add support for copying console messages to a remote gdb

Reviewed by:	kan

sys/conf/files

@@ -1088,6 +1088,7 @@ fs/umapfs/umap_vnops.c		optional umapfs
 fs/unionfs/union_subr.c		optional unionfs
 fs/unionfs/union_vfsops.c	optional unionfs
 fs/unionfs/union_vnops.c	optional unionfs
+gdb/gdb_cons.c			optional gdb
 gdb/gdb_main.c			optional gdb
 gdb/gdb_packet.c		optional gdb
 geom/bde/g_bde.c		optional geom_bde

sys/gdb/gdb_cons.c

@@ -0,0 +1,172 @@
+/*-
+ * Copyright (c) 2006 Sam Leffler
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/* 
+ * Support for redirecting console msgs to gdb.  We register
+ * a pseudo console to hook cnputc and send stuff to the gdb
+ * port.  The only trickiness here is buffering output so this
+ * isn't dog slow.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/cons.h>
+#include <sys/kdb.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/reboot.h>
+#include <sys/sysctl.h>
+
+#include <machine/gdb_machdep.h>
+#include <machine/kdb.h>
+
+#include <gdb/gdb.h>
+#include <gdb/gdb_int.h>
+
+struct gdbcons {
+	int	npending;
+	/* /2 for hex conversion, -6 for protocol glue */
+	char	buf[GDB_BUFSZ/2 - 6];
+	struct callout flush;
+};
+static struct gdbcons state = { -1 };
+
+static	int gdbcons_enable = 0;
+SYSCTL_INT(_debug, OID_AUTO, gdbcons, CTLFLAG_RW, &gdbcons_enable,
+	    0, "copy console messages to gdb");
+TUNABLE_INT("debug.gdbcons", &gdbcons_enable);
+
+static void
+gdb_cnprobe(struct consdev *cp)
+{
+	sprintf(cp->cn_name, "gdb");
+	cp->cn_pri = CN_LOW;		/* XXX no way to say "write only" */
+}
+
+static void
+gdb_cninit(struct consdev *cp)
+{
+	struct gdbcons *c = &state;
+
+	/* setup tx buffer and callout */
+	if (c->npending == -1) {
+		c->npending = 0;
+		callout_init(&c->flush, CALLOUT_MPSAFE);
+		cp->cn_arg = c;
+	}
+}
+
+static int
+gdb_nogetc(struct consdev *cp)
+{
+	return -1;
+}
+
+static void
+gdb_tx_puthex(int c)
+{
+	const char *hex = "0123456789abcdef";
+
+	gdb_tx_char(hex[(c>>4)&0xf]);
+	gdb_tx_char(hex[(c>>0)&0xf]);
+}
+
+static void
+gdb_cnflush(void *arg)
+{
+	struct gdbcons *gc = arg;
+	int i;
+
+	gdb_tx_begin('O');
+	for (i = 0; i < gc->npending; i++)
+		gdb_tx_puthex(gc->buf[i]);
+	gdb_tx_end();
+	gc->npending = 0;
+}
+
+/*
+ * This glop is to figure out when it's safe to use callouts
+ * to defer buffer flushing.  There's probably a better way
+ * and/or an earlier point in the boot process when it's ok.
+ */
+static int calloutok = 0;
+static void
+oktousecallout(void *data __unused)
+{
+	calloutok = 1;
+}
+SYSINIT(gdbhack, SI_SUB_RUN_SCHEDULER, SI_ORDER_ANY, oktousecallout, NULL)
+
+static void
+gdb_cnputc(struct consdev *cp, int c)
+{
+	struct gdbcons *gc;
+
+	if (gdbcons_enable && gdb_cur != NULL && gdb_listening) {
+		gc = cp->cn_arg;
+		if (gc->npending != 0) {
+			/*
+			 * Cancel any pending callout and flush the
+			 * buffer if there's no space for this byte.
+			 */
+			if (calloutok)
+				callout_stop(&gc->flush);
+			if (gc->npending == sizeof(gc->buf))
+				gdb_cnflush(gc);
+		}
+		gc->buf[gc->npending++] = c;
+		/*
+		 * Flush on end of line; this is especially helpful
+		 * during boot when we don't have callouts to flush
+		 * the buffer.  Otherwise we defer flushing; a 1/4 
+		 * second is a guess.
+		 */
+		if (c == '\n')
+			gdb_cnflush(gc);
+		else if (calloutok)
+			callout_reset(&gc->flush, hz/4, gdb_cnflush, gc);
+	}
+}
+
+/* NB: no get interface, we supply nogetc for checkc too */
+CONS_DRIVER(gdb, gdb_cnprobe, gdb_cninit, NULL, gdb_nogetc, gdb_nogetc,
+	gdb_cnputc, NULL);
+
+/*
+ * Our console device only gets attached if the system is booted
+ * with RB_MULTIPLE set so gdb_init also calls us to attach the
+ * console so we're setup regardless.
+ */
+void
+gdb_consinit(void)
+{
+	gdb_cnprobe(&gdb_consdev);
+	gdb_cninit(&gdb_consdev);
+	cnadd(&gdb_consdev);
+}

