Add "ddb capture print" and "ddb capture status" commands do ddb(8),

alowing the DDB output capture buffer to be easily extracted from
user space.  Both of these commands include -M/-N arguments, allowing
them to be used with kernel crash dumps (or /dev/mem).

This makes it easier to use DDB scripting and output capture with
minidumps or full dumps rather than with text dumps, allowing DDB
output (scripted or otherwise) to be easily extracted from a crash
dump.

MFC after:	1 week
Discussed with:	brooks, jhb

5 files changed, 297 insertions, 5 deletions

diff --git a/sbin/ddb/Makefile b/sbin/ddb/Makefile
index 1ae724b..b9189c1 100644
--- a/sbin/ddb/Makefile
+++ b/sbin/ddb/Makefile
@@ -1,8 +1,11 @@
 # $FreeBSD$
 
 PROG=	ddb
-SRCS=	ddb.c ddb_script.c
+SRCS=	ddb.c ddb_capture.c ddb_script.c
 MAN=	ddb.8
 WARNS=	3
 
+DPADD=	${LIBKVM}
+LDADD=	-lkvm
+
 .include <bsd.prog.mk>
diff --git a/sbin/ddb/ddb.8 b/sbin/ddb/ddb.8
index 0165f56..90ceb63 100644
--- a/sbin/ddb/ddb.8
+++ b/sbin/ddb/ddb.8
@@ -1,5 +1,5 @@
 .\"-
-.\" Copyright (c) 2007 Robert N. M. Watson
+.\" Copyright (c) 2007-2008 Robert N. M. Watson
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 4, 2008
+.Dd April 24, 2008
 .Dt DDB 8
 .Os
 .Sh NAME
@@ -33,6 +33,16 @@
 .Nd "configure DDB kernel debugger properties"
 .Sh SYNOPSIS
 .Nm
+.Cm capture
+.Op Fl M core
+.Op Fl N system
+.Cm print
+.Nm
+.Cm capture
+.Op Fl M core
+.Op Fl N system
+.Cm status
+.Nm
 .Cm script
 .Ar scriptname
 .Nm
@@ -67,6 +77,33 @@ utility.
 Whitespace at the beginning of lines will be ignored as will lines where the
 first non-whitespace character is
 .Ql # .
+.Sh OUTPUT CAPTURE
+The
+.Nm
+utility can be used to extract the contents of the
+.Xr ddb 4
+output capture buffer of the current live kernel, or from the crash dump of a
+kernel on disk.
+The following debugger commands are available from the command line:
+.Bl -tag -width indent
+.It Xo
+.Ic Cm capture
+.Op Fl M Ar core
+.Op Fl N Ar system
+.Cm print
+.Xc
+Print the current contents of the
+.Xr ddb 4
+output capture buffer.
+.It Xo
+.Ic Cm capture
+.Op Fl M Ar core
+.Op Fl N Ar system
+.Cm status
+.Xc
+Print the current status of the
+.Xr ddb 4
+output capture buffer.
 .Sh SCRIPTING
 The
 .Nm
diff --git a/sbin/ddb/ddb.c b/sbin/ddb/ddb.c
index 5e86efc..f5c5dd0 100644
--- a/sbin/ddb/ddb.c
+++ b/sbin/ddb/ddb.c
@@ -43,7 +43,9 @@ void
 usage(void)
 {
 
-	fprintf(stderr, "usage: ddb script scriptname\n");
+	fprintf(stderr, "usage: ddb capture [-M core] [-N system] print\n");
+	fprintf(stderr, "       ddb capture [-M core] [-N system] status\n");
+	fprintf(stderr, "       ddb script scriptname\n");
 	fprintf(stderr, "       ddb script scriptname=script\n");
 	fprintf(stderr, "       ddb scripts\n");
 	fprintf(stderr, "       ddb unscript scriptname\n");
@@ -103,7 +105,9 @@ ddb_main(int argc, char *argv[])
 	if (argc < 1)
 		usage();
 
-	if (strcmp(argv[0], "script") == 0)
+	if (strcmp(argv[0], "capture") == 0)
+		ddb_capture(argc, argv);
+	else if (strcmp(argv[0], "script") == 0)
 		ddb_script(argc, argv);
 	else if (strcmp(argv[0], "scripts") == 0)
 		ddb_scripts(argc, argv);
diff --git a/sbin/ddb/ddb.h b/sbin/ddb/ddb.h
index 50128bd..8363bcc 100644
--- a/sbin/ddb/ddb.h
+++ b/sbin/ddb/ddb.h
@@ -29,6 +29,7 @@
 #ifndef DDB_H
 #define	DDB_H
 
