Preserve perf initialization errors

* runtime/perf.c (_stp_perf_init): Pass through ERR_PTRs, and create our
  own -ENOMEM for allocation failures.
* tapset-perfmon.cxx (perf_derived_probe_group::emit_module_init): Check
  IS_ERR for registration status.

2 files changed, 10 insertions, 5 deletions

diff --git a/runtime/perf.c b/runtime/perf.c
index 7f1aaf74..053e0880 100644
--- a/runtime/perf.c
+++ b/runtime/perf.c
@@ -32,17 +32,20 @@ static Perf *_stp_perf_init (struct perf_event_attr *attr,
 			     perf_overflow_handler_t callback,
 			     const char *pp, void (*ph) (struct context *) )
 {
+	long rc = -EINVAL;
 	int cpu;
 	Perf *pe;
 
 	pe = (Perf *) _stp_kmalloc (sizeof(Perf));
 	if (pe == NULL)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	/* allocate space for the event descriptor for each cpu */
 	pe->pd = (perfcpu *) _stp_alloc_percpu (sizeof(perfcpu));
-	if (pe->pd == NULL)
+	if (pe->pd == NULL) {
+		rc = -ENOMEM;
 		goto exit1;
+	}
 
 	/* initialize event on each processor */
 	stp_for_each_cpu(cpu) {
@@ -52,6 +55,7 @@ static Perf *_stp_perf_init (struct perf_event_attr *attr,
 							  callback);
 
 		if (IS_ERR(*event)) {
+			rc = PTR_ERR(*event);
 			*event = NULL;
 			goto exit2;
 		}
@@ -69,7 +73,7 @@ exit2:
 	_stp_free_percpu(pe->pd);
 exit1:
 	_stp_kfree(pe);
-	return NULL;
+	return ERR_PTR(rc);
 }
 
 /** Delete performance event.
diff --git a/tapset-perfmon.cxx b/tapset-perfmon.cxx
index 05a2bcd8..5c2d73e8 100644
--- a/tapset-perfmon.cxx
+++ b/tapset-perfmon.cxx
@@ -152,8 +152,9 @@ perf_derived_probe_group::emit_module_init (systemtap_session& s)
   s.op->newline() << "for (i=0; i<" << probes.size() << "; i++) {";
   s.op->newline(1) << "struct stap_perf_probe* stp = & stap_perf_probes [i];";
   s.op->newline() << "stp->perf = _stp_perf_init(&stp->attr, stp->cb, stp->pp, stp->ph);";
-  s.op->newline() << "if (stp->perf == NULL) {";
-  s.op->newline(1) << "rc = -EINVAL;";
+  s.op->newline() << "if (IS_ERR(stp->perf)) {";
+  s.op->newline(1) << "rc = PTR_ERR(stp->perf);";
+  s.op->newline() << "stp->perf = NULL;";
   s.op->newline() << "probe_point = stp->pp;";
   s.op->newline() << "for (j=0; j<i; j++) {";
   s.op->newline(1) << "stp = & stap_perf_probes [j];";