Add source command to build source archive from debuginfo

Author: brancz

README.md

@@ -27,5 +27,8 @@ Commands:
   buildid <path>
     Extract buildid.
 
+  source <debuginfo-path> [<out-path>]
+    Build a source archive by discovering files from a given debuginfo file.
+
 Run "parca-debuginfo <command> --help" for more information on a command.
 ```

cmd/parca-debuginfo/main.go

@@ -15,8 +15,10 @@
 package main
 
 import (
+	"archive/tar"
 	"context"
 	"crypto/tls"
+	"debug/dwarf"
 	"debug/elf"
 	"errors"
 	"fmt"
@@ -28,6 +30,7 @@ import (
 	"github.com/alecthomas/kong"
 	"github.com/go-kit/log"
 	grpc_prometheus "github.com/grpc-ecosystem/go-grpc-prometheus"
+	"github.com/klauspost/compress/zstd"
 	grun "github.com/oklog/run"
 	"github.com/parca-dev/parca-agent/pkg/buildid"
 	"github.com/parca-dev/parca-agent/pkg/debuginfo"
@@ -72,6 +75,11 @@ type flags struct {
 	Buildid struct {
 		Path string `kong:"required,arg,name='path',help='Paths to extract buildid.',type:'path'"`
 	} `cmd:"" help:"Extract buildid."`
+
+	Source struct {
+		DebuginfoPath string `kong:"required,arg,name='debuginfo-path',help='Path to debuginfo file',type:'path'"`
+		OutPath       string `kong:"arg,name='out-path',help='Path to output archive file',type:'path',default='source.tar.zstd'"`
+	} `cmd:"" help:"Build a source archive by discovering files from a given debuginfo file."`
 }
 
 func main() {
@@ -335,6 +343,99 @@ func run(kongCtx *kong.Context, flags flags) error {
 			cancel()
 		})
 
+	case "source <debuginfo-path>":
+		g.Add(func() error {
+			f, err := elf.Open(flags.Source.DebuginfoPath)
+			if err != nil {
+				return fmt.Errorf("open elf: %w", err)
+			}
+			defer f.Close()
+
+			sf, err := os.Create(flags.Source.OutPath)
+			if err != nil {
+				return fmt.Errorf("create source archive: %w", err)
+			}
+			defer sf.Close()
+
+			zw, err := zstd.NewWriter(sf)
+			if err != nil {
+				return fmt.Errorf("create zstd writer: %w", err)
+			}
+
+			tw := tar.NewWriter(zw)
+
+			d, err := f.DWARF()
+			if err != nil {
+				return fmt.Errorf("get dwarf data: %w", err)
+			}
+
+			r := d.Reader()
+			seen := map[string]struct{}{}
+			for {
+				e, err := r.Next()
+				if err != nil {
+					return fmt.Errorf("read DWARF entry: %w", err)
+				}
+				if e == nil {
+					break
+				}
+
+				if e.Tag == dwarf.TagCompileUnit {
+					lr, err := d.LineReader(e)
+					if err != nil {
+						return fmt.Errorf("get line reader: %w", err)
+					}
+
+					if lr == nil {
+						continue
+					}
+
+					for _, lineFile := range lr.Files() {
+						if lineFile == nil {
+							continue
+						}
+						if _, ok := seen[lineFile.Name]; !ok {
+							sourceFile, err := os.Open(lineFile.Name)
+							if errors.Is(err, os.ErrNotExist) {
+								fmt.Fprintf(os.Stderr, "skipping file %q: does not exist\n", lineFile.Name)
+								seen[lineFile.Name] = struct{}{}
+								continue
+							}
+							if err != nil {
+								return fmt.Errorf("open file: %w", err)
+							}
+
+							stat, err := sourceFile.Stat()
+							if err != nil {
+								return fmt.Errorf("stat file: %w", err)
+							}
+
+							if err := tw.WriteHeader(&tar.Header{
+								Name: lineFile.Name,
+								Size: stat.Size(),
+							}); err != nil {
+								return fmt.Errorf("write tar header: %w", err)
+							}
+
+							if _, err = io.Copy(tw, sourceFile); err != nil {
+								return fmt.Errorf("copy file to tar: %w", err)
+							}
+
+							if err := sourceFile.Close(); err != nil {
+								return fmt.Errorf("close file: %w", err)
+							}
+
+							seen[lineFile.Name] = struct{}{}
+						}
+					}
+				}
+			}
+
+			return nil
+		}, func(error) {
+			cancel()
+		})
+
 	default:
 		cancel()
 		return errors.New("unknown command: " + kongCtx.Command())

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/alecthomas/kong v0.8.0
 	github.com/go-kit/log v0.2.1
 	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0
+	github.com/klauspost/compress v1.16.7
 	github.com/oklog/run v1.1.0
 	github.com/parca-dev/parca v0.18.1-0.20230816074650-c9b9bed904c3
 	github.com/parca-dev/parca-agent v0.12.1-0.20230216133018-8dd5ccaeef0f
@@ -64,7 +65,6 @@ require (
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/huaweicloud/huaweicloud-sdk-go-obs v3.23.3+incompatible // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
-	github.com/klauspost/compress v1.16.7 // indirect
 	github.com/klauspost/cpuid/v2 v2.2.5 // indirect
 	github.com/kylelemons/godebug v1.1.0 // indirect
 	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect