Document the support in the kernel for hardware debug registers on the

ix86 platform which allows for hardware watchpoints, etc...

Submitted by:	Brian Dean <brdean@unx.sas.com>

lib/libc/sys/ptrace.2

@@ -202,6 +202,23 @@ it loads the traced process' floating-point registers from the
 .Aq Pa machine/reg.h )
 pointed to by
 .Fa addr .
+.It Dv PT_GETDBREGS
+This request reads the traced process' debug registers into
+the
+.Dq Li "struct dbreg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
+.It Dv PT_SETDBREGS
+This request is the converse of
+.Dv PT_GETDBREGS ;
+it loads the traced process' debug registers from the
+.Dq Li "struct dbreg"
+(defined in
+.Aq Pa machine/reg.h )
+pointed to by
+.Fa addr .
 .El
 .Sh RETURN VALUES
 Some requests can cause
@@ -250,8 +267,10 @@ was neither 0 nor a legal signal number.
 .Dv PT_GETREGS ,
 .Dv PT_SETREGS ,
 .Dv PT_GETFPREGS ,
+.Dv PT_SETFPREGS ,
+.Dv PT_GETDBREGS ,
 or
-.Dv PT_SETFPREGS
+.Dv PT_SETDBREGS
 was attempted on a process with no valid register set.  (This is
 normally true only of system processes.)
 .El

share/man/man5/procfs.5

@@ -74,6 +74,13 @@ prefix,
 in which case that signal is delivered to the process
 (see
 .Xr sigaction 2 ).
+.It Pa dbregs
+The debug registers as defined by
+.Dv "struct dbregs"
+in
+.Pa <machine/reg.h> .
+.Pa dbregs
+is currently only implemented on the i386 architecture.
 .It Pa etype
 The type of the executable referenced by the
 .Pa file

sys/amd64/include/reg.h

@@ -118,6 +118,9 @@ struct fpreg {
 	unsigned char	fpr_pad[64];
 };
 
+/*
+ * Register set accessible via /proc/$pid/dbregs.
+ */
 struct dbreg {
 	unsigned int  dr0;	/* debug address register 0 */
 	unsigned int  dr1;	/* debug address register 1 */

sys/i386/include/reg.h

@@ -118,6 +118,9 @@ struct fpreg {
 	unsigned char	fpr_pad[64];
 };
 
+/*
+ * Register set accessible via /proc/$pid/dbregs.
+ */
 struct dbreg {
 	unsigned int  dr0;	/* debug address register 0 */
 	unsigned int  dr1;	/* debug address register 1 */