svn commit: r342706 - stable/11/usr.bin/ktrdump

[John Baldwin]

Author: jhb
Date: Wed Jan  2 19:48:17 2019
New Revision: 342706
URL: https://svnweb.freebsd.org/changeset/base/342706

Log:
  MFC 339620: Add a "live" mode to ktrdump.
  
  Support a "live" mode in ktrdump enabled via the -l flag.  In this
  mode, ktrdump polls the kernel's trace buffer periodically (currently
  hardcoded as a 50 millisecond interval) and dumps any newly added
  entries.  Fancier logic for the timeout (e.g. a command line option or
  some kind of backoff based on the time since the last entry) can be
  added later as the need arises.
  
  Note that this does not include the capsicum fixes from the original
  commit since ktrdump in stable/11 is not capsicum-ized.

Modified:
  stable/11/usr.bin/ktrdump/ktrdump.8
  stable/11/usr.bin/ktrdump/ktrdump.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/usr.bin/ktrdump/ktrdump.8
==============================================================================
--- stable/11/usr.bin/ktrdump/ktrdump.8	Wed Jan  2 19:46:01 2019	(r342705)
+++ stable/11/usr.bin/ktrdump/ktrdump.8	Wed Jan  2 19:48:17 2019	(r342706)
@@ -25,7 +25,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 6, 2015
+.Dd October 22, 2018
 .Dt KTRDUMP 8
 .Os
 .Sh NAME
@@ -33,7 +33,7 @@
 .Nd print kernel ktr trace buffer
 .Sh SYNOPSIS
 .Nm
-.Op Fl cfqrtH
+.Op Fl cflqrtH
 .Op Fl i Ar ktrfile
 .Op Fl M Ar core
 .Op Fl N Ar system
@@ -47,6 +47,9 @@ The following options are available:
 .Bl -tag -width ".Fl i Ar ktrfile"
 .It Fl c
 Print the CPU number that each entry was logged from.
+.It Fl l
+Poll the kernel ktr trace buffer periodically dumping any new events after
+each poll.
 .It Fl f
 Print the file and line number that each entry was logged from.
 .It Fl q

Modified: stable/11/usr.bin/ktrdump/ktrdump.c
==============================================================================
--- stable/11/usr.bin/ktrdump/ktrdump.c	Wed Jan  2 19:46:01 2019	(r342705)
+++ stable/11/usr.bin/ktrdump/ktrdump.c	Wed Jan  2 19:48:17 2019	(r342706)
@@ -48,7 +48,7 @@ __FBSDID("$FreeBSD$");
 
 #define	SBUFLEN	128
 #define	USAGE \
-	"usage: ktrdump [-cfqrtH] [-i ktrfile] [-M core] [-N system] [-o outfile]\n"
+	"usage: ktrdump [-cflqrtH] [-i ktrfile] [-M core] [-N system] [-o outfile]\n"
 
 static void usage(void);
 
@@ -62,6 +62,7 @@ static struct nlist nl[] = {
 
 static int cflag;
 static int fflag;
+static int lflag;
 static int Mflag;
 static int Nflag;
 static int qflag;
@@ -106,7 +107,7 @@ main(int ac, char **av)
 	 * Parse commandline arguments.
 	 */
 	out = stdout;
-	while ((c = getopt(ac, av, "cfqrtHe:i:m:M:N:o:")) != -1)
+	while ((c = getopt(ac, av, "cflqrtHe:i:m:M:N:o:")) != -1)
 		switch (c) {
 		case 'c':
 			cflag = 1;
@@ -126,6 +127,9 @@ main(int ac, char **av)
 			if ((in = open(optarg, O_RDONLY)) == -1)
 				err(1, "%s", optarg);
 			break;
+		case 'l':
+			lflag = 1;
+			break;
 		case 'M':
 		case 'm':
 			if (strlcpy(corefile, optarg, sizeof(corefile))
@@ -226,15 +230,29 @@ main(int ac, char **av)
 		fprintf(out, "\n");
 	}
 
+	tlast = -1;
 	/*
 	 * Now tear through the trace buffer.
+	 *
+	 * In "live" mode, find the oldest entry (first non-NULL entry
+	 * after index2) and walk forward.  Otherwise, start with the
+	 * most recent entry and walk backwards.
 	 */
 	if (!iflag) {
-		i = index - 1;
-		if (i < 0)
-			i = entries - 1;
+		if (lflag) {
+			i = index2 + 1 % entries;
+			while (buf[i].ktr_desc == NULL && i != index) {
+				i++;
+				if (i == entries)
+					i = 0;
+			}
+		} else {
+			i = index - 1;
+			if (i < 0)
+				i = entries - 1;
+		}
 	}
-	tlast = -1;
+dump_entries:
 	for (;;) {
 		if (buf[i].ktr_desc == NULL)
 			break;
@@ -306,14 +324,40 @@ next:			if ((c = *p++) == '\0')
 			 * 'index2' were in flux while the KTR buffer was
 			 * being copied to userspace we don't dump them.
 			 */
-			if (i == index2)
-				break;
-			if (--i < 0)
-				i = entries - 1;
+			if (lflag) {
+				if (++i == entries)
+					i = 0;
+				if (i == index)
+					break;
+			} else {
+				if (i == index2)
+					break;
+				if (--i < 0)
+					i = entries - 1;
+			}
 		} else {
 			if (++i == entries)
 				break;
 		}
+	}
+
+	/*
+	 * In "live" mode, poll 'ktr_idx' periodically and dump any
+	 * new entries since our last pass through the ring.
+	 */
+	if (lflag && !iflag) {
+		while (index == index2) {
+			usleep(50 * 1000);
+			if (kvm_read(kd, nl[2].n_value, &index2,
+			    sizeof(index2)) == -1)
+				errx(1, "%s", kvm_geterr(kd));
+		}
+		i = index;
+		index = index2;
+		if (kvm_read(kd, bufptr, buf, sizeof(*buf) * entries) == -1 ||
+		    kvm_read(kd, nl[2].n_value, &index2, sizeof(index2)) == -1)
+			errx(1, "%s", kvm_geterr(kd));
+		goto dump_entries;
 	}
 
 	return (0);