diff --git a/c/os/os.go b/c/os/os.go
index 563f0071..e3efb039 100644
--- a/c/os/os.go
+++ b/c/os/os.go
@@ -320,3 +320,11 @@ func Getgid() GidT
 func Getegid() GidT
 
 // -----------------------------------------------------------------------------
+
+//go:linkname Getrlimit C.getrlimit
+func Getrlimit(resource c.Int, rlp *syscall.Rlimit) c.Int
+
+//go:linkname Setrlimit C.setrlimit
+func Setrlimit(resource c.Int, rlp *syscall.Rlimit) c.Int
+
+// -----------------------------------------------------------------------------
diff --git a/internal/lib/syscall/exec_libc2.go b/internal/lib/syscall/exec_libc2.go
index 074632ac..e696f404 100644
--- a/internal/lib/syscall/exec_libc2.go
+++ b/internal/lib/syscall/exec_libc2.go
@@ -7,9 +7,6 @@
 package syscall
 
 import (
-	"runtime"
-	"unsafe"
-
 	"github.com/goplus/llgo/c"
 )
 
@@ -59,13 +56,13 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 	// Declare all variables at top in case any
 	// declarations require heap allocation (e.g., err1).
 	var (
-		r1              uintptr
-		nextfd          int
-		i               int
-		err             error
-		pgrp            c.Int
-		cred            *Credential
-		ngroups, groups uintptr
+		r1     uintptr
+		nextfd int
+		i      int
+		// err             error
+		// pgrp            c.Int
+		cred *Credential
+		// ngroups, groups uintptr
 	)
 
 	rlim, rlimOK := origRlimitNofile.Load().(Rlimit)
@@ -85,47 +82,58 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 
 	// About to call fork.
 	// No more allocation or calls of non-assembly functions.
-	runtime_BeforeFork()
-	r1, _, err1 = rawSyscall(abi.FuncPCABI0(libc_fork_trampoline), 0, 0, 0)
+	// runtime_BeforeFork()
+	r1, err1 = fork()
 	if err1 != 0 {
-		runtime_AfterFork()
+		// runtime_AfterFork()
 		return 0, err1
 	}
 
 	if r1 != 0 {
 		// parent; return PID
-		runtime_AfterFork()
+		// runtime_AfterFork()
 		return int(r1), 0
 	}
 
 	// Fork succeeded, now in child.
 
+	// TODO(xsw): check this
 	// Enable tracing if requested.
 	if sys.Ptrace {
+		/* TODO(xsw):
 		if err = ptrace(PTRACE_TRACEME, 0, 0, 0); err != nil {
 			err1 = err.(Errno)
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Ptrace")
 	}
 
 	// Session ID
 	if sys.Setsid {
+		/* TODO(xsw):
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setsid_trampoline), 0, 0, 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Setsid")
 	}
 
 	// Set process group
 	if sys.Setpgid || sys.Foreground {
+		/* TODO(xsw):
 		// Place child in process group.
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_setpgid_trampoline), 0, uintptr(sys.Pgid), 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Setpgid")
 	}
 
 	if sys.Foreground {
+		/* TODO(xsw):
 		// This should really be pid_t, however _C_int (aka int32) is
 		// generally equivalent.
 		pgrp = _C_int(sys.Pgid)
@@ -142,22 +150,28 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Foreground")
 	}
 
 	// Restore the signal mask. We do this after TIOCSPGRP to avoid
 	// having the kernel send a SIGTTOU signal to the process group.
-	runtime_AfterForkInChild()
+	// runtime_AfterForkInChild()
 
 	// Chroot
 	if chroot != nil {
+		/* TODO(xsw):
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_chroot_trampoline), uintptr(unsafe.Pointer(chroot)), 0, 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - chroot")
 	}
 
 	// User and groups
 	if cred = sys.Credential; cred != nil {
+		/* TODO(xsw):
 		ngroups = uintptr(len(cred.Groups))
 		groups = uintptr(0)
 		if ngroups > 0 {
@@ -177,19 +191,25 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Credential")
 	}
 
 	// Chdir
 	if dir != nil {
+		/* TODO(xsw):
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_chdir_trampoline), uintptr(unsafe.Pointer(dir)), 0, 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - dir")
 	}
 
 	// Pass 1: look for fd[i] < i and move those up above len(fd)
 	// so that pass 2 won't stomp on an fd it needs later.
 	if pipe < nextfd {
+		/* TODO(xsw):
 		if runtime.GOOS == "openbsd" {
 			_, _, err1 = rawSyscall(dupTrampoline, uintptr(pipe), uintptr(nextfd), O_CLOEXEC)
 		} else {
@@ -204,9 +224,12 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 		}
 		pipe = nextfd
 		nextfd++
+		*/
+		panic("todo: syscall.forkAndExecInChild - pipe < nextfd")
 	}
 	for i = 0; i < len(fd); i++ {
 		if fd[i] >= 0 && fd[i] < i {
+			/* TODO(xsw):
 			if nextfd == pipe { // don't stomp on pipe
 				nextfd++
 			}
@@ -224,16 +247,22 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 			}
 			fd[i] = nextfd
 			nextfd++
+			*/
+			panic("todo: syscall.forkAndExecInChild - for fd")
 		}
 	}
 
