[GDB] Remote debugging over UDP

This commit implements GDB over UDP.  Using UDP is more complex than
serial and has required some restructuring.

The GDB stub is now built using one or both of GDBSERIAL and GDBUDP
config.h options.

To enter the debugger, execute the gPXE shell command:
gdbstub <transport> [<options>...]

Where <transport> is "serial" or "udp".  For "udp", the name of a
configured network device is required:
gdbstub udp net0

The GDB stub listens on UDP port 43770 by default.

1 files changed, 47 insertions, 42 deletions

diff --git a/src/core/gdbstub.c b/src/core/gdbstub.c
index df50dc81..c331b85b 100644
--- a/src/core/gdbstub.c
+++ b/src/core/gdbstub.c
@@ -24,22 +24,24 @@
  */
 
 #include <stdlib.h>
-#include <stddef.h>
 #include <stdio.h>
+#include <string.h>
 #include <ctype.h>
 #include <byteswap.h>
-#include <gpxe/process.h>
-#include <gpxe/serial.h>
+#include <gpxe/gdbstub.h>
 #include "gdbmach.h"
 
 enum {
-	POSIX_EINVAL = 0x1c /* used to report bad arguments to GDB */
+	POSIX_EINVAL = 0x1c,  /* used to report bad arguments to GDB */
+	SIZEOF_PAYLOAD = 256, /* buffer size of GDB payload data */
 };
 
 struct gdbstub {
+	struct gdb_transport *trans;
+	int exit_handler; /* leave interrupt handler */
+
 	int signo;
 	gdbreg_t *regs;
-	int exit_handler; /* leave interrupt handler */
 
 	void ( * parse ) ( struct gdbstub *stub, char ch );
 	uint8_t cksum1;
@@ -47,10 +49,15 @@ struct gdbstub {
 	/* Buffer for payload data when parsing a packet.  Once the
 	 * packet has been received, this buffer is used to hold
 	 * the reply payload. */
-	char payload [ 256 ];
-	int len;
+	char buf [ SIZEOF_PAYLOAD + 4 ]; /* $...PAYLOAD...#XX */
+	char *payload;                   /* start of payload */
+	int len;                         /* length of payload */
 };
 
+/* Transports */
+static struct gdb_transport gdb_transport_start[0] __table_start ( struct gdb_transport, gdb_transports );
+static struct gdb_transport gdb_transport_end[0] __table_end ( struct gdb_transport, gdb_transports );
+
 /* Packet parser states */
 static void gdbstub_state_new ( struct gdbstub *stub, char ch );
 static void gdbstub_state_data ( struct gdbstub *stub, char ch );
@@ -132,29 +139,13 @@ static uint8_t gdbstub_cksum ( char *data, int len ) {
 	return cksum;
 }
 
-static int gdbstub_getchar ( struct gdbstub *stub ) {
-	if ( stub->exit_handler ) {
-		return -1;
-	}
-	return serial_getc();
-}
-
-static void gdbstub_putchar ( struct gdbstub * stub __unused, char ch ) {
-	serial_putc ( ch );
-}
-
 static void gdbstub_tx_packet ( struct gdbstub *stub ) {
 	uint8_t cksum = gdbstub_cksum ( stub->payload, stub->len );
-	int i;
-
-	gdbstub_putchar ( stub, '$' );
-	for ( i = 0; i < stub->len; i++ ) {
-		gdbstub_putchar ( stub, stub->payload [ i ] );
-	}
-	gdbstub_putchar ( stub, '#' );
-	gdbstub_putchar ( stub, gdbstub_to_hex_digit ( cksum >> 4 ) );
-	gdbstub_putchar ( stub, gdbstub_to_hex_digit ( cksum ) );
-
+	stub->buf [ 0 ] = '$';
+	stub->buf [ stub->len + 1 ] = '#';
+	stub->buf [ stub->len + 2 ] = gdbstub_to_hex_digit ( cksum >> 4 );
+	stub->buf [ stub->len + 3 ] = gdbstub_to_hex_digit ( cksum );
+	stub->trans->send ( stub->buf, stub->len + 4 );
 	stub->parse = gdbstub_state_wait_ack;
 }
 
