[CWS] optimize os.Stat in hash resolver because of heavy usage (#29120

)

pkg/security/resolvers/hash/resolver_linux.go

@@ -18,7 +18,6 @@ import (
 	"io/fs"
 	"os"
 	"slices"
-	"syscall"
 
 	"github.com/DataDog/datadog-go/v5/statsd"
 	"github.com/glaslos/ssdeep"
@@ -215,18 +214,17 @@ type fileUniqKey struct {
 }
 
 func getFileInfo(path string) (fs.FileMode, int64, fileUniqKey, error) {
-	fileInfo, err := os.Stat(path)
+	stat, err := utils.UnixStat(path)
 	if err != nil {
 		return 0, 0, fileUniqKey{}, err
 	}
 
-	stat := fileInfo.Sys().(*syscall.Stat_t)
 	fkey := fileUniqKey{
 		dev:   stat.Dev,
 		inode: stat.Ino,
 	}
 
-	return fileInfo.Mode(), fileInfo.Size(), fkey, nil
+	return utils.UnixStatModeToGoFileMode(stat.Mode), stat.Size, fkey, nil
 }
 
 // hash hashes the provided file event

pkg/security/utils/stat_unix.go

@@ -0,0 +1,59 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016-present Datadog, Inc.
+
+//go:build unix
+
+// Package utils holds utils related files
+package utils
+
+import (
+	"io/fs"
+	"syscall"
+)
+
+// UnixStat is an unix only equivalent to os.Stat, but alloc-free,
+// and returning directly the platform-specific syscall.Stat_t structure.
+func UnixStat(path string) (syscall.Stat_t, error) {
+	var stat syscall.Stat_t
+	var err error
+	for {
+		err := syscall.Stat(path, &stat)
+		if err != syscall.EINTR {
+			break
+		}
+	}
+	return stat, err
+}
+
+// UnixStatModeToGoFileMode converts a Unix mode to a Go fs.FileMode.
+func UnixStatModeToGoFileMode(mode uint32) fs.FileMode {
+	fsmode := fs.FileMode(mode & 0777)
+	switch mode & syscall.S_IFMT {
+	case syscall.S_IFBLK:
+		fsmode |= fs.ModeDevice
+	case syscall.S_IFCHR:
+		fsmode |= fs.ModeDevice | fs.ModeCharDevice
+	case syscall.S_IFDIR:
+		fsmode |= fs.ModeDir
+	case syscall.S_IFIFO:
+		fsmode |= fs.ModeNamedPipe
+	case syscall.S_IFLNK:
+		fsmode |= fs.ModeSymlink
+	case syscall.S_IFREG:
+		// nothing to do
+	case syscall.S_IFSOCK:
+		fsmode |= fs.ModeSocket
+	}
+	if mode&syscall.S_ISGID != 0 {
+		fsmode |= fs.ModeSetgid
+	}
+	if mode&syscall.S_ISUID != 0 {
+		fsmode |= fs.ModeSetuid
+	}
+	if mode&syscall.S_ISVTX != 0 {
+		fsmode |= fs.ModeSticky
+	}
+	return fsmode
+}