diff --git a/lib/libc/sys/ptrace.2 b/lib/libc/sys/ptrace.2
index 20ee4d979df6..dc66d1d77d44 100644
--- a/lib/libc/sys/ptrace.2
+++ b/lib/libc/sys/ptrace.2
@@ -1,4 +1,4 @@
-.\"	$Id$
+.\"	$Id: ptrace.2,v 1.2 1996/01/20 17:56:06 nate Exp $
 .\"	$NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $
 .\"
 .\" This file is in the public domain.
@@ -75,7 +75,7 @@ and data, which is why there are two requests: conceptually,
 .Dv PT_READ_I
 reads from the instruction space and
 .Dv PT_READ_D
-reads from the data space.  In the current NetBSD implementation, these
+reads from the data space.  In the current FreeBSD implementation, these
 two requests are completely identical.  The
 .Fa addr
 argument specifies the address (in the traced process' virtual address
@@ -145,6 +145,61 @@ The traced process terminates, as if
 had been used with
 .Dv SIGKILL
 given as the signal to be delivered.
+.It Dv PT_ATTACH
+This request allows a process to gain control of an otherwise unrelated
+process and begin tracing it.  It does not need any cooperation from
+the to-be-traced process.  In this case,
+.Fa pid
+specifies the process ID of the to-be-traced process, and the other two
+arguments are ignored.  This request requires that the target process
+must have the same real UID as the tracing process, and that it must
+not be executing a setuid or setgid executable.  (If the tracing
+process is running as root, these restrictions do not apply.)  The
+tracing process will see the newly-traced process stop and may then
+control it as if it had been traced all along.
+.It Dv PT_DETACH
+This request is like PT_CONTINUE, except that it does not allow
+specifying an alternate place to continue execution, and after it
+succeeds, the traced process is no longer traced and continues
+execution normally.
+.El
+.Pp
+Additionally, machine-specific requests can exist.  On the i386, these
+are:
+.Bl -tag -width 12n
+.It Dv PT_GETREGS
+This request reads the traced process' machine registers into the
+.Dq Li "struct reg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
+.It Dv PT_SETREGS
+This request is the converse of
+.Dv PT_GETREGS ;
+it loads the traced process' machine registers from the
+.Dq Li "struct reg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
+.It Dv PT_GETFPREGS
+This request reads the traced process' floating-point registers into
+the
+.Dq Li "struct fpreg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
+.It Dv PT_SETFPREGS
+This request is the converse of
+.Dv PT_GETFPREGS ;
+it loads the traced process' floating-point registers from the
+.Dq Li "struct fpreg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
 .El
 .Sh ERRORS
 Some requests can cause
@@ -164,6 +219,10 @@ No process having the specified process ID exists.
 .It Bq Er EINVAL
 .Bl -bullet -compact
 .It
+A process attempted to use
+.Dv PT_ATTACH
+on itself.
+.It
 The
 .Fa request
 was not one of the legal requests.
@@ -182,12 +241,40 @@ The signal number (in
 to
 .Dv PT_CONTINUE
 was neither 0 nor a legal signal number.
+.It
+.Dv PT_GETREGS ,
+.Dv PT_SETREGS ,
+.Dv PT_GETFPREGS ,
+or
+.Dv PT_SETFPREGS
+was attempted on a process with no valid register set.  (This is
+normally true only of system processes.)
+.El
+.It Bq Er EBUSY
+.Bl -bullet -compact
+.It
+.Dv PT_ATTACH
+was attempted on a process that was already being traced.
+.It
+A request attempted to manipulate a process that was being traced by
+some process other than the one making the request.
+.It
+A request (other than
+.Dv PT_ATTACH )
+specified a process that wasn't stopped.
 .El
 .It Bq Er EPERM
 .Bl -bullet -compact
 .It
-A request
+A request (other than
+.Dv PT_ATTACH )
 attempted to manipulate a process that wasn't being traced at all.
+.It
+An attempt was made to use
+.Dv PT_ATTACH
+on a process in violation of the requirements listed under
+.Dv PT_ATTACH
+above.
 .El
 .Sh SEE ALSO
 .Xr sigaction 2