I386_SET_WATCH(3)

NAME
i386_clr_watch, i386_set_watch - manage i386 debug register values

LIBRARY
libc

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 debug registers as indicated by the arguments. The watchnum argument specifies 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 process.

RETURN VALUES
On success, the i386_clr_watch() function returns 0. On error, -1 returned which indicates that watchnum is invalid (not in the range of 0-3). If the specified watchnum was already disabled, no error is returned.

On success, the i386_set_watch() function returns the watchnum argument, or the watchnum actually used in the case where the specified watchnum was -1. On error, the i386_set_watch() function returns -1 indicating that the watchpoint could not established because either no more watchpoints are available, or watchnum, size, or access is invalid.

SEE ALSO
ptrace(2), procfs(4)

AUTHORS
This man page was written by Brian S. Dean.