add StartProcess functionality (fix)

Author: leongross

src/os/exec_linux.go

@@ -0,0 +1,110 @@
+// Copyright 2009 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 posix || aix || linux || dragonfly || freebsd || (js && wasm) || netbsd || openbsd || solaris || wasip1
+// +build posix aix linux dragonfly freebsd js,wasm netbsd openbsd solaris wasip1
+
+package os
+
+import (
+	"errors"
+	"runtime"
+	"syscall"
+)
+
+// The only signal values guaranteed to be present in the os package on all
+// systems are os.Interrupt (send the process an interrupt) and os.Kill (force
+// the process to exit). On Windows, sending os.Interrupt to a process with
+// os.Process.Signal is not implemented; it will return an error instead of
+// sending a signal.
+var (
+	Interrupt Signal = syscall.SIGINT
+	Kill      Signal = syscall.SIGKILL
+)
+
+// Keep compatible with golang and always succeed and return new proc with pid on Linux.
+func findProcess(pid int) (*Process, error) {
+	return &Process{Pid: pid}, nil
+}
+
+func (p *Process) release() error {
+	// NOOP for unix.
+	p.Pid = -1
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(p, nil)
+	return nil
+}
+
+// This function is a wrapper around the forkExec function, which is a wrapper around the fork and execve system calls.
+// The StartProcess function creates a new process by forking the current process and then calling execve to replace the current process with the new process.
+// It thereby replaces the newly created process with the specified command and arguments.
+// Differences to upstream golang implementation (https://cs.opensource.google/go/go/+/master:src/syscall/exec_unix.go;l=143):
+// * No setting of Process Attributes
+// * Ignoring Ctty
+// * No ForkLocking (might be introduced by #4273)
+// * No parent-child communication via pipes (TODO)
+// * No waiting for crashes child processes to prohibit zombie process accumulation / Wait status checking (TODO)
+func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
+	var (
+		ret uintptr
+	)
+
+	if len(argv) == 0 {
+		return 0, errors.New("exec: no argv")
+	}
+
+	if attr == nil {
+		attr = new(ProcAttr)
+	}
+
+	argv0p, err := syscall.BytePtrFromString(argv0)
+	if err != nil {
+		return 0, err
+	}
+	argvp, err := syscall.SlicePtrFromStrings(argv)
+	if err != nil {
+		return 0, err
+	}
+	envp, err := syscall.SlicePtrFromStrings(attr.Env)
+	if err != nil {
+		return 0, err
+	}
+
+	if (runtime.GOOS == "freebsd" || runtime.GOOS == "dragonfly") && len(argv) > 0 && len(argv[0]) > len(argv0) {
+		argvp[0] = argv0p
+	}
+
+	pid = syscall.Fork()
+	if ret < 0 {
+		return 0, errors.New("fork failed")
+	}
+
+	if ret != 0 {
+		// if fd == 0 code runs in parent
+		return int(ret), nil
+	} else {
+		// else code runs in child, which then should exec the new process
+		ret = syscall.Execve(argv0, argv, envp)
+		if ret != 0 {
+			// exec failed
+			syscall.Exit(1)
+		}
+		// 3. TODO: use pipes to communicate back child status
+		return int(ret), nil
+	}
+}
+
+// In Golang, the idiomatic way to create a new process is to use the StartProcess function.
+// Since the Model of operating system processes in tinygo differs from the one in Golang, we need to implement the StartProcess function differently.
+// The startProcess function is a wrapper around the forkExec function, which is a wrapper around the fork and execve system calls.
+// The StartProcess function creates a new process by forking the current process and then calling execve to replace the current process with the new process.
+// It thereby replaces the newly created process with the specified command and arguments.
+func startProcess(name string, argv []string, attr *ProcAttr) (p *Process, err error) {
+	pid, err := ForkExec(name, argv, attr)
+	if err != nil {
+		return nil, err
+	}
+
+	return findProcess(pid)
+}

src/os/exec_other.go

@@ -0,0 +1,21 @@
+//go:build !aix && !android && !freebsd && !linux && !netbsd && !openbsd && !plan9 && !solaris
+// +build !aix,!android,!freebsd,!linux,!netbsd,!openbsd,!plan9,!solaris
+
+package os
+
+func findProcess(pid int) (*Process, error) {
+	return &Process{Pid: pid}, nil
+}
+
+func (p *Process) release() error {
+	p.Pid = -1
+	return nil
+}
+
+func forkExec(_ string, _ []string, _ *ProcAttr) (pid int, err error) {
+	return 0, ErrNotImplemented
+}
+
+func startProcess(_ string, _ []string, _ *ProcAttr) (proc *Process, err error) {
+	return &Process{Pid: 0}, ErrNotImplemented
+}

src/os/exec_posix.go

@@ -0,0 +1,29 @@
+package os_test
+
+import (
+	. "os"
+	"runtime"
+	"testing"
+)
+
+// Test the functionality of the forkExec function, which is used to fork and exec a new process.
+// This test is not run on Windows, as forkExec is not supported on Windows.
+// This test is not run on Plan 9, as forkExec is not supported on Plan 9.
+func TestForkExec(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Logf("skipping test on %s", runtime.GOOS)
+		return
+	}
+
+	proc, err := StartProcess("echo", []string{"echo", "hello", "world"}, &ProcAttr{})
+	if err != nil {
+		t.Fatalf("forkExec failed: %v", err)
+		return
+	}
+
+	if proc.Pid == 0 {
+		t.Fatalf("forkExec failed: new process has pid 0")
+	} else {
+		t.Logf("forkExec succeeded: new process has pid %d", proc)
+	}
+}

src/os/exec_posix_test.go

@@ -0,0 +1,7 @@
+//go:build unix
+
+package syscall
+
+// Implemented in runtime package.
+func runtime_BeforeExec()
+func runtime_AfterExec()

src/syscall/exec_unix.go

@@ -1,3 +1,6 @@
+//go:build linux || unix
+// +build linux unix
+
 package syscall
 
 import "errors"