[PATCH,RFC 2.6.14 12/15] KGDB: netpoll-based ethernet driver

[Tom Rini <trini@kernel.crashing.org>]

This is the simple KGDB over Ethernet I/O driver that uses netpoll for all of
the heavy lifting.  At one point this was very similar to the version Matt
Mackall wrote and is currently in Andrew's tree.  Since then it has been
reworked to fit into our model.

 drivers/net/Makefile |    1 
 drivers/net/kgdboe.c |  189 +++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/Kconfig.debug    |   24 ++++++
 3 files changed, 214 insertions(+)

Index: linux-2.6.14/drivers/net/kgdboe.c
===================================================================
--- /dev/null
+++ linux-2.6.14/drivers/net/kgdboe.c
@@ -0,0 +1,189 @@
+/*
+ * drivers/net/kgdboe.c
+ *
+ * A network interface for GDB.
+ * Based upon 'gdbserial' by David Grothe <dave@gcom.com>
+ * and Scott Foehner <sfoehner@engr.sgi.com>
+ *
+ * Maintainers: Amit S. Kale <amitkale@linsyssoft.com> and
+ * 		Tom Rini <trini@kernel.crashing.org>
+ *
+ * 2004 (c) Amit S. Kale <amitkale@linsyssoft.com>
+ * 2004-2005 (c) MontaVista Software, Inc.
+ * 2005 (c) Wind River Systems, Inc.
+ *
+ * Contributors at various stages not listed above:
+ * San Mehat <nettwerk@biodome.org>, Robert Walsh <rjwalsh@durables.org>,
+ * wangdi <wangdi@clusterfs.com>, Matt Mackall <mpm@selenic.com>,
+ * Pavel Machek <pavel@suse.cz>, Jason Wessel <jason.wessel@windriver.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ */
+
+#include <linux/kernel.h>
+#include <linux/interrupt.h>
+#include <linux/string.h>
+#include <linux/kgdb.h>
+#include <linux/netpoll.h>
+#include <linux/init.h>
+
+#include <asm/atomic.h>
+
+#define IN_BUF_SIZE 512		/* power of 2, please */
+#define OUT_BUF_SIZE 30		/* We don't want to send too big of a packet. */
+
+static char in_buf[IN_BUF_SIZE], out_buf[OUT_BUF_SIZE];
+static int in_head, in_tail, out_count;
+static atomic_t in_count;
+/* 0 = unconfigured, 1 = netpoll options parsed, 2 = fully configured. */
+static int configured;
+static struct kgdb_io local_kgdb_io_ops;
+
+MODULE_DESCRIPTION("KGDB driver for network interfaces");
+MODULE_LICENSE("GPL");
+static char config[256];
+module_param_string(kgdboe, config, 256, 0);
+MODULE_PARM_DESC(kgdboe, " kgdboe=[src-port]@[src-ip]/[dev],"
+		 "[tgt-port]@<tgt-ip>/<tgt-macaddr>\n");
+
+static void rx_hook(struct netpoll *np, int port, char *msg, int len)
+{
+	int i;
+
+	np->remote_port = port;
+
+	/*
+	 * This could be GDB trying to attach.  But it could also be GDB
+	 * finishing up a session, with kgdb_connected=0 but GDB sending
+	 * an ACK for the final packet.  To make sure we don't try and
+	 * make a breakpoint when GDB is leaving, make sure that if
+	 * !kgdb_connected the only len == 1 packet we allow is ^C.
+	 */
+	if (!kgdb_connected && (len != 1 || msg[0] == 3) &&
+	    !atomic_read(&kgdb_setting_breakpoint))
+		tasklet_schedule(&kgdb_tasklet_breakpoint);
+
+	for (i = 0; i < len; i++) {
+		if (msg[i] == 3)
+			tasklet_schedule(&kgdb_tasklet_breakpoint);
+
+		if (atomic_read(&in_count) >= IN_BUF_SIZE) {
+			/* buffer overflow, clear it */
+			in_head = in_tail = 0;
+			atomic_set(&in_count, 0);
+			break;
+		}
+		in_buf[in_head++] = msg[i];
+		in_head &= (IN_BUF_SIZE - 1);
+		atomic_inc(&in_count);
+	}
+}
+
+static struct netpoll np = {
+	.name = "kgdboe",
+	.dev_name = "eth0",
+	.rx_hook = rx_hook,
+	.local_port = 6443,
+	.remote_port = 6442,
+	.remote_mac = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+};
+
+static void eth_pre_exception_handler(void)
+{
+	netpoll_set_trap(1);
+}
+
+static void eth_post_exception_handler(void)
+{
+	netpoll_set_trap(0);
+}
+
+static int eth_get_char(void)
+{
+	int chr;
+
+	while (atomic_read(&in_count) == 0)
+		netpoll_poll(&np);
+
+	chr = in_buf[in_tail++];
+	in_tail &= (IN_BUF_SIZE - 1);
+	atomic_dec(&in_count);
+	return chr;
+}
+
+static void eth_flush_buf(void)
+{
+	if (out_count && np.dev) {
+		netpoll_send_udp(&np, out_buf, out_count);
+		memset(out_buf, 0, sizeof(out_buf));
+		out_count = 0;
+	}
+}
+
+static void eth_put_char(u8 chr)
+{
+	out_buf[out_count++] = chr;
+	if (out_count == OUT_BUF_SIZE)
+		eth_flush_buf();
+}
+
+static int option_setup(char *opt)
+{
+	configured = !netpoll_parse_options(&np, opt);
+	return 0;
+}
+__setup("kgdboe=", option_setup);
+
+static int init_kgdboe(void)
+{
+	/* Already done? */
+	if (configured == 2)
+		return 0;
+
+	if (strlen(config))
+		option_setup(config);
+
+	if (!configured) {
+		printk("kgdboe: configuration incorrect - kgdboe not "
+		       "loaded.\n");
+		printk("  Usage: kgdboe=[src-port]@[src-ip]/[dev],[tgt-port]"
+		       "@<tgt-ip>/<tgt-macaddr>\n");
+		return -EINVAL;
+	}
+
+	if (netpoll_setup(&np)) {
+		printk("kgdboe: netpoll_setup failed kgdboe failed\n");
+		return -EINVAL;
+	}
+
+	if (kgdb_register_io_module(&local_kgdb_io_ops))
+		return -EINVAL;
+
+	printk(KERN_INFO "kgdboe: debugging over ethernet enabled\n");
+
+	configured = 2;
+
+	return 0;
+}
+
+static void cleanup_kgdboe(void)
+{
+	netpoll_cleanup(&np);
+	configured = 0;
+
+	kgdb_unregister_io_module(&local_kgdb_io_ops);
+}
+
+static struct kgdb_io local_kgdb_io_ops = {
+	.read_char = eth_get_char,
+	.write_char = eth_put_char,
+	.init = init_kgdboe,
+	.flush = eth_flush_buf,
+	.pre_exception = eth_pre_exception_handler,
+	.post_exception = eth_post_exception_handler
+};
+
+module_init(init_kgdboe);
+module_exit(cleanup_kgdboe);
Index: linux-2.6.14/drivers/net/Makefile
===================================================================
--- linux-2.6.14.orig/drivers/net/Makefile
+++ linux-2.6.14/drivers/net/Makefile
@@ -201,3 +201,4 @@ obj-$(CONFIG_IRDA) += irda/
 obj-$(CONFIG_ETRAX_ETHERNET) += cris/
 
 obj-$(CONFIG_NETCONSOLE) += netconsole.o
+obj-$(CONFIG_KGDBOE) += kgdboe.o
Index: linux-2.6.14/lib/Kconfig.debug
===================================================================
--- linux-2.6.14.orig/lib/Kconfig.debug
+++ linux-2.6.14/lib/Kconfig.debug
@@ -241,6 +241,18 @@ config KGDB_8250_NOMODULE
 	  GDB.  This is independent of the normal (SERIAL_8250) driver
 	  for this chipset.
 
+config KGDBOE_NOMODULE
+	bool "KGDB: On ethernet - in kernel"
+	select KGDBOE
+	select NETPOLL
+	select NETPOLL_TRAP
+	select NETPOLL_RX
+	help
+	  Uses the NETPOLL API to communicate with the host GDB via UDP.
+	  In order for this to work, the ethernet interface specified must
+	  support the NETPOLL API, and this must be initialized at boot.
+	  See the documentation for syntax.
+
 config KGDB_MPSC
 	bool "KGDB on MV64x60 MPSC"
 	depends on SERIAL_MPSC
@@ -260,6 +272,18 @@ config KGDB_SIBYTE
 	depends on MIPS && SIBYTE_SB1xxx_SOC
 endchoice
 
+config KGDBOE
+	tristate "KGDB: On ethernet" if !KGDBOE_NOMODULE
+	depends on m && KGDB_ONLY_MODULES
+	select NETPOLL
+	select NETPOLL_TRAP
+	select NETPOLL_RX
+	help
+	  Uses the NETPOLL API to communicate with the host GDB via UDP.
+	  In order for this to work, the ethernet interface specified must
+	  support the NETPOLL API, and this must be initialized at boot.
+	  See the documentation for syntax.
+
 config KGDB_8250
 	tristate "KGDB: On generic serial port (8250)" if !KGDB_8250_NOMODULE
 	depends on m && KGDB_ONLY_MODULES

-- 
Tom