- >500 static DTrace probes for the linuxulator

- DTrace scripts to check for errors, performance, ...
  they serve mostly as examples of what you can do with the static probe;s
  with moderate load the scripts may be overwhelmed, excessive lock-tracing
  may influence program behavior (see the last design decission)

Design decissions:
 - use "linuxulator" as the provider for the native bitsize; add the
   bitsize for the non-native emulation (e.g. "linuxuator32" on amd64)
 - Add probes only for locks which are acquired in one function and released
   in another function. Locks which are aquired and released in the same
   function should be easy to pair in the code, inter-function
   locking is more easy to verify in DTrace.
 - Probes for locks should be fired after locking and before releasing to
   prevent races (to provide data/function stability in DTrace, see the
   man-page of "dtrace -v ..." and the corresponding DTrace docs).

1 files changed, 54 insertions, 4 deletions

diff --git a/sys/compat/linux/linux_sysctl.c b/sys/compat/linux/linux_sysctl.c
index 9111dbe..b2c10e1 100644
--- a/sys/compat/linux/linux_sysctl.c
+++ b/sys/compat/linux/linux_sysctl.c
@@ -30,12 +30,15 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_compat.h"
+#include "opt_kdtrace.h"
 
 #include <sys/param.h>
+#include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/proc.h>
+#include <sys/sdt.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
 #include <sys/sbuf.h>
@@ -48,6 +51,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/../linux/linux_proto.h>
 #endif
 
+#include <compat/linux/linux_dtrace.h>
 #include <compat/linux/linux_util.h>
 
 #define	LINUX_CTL_KERN		1
@@ -65,23 +69,49 @@ __FBSDID("$FreeBSD$");
 #define	LINUX_KERN_OSREV	3
 #define	LINUX_KERN_VERSION	4
 
+/* DTrace init */
+LIN_SDT_PROVIDER_DECLARE(LINUX_DTRACE);
+
+/**
+ * DTrace probes in this module.
+ */
+LIN_SDT_PROBE_DEFINE2(sysctl, handle_string, entry, "struct l___sysctl_args *",
+    "char *");
+LIN_SDT_PROBE_DEFINE1(sysctl, handle_string, copyout_error, "int");
+LIN_SDT_PROBE_DEFINE1(sysctl, handle_string, return, "int");
+LIN_SDT_PROBE_DEFINE2(sysctl, linux_sysctl, entry, "struct l___sysctl_args *",
+    "struct thread *");
+LIN_SDT_PROBE_DEFINE1(sysctl, linux_sysctl, copyin_error, "int");
+LIN_SDT_PROBE_DEFINE2(sysctl, linux_sysctl, wrong_length, "int", "int");
+LIN_SDT_PROBE_DEFINE1(sysctl, linux_sysctl, unsupported_sysctl, "char *");
+LIN_SDT_PROBE_DEFINE1(sysctl, linux_sysctl, return, "int");
+
 static int
 handle_string(struct l___sysctl_args *la, char *value)
 {
 	int error;
 
+	LIN_SDT_PROBE2(sysctl, handle_string, entry, la, value);
+
 	if (la->oldval != 0) {
 		l_int len = strlen(value);
 		error = copyout(value, PTRIN(la->oldval), len + 1);
 		if (!error && la->oldlenp != 0)
 			error = copyout(&len, PTRIN(la->oldlenp), sizeof(len));
-		if (error)
+		if (error) {
+			LIN_SDT_PROBE1(sysctl, handle_string, copyout_error,
+			    error);
+			LIN_SDT_PROBE1(sysctl, handle_string, return, error);
 			return (error);
+		}
 	}
 
-	if (la->newval != 0)
+	if (la->newval != 0) {
+		LIN_SDT_PROBE1(sysctl, handle_string, return, ENOTDIR);
 		return (ENOTDIR);
+	}
 
+	LIN_SDT_PROBE1(sysctl, handle_string, return, 0);
 	return (0);
 }
 
@@ -91,18 +121,30 @@ linux_sysctl(struct thread *td, struct linux_sysctl_args *args)
 	struct l___sysctl_args la;
 	struct sbuf *sb;
 	l_int *mib;
+	char *sysctl_string;
 	int error, i;
 
+	LIN_SDT_PROBE2(sysctl, linux_sysctl, entry, td, args->args);
+
 	error = copyin(args->args, &la, sizeof(la));
-	if (error)
+	if (error) {
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, copyin_error, error);
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, return, error);
 		return (error);
+	}
 
-	if (la.nlen <= 0 || la.nlen > LINUX_CTL_MAXNAME)
+	if (la.nlen <= 0 || la.nlen > LINUX_CTL_MAXNAME) {
+		LIN_SDT_PROBE2(sysctl, linux_sysctl, wrong_length, la.nlen,
+		    LINUX_CTL_MAXNAME);
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, return, ENOTDIR);
 		return (ENOTDIR);
+	}
 
 	mib = malloc(la.nlen * sizeof(l_int), M_TEMP, M_WAITOK);
 	error = copyin(PTRIN(la.name), mib, la.nlen * sizeof(l_int));
 	if (error) {
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, copyin_error, error);
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, return, error);
 		free(mib, M_TEMP);
 		return (error);
 	}
@@ -116,6 +158,7 @@ linux_sysctl(struct thread *td, struct linux_sysctl_args *args)
 		case LINUX_KERN_VERSION:
 			error = handle_string(&la, version);
 			free(mib, M_TEMP);
+			LIN_SDT_PROBE1(sysctl, linux_sysctl, return, error);
 			return (error);
 		default:
 			break;
@@ -128,16 +171,23 @@ linux_sysctl(struct thread *td, struct linux_sysctl_args *args)
 	sb = sbuf_new(NULL, NULL, 20 + la.nlen * 5, SBUF_AUTOEXTEND);
 	if (sb == NULL) {
 		linux_msg(td, "sysctl is not implemented");
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, unsupported_sysctl,
+		    "unknown sysctl, ENOMEM during lookup");
 	} else {
 		sbuf_printf(sb, "sysctl ");
 		for (i = 0; i < la.nlen; i++)
 			sbuf_printf(sb, "%c%d", (i) ? ',' : '{', mib[i]);
 		sbuf_printf(sb, "} is not implemented");
 		sbuf_finish(sb);
+		sysctl_string = sbuf_data(sb);
 		linux_msg(td, "%s", sbuf_data(sb));
+		LIN_SDT_PROBE1(sysctl, linux_sysctl, unsupported_sysctl,
+		    sysctl_string);
 		sbuf_delete(sb);
 	}
 
 	free(mib, M_TEMP);
+
+	LIN_SDT_PROBE1(sysctl, linux_sysctl, return, ENOTDIR);
 	return (ENOTDIR);
 }