svn commit: r263196 - head/usr.bin/ktrdump

[Neel Natu]

Author: neel
Date: Fri Mar 14 22:07:08 2014
New Revision: 263196
URL: http://svnweb.freebsd.org/changeset/base/263196

Log:
  Don't dump entries that were modified during the time the KTR buffer was being
  copied to userspace. Failing to do this would result in entries at the bottom
  of the ktrdump output to be more recent than entries at the top.
  
  With this change the timestamps are monotonically decreasing going from the
  top to the bottom of the ktrdump output.

Modified:
  head/usr.bin/ktrdump/ktrdump.c

Modified: head/usr.bin/ktrdump/ktrdump.c
==============================================================================
--- head/usr.bin/ktrdump/ktrdump.c	Fri Mar 14 21:45:37 2014	(r263195)
+++ head/usr.bin/ktrdump/ktrdump.c	Fri Mar 14 22:07:08 2014	(r263196)
@@ -93,7 +93,7 @@ main(int ac, char **av)
 	char *p;
 	int version;
 	int entries;
-	int index;
+	int index, index2;
 	int parm;
 	int in;
 	int c;
@@ -182,7 +182,8 @@ main(int ac, char **av)
 		if (kvm_read(kd, nl[2].n_value, &index, sizeof(index)) == -1 ||
 		    kvm_read(kd, nl[3].n_value, &bufptr,
 		    sizeof(bufptr)) == -1 ||
-		    kvm_read(kd, bufptr, buf, sizeof(*buf) * entries) == -1)
+		    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));
 	}
 
@@ -289,7 +290,14 @@ next:			if ((c = *p++) == '\0')
 		    parms[4], parms[5]);
 		fprintf(out, "\n");
 		if (!iflag) {
-			if (i == index)
+			/*
+			 * 'index' and 'index2' are the values of 'ktr_idx'
+			 * before and after the KTR buffer was copied into
+			 * 'buf'. Since the KTR entries between 'index' and
+			 * '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;