 	// Pass 2: dup fd[i] down onto i.
 	for i = 0; i < len(fd); i++ {
 		if fd[i] == -1 {
+			/* TODO(xsw):
 			rawSyscall(abi.FuncPCABI0(libc_close_trampoline), uintptr(i), 0, 0)
 			continue
+			*/
+			panic("todo: syscall.forkAndExecInChild - fd[i] == -1")
 		}
 		if fd[i] == i {
+			/* TODO(xsw):
 			// dup2(i, i) won't clear close-on-exec flag on Linux,
 			// probably not elsewhere either.
 			_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_fcntl_trampoline), uintptr(fd[i]), F_SETFD, 0)
@@ -241,13 +270,18 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 				goto childerror
 			}
 			continue
+			*/
+			panic("todo: syscall.forkAndExecInChild - fd[i] == i")
 		}
+		/* TODO(xsw):
 		// The new fd is created NOT close-on-exec,
 		// which is exactly what we want.
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_dup2_trampoline), uintptr(fd[i]), uintptr(i), 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - dup2")
 	}
 
 	// By convention, we don't close-on-exec the fds we are
@@ -255,40 +289,58 @@ func forkAndExecInChild(argv0 *c.Char, argv, envv **c.Char, chroot, dir *c.Char,
 	// Programs that know they inherit fds >= 3 will need
 	// to set them close-on-exec.
 	for i = len(fd); i < 3; i++ {
+		/* TODO(xsw):
 		rawSyscall(abi.FuncPCABI0(libc_close_trampoline), uintptr(i), 0, 0)
+		*/
+		panic("todo: syscall.forkAndExecInChild - for i")
 	}
 
 	// Detach fd 0 from tty
 	if sys.Noctty {
+		/* TODO(xsw):
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_ioctl_trampoline), 0, uintptr(TIOCNOTTY), 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Noctty")
 	}
 
 	// Set the controlling TTY to Ctty
 	if sys.Setctty {
+		/* TODO(xsw):
 		_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_ioctl_trampoline), uintptr(sys.Ctty), uintptr(TIOCSCTTY), 0)
 		if err1 != 0 {
 			goto childerror
 		}
+		*/
+		panic("todo: syscall.forkAndExecInChild - sys.Setctty")
 	}
 
 	// Restore original rlimit.
 	if rlimOK && rlim.Cur != 0 {
+		/* TODO(xsw):
 		rawSyscall(abi.FuncPCABI0(libc_setrlimit_trampoline), uintptr(RLIMIT_NOFILE), uintptr(unsafe.Pointer(&rlim)), 0)
+		*/
+		panic("todo: syscall.forkAndExecInChild - rlimOK")
 	}
 
+	/* TODO(xsw):
 	// Time to exec.
 	_, _, err1 = rawSyscall(abi.FuncPCABI0(libc_execve_trampoline),
 		uintptr(unsafe.Pointer(argv0)),
 		uintptr(unsafe.Pointer(&argv[0])),
 		uintptr(unsafe.Pointer(&envv[0])))
+	*/
+	panic("todo: syscall.forkAndExecInChild - execve")
 
