ktrsyscall(struct proc *p, register_t code, size_t argsize, register_t
     args[]);

     void
     ktrsysret(struct proc *p, register_t code, int error, register_t retval);

DESCRIPTION
     This interface is meant for kernel subsystems and machine dependent code
     to inform the user about the events occurring to the process should
     tracing of such be enabled using the ktrace(2) system call.  Each of the
     functions (except for KTRPOINT) is meant for a particular type of event
     and is described below.

     The KTRPOINT() macro should be used before calling any of the other
     tracing functions to verify that tracing for that particular type of
     events has been enabled.  Possible values for the type argument are a
     mask of the KTRFAC_ values described in ktrace(2).

     ktrcsw() is called during the context switching.  The user argument is a
     boolean value specifying whether the process has been put into a waiting
     state (true) or placed onto a running queue (false).  Furthermore the
     user argument indicates whether a voluntary (false) or an involuntary
     (true) switching has happened.

     ktremul() should be called every time emulation for the execution
     environment is changed and thus the name of which is given in the name
     argument.

     ktrgenio() should be called for each generic input/output transaction
     that is described by the fd file descriptor, rw transaction type (consult
     sys/sys/uio.h for the enum uio_rw definition), iov input/output data
     vector, len size of the iov vector, and, lastly, error status of the
     transaction.

     ktrnamei() should be called every time a namei(9) operation is performed
     over the path name.

     ktrpsig() should be called for each signal sig posted for the traced
     process.  The action taken is one of SIG_DFL, SIG_IGN, or SIG_ERR as
     described in the sigaction(2) document.  mask is the current traced
     process' signal mask.  Signal-specific code and siginfo_t structure as
     described in <sys/siginfo.h> are given in the code and si arguments
     respectively.

     ktrsyscall() should be called for each system call number code executed
     with arguments in args of total count of argsize.

     ktrsysret() should be called for a return from each system call number
     code and error number of error as described in errno(2) and a return
     value in retval that is syscall dependent.

CODE REFERENCES
     The process tracing facility is implemented in sys/kern/kern_ktrace.c.

SEE ALSO
     errno(2), ktrace(2), syscall(2), namei(9), syscall(9)

HISTORY
     The process tracing facility first appeared in 4.4BSD.

     The ktrace section manual page appeared in OpenBSD 3.4.

OpenBSD 4.9			 May 31, 2007			   OpenBSD 4.9

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