diff --git a/internal/lib/syscall/ztypes_aix_ppc64.go b/c/syscall/ztypes_aix_ppc64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_aix_ppc64.go
rename to c/syscall/ztypes_aix_ppc64.go
diff --git a/internal/lib/syscall/ztypes_darwin_amd64.go b/c/syscall/ztypes_darwin_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_darwin_amd64.go
rename to c/syscall/ztypes_darwin_amd64.go
diff --git a/internal/lib/syscall/ztypes_darwin_arm64.go b/c/syscall/ztypes_darwin_arm64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_darwin_arm64.go
rename to c/syscall/ztypes_darwin_arm64.go
diff --git a/internal/lib/syscall/ztypes_dragonfly_amd64.go b/c/syscall/ztypes_dragonfly_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_dragonfly_amd64.go
rename to c/syscall/ztypes_dragonfly_amd64.go
diff --git a/internal/lib/syscall/ztypes_freebsd_386.go b/c/syscall/ztypes_freebsd_386.go
similarity index 100%
rename from internal/lib/syscall/ztypes_freebsd_386.go
rename to c/syscall/ztypes_freebsd_386.go
diff --git a/internal/lib/syscall/ztypes_freebsd_amd64.go b/c/syscall/ztypes_freebsd_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_freebsd_amd64.go
rename to c/syscall/ztypes_freebsd_amd64.go
diff --git a/internal/lib/syscall/ztypes_freebsd_arm.go b/c/syscall/ztypes_freebsd_arm.go
similarity index 100%
rename from internal/lib/syscall/ztypes_freebsd_arm.go
rename to c/syscall/ztypes_freebsd_arm.go
diff --git a/internal/lib/syscall/ztypes_freebsd_arm64.go b/c/syscall/ztypes_freebsd_arm64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_freebsd_arm64.go
rename to c/syscall/ztypes_freebsd_arm64.go
diff --git a/internal/lib/syscall/ztypes_freebsd_riscv64.go b/c/syscall/ztypes_freebsd_riscv64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_freebsd_riscv64.go
rename to c/syscall/ztypes_freebsd_riscv64.go
diff --git a/internal/lib/syscall/ztypes_linux_386.go b/c/syscall/ztypes_linux_386.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_386.go
rename to c/syscall/ztypes_linux_386.go
diff --git a/internal/lib/syscall/ztypes_linux_amd64.go b/c/syscall/ztypes_linux_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_amd64.go
rename to c/syscall/ztypes_linux_amd64.go
diff --git a/internal/lib/syscall/ztypes_linux_arm.go b/c/syscall/ztypes_linux_arm.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_arm.go
rename to c/syscall/ztypes_linux_arm.go
diff --git a/internal/lib/syscall/ztypes_linux_arm64.go b/c/syscall/ztypes_linux_arm64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_arm64.go
rename to c/syscall/ztypes_linux_arm64.go
diff --git a/internal/lib/syscall/ztypes_linux_loong64.go b/c/syscall/ztypes_linux_loong64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_loong64.go
rename to c/syscall/ztypes_linux_loong64.go
diff --git a/internal/lib/syscall/ztypes_linux_mips.go b/c/syscall/ztypes_linux_mips.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_mips.go
rename to c/syscall/ztypes_linux_mips.go
diff --git a/internal/lib/syscall/ztypes_linux_mips64.go b/c/syscall/ztypes_linux_mips64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_mips64.go
rename to c/syscall/ztypes_linux_mips64.go
diff --git a/internal/lib/syscall/ztypes_linux_mips64le.go b/c/syscall/ztypes_linux_mips64le.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_mips64le.go
rename to c/syscall/ztypes_linux_mips64le.go
diff --git a/internal/lib/syscall/ztypes_linux_mipsle.go b/c/syscall/ztypes_linux_mipsle.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_mipsle.go
rename to c/syscall/ztypes_linux_mipsle.go
diff --git a/internal/lib/syscall/ztypes_linux_ppc64.go b/c/syscall/ztypes_linux_ppc64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_ppc64.go
rename to c/syscall/ztypes_linux_ppc64.go
diff --git a/internal/lib/syscall/ztypes_linux_ppc64le.go b/c/syscall/ztypes_linux_ppc64le.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_ppc64le.go
rename to c/syscall/ztypes_linux_ppc64le.go
diff --git a/internal/lib/syscall/ztypes_linux_riscv64.go b/c/syscall/ztypes_linux_riscv64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_riscv64.go
rename to c/syscall/ztypes_linux_riscv64.go
diff --git a/internal/lib/syscall/ztypes_linux_s390x.go b/c/syscall/ztypes_linux_s390x.go
similarity index 100%
rename from internal/lib/syscall/ztypes_linux_s390x.go
rename to c/syscall/ztypes_linux_s390x.go
diff --git a/internal/lib/syscall/ztypes_netbsd_386.go b/c/syscall/ztypes_netbsd_386.go
similarity index 100%
rename from internal/lib/syscall/ztypes_netbsd_386.go
rename to c/syscall/ztypes_netbsd_386.go
diff --git a/internal/lib/syscall/ztypes_netbsd_amd64.go b/c/syscall/ztypes_netbsd_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_netbsd_amd64.go
rename to c/syscall/ztypes_netbsd_amd64.go
diff --git a/internal/lib/syscall/ztypes_netbsd_arm.go b/c/syscall/ztypes_netbsd_arm.go
similarity index 100%
rename from internal/lib/syscall/ztypes_netbsd_arm.go
rename to c/syscall/ztypes_netbsd_arm.go
diff --git a/internal/lib/syscall/ztypes_netbsd_arm64.go b/c/syscall/ztypes_netbsd_arm64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_netbsd_arm64.go
rename to c/syscall/ztypes_netbsd_arm64.go
diff --git a/internal/lib/syscall/ztypes_openbsd_386.go b/c/syscall/ztypes_openbsd_386.go
similarity index 100%
rename from internal/lib/syscall/ztypes_openbsd_386.go
rename to c/syscall/ztypes_openbsd_386.go
diff --git a/internal/lib/syscall/ztypes_openbsd_amd64.go b/c/syscall/ztypes_openbsd_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_openbsd_amd64.go
rename to c/syscall/ztypes_openbsd_amd64.go
diff --git a/internal/lib/syscall/ztypes_openbsd_arm.go b/c/syscall/ztypes_openbsd_arm.go
similarity index 100%
rename from internal/lib/syscall/ztypes_openbsd_arm.go
rename to c/syscall/ztypes_openbsd_arm.go
diff --git a/internal/lib/syscall/ztypes_openbsd_arm64.go b/c/syscall/ztypes_openbsd_arm64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_openbsd_arm64.go
rename to c/syscall/ztypes_openbsd_arm64.go
diff --git a/internal/lib/syscall/ztypes_openbsd_mips64.go b/c/syscall/ztypes_openbsd_mips64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_openbsd_mips64.go
rename to c/syscall/ztypes_openbsd_mips64.go
diff --git a/internal/lib/syscall/ztypes_solaris_amd64.go b/c/syscall/ztypes_solaris_amd64.go
similarity index 100%
rename from internal/lib/syscall/ztypes_solaris_amd64.go
rename to c/syscall/ztypes_solaris_amd64.go
diff --git a/internal/build/build.go b/internal/build/build.go
index 363598c5..15b687a6 100644
--- a/internal/build/build.go
+++ b/internal/build/build.go
@@ -664,8 +664,6 @@ func canSkipToBuild(pkgPath string) bool {
 	switch pkgPath {
 	case "unsafe":
 		return true
-	case "internal/oserror":
-		return false
 	default:
 		return strings.HasPrefix(pkgPath, "internal/") ||
 			strings.HasPrefix(pkgPath, "runtime/internal/")
@@ -679,6 +677,7 @@ var hasAltPkg = map[string]none{
 	"fmt":                  {},
 	"internal/abi":         {},
 	"internal/bytealg":     {},
+	"internal/oserror":     {},
 	"internal/reflectlite": {},
 	//"io":                 {},
 	//"io/fs":              {},
diff --git a/internal/lib/syscall/errors.go b/internal/lib/internal/oserror/errors.go
similarity index 70%
rename from internal/lib/syscall/errors.go
rename to internal/lib/internal/oserror/errors.go
index e35f780d..b9124224 100644
--- a/internal/lib/syscall/errors.go
+++ b/internal/lib/internal/oserror/errors.go
@@ -2,11 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package syscall
+// Package oserror defines errors values used in the os package.
+//
+// These types are defined here to permit the syscall package to reference them.
+package oserror
 
+// llgo:skipall
 import "errors"
 
-// from internal/oserror
 var (
 	ErrInvalid    = errors.New("invalid argument")
 	ErrPermission = errors.New("permission denied")
diff --git a/internal/lib/os/stat_unix.go b/internal/lib/os/stat_unix.go
index 1c826576..04ae7304 100644
--- a/internal/lib/os/stat_unix.go
+++ b/internal/lib/os/stat_unix.go
@@ -6,6 +6,8 @@
 
 package os
 
+import "syscall"
+
 // Stat returns the FileInfo structure describing file.
 // If there is an error, it will be of type *PathError.
 func (f *File) Stat() (FileInfo, error) {
@@ -26,7 +28,6 @@ func (f *File) Stat() (FileInfo, error) {
 
 // statNolog stats a file with no test logging.
 func statNolog(name string) (FileInfo, error) {
-	/* TODO(xsw):
 	var fs fileStat
 	err := ignoringEINTR(func() error {
 		return syscall.Stat(name, &fs.sys)
@@ -36,13 +37,10 @@ func statNolog(name string) (FileInfo, error) {
 	}
 	fillFileStatFromSys(&fs, name)
 	return &fs, nil
-	*/
-	panic("todo: os.statNolog")
 }
 
 // lstatNolog lstats a file with no test logging.
 func lstatNolog(name string) (FileInfo, error) {
-	/* TODO(xsw):
 	var fs fileStat
 	err := ignoringEINTR(func() error {
 		return syscall.Lstat(name, &fs.sys)
@@ -52,6 +50,4 @@ func lstatNolog(name string) (FileInfo, error) {
 	}
 	fillFileStatFromSys(&fs, name)
 	return &fs, nil
-	*/
-	panic("todo: os.lstatNolog")
 }
diff --git a/internal/lib/syscall/syscall.go b/internal/lib/syscall/syscall.go
index 045dc87b..6dffaf47 100644
--- a/internal/lib/syscall/syscall.go
+++ b/internal/lib/syscall/syscall.go
@@ -22,8 +22,12 @@ import (
 
 	"github.com/goplus/llgo/c"
 	"github.com/goplus/llgo/c/os"
+	"github.com/goplus/llgo/c/syscall"
 )
 
+type Timespec syscall.Timespec
+type Timeval syscall.Timeval
+
 // Unix returns the time stored in ts as seconds plus nanoseconds.
 func (ts *Timespec) Unix() (sec int64, nsec int64) {
 	return int64(ts.Sec), int64(ts.Nsec)
diff --git a/internal/lib/syscall/syscall_unix.go b/internal/lib/syscall/syscall_unix.go
index b0b2a72f..30d66e4f 100644
--- a/internal/lib/syscall/syscall_unix.go
+++ b/internal/lib/syscall/syscall_unix.go
@@ -11,6 +11,7 @@ import (
 	"unsafe"
 
 	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/internal/lib/internal/oserror"
 )
 
 var (
@@ -28,11 +29,11 @@ func (e Errno) Error() string {
 
 func (e Errno) Is(target error) bool {
 	switch target {
-	case ErrPermission:
+	case oserror.ErrPermission:
 		return e == EACCES || e == EPERM
-	case ErrExist:
+	case oserror.ErrExist:
 		return e == EEXIST || e == ENOTEMPTY
-	case ErrNotExist:
+	case oserror.ErrNotExist:
 		return e == ENOENT
 	case errors.ErrUnsupported:
 		return e == ENOSYS || e == ENOTSUP || e == EOPNOTSUPP
diff --git a/internal/lib/time/time.go b/internal/lib/time/time.go
index c20799ab..7f748569 100644
--- a/internal/lib/time/time.go
+++ b/internal/lib/time/time.go
@@ -1021,6 +1021,36 @@ func unixTime(sec int64, nsec int32) Time {
 	return Time{uint64(nsec), sec + unixToInternal, Local}
 }
 
+// Unix returns the local Time corresponding to the given Unix time,
+// sec seconds and nsec nanoseconds since January 1, 1970 UTC.
+// It is valid to pass nsec outside the range [0, 999999999].
+// Not all sec values have a corresponding time value. One such
+// value is 1<<63-1 (the largest int64 value).
+func Unix(sec int64, nsec int64) Time {
+	if nsec < 0 || nsec >= 1e9 {
+		n := nsec / 1e9
+		sec += n
+		nsec -= n * 1e9
+		if nsec < 0 {
+			nsec += 1e9
+			sec--
+		}
+	}
+	return unixTime(sec, int32(nsec))
+}
+
+// UnixMilli returns the local Time corresponding to the given Unix time,
+// msec milliseconds since January 1, 1970 UTC.
+func UnixMilli(msec int64) Time {
+	return Unix(msec/1e3, (msec%1e3)*1e6)
+}
+
+// UnixMicro returns the local Time corresponding to the given Unix time,
+// usec microseconds since January 1, 1970 UTC.
+func UnixMicro(usec int64) Time {
+	return Unix(usec/1e6, (usec%1e6)*1e3)
+}
+
 func isLeap(year int) bool {
 	return year%4 == 0 && (year%100 != 0 || year%400 == 0)
 }