+void	ddb_capture(int argc, char *argv[]);
 void	ddb_script(int argc, char *argv[]);
 void	ddb_scripts(int argc, char *argv[]);
 void	ddb_unscript(int argc, char *argv[]);
diff --git a/sbin/ddb/ddb_capture.c b/sbin/ddb/ddb_capture.c
new file mode 100644
index 0000000..9f83acb
--- /dev/null
+++ b/sbin/ddb/ddb_capture.c
@@ -0,0 +1,247 @@
+/*-
+ * Copyright (c) 2008 Robert N. M. Watson
+ * 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 AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR CONTRIBUTORS 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.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/sysctl.h>
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <kvm.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include "ddb.h"
+
+/*
+ * Interface with the ddb(4) capture buffer of a live kernel using sysctl, or
+ * for a crash dump using libkvm.
+ */
+#define	SYSCTL_DDB_CAPTURE_BUFOFF	"debug.ddb.capture.bufoff"
+#define	SYSCTL_DDB_CAPTURE_BUFSIZE	"debug.ddb.capture.bufsize"
+#define	SYSCTL_DDB_CAPTURE_MAXBUFSIZE	"debug.ddb.capture.maxbufsize"
+#define	SYSCTL_DDB_CAPTURE_DATA		"debug.ddb.capture.data"
+#define	SYSCTL_DDB_CAPTURE_INPROGRESS	"debug.ddb.capture.inprogress"
+
+static struct nlist namelist[] = {
+#define X_DB_CAPTURE_BUF	0
+	{ .n_name = "_db_capture_buf" },
+#define X_DB_CAPTURE_BUFSIZE	1
+	{ .n_name = "_db_capture_bufsize" },
+#define X_DB_CAPTURE_MAXBUFSIZE	2
+	{ .n_name = "_db_capture_maxbufsize" },
+#define X_DB_CAPTURE_BUFOFF	3
+	{ .n_name = "_db_capture_bufoff" },
+#define	X_DB_CAPTURE_INPROGRESS	4
+	{ .n_name = "_db_capture_inprogress" },
+	{ .n_name = "" },
+};
+
+static int
+kread(kvm_t *kvm, void *kvm_pointer, void *address, size_t size,
+    size_t offset)
+{
+	ssize_t ret;
+
+	ret = kvm_read(kvm, (unsigned long)kvm_pointer + offset, address,
+	    size);
+	if (ret < 0 || (size_t)ret != size)
+		return (-1);
+	return (0);
+}
+
+static int
+kread_symbol(kvm_t *kvm, int index, void *address, size_t size,
+    size_t offset)
+{
+	ssize_t ret;
+
+	ret = kvm_read(kvm, namelist[index].n_value + offset, address, size);
+	if (ret < 0 || (size_t)ret != size)
+		return (-1);
+	return (0);
+}
+
+static void
+ddb_capture_print_kvm(kvm_t *kvm)
+{
+	u_int db_capture_bufsize;
+	char *buffer, *db_capture_buf;
+
+	if (kread_symbol(kvm, X_DB_CAPTURE_BUF, &db_capture_buf,
+	    sizeof(db_capture_buf), 0) < 0)
+		errx(-1, "kvm: unable to read db_capture_buf");
+
+	if (kread_symbol(kvm, X_DB_CAPTURE_BUFSIZE, &db_capture_bufsize,
+	    sizeof(db_capture_bufsize), 0) < 0)
+		errx(-1, "kvm: unable to read db_capture_bufsize");
+
+	buffer = malloc(db_capture_bufsize + 1);
+	if (buffer == NULL)
+		err(-1, "malloc: db_capture_bufsize (%u)",
+		    db_capture_bufsize);
+	bzero(buffer, db_capture_bufsize + 1);
+
+	if (kread(kvm, db_capture_buf, buffer, db_capture_bufsize, 0) < 0)
+		errx(-1, "kvm: unable to read buffer");
+
+	printf("%s\n", buffer);
+	free(buffer);
+}
+
+static void
+ddb_capture_print_sysctl(void)
+{
+	size_t buflen, len;
+	char *buffer;
+	int ret;
+
+repeat:
+	if (sysctlbyname(SYSCTL_DDB_CAPTURE_DATA, NULL, &buflen, NULL, 0) < 0)
