.\" Copyright (c) 2000 Brian S. Dean
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.\" $FreeBSD$
.\"
.Dd August 24, 2000
.Os
.Dt I386_SET_WATCH 3
.Sh NAME
.Nm i386_clr_watch ,
.Nm i386_set_watch
.Nd manage i386 debug register values
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <machine/reg.h>
.Fd #include <machine/sysarch.h>
.Ft int
.Fn i386_clr_watch "int watchnum" "struct dbreg *d"
.Ft int
.Fn i386_set_watch "int watchnum" "unsigned int watchaddr" "int size" "int access" "struct dbreg *d"
.Sh DESCRIPTION
.Fn i386_clr_watch
will disable the indicated watch point within the specified debug
register set.
.Pp
.Fn i386_set_watch
will set up the specified debug registers as indicated by the
parameters.  The
.Fa watchnum
argument specifies which watch register is used, 0, 1, 2, 3, or -1.  If
.Fa watchnum
is -1, a free watch register is found and used.  If there are no free
watch registers, an error code of -1 is returned.  
.Fa Watchaddr
specifies the watch address, 
.Fa size
specifies the size in bytes of the area to be watched (1, 2, or 4 bytes),
and
.Fa access
specifes the type of watch point:
.Pp
.Bd -literal -offset indent -compact
DBREG_DR7_EXEC	  An execution breakpoint.
DBREG_DR7_WRONLY  Break only when the watch area is written to.
DBREG_DR7_RDWR	  Break when the watch area is read from or written
                  to.
.Ed
.Pp
Note that these functions do not actually set or clear breakpoints;
they manipulate the indicated debug register set.  You must use
.Xr ptrace 2
to retrieve and install the debug register values for a process.
.Sh RETURN VALUES
.Fn i386_clr_watch
returns 0 on success, or -1 if
.Fa watchnum
is invalid (not in the range of 0-3).
.Pp
.Fn i386_set_watch
will return the
.Fa watchnum
argument, or the watchnum actually used in the case that
.Fa watchnum
is -1 on success.  On error,
.Fn i386_set_watch
will return -1 indicating that the watchpoint could not be set up
because either no more watchpoints are available, or
.Fa watchnum ,
.Fa size ,
or
.Fa access
is invalid.
.Sh SEE ALSO
.Xr ptrace 2 ,
.Xr procfs 5
.Sh AUTHORS
This man page was written by
.An Brian S. Dean .