Address pair-review feedback and move prctl mapping support from PR #36

- Fix JIT region check to use >= for lower bound (half-open interval [start, end))
  matching V8 and HotSpot conventions
- Reuse map lookup value to avoid double hashing of RawMapping struct key
- Wrap CalculatePrefixList error for better debugging
- Log stale prefix deletion errors instead of silently discarding
- Move prctl(PR_SET_VMA) named anonymous mapping support from process/process.go
  (was in PR #36 but is needed here for findJITRegion labeled detection)
- Remove stale 'assume all anonymous' comment
- Rebuild BPF blobs for >= fix

Author: dalehamel

interpreter/ruby/ruby.go

@@ -1342,8 +1342,8 @@ func (r *rubyInstance) SynchronizeMappings(ebpf interpreter.EbpfHandler,
 			continue
 		}
 
-		if _, exists := r.mappings[*m]; exists {
-			*r.mappings[*m] = r.mappingGeneration
+		if gen, exists := r.mappings[*m]; exists {
+			*gen = r.mappingGeneration
 			continue
 		}
 
@@ -1352,12 +1352,11 @@ func (r *rubyInstance) SynchronizeMappings(ebpf interpreter.EbpfHandler,
 		mappingGeneration := r.mappingGeneration
 		r.mappings[*m] = &mappingGeneration
 
-		// Just assume all anonymous and executable mappings are Ruby for now
 		log.Debugf("Enabling Ruby interpreter for %#x/%#x", m.Vaddr, m.Length)
 
 		prefixes, err := lpm.CalculatePrefixList(m.Vaddr, m.Vaddr+m.Length)
 		if err != nil {
-			return fmt.Errorf("new anonymous mapping lpm failure %#x/%#x", m.Vaddr, m.Length)
+			return fmt.Errorf("new anonymous mapping lpm failure %#x/%#x: %w", m.Vaddr, m.Length, err)
 		}
 
 		for _, prefix := range prefixes {
@@ -1386,8 +1385,9 @@ func (r *rubyInstance) SynchronizeMappings(ebpf interpreter.EbpfHandler,
 		if *generationPtr == r.mappingGeneration {
 			continue
 		}
-		log.Debugf("Delete Ruby prefix %#v", prefix)
-		_ = ebpf.DeletePidInterpreterMapping(pid, prefix)
+		if err := ebpf.DeletePidInterpreterMapping(pid, prefix); err != nil {
+			log.Debugf("Failed to delete Ruby prefix %#v: %v", prefix, err)
+		}
 		delete(r.prefixes, prefix)
 	}
 	for m, generationPtr := range r.mappings {

process/process.go

@@ -282,6 +282,9 @@ func iterateMappings(mapsFile io.Reader, callback func(m RawMapping) bool) (uint
 				inode = vdsoInode
 			} else if fields[5] == "" {
 				// This is an anonymous mapping, keep it
+			} else if strings.HasPrefix(fields[5], "[anon:") {
+				// This is an anonymous mapping named with prctl(PR_SET_VMA), keep the name
+				path = trimMappingPath(fields[5])
 			} else {
 				// Ignore other mappings that are invalid, non-existent or are special pseudo-files
 				continue

support/ebpf/ruby_tracer.ebpf.c

@@ -451,7 +451,7 @@ static EBPF_INLINE ErrorCode walk_ruby_stack(
   }
 
   if (
-    rubyinfo->jit_start > 0 && record->state.pc > rubyinfo->jit_start &&
+    rubyinfo->jit_start > 0 && record->state.pc >= rubyinfo->jit_start &&
     record->state.pc < rubyinfo->jit_end) {
     record->rubyUnwindState.jit_detected = true;