[GDB] Add GDB stub for remote debugging

See http://etherboot.org/wiki/dev/gdbstub for documentation.

1 files changed, 330 insertions, 0 deletions

diff --git a/src/core/gdbstub.c b/src/core/gdbstub.c
new file mode 100644
index 00000000..213887b5
--- /dev/null
+++ b/src/core/gdbstub.c
@@ -0,0 +1,330 @@
+/*
+ * Copyright (C) 2008 Stefan Hajnoczi <stefanha@gmail.com>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+/**
+ * @file
+ *
+ * GDB stub for remote debugging
+ *
+ */
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <ctype.h>
+#include <assert.h>
+#include <gpxe/process.h>
+#include <gpxe/serial.h>
+#include "gdbmach.h"
+
+enum {
+	POSIX_EINVAL = 0x1c /* used to report bad arguments to GDB */
+};
+
+struct gdbstub {
+	int signo;
+	gdbreg_t *regs;
+	int exit_handler; /* leave interrupt handler */
+
+	void ( * parse ) ( struct gdbstub *stub, char ch );
+	uint8_t cksum1;
+
+	/* 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;
+};
+
+/* Packet parser states */
+static void gdbstub_state_new ( struct gdbstub *stub, char ch );
+static void gdbstub_state_data ( struct gdbstub *stub, char ch );
+static void gdbstub_state_cksum1 ( struct gdbstub *stub, char ch );
+static void gdbstub_state_cksum2 ( struct gdbstub *stub, char ch );
+static void gdbstub_state_wait_ack ( struct gdbstub *stub, char ch );
+
+static uint8_t gdbstub_from_hex_digit ( char ch ) {
+	return ( isdigit ( ch ) ? ch - '0' : tolower ( ch ) - 'a' + 0xa ) & 0xf;
+}
+
+static uint8_t gdbstub_to_hex_digit ( uint8_t b ) {
+	b &= 0xf;
+	return ( b < 0xa ? '0' : 'a' - 0xa ) + b;
+}
+
+static void gdbstub_from_hex_buf ( char *dst, char *src, int len ) {
+	while ( len-- > 0 ) {
+		*dst = gdbstub_from_hex_digit ( *src++ );
+		if ( len-- > 0 ) {
+			*dst = (*dst << 4) | gdbstub_from_hex_digit ( *src++ );
+		}
+		dst++;
+	}
+}
+
+static void gdbstub_to_hex_buf ( char *dst, char *src, int len ) {
+	while ( len-- > 0 ) {
+		*dst++ = gdbstub_to_hex_digit ( *src >> 4 );
+		*dst++ = gdbstub_to_hex_digit ( *src++ );
+	}
+}
+
+static uint8_t gdbstub_cksum ( char *data, int len ) {
+	uint8_t cksum = 0;
+	while ( len-- > 0 ) {
+		cksum += ( uint8_t ) *data++;
+	}
+	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->parse = gdbstub_state_wait_ack;
+}
+
+/* GDB commands */
+static void gdbstub_send_ok ( struct gdbstub *stub ) {
+	stub->payload [ 0 ] = 'O';
+	stub->payload [ 1 ] = 'K';
+	stub->len = 2;
+	gdbstub_tx_packet ( stub );
+}
+
+static void gdbstub_send_num_packet ( struct gdbstub *stub, char reply, int num ) {
+	stub->payload [ 0 ] = reply;
+	stub->payload [ 1 ] = gdbstub_to_hex_digit ( ( char ) num >> 4 );
+	stub->payload [ 2 ] = gdbstub_to_hex_digit ( ( char ) num );
+	stub->len = 3;
+	gdbstub_tx_packet ( stub );
+}
+
+/* Format is arg1,arg2,...,argn:data where argn are hex integers and data is not an argument */
+static int gdbstub_get_packet_args ( struct gdbstub *stub, unsigned long *args, int nargs, int *stop_idx ) {
+	int i;
+	char ch = 0;
+	int argc = 0;
+	unsigned long val = 0;
+	for ( i = 1; i < stub->len && argc < nargs; i++ ) {
+		ch = stub->payload [ i ];
+		if ( ch == ':' ) {
+			break;
+		} else if ( ch == ',' ) {
+			args [ argc++ ] = val;
+			val = 0;
+		} else {
+			val = ( val << 4 ) | gdbstub_from_hex_digit ( ch );
+		}
+	}
+	if ( stop_idx ) {
+		*stop_idx = i;
+	}
+	if ( argc < nargs ) {
+		args [ argc++ ] = val;
+	}
+	return ( ( i == stub->len || ch == ':' ) && argc == nargs );
+}
+
+static void gdbstub_send_errno ( struct gdbstub *stub, int errno ) {
+	gdbstub_send_num_packet ( stub, 'E', errno );
+}
+
+static void gdbstub_report_signal ( struct gdbstub *stub ) {
+	gdbstub_send_num_packet ( stub, 'S', stub->signo );
+}
+
+static void gdbstub_read_regs ( struct gdbstub *stub ) {
+	gdbstub_to_hex_buf ( stub->payload, ( char * ) stub->regs, GDBMACH_SIZEOF_REGS );
+	stub->len = GDBMACH_SIZEOF_REGS * 2;
+	gdbstub_tx_packet ( stub );
+}
+