+		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_DATA);
+	if (buflen == 0)
+		return;
+	buffer = malloc(buflen);
+	if (buffer == NULL)
+		err(EX_OSERR, "malloc");
+	bzero(buffer, buflen);
+	len = buflen;
+	ret = sysctlbyname(SYSCTL_DDB_CAPTURE_DATA, buffer, &len, NULL, 0);
+	if (ret < 0 && errno != ENOMEM)
+		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_DATA);
+	if (ret < 0) {
+		free(buffer);
+		goto repeat;
+	}
+
+	printf("%s\n", buffer);
+	free(buffer);
+}
+
+static void
+ddb_capture_status_kvm(kvm_t *kvm)
+{
+	u_int db_capture_bufoff, db_capture_bufsize, db_capture_inprogress;
+
+	if (kread_symbol(kvm, X_DB_CAPTURE_BUFOFF, &db_capture_bufoff,
+	    sizeof(db_capture_bufoff), 0) < 0)
+		errx(-1, "kvm: unable to read db_capture_bufoff");
+	if (kread_symbol(kvm, X_DB_CAPTURE_BUFSIZE, &db_capture_bufsize,
+	    sizeof(db_capture_bufsize), 0) < 0)
+		errx(-1, "kvm: unable to read db_capture_bufsize");
+	if (kread_symbol(kvm, X_DB_CAPTURE_INPROGRESS,
+	    &db_capture_inprogress, sizeof(db_capture_inprogress), 0) < 0)
+		err(-1, "kvm: unable to read db_capture_inpgoress");
+	printf("%u/%u bytes used\n", db_capture_bufoff, db_capture_bufsize);
+	if (db_capture_inprogress)
+		printf("capture is on\n");
+	else
+		printf("capture is off\n");
+
+}
+
+static void
+ddb_capture_status_sysctl(void)
+{
+	u_int db_capture_bufoff, db_capture_bufsize, db_capture_inprogress;
+	size_t len;
+
+	len = sizeof(db_capture_bufoff);
+	if (sysctlbyname(SYSCTL_DDB_CAPTURE_BUFOFF, &db_capture_bufoff, &len,
+	    NULL, 0) < 0)
+		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_BUFOFF);
+	len = sizeof(db_capture_bufoff);
+	if (sysctlbyname(SYSCTL_DDB_CAPTURE_BUFSIZE, &db_capture_bufsize,
+	    &len, NULL, 0) < 0)
+		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_BUFSIZE);
+	len = sizeof(db_capture_inprogress);
+	if (sysctlbyname(SYSCTL_DDB_CAPTURE_INPROGRESS,
+	    &db_capture_inprogress, &len, NULL, 0) < 0)
+		err(EX_OSERR, "sysctl: %s", SYSCTL_DDB_CAPTURE_INPROGRESS);
+	printf("%u/%u bytes used\n", db_capture_bufoff, db_capture_bufsize);
+	if (db_capture_inprogress)
+		printf("capture is on\n");
+	else
+		printf("capture is off\n");
+}
+
+void
+ddb_capture(int argc, char *argv[])
+{
+	char *mflag, *nflag, errbuf[_POSIX2_LINE_MAX];
+	kvm_t *kvm;
+	int ch;
+
+	mflag = NULL;
+	nflag = NULL;
+	while ((ch = getopt(argc, argv, "M:N:")) != -1) {
+		switch (ch) {
+		case 'M':
+			mflag = optarg;
+			break;
+
+		case 'N':
+			nflag = optarg;
+			break;
+
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 1)
+		usage();
+
+	if (mflag != NULL) {
+		kvm = kvm_openfiles(nflag, mflag, NULL, O_RDONLY, errbuf);
+		if (kvm == NULL)
+			errx(-1, "ddb_capture: kvm_openfiles: %s", errbuf);
+		if (kvm_nlist(kvm, namelist) != 0)
+			errx(-1, "ddb_capture: kvm_nlist");
+	} else if (nflag != NULL)
+		usage();
+	if (strcmp(argv[0], "print") == 0) {
+		if (kvm != NULL)
+			ddb_capture_print_kvm(kvm);
+		else
+			ddb_capture_print_sysctl();
+	} else if (strcmp(argv[0], "status") == 0) {
+		if (kvm != NULL)
+			ddb_capture_status_kvm(kvm);
+		else
+			ddb_capture_status_sysctl();
+	} else
+		usage();
+}