diff --git a/sys/arm64/arm64/debug_monitor.c b/sys/arm64/arm64/debug_monitor.c
--- a/sys/arm64/arm64/debug_monitor.c
+++ b/sys/arm64/arm64/debug_monitor.c
@@ -28,6 +28,7 @@
  */
 
 #include "opt_ddb.h"
+#include "opt_gdb.h"
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
@@ -181,7 +182,7 @@
 	isb();
 }
 
-#ifdef DDB
+#if defined(DDB) || defined(GDB)
 void
 kdb_cpu_set_singlestep(void)
 {
@@ -254,7 +255,9 @@
 
 	return (dbg_remove_watchpoint(NULL, addr, size));
 }
+#endif /* DDB || GDB */
 
+#ifdef DDB
 static const char *
 dbg_watchtype_str(uint32_t type)
 {
diff --git a/sys/conf/files.arm b/sys/conf/files.arm
--- a/sys/conf/files.arm
+++ b/sys/conf/files.arm
@@ -19,8 +19,7 @@
 arm/arm/db_disasm.c		optional	ddb
 arm/arm/db_interface.c		optional	ddb
 arm/arm/db_trace.c		optional	ddb
-arm/arm/debug_monitor.c		optional	ddb armv6
-arm/arm/debug_monitor.c		optional	ddb armv7
+arm/arm/debug_monitor.c		optional	ddb | gdb
 arm/arm/disassem.c		optional	ddb
 arm/arm/dump_machdep.c		standard
 arm/arm/elf_machdep.c		standard
diff --git a/sys/conf/files.x86 b/sys/conf/files.x86
--- a/sys/conf/files.x86
+++ b/sys/conf/files.x86
@@ -320,7 +320,7 @@
 x86/x86/busdma_bounce.c		standard
 x86/x86/busdma_machdep.c	standard
 x86/x86/cpu_machdep.c		standard
-x86/x86/dbreg.c			optional	ddb
+x86/x86/dbreg.c			optional	ddb | gdb
 x86/x86/dump_machdep.c		standard
 x86/x86/fdt_machdep.c		optional	fdt
 x86/x86/identcpu.c		standard
diff --git a/sys/gdb/gdb_main.c b/sys/gdb/gdb_main.c
--- a/sys/gdb/gdb_main.c
+++ b/sys/gdb/gdb_main.c
@@ -618,6 +618,100 @@
 #endif
 }
 
+/*
+ * Handle a 'Z' packet: set a breakpoint or watchpoint.
+ *
+ * Currently, only watchpoints are supported.
+ */
+static void
+gdb_z_insert(void)
+{
+	intmax_t addr, length;
+	char ztype;
+	int error;
+
+	ztype = gdb_rx_char();
+	if (gdb_rx_char() != ',' || gdb_rx_varhex(&addr) ||
+	    gdb_rx_char() != ',' || gdb_rx_varhex(&length)) {
+		error = EINVAL;
+		goto fail;
+	}
+
+	switch (ztype) {
+	case '2': /* write watchpoint */
+		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
+		    (vm_size_t)length, KDB_DBG_ACCESS_W);
+		break;
+	case '3': /* read watchpoint */
+		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
+		    (vm_size_t)length, KDB_DBG_ACCESS_R);
+		break;
+	case '4': /* access (RW) watchpoint */
+		error = kdb_cpu_set_watchpoint((vm_offset_t)addr,
+		    (vm_size_t)length, KDB_DBG_ACCESS_RW);
+		break;
+	case '1': /* hardware breakpoint */
+	case '0': /* software breakpoint */
+		/* Not implemented. */
+		gdb_tx_empty();
+		return;
+	default:
+		error = EINVAL;
+		break;
+	}
+	if (error != 0)
+		goto fail;
+	gdb_tx_ok();
+	return;
+fail:
+	gdb_tx_err(error);
+	return;
+}
+
+/*
+ * Handle a 'z' packet; clear a breakpoint or watchpoint.
+ *
+ * Currently, only watchpoints are supported.
+ */
+static void
+gdb_z_remove(void)
+{
+	intmax_t addr, length;
+	char ztype;
+	int error;
+
+	ztype = gdb_rx_char();
+	if (gdb_rx_char() != ',' || gdb_rx_varhex(&addr) ||
+	    gdb_rx_char() != ',' || gdb_rx_varhex(&length)) {
+		error = EINVAL;
+		goto fail;
+	}
+
+	switch (ztype) {
+	case '2': /* write watchpoint */
+	case '3': /* read watchpoint */
+	case '4': /* access (RW) watchpoint */
+		error = kdb_cpu_clr_watchpoint((vm_offset_t)addr,
+		    (vm_size_t)length);
+		break;
+	case '1': /* hardware breakpoint */
+	case '0': /* software breakpoint */
+		/* Not implemented. */
+		gdb_tx_empty();
+		return;
+	default:
+		error = EINVAL;
+		break;
+	}
+	if (error != 0)
+		goto fail;
+	gdb_tx_ok();
+	return;
+fail:
+	gdb_tx_err(error);
+	return;
+}
+
 static int
 gdb_trap(int type, int code)
 {
@@ -868,6 +962,14 @@
 				gdb_tx_err(ENOENT);
 			break;
 		}
+		case 'z': {	/* Remove watchpoint. */
+			gdb_z_remove();
+			break;
+		}
+		case 'Z': {	/* Set watchpoint. */
+			gdb_z_insert();
+			break;
+		}
 		case EOF:
 			/* Empty command. Treat as unknown command. */
 			/* FALLTHROUGH */
diff --git a/sys/x86/x86/mp_x86.c b/sys/x86/x86/mp_x86.c
--- a/sys/x86/x86/mp_x86.c
+++ b/sys/x86/x86/mp_x86.c
@@ -32,6 +32,7 @@
 #endif
 #include "opt_cpu.h"
 #include "opt_ddb.h"
+#include "opt_gdb.h"
 #include "opt_kstack_pages.h"
 #include "opt_pmap.h"
 #include "opt_sched.h"
@@ -1520,7 +1521,7 @@
 	 */
 	invltlb_glob();
 
-#if defined(__amd64__) && defined(DDB)
+#if defined(__amd64__) && (defined(DDB) || defined(GDB))
 	amd64_db_resume_dbreg();
 #endif