i386_set_watch(3)

NAME

i386_clr_watch, i386_set_watch - manage i386 debug register

values

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <machine/reg.h>
#include <machine/sysarch.h>
int
i386_clr_watch(int watchnum, struct dbreg *d);
int
i386_set_watch(int  watchnum,  unsigned  int  watchaddr, int
size,
        int access, struct dbreg *d);

DESCRIPTION

The i386_clr_watch() function will disable the indicated

watch point
within the specified debug register set.

The i386_set_watch() function will set up the specified de

bug registers
as indicated by the arguments. The watchnum argument speci

fies which
watch register is used, 0, 1, 2, 3, or -1. If 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. The watchaddr argument

specifies the
watch address, size specifies the size in bytes of the area

to be watched
(1, 2, or 4 bytes), and access specifies the type of watch

point:

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.

Note that these functions do not actually set or clear

breakpoints; they
manipulate the indicated debug register set. You must use

ptrace(2) to
retrieve and install the debug register values for a pro

cess.

RETURN VALUES

The i386_clr_watch() function returns 0 on success, or -1 if

watchnum is
invalid (not in the range of 0-3).

The i386_set_watch() function will return the watchnum argu

ment, or the
watchnum actually used in the case that watchnum is -1 on

success. On
error, i386_set_watch() will return -1 indicating that the

watchpoint
could not be set up because either no more watchpoints are

available, or
watchnum, size, or access is invalid.

SEE ALSO

ptrace(2), procfs(5)

AUTHORS

This man page was written by Brian S. Dean.

BSD August 24, 2000

BSD