Makefile: generate fileids.json from C file

Add a simple utility to add a json file with the filename to fileid
mapping so that userspace can translate ids to names. This is meant to
be used by tetra, so add it as a dependency in tetra's build.

Signed-off-by: Kornilios Kourtis <[email protected]>

Makefile

@@ -105,6 +105,13 @@ clean: cli-clean tarball-clean
 
 ##@ Build and install
 
+pkg/errmetrics/fileids.json: bpf/lib/fileids.h
+	go run ./cmd/bpf-fileids bpf/lib/fileids.h pkg/errmetrics/fileids.json
+
+.PHONY: fileids
+fileids: pkg/errmetrics/fileids.json
+
+
 .PHONY: tetragon
 tetragon: ## Compile the Tetragon agent.
 	$(GO_BUILD) ./cmd/tetragon/
@@ -114,7 +121,7 @@ tetragon-operator: ## Compile the Tetragon operator.
 	$(GO_BUILD) -o $@ ./operator
 
 .PHONY: tetra
-tetra: ## Compile the Tetragon gRPC client.
+tetra: fileids ## Compile the Tetragon gRPC client.
 	$(GO_BUILD) ./cmd/tetra/
 
 .PHONY: tetragon-bpf

bpf/lib/bpf_errmetrics.h

@@ -5,6 +5,7 @@
 
 #include "compiler.h"
 
+// should match: pkg/errmetrics/map.go:MapKey
 struct errmetrics_key {
 	__u16 error;
 	__u8 file_id;
@@ -29,7 +30,7 @@ struct {
 	__uint(type, BPF_MAP_TYPE_LRU_PERCPU_HASH);
 	__uint(max_entries, 1024);
 	__type(key, struct errmetrics_key);
-	__type(value, __u32);
+	__type(value, __u32); // counter, should match pkg/errmetrics/map.go:MapVal
 } tg_errmetrics_map SEC(".maps");
 
 FUNC_INLINE void

cmd/bpf-fileids/fileids.go

@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Tetragon
+
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// json entry
+type Entry struct {
+	ID       int    `json:"id"`
+	Filename string `json:"filename"`
+}
+
+func initFileIDs(fname string) []Entry {
+	entryRe := regexp.MustCompile(`fileid__\("([^"]+)", *([0-9]+)\)`)
+	f, err := os.Open(fname)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error opening '%s': %v", fname, err)
+		os.Exit(1)
+	}
+	defer f.Close()
+
+	ret := []Entry{}
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if strings.HasPrefix(line, "//") {
+			continue
+		}
+
+		m := entryRe.FindStringSubmatch(line)
+		if len(m) == 3 {
+			id, err := strconv.ParseInt(m[2], 0, 32)
+			if err != nil {
+				continue
+			}
+			ret = append(ret, Entry{int(id), m[1]})
+		}
+
+	}
+	// NB: no need to check scanner.Err()
+	return ret
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <fileids.h> <out.json>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	fname := os.Args[1]
+	fileIDs := initFileIDs(fname)
+	b, err := json.MarshalIndent(fileIDs, "", "  ")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error marshalling file ids: %v", err)
+		os.Exit(1)
+	}
+
+	outFname := os.Args[2]
+	err = os.WriteFile(outFname, b, 0622)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error writing file: %v", err)
+		os.Exit(1)
+	}
+}

pkg/errmetrics/errmetrics.go

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Tetragon
+
+package errmetrics
+
+import (
+	_ "embed"
+	"encoding/json"
+	"sync"
+)
+
+var (
+	MapName = "tg_errmetrics_map"
+)
+
+// json entry
+type Entry struct {
+	ID       int    `json:"id"`
+	Filename string `json:"filename"`
+}
+
+//go:embed fileids.json
+var fileIDsJSON []byte
+
+var getFileIDs = sync.OnceValues(func() (map[int]string, error) {
+	var entries []Entry
+	if err := json.Unmarshal(fileIDsJSON, &entries); err != nil {
+		return nil, err
+	}
+
+	ret := map[int]string{}
+	for _, e := range entries {
+		ret[e.ID] = e.Filename
+	}
+	return ret, nil
+})

pkg/errmetrics/fileids.json

@@ -0,0 +1,6 @@
+[
+  {
+    "id": 112,
+    "filename": "cgroup/bpf_cgtracker.c"
+  }
+]

pkg/errmetrics/map.go

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright Authors of Tetragon
+
+package errmetrics
+
+import (
+	"fmt"
+	"syscall"
+
+	"github.com/cilium/ebpf"
+	"golang.org/x/sys/unix"
+)
+
+type Map struct {
+	*ebpf.Map
+}
+
+func OpenMap(fname string) (Map, error) {
+	m, err := ebpf.LoadPinnedMap(fname, &ebpf.LoadPinOptions{
+		ReadOnly: true,
+	})
+
+	if err != nil {
+		return Map{}, err
+	}
+
+	return Map{m}, err
+}
+
+// NB: should match bpf/lib/bpf_errmetrics.h:errmetrics_key
+type MapKey struct {
+	Err    uint16
+	FileID uint8
+	Pad1   uint8
+	LineNR uint16
+	Pad2   uint16
+}
+
+type MapVal = uint32
+
+type DumpEntry struct {
+	Location string
+	Error    string
+	Count    int
+}
+
+func (m Map) Dump() ([]DumpEntry, error) {
+	var key MapKey
+	var val []MapVal
+	var ret []DumpEntry
+
+	fileIDs, err := getFileIDs()
+	if err != nil {
+		return nil, err
+	}
+	iter := m.Iterate()
+	for iter.Next(&key, &val) {
+		fname, ok := fileIDs[int(key.FileID)]
+		if !ok {
+			fname = "<unknown>"
+		}
+		count := 0
+		for _, v := range val {
+			count += int(v)
+		}
+		ret = append(ret, DumpEntry{
+			Location: fmt.Sprintf("bpf/%s:%d", fname, key.LineNR),
+			Error:    fmt.Sprintf("%s (%d)", unix.ErrnoName(syscall.Errno(key.Err)), key.Err),
+			Count:    count,
+		})
+	}
+
+	return ret, nil
+}

pkg/sensors/base/base.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 	"testing"
 
+	"github.com/cilium/tetragon/pkg/errmetrics"
 	"github.com/cilium/tetragon/pkg/ksyms"
 	"github.com/cilium/tetragon/pkg/logger"
 	"github.com/cilium/tetragon/pkg/mbset"
@@ -69,7 +70,7 @@ var (
 
 	MatchBinariesSetMap = program.MapBuilder(mbset.MapName, Execve)
 
-	ErrMetricsMap = program.MapBuilder("tg_errmetrics_map", Execve)
+	ErrMetricsMap = program.MapBuilder(errmetrics.MapName, Execve)
 )
 
 func setupPrograms() {