Fix for insn probe: Call arch_has_*_step() prior to calling utrace_control

The attached patch is version 2 for the problem I reported earlier
today.

Frank, is this more what you had in mind?  With this patch, there's no
need for the user to look at the system log.  Error messages are sent to
stderr:

	ERROR: insn probe init: arch does not support block step mode
	ERROR: probe process("/test").function("doit1@/test.c:22").return registration error (rc -1)

-Maynard

1 files changed, 16 insertions, 0 deletions

diff --git a/tapsets.cxx b/tapsets.cxx
index 352930ee..1b55684b 100644
--- a/tapsets.cxx
+++ b/tapsets.cxx
@@ -6570,6 +6570,22 @@ itrace_derived_probe_group::emit_module_init (systemtap_session& s)
   s.op->newline() << "for (i=0; i<" << num_probes << "; i++) {";
   s.op->indent(1);
   s.op->newline() << "struct stap_itrace_probe *p = &stap_itrace_probes[i];";
+
+  // 'arch_has_single_step' needs to be defined for either single step mode
+  // or branch mode.
+  s.op->newline() << "if (!arch_has_single_step()) {";
+  s.op->indent(1);
+  s.op->newline() << "_stp_error (\"insn probe init: arch does not support step mode\");";
+  s.op->newline() << "rc = -EPERM;";
+  s.op->newline() << "break;";
+  s.op->newline(-1) << "}";
+  s.op->newline() << "if (!p->single_step && !arch_has_block_step()) {";
+  s.op->indent(1);
+  s.op->newline() << "_stp_error (\"insn probe init: arch does not support block step mode\");";
+  s.op->newline() << "rc = -EPERM;";
+  s.op->newline() << "break;";
+  s.op->newline(-1) << "}";
+
   s.op->newline() << "rc = stap_register_task_finder_target(&p->tgt);";
   s.op->newline(-1) << "}";
 }