.\"	$OpenBSD: ktrace.9,v 1.5 2003/10/26 15:07:25 jmc Exp $
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.\" Copyright (c) 2003 Michael Shalayeff
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.Dd July 21, 2003
.Dt KTRACE 9
.Os
.Sh NAME
.Nm ktrcsw ,
.Nm ktremul ,
.Nm ktrgenio ,
.Nm ktrnamei ,
.Nm ktrpsig ,
.Nm ktrsyscall ,
.Nm ktrsysret ,
.Nm KTRPOINT
.Nd "process tracing kernel interface"
.Sh SYNOPSIS
.Fd #include <sys/param.h>
.Fd #include <sys/proc.h>
.Fd #include <sys/ktrace.h>
.Fn KTRPOINT "struct proc *p" "int type"
.Ft void
.Fn ktrcsw "struct proc *p" "int out" "int user"
.Ft void
.Fn ktremul "struct proc *p" "char *emul"
.Ft void
.Fn ktrgenio "struct proc *p" "int fd" "enum uio_rw rw" "struct iovec *iov" "int len" "int error"
.Ft void
.Fn ktrnamei "struct proc *p" "char *path"
.Ft void
.Fn ktrpsig "struct proc *p" "int sig" "sig_t action" "int mask" "int code" "siginfo_t *si"
.Ft void
.Fn ktrsyscall "struct proc *p" "register_t code" "size_t argsize" "register_t args[]"
.Ft void
.Fn ktrsysret "struct proc *p" "register_t code" "int error" "register_t retval"
.Sh 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
.Xr ktrace 2
system call.
Each of the functions (except for
.Nm KTRPOINT )
is meant for a particular type of event and is described below.
.Pp
The
.Fn 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
.Fa type
argument are a mask of the KTRFAC_ values described in
.Xr ktrace 2 .
.Pp
.Fn ktrcsw
is called during the context switching.
The
.Fa 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
.Fa user
argument indicates whether a voluntary (false) or an involuntary (true)
switching has happened.
.Pp
.Fn ktremul
should be called every time emulation for the execution environment
is changed and thus the name of which is given in the
.Fa name
argument.
.Pp
.Fn ktrgenio
should be called for each generic input/output transaction that is
described by the
.Fa fd
file descriptor,
.Fa rw
transaction type (consult
.Pa sys/sys/uio.h
for the
.Nm enum uio_rw
definition),
.Fa iov
input/output data vector,
.Fa len
size of the
.Fa iov
vector,
and, lastly,
.Fa error
status of the transaction.
.Pp
.Fn ktrnamei
should be called every time a
.Xr namei 9
operation is performed over the
.Fa path
name.
.Pp
.Fn ktrpsig
should be called for each signal
.Fa sig
posted for the traced process.
The
.Fa action
taken is one of
.Nm SIG_DFL ,
.Nm SIG_IGN ,
or
.Nm SIG_ERR
as described in the
.Xr sigaction 2
document.
.Fa mask
is the current traced process' signal mask.
Signal-specific code and
.Em siginfo_t
structure as described in
.Aq Pa sys/siginfo.h
are given in the
.Fa code
and
.Fa si
arguments respectively.
.Pp
.Fn ktrsyscall
should be called for each system call number
.Fa code
executed with arguments in
.Fa args
of total count of
.Fa argsize .
.Pp
.Fn ktrsysret
should be called for a return from each system call number
.Fa code
and error number of
.Fa error
as described in
.Xr errno 2
and a return value in
.Fa retval
that is syscall dependent.
.Sh CODE REFERENCES
The process tracing facility is implemented in
.Pa sys/kern/kern_ktrace.c .
.Sh SEE ALSO
.Xr errno 2 ,
.Xr ktrace 2 ,
.Xr syscall 2 ,
.Xr namei 9 ,
.Xr syscall 9
.Sh HISTORY
The process tracing facility first appeared in
.Bx 4.4 .
.Pp
The
.Nm ktrace
section manual page appeared in
.Ox 3.4 .