test debug/gosym

tests/gosym_test.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"bytes"
+	"debug/buildinfo"
+	"debug/elf"
+	"debug/gosym"
+	"encoding/binary"
+	"strings"
+	"testing"
+)
+
+func getPclntab(file *elf.File) *elf.Section {
+
+	sectionLabel := ".gopclntab"
+	section := file.Section(sectionLabel)
+	if section != nil {
+		return section
+	}
+	// binary may be built with -pie
+	sectionLabel = ".data.rel.ro.gopclntab"
+	section = file.Section(sectionLabel)
+	if section != nil {
+		return section
+	}
+	sectionLabel = ".data.rel.ro"
+	section = file.Section(sectionLabel)
+	if section != nil {
+		return section
+	}
+	return nil
+}
+
+// From go/src/debug/gosym/pclntab.go
+const (
+	go12magic  = 0xfffffffb
+	go116magic = 0xfffffffa
+	go118magic = 0xfffffff0
+	go120magic = 0xfffffff1
+)
+
+// Select the magic number based on the Go version
+func magicNumber(goVersion string) []byte {
+	bs := make([]byte, 4)
+	var magic uint32
+	if strings.Compare(goVersion, "go1.20") >= 0 {
+		magic = go120magic
+	} else if strings.Compare(goVersion, "go1.18") >= 0 {
+		magic = go118magic
+	} else if strings.Compare(goVersion, "go1.16") >= 0 {
+		magic = go116magic
+	} else {
+		magic = go12magic
+	}
+	binary.LittleEndian.PutUint32(bs, magic)
+	return bs
+}
+
+const FuncitonName = "crypto/tls.(*Conn).Read"
+
+// readelf -sW ./testdata/docker_aarch64/docker | grep $FUNCTION
+// 6649: 0000000000635cb0   928 FUNC    LOCAL  DEFAULT    6 crypto/tls.(*Conn).Read
+
+// in ida:
+// .text:0000000000635CB0
+// .text:0000000000635CB0
+// .text:0000000000635CB0  ; retval_635CB0 __golang crypto_tls__ptr_Conn_Read(crypto_tls_Conn_0 *c, _slice_uint8 b)
+// .text:0000000000635CB0    crypto_tls._ptr_Conn.Read               ; CODE XREF: crypto_tls._ptr_Conn.Read+390↓j
+// .text:0000000000635CB0
+
+const FunctionAddress = 0x0000000000635cb0
+
+func TestDockerSymbolFromPclntab(t *testing.T) {
+	path := "./docker_binary/arm64"
+
+	// Read the build information of the Go application
+	buildInfo, err := buildinfo.ReadFile(path)
+	if err != nil {
+		t.Fatal("get biuldinfo error:", err)
+	}
+
+	file, err := elf.Open(path)
+	if err != nil {
+		t.Fatal("elf open error:", err)
+	}
+
+	section := getPclntab(file)
+	if section == nil {
+		t.Fatalf("con't get pclntab")
+	}
+
+	tableData, err := section.Data()
+	if err != nil {
+		t.Fatalf("found section but could not read pclntab from %s ", path)
+	}
+	// Find .gopclntab by magic number even if there is no section label
+	magic := magicNumber(buildInfo.GoVersion)
+	pclntabIndex := bytes.Index(tableData, magic)
+	if pclntabIndex < 0 {
+		t.Fatalf("could not find magic number in %s ", path)
+	}
+	tableData = tableData[pclntabIndex:]
+
+	addr := file.Section(".text").Addr
+	lineTable := gosym.NewLineTable(tableData, addr)
+	symTable, err := gosym.NewTable([]byte{}, lineTable)
+	if err != nil {
+		t.Fatalf("gosym.NewTable error: ", err)
+	}
+	// when this symTab builded, this function address is error,
+	// this functino index = 6626,
+	// you can set condition breakpoint in `/usr/lib/go/src/debug/gosym/pclntab.go:308` with `i==6626`, this code build this functino.
+	f := symTable.LookupFunc(FuncitonName)
+	if f == nil {
+		t.Fatalf("con't looup symbol %s", FuncitonName)
+	}
+	if f.Value != FunctionAddress {
+		t.Fatalf("error symbol address: got[0x%08x] vs want[0x%08x]", f.Value, FunctionAddress)
+	}
+
+}