@@ -229,7 +220,7 @@ static void gdbstub_read_mem ( struct gdbstub *stub ) {
 		gdbstub_send_errno ( stub, POSIX_EINVAL );
 		return;
 	}
-	args [ 1 ] = ( args [ 1 ] < sizeof stub->payload / 2 ) ? args [ 1 ] : sizeof stub->payload / 2;
+	args [ 1 ] = ( args [ 1 ] < SIZEOF_PAYLOAD / 2 ) ? args [ 1 ] : SIZEOF_PAYLOAD / 2;
 	gdbstub_to_hex_buf ( stub->payload, ( char * ) args [ 0 ], args [ 1 ] );
 	stub->len = args [ 1 ] * 2;
 	gdbstub_tx_packet ( stub );
@@ -306,7 +297,7 @@ static void gdbstub_state_data ( struct gdbstub *stub, char ch ) {
 		stub->len = 0; /* retry new packet */
 	} else {
 		/* If the length exceeds our buffer, let the checksum fail */
-		if ( stub->len < ( int ) sizeof stub->payload ) {
+		if ( stub->len < SIZEOF_PAYLOAD ) {
 			stub->payload [ stub->len++ ] = ch;
 		}
 	}
@@ -325,12 +316,12 @@ static void gdbstub_state_cksum2 ( struct gdbstub *stub, char ch ) {
 	their_cksum = stub->cksum1 + gdbstub_from_hex_digit ( ch );
 	our_cksum = gdbstub_cksum ( stub->payload, stub->len );
 	if ( their_cksum == our_cksum ) {
-		gdbstub_putchar ( stub, '+' );
+		stub->trans->send ( "+", 1 );
 		if ( stub->len > 0 ) {
 			gdbstub_rx_packet ( stub );
 		}
 	} else {
-		gdbstub_putchar ( stub, '-' );
+		stub->trans->send ( "-", 1 );
 	}
 }
 
@@ -351,23 +342,37 @@ static struct gdbstub stub = {
 };
 
 __cdecl void gdbstub_handler ( int signo, gdbreg_t *regs ) {
-	int ch;
+	char packet [ SIZEOF_PAYLOAD + 4 ];
+	size_t len, i;
+
+	/* A transport must be set up */
+	if ( !stub.trans ) {
+		return;
+	}
+
 	stub.signo = signo;
 	stub.regs = regs;
 	stub.exit_handler = 0;
 	gdbstub_report_signal ( &stub );
-	while ( ( ch = gdbstub_getchar( &stub ) ) != -1 ) {
-		gdbstub_parse ( &stub, ch );
+	while ( !stub.exit_handler && ( len = stub.trans->recv ( packet, sizeof ( packet ) ) ) > 0 ) {
+		for ( i = 0; i < len; i++ ) {
+			gdbstub_parse ( &stub, packet [ i ] );
+		}
 	}
 }
 
-/* Activity monitor to detect packets from GDB when we are not active */
-static void gdbstub_activity_step ( struct process *process __unused ) {
-	if ( serial_ischar() ) {
-		gdbmach_breakpoint();
+struct gdb_transport *find_gdb_transport ( const char *name ) {
+	struct gdb_transport *trans;
+	for ( trans = gdb_transport_start; trans < gdb_transport_end; trans++ ) {
+		if ( strcmp ( trans->name, name ) == 0 ) {
+			return trans;
+		}
 	}
+	return NULL;
 }
 
-struct process gdbstub_activity_process __permanent_process = {
-	.step = gdbstub_activity_step,
-};
+void gdbstub_start ( struct gdb_transport *trans ) {
+	stub.trans = trans;
+	stub.payload = &stub.buf [ 1 ];
+	gdbmach_breakpoint();
+}