-childerror:
+	//	childerror:
+	/* TODO(xsw):
 	// send error code on pipe
 	rawSyscall(abi.FuncPCABI0(libc_write_trampoline), uintptr(pipe), uintptr(unsafe.Pointer(&err1)), unsafe.Sizeof(err1))
 	for {
 		rawSyscall(abi.FuncPCABI0(libc_exit_trampoline), 253, 0, 0)
 	}
+	*/
+	// panic("todo: syscall.forkAndExecInChild - childerror")
 }
diff --git a/internal/lib/syscall/rlimit.go b/internal/lib/syscall/rlimit.go
new file mode 100644
index 00000000..a4f6d724
--- /dev/null
+++ b/internal/lib/syscall/rlimit.go
@@ -0,0 +1,52 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix
+
+package syscall
+
+import (
+	"sync/atomic"
+
+	"github.com/goplus/llgo/c/syscall"
+)
+
+// origRlimitNofile, if not {0, 0}, is the original soft RLIMIT_NOFILE.
+// When we can assume that we are bootstrapping with Go 1.19,
+// this can be atomic.Pointer[Rlimit].
+var origRlimitNofile atomic.Value // of Rlimit
+
+// Some systems set an artificially low soft limit on open file count, for compatibility
+// with code that uses select and its hard-coded maximum file descriptor
+// (limited by the size of fd_set).
+//
+// Go does not use select, so it should not be subject to these limits.
+// On some systems the limit is 256, which is very easy to run into,
+// even in simple programs like gofmt when they parallelize walking
+// a file tree.
+//
+// After a long discussion on go.dev/issue/46279, we decided the
+// best approach was for Go to raise the limit unconditionally for itself,
+// and then leave old software to set the limit back as needed.
+// Code that really wants Go to leave the limit alone can set the hard limit,
+// which Go of course has no choice but to respect.
+func init() {
+	var lim Rlimit
+	if err := Getrlimit(syscall.RLIMIT_NOFILE, &lim); err == nil && lim.Cur != lim.Max {
+		origRlimitNofile.Store(lim)
+		lim.Cur = lim.Max
+		adjustFileLimit(&lim)
+		setrlimit(syscall.RLIMIT_NOFILE, &lim)
+	}
+}
+
+func Setrlimit(resource int, rlim *Rlimit) error {
+	err := setrlimit(resource, rlim)
+	if err == nil && resource == syscall.RLIMIT_NOFILE {
+		// Store zeroes in origRlimitNofile to tell StartProcess
+		// to not adjust the rlimit in the child process.
+		origRlimitNofile.Store(Rlimit{0, 0})
+	}
+	return err
+}
diff --git a/internal/lib/syscall/rlimit_darwin.go b/internal/lib/syscall/rlimit_darwin.go
new file mode 100644
index 00000000..73e49646
--- /dev/null
+++ b/internal/lib/syscall/rlimit_darwin.go
@@ -0,0 +1,20 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build darwin
+
+package syscall
+
+// adjustFileLimit adds per-OS limitations on the Rlimit used for RLIMIT_NOFILE. See rlimit.go.
+func adjustFileLimit(lim *Rlimit) {
+	// On older macOS, setrlimit(RLIMIT_NOFILE, lim) with lim.Cur = infinity fails.
+	// Set to the value of kern.maxfilesperproc instead.
+	n, err := SysctlUint32("kern.maxfilesperproc")
+	if err != nil {
+		return
+	}
+	if lim.Cur > uint64(n) {
+		lim.Cur = uint64(n)
+	}
+}
diff --git a/internal/lib/syscall/rlimit_stub.go b/internal/lib/syscall/rlimit_stub.go
new file mode 100644
index 00000000..e8f839dd
--- /dev/null
+++ b/internal/lib/syscall/rlimit_stub.go
@@ -0,0 +1,10 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build aix || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+
+package syscall
+
+// adjustFileLimit adds per-OS limitations on the Rlimit used for RLIMIT_NOFILE. See rlimit.go.
+func adjustFileLimit(lim *Rlimit) {}
diff --git a/internal/lib/syscall/syscall.go b/internal/lib/syscall/syscall.go
index bf940729..dce7fd0c 100644
--- a/internal/lib/syscall/syscall.go
+++ b/internal/lib/syscall/syscall.go
@@ -85,6 +85,14 @@ func Kill(pid int, signum Signal) (err error) {
 	return Errno(ret)
 }
 
+func fork() (uintptr, Errno) {
+	ret := os.Fork()
+	if ret >= 0 {
+		return uintptr(ret), Errno(0)
+	}
+	return 0, Errno(os.Errno)
+}
+
 func wait4(pid int, wstatus *c.Int, options int, rusage *syscall.Rusage) (wpid int, err error) {
 	ret := os.Wait4(os.PidT(pid), wstatus, c.Int(options), rusage)
 	if ret >= 0 {
@@ -164,3 +172,21 @@ func Pipe(p []int) (err error) {
 	}
 	return Errno(ret)
 }
+
+type Rlimit syscall.Rlimit
+
+func Getrlimit(which int, lim *Rlimit) (err error) {
+	ret := os.Getrlimit(c.Int(which), (*syscall.Rlimit)(lim))
+	if ret == 0 {
+		return nil
+	}
+	return Errno(ret)
+}
+
+func setrlimit(which int, lim *Rlimit) (err error) {
+	ret := os.Setrlimit(c.Int(which), (*syscall.Rlimit)(lim))
+	if ret == 0 {
+		return nil
+	}
+	return Errno(ret)
+}
diff --git a/internal/lib/syscall/syscall_bsd.go b/internal/lib/syscall/syscall_bsd.go
index b74cb8ea..715b463d 100644
--- a/internal/lib/syscall/syscall_bsd.go
+++ b/internal/lib/syscall/syscall_bsd.go
@@ -439,8 +439,10 @@ func Sysctl(name string) (value string, err error) {
 	}
 	return string(buf[0:n]), nil
 }
+*/
 
 func SysctlUint32(name string) (value uint32, err error) {
+	/* TODO(xsw):
 	// Translate name to mib number.
 	mib, err := nametomib(name)
 	if err != nil {
@@ -457,8 +459,11 @@ func SysctlUint32(name string) (value uint32, err error) {
 		return 0, EIO
 	}
 	return *(*uint32)(unsafe.Pointer(&buf[0])), nil
+	*/
+	panic("todo: syscall.SysctlUint32")
 }
 
+/*
 //sys	utimes(path string, timeval *[2]Timeval) (err error)
 
 func Utimes(path string, tv []Timeval) (err error) {