+static void gdbstub_write_regs ( struct gdbstub *stub ) {
+	if ( stub->len != 1 + GDBMACH_SIZEOF_REGS * 2 ) {
+		gdbstub_send_errno ( stub, POSIX_EINVAL );
+		return;
+	}
+	gdbstub_from_hex_buf ( ( char * ) stub->regs, &stub->payload [ 1 ], stub->len );
+	gdbstub_send_ok ( stub );
+}
+
+static void gdbstub_read_mem ( struct gdbstub *stub ) {
+	unsigned long args [ 2 ];
+	if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], NULL ) ) {
+		gdbstub_send_errno ( stub, POSIX_EINVAL );
+		return;
+	}
+	args [ 1 ] = ( args [ 1 ] < sizeof stub->payload / 2 ) ? args [ 1 ] : sizeof stub->payload / 2;
+	gdbstub_to_hex_buf ( stub->payload, ( char * ) args [ 0 ], args [ 1 ] );
+	stub->len = args [ 1 ] * 2;
+	gdbstub_tx_packet ( stub );
+}
+
+static void gdbstub_write_mem ( struct gdbstub *stub ) {
+	unsigned long args [ 2 ];
+	int colon;
+	if ( !gdbstub_get_packet_args ( stub, args, sizeof args / sizeof args [ 0 ], &colon ) ||
+			colon >= stub->len || stub->payload [ colon ] != ':' ||
+			( stub->len - colon - 1 ) % 2 != 0 ) {
+		gdbstub_send_errno ( stub, POSIX_EINVAL );
+		return;
+	}
+	gdbstub_from_hex_buf ( ( char * ) args [ 0 ], &stub->payload [ colon + 1 ], stub->len - colon - 1 );
+	gdbstub_send_ok ( stub );
+}
+
+static void gdbstub_continue ( struct gdbstub *stub, int single_step ) {
+	gdbreg_t pc;
+	if ( stub->len > 1 && gdbstub_get_packet_args ( stub, &pc, 1, NULL ) ) {
+		gdbmach_set_pc ( stub->regs, pc );
+	}
+	gdbmach_set_single_step ( stub->regs, single_step );
+	stub->exit_handler = 1;
+	/* Reply will be sent when we hit the next breakpoint or interrupt */
+}
+
+static void gdbstub_rx_packet ( struct gdbstub *stub ) {
+	switch ( stub->payload [ 0 ] ) {
+		case '?':
+			gdbstub_report_signal ( stub );
+			break;
+		case 'g':
+			gdbstub_read_regs ( stub );
+			break;
+		case 'G':
+			gdbstub_write_regs ( stub );
+			break;
+		case 'm':
+			gdbstub_read_mem ( stub );
+			break;
+		case 'M':
+			gdbstub_write_mem ( stub );
+			break;
+		case 'c':
+			gdbstub_continue ( stub, 0 );
+			break;
+		case 's':
+			gdbstub_continue ( stub, 1 );
+			break;
+		default:
+			stub->len = 0;
+			gdbstub_tx_packet ( stub );
+			break;
+	}
+}
+
+/* GDB packet parser */
+static void gdbstub_state_new ( struct gdbstub *stub, char ch ) {
+	if ( ch == '$' ) {
+		stub->len = 0;
+		stub->parse = gdbstub_state_data;
+	}
+}
+
+static void gdbstub_state_data ( struct gdbstub *stub, char ch ) {
+	if ( ch == '#' ) {
+		stub->parse = gdbstub_state_cksum1;
+	} else if ( 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 ) {
+			stub->payload [ stub->len++ ] = ch;
+		}
+	}
+}
+
+static void gdbstub_state_cksum1 ( struct gdbstub *stub, char ch ) {
+	stub->cksum1 = gdbstub_from_hex_digit ( ch ) << 4;
+	stub->parse = gdbstub_state_cksum2;
+}
+
+static void gdbstub_state_cksum2 ( struct gdbstub *stub, char ch ) {
+	uint8_t their_cksum;
+	uint8_t our_cksum;
+
+	stub->parse = gdbstub_state_new;
+	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, '+' );
+		if ( stub->len > 0 ) {
+			gdbstub_rx_packet ( stub );
+		}
+	} else {
+		gdbstub_putchar ( stub, '-' );
+	}
+}
+
+static void gdbstub_state_wait_ack ( struct gdbstub *stub, char ch ) {
+	if ( ch == '+' ) {
+		stub->parse = gdbstub_state_new;
+	} else if ( ch == '-' ) {
+		gdbstub_tx_packet ( stub ); /* retransmit */
+	}
+}
+
+static void gdbstub_parse ( struct gdbstub *stub, char ch ) {
+	stub->parse ( stub, ch );
+}
+
+static struct gdbstub stub = {
+	.parse = gdbstub_state_new
+};
+
+__cdecl void gdbstub_handler ( int signo, gdbreg_t *regs ) {
+	int ch;
+	stub.signo = signo;
+	stub.regs = regs;
+	stub.exit_handler = 0;
+	gdbstub_report_signal ( &stub );
+	while ( ( ch = gdbstub_getchar( &stub ) ) != -1 ) {
+		gdbstub_parse ( &stub, ch );
+	}
+}
+
+/* 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 process gdbstub_activity_process __permanent_process = {
+	.step = gdbstub_activity_step,
+};