sdt: support min and max kernel versions for probe dependencies

The underlying probes that are used to trigger SDT probes may be kernel
version dependent.  Adding optional minimum and maximum specifications
(using DT_VERSION_NUMBER(x, y, z)) allows us to specify what kernels a
certain dependency can be expected to work on.

Signed-off-by: Kris Van Hees <kris.van.hees@oracle.com>
Reviewed-by: Eugene Loh <eugene.loh@oracle.com>

libdtrace/dt_provider_sdt.c

@@ -87,6 +87,16 @@ dt_sdt_enable(dtrace_hdl_t *dtp, dt_probe_t *prp)
 		if (strcmp(prp->desc->prb, dep->name) != 0)
 			continue;
 
+		/*
+		 * If the dependency specifies a minimum and/or maximum kernel
+		 * version, skip this dependency if the runtime kernel version
+		 * does not fall in the specified range.
+		 */
+		if (dep->kver_min && dtp->dt_kernver < dep->kver_min)
+			continue;
+		if (dep->kver_max && dtp->dt_kernver > dep->kver_max)
+			continue;
+
 		if (dtrace_str2desc(dtp, dep->spec, dep->str, &pd) == -1)
 			return;
 

libdtrace/dt_provider_sdt.h

@@ -19,14 +19,16 @@ extern "C" {
  * Probe dependencies
  *
  * SDT probes are implemented using probes made available by other providers.
- * THe probe dependency table associates each SDT probe with one or more probe
- * specifications (possibly containing wildcards).  Each matching probe will
- * have SDT lockstat probe added as a dependent probe.
+ * The probe dependency table associates each SDT probe with one or more probe
+ * specifications (possibly containing wildcards).  An optional min and/or max
+ * kernel version can be specified (assigned using DT_VERSION_NUMBER(x, y, z)).
  */
 typedef struct probe_dep {
 	const char		*name;			/* probe name */
 	dtrace_probespec_t	spec;			/* spec type */
 	const char		*str;			/* spec string */
+	dt_version_t		kver_min;		/* minimum kernver */
+	dt_version_t		kver_max;		/* maximum kernver */
 } probe_dep_t;
 
 /*