sys/gdb/gdb_int.h

@@ -31,6 +31,9 @@
 
 extern struct gdb_dbgport *gdb_cur;
 
+extern int gdb_listening;
+void gdb_consinit(void);
+
 extern char *gdb_rxp;
 extern size_t gdb_rxsz;
 extern char *gdb_txp;

sys/gdb/gdb_main.c

@@ -50,6 +50,7 @@ GDB_DBGPORT(null, NULL, NULL, NULL, NULL, NULL, NULL);
 SET_DECLARE(gdb_dbgport_set, struct gdb_dbgport);
 
 struct gdb_dbgport *gdb_cur = NULL;
+int gdb_listening = 0;
 
 static int
 gdb_init(void)
@@ -82,9 +83,10 @@ gdb_init(void)
 		gdb_cur->gdb_init();
 		printf("GDB: current port: %s\n", gdb_cur->gdb_name);
 	}
-	if (gdb_cur != NULL)
+	if (gdb_cur != NULL) {
 		cur_pri = (boothowto & RB_GDB) ? 2 : 0;
-	else
+		gdb_consinit();
+	} else
 		cur_pri = -1;
 	return (cur_pri);
 }
@@ -94,6 +96,7 @@ gdb_trap(int type, int code)
 {
 	struct thread *thr_iter;
 
+	gdb_listening = 0;
 	/*
 	 * Send a T packet. We currently do not support watchpoints (the
 	 * awatch, rwatch or watch elements).
@@ -126,6 +129,7 @@ gdb_trap(int type, int code)
 				gdb_cpu_setreg(GDB_REG_PC, &pc);
 			}
 			kdb_cpu_clear_singlestep();
+			gdb_listening = 1;
 			return (1);
 		}
 		case 'C': {	/* Continue with signal. */
@@ -137,6 +141,7 @@ gdb_trap(int type, int code)
 				gdb_cpu_setreg(GDB_REG_PC, &pc);
 			}
 			kdb_cpu_clear_singlestep();
+			gdb_listening = 1;
 			return (1);
 		}
 		case 'g': {	/* Read registers. */
@@ -171,6 +176,7 @@ gdb_trap(int type, int code)
 		}
 		case 'k':	/* Kill request. */
 			kdb_cpu_clear_singlestep();
+			gdb_listening = 1;
 			return (1);
 		case 'm': {	/* Read memory. */
 			uintmax_t addr, size;
@@ -243,6 +249,7 @@ gdb_trap(int type, int code)
 				gdb_cpu_setreg(GDB_REG_PC, &pc);
 			}
 			kdb_cpu_set_singlestep();
+			gdb_listening = 1;
 			return (1);
 		}
 		case 'S': {	/* Step with signal. */
@@ -254,6 +261,7 @@ gdb_trap(int type, int code)
 				gdb_cpu_setreg(GDB_REG_PC, &pc);
 			}
 			kdb_cpu_set_singlestep();
+			gdb_listening = 1;
 			return (1);
 		}
 		case 'T': {	/* Thread alive. */