bpflbr: Add lbr stack

Signed-off-by: Leon Hwang <[email protected]>

internal/bpflbr/lbr_stack.go

@@ -0,0 +1,165 @@
+// Copyright 2024 Leon Hwang.
+// SPDX-License-Identifier: Apache-2.0
+
+package bpflbr
+
+import (
+	"fmt"
+	"io"
+)
+
+type branchEndpoint struct {
+	addr uintptr
+
+	funcName     string
+	offset       uintptr
+	endpointName string // ${funcName}+${offset}
+
+	fileName string
+	fileLine uint32
+	lineInfo string // (${fileName}:${fileLine})
+}
+
+func (b *branchEndpoint) updateInfo() {
+	b.endpointName = fmt.Sprintf("%#x:%s+%#x", b.addr, b.funcName, b.offset)
+	if b.fileName != "" {
+		b.lineInfo = fmt.Sprintf("(%s:%d)", b.fileName, b.fileLine)
+	}
+}
+
+func (b *branchEndpoint) format(f string) string {
+	switch {
+	case b.endpointName != "" && b.lineInfo != "":
+		return fmt.Sprintf(f, b.endpointName, b.lineInfo)
+	case b.endpointName != "":
+		return fmt.Sprintf(f, b.endpointName, "")
+	case b.lineInfo != "":
+		return fmt.Sprintf(f, "", b.lineInfo)
+	default:
+		return fmt.Sprintf(f, fmt.Sprintf("%#x", b.addr), "")
+	}
+}
+
+type branchEntry struct {
+	from, to *branchEndpoint
+}
+
+func (e *branchEntry) format(leftFmt, rightFmt string) string {
+	l, r := e.from.format(leftFmt), e.to.format(rightFmt)
+	return fmt.Sprintf("%s -> %s", l, r)
+}
+
+type branchRecord struct {
+	entries []branchEntry
+	last    int
+
+	maxFromNameLen, maxFromLinfoLen int
+	maxToNameLen, maxToLinfoLen     int
+}
+
+func newBranchRecord(entry branchEntry) *branchRecord {
+	r := &branchRecord{
+		entries: make([]branchEntry, 0, 32),
+		last:    -1,
+	}
+	r.addEntry(entry)
+	return r
+}
+
+func (r *branchRecord) addEntry(entry branchEntry) {
+	r.entries = append(r.entries, entry)
+	r.last++
+
+	r.maxFromNameLen = max(r.maxFromNameLen, len(entry.from.endpointName))
+	r.maxFromLinfoLen = max(r.maxFromLinfoLen, len(entry.from.lineInfo))
+	r.maxToNameLen = max(r.maxToNameLen, len(entry.to.endpointName))
+	r.maxToLinfoLen = max(r.maxToLinfoLen, len(entry.to.lineInfo))
+}
+
+func (r *branchRecord) appendRecord(record *branchRecord) {
+	r.entries = append(r.entries, record.entries...)
+	r.last += len(record.entries)
+
+	r.maxFromNameLen = max(r.maxFromNameLen, record.maxFromNameLen)
+	r.maxFromLinfoLen = max(r.maxFromLinfoLen, record.maxFromLinfoLen)
+	r.maxToNameLen = max(r.maxToNameLen, record.maxToNameLen)
+	r.maxToLinfoLen = max(r.maxToLinfoLen, record.maxToLinfoLen)
+}
+
+type lbrStack struct {
+	last  int
+	stack []*branchRecord
+}
+
+func newLBRStack() *lbrStack {
+	return &lbrStack{
+		stack: make([]*branchRecord, 0, 32),
+	}
+}
+
+func (s *lbrStack) reset() {
+	s.last = 0
+	s.stack = s.stack[:0]
+}
+
+func (s *lbrStack) addRecord(record *branchRecord) {
+	s.stack = append(s.stack, record)
+	s.last++
+}
+
+func (s *lbrStack) pushFirstEntry(entry branchEntry) {
+	s.stack = append(s.stack, newBranchRecord(entry))
+}
+
+func (s *lbrStack) pushEntry(entry branchEntry) {
+	lastRecord := s.stack[s.last]
+	lastEntry := lastRecord.entries[lastRecord.last]
+	sameCallStack := lastEntry.to.funcName == entry.from.funcName
+
+	if sameCallStack {
+		lastRecord.addEntry(entry)
+	} else {
+		s.addRecord(newBranchRecord(entry))
+	}
+}
+
+func (s *lbrStack) outputRecord(w io.Writer, lfmt, rfmt string, r *branchRecord, idx int) {
+	fmt.Fprintf(w, "[#%02d] %s\n", idx, r.entries[0].format(lfmt, rfmt))
+
+	i := 1
+	for ; i < len(r.entries); i++ {
+		entry := r.entries[i]
+		fmt.Fprintf(w, "      %s\n", entry.format(lfmt, rfmt))
+	}
+}
+
+func (s *lbrStack) getLeftFmt() string {
+	var maxFromNameLen, maxFromLinfoLen int
+	for _, r := range s.stack {
+		maxFromNameLen = max(maxFromNameLen, r.maxFromNameLen)
+		maxFromLinfoLen = max(maxFromLinfoLen, r.maxFromLinfoLen)
+	}
+
+	return fmt.Sprintf("%%-%ds %%-%ds", maxFromNameLen, maxFromLinfoLen)
+}
+
+func (s *lbrStack) getRightFmt() string {
+	var maxToNameLen, maxToLinfoLen int
+	for _, r := range s.stack {
+		maxToNameLen = max(maxToNameLen, r.maxToNameLen)
+		maxToLinfoLen = max(maxToLinfoLen, r.maxToLinfoLen)
+	}
+
+	return fmt.Sprintf("%%-%ds %%-%ds", maxToNameLen, maxToLinfoLen)
+}
+
+func (s *lbrStack) output(w io.Writer) {
+	idx := 31
+	lfmt := s.getLeftFmt()
+	rfmt := s.getRightFmt()
+
+	for _, r := range s.stack {
+		s.outputRecord(w, lfmt, rfmt, r, idx)
+		idx--
+	}
+}