chore(cmd/bpf-fileids): leverage cgo instead of manually parsing c header.

Signed-off-by: Federico Di Pierro <[email protected]>

Author: FedeDP

Makefile

@@ -105,7 +105,7 @@ clean: cli-clean tarball-clean
 ##@ Build and install
 
 pkg/errmetrics/fileids.json: bpf/tetragon/fileids.h
-	go run ./cmd/bpf-fileids bpf/tetragon/fileids.h pkg/errmetrics/fileids.json
+	go run ./cmd/bpf-fileids pkg/errmetrics/fileids.json
 
 .PHONY: fileids
 fileids: pkg/errmetrics/fileids.json

cmd/bpf-fileids/fileids.go

@@ -3,14 +3,38 @@
 
 package main
 
+/*
+typedef struct {
+	const char *filename;
+	int id;
+}  fileid_t;
+
+const fileid_t *get_fileids() {
+    static fileid_t fileids[] = {
+#define fileid__(f, id)                  { f, id },
+#include "../../bpf/tetragon/fileids.h"
+#undef fileid__
+		{ NULL, -1 }
+	};
+	return fileids;
+}
+
+size_t get_fileids_len() {
+    const fileid_t *fileids = get_fileids();
+	size_t len = 0;
+	while (fileids[len].filename != NULL) {
+		len++;
+	}
+	return len;
+}
+*/
+import "C"
+
 import (
-	"bufio"
 	"encoding/json"
 	"fmt"
 	"os"
-	"regexp"
-	"strconv"
-	"strings"
+	"unsafe"
 )
 
 // json entry
@@ -19,52 +43,37 @@ type Entry struct {
 	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)
+func loadFileIDs() []Entry {
+	fileidsLen := C.get_fileids_len()
+	cArrayPtr := C.get_fileids()
+	if cArrayPtr == nil {
+		fmt.Fprintf(os.Stderr, "Failed to allocate C array.")
 		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]})
-		}
-
+	goSlice := (*[1 << 30]C.fileid_t)(unsafe.Pointer(cArrayPtr))[:fileidsLen:fileidsLen]
+	var ret []Entry
+	for _, fileid := range goSlice {
+		id := int(fileid.id)
+		name := C.GoString(fileid.filename)
+		ret = append(ret, Entry{id, name})
 	}
-	// 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])
+	if len(os.Args) < 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <out.json>\n", os.Args[0])
 		os.Exit(1)
 	}
 
-	fname := os.Args[1]
-	fileIDs := initFileIDs(fname)
+	fileIDs := loadFileIDs()
 	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]
+	outFname := os.Args[1]
 	err = os.WriteFile(outFname, b, 0622)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "error writing file: %v", err)