replace raw syscall implementation with musl wrapper

Signed-off-by: leongross <leon.gross@9elements.com>

builder/musl.go

@@ -136,6 +136,7 @@ var libMusl = Library{
 			"thread/*.c",
 			"time/*.c",
 			"unistd/*.c",
+			"process/*.c",
 		}
 		if arch == "arm" {
 			// These files need to be added to the start for some reason.

src/os/exec_linux.go

@@ -22,6 +22,12 @@ var (
 	Kill      Signal = syscall.SIGKILL
 )
 
+var (
+	ErrNotImplementedDir   = errors.New("directory setting not implemented")
+	ErrNotImplementedSys   = errors.New("sys setting not implemented")
+	ErrNotImplementedFiles = errors.New("files setting not implemented")
+)
+
 // 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
@@ -57,7 +63,9 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 		attr = new(ProcAttr)
 	}
 
-	pid, err = fork()
+	p, err := fork()
+	pid = int(p)
+
 	if err != nil {
 		return 0, err
 	} else {
@@ -78,6 +86,20 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 // 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) {
+	if attr != nil {
+		if attr.Dir != "" {
+			return nil, ErrNotImplementedDir
+		}
+
+		if attr.Sys != nil {
+			return nil, ErrNotImplementedSys
+		}
+
+		if len(attr.Files) != 0 {
+			return nil, ErrNotImplementedFiles
+		}
+	}
+
 	pid, err := forkExec(name, argv, attr)
 	if err != nil {
 		return nil, err

src/os/exec_linux_test.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	. "os"
 	"runtime"
+	"syscall"
 	"testing"
 )
 
@@ -27,10 +28,9 @@ func TestForkExec(t *testing.T) {
 		t.Fatalf("forkExec failed: new process has pid 0")
 	}
 	t.Logf("forkExec succeeded: new process has pid %d", proc)
-
 }
 
-func TestForkExecInvalid(t *testing.T) {
+func TestForkExecErrNotExist(t *testing.T) {
 	proc, err := StartProcess("invalid", []string{"invalid"}, &ProcAttr{})
 	if !errors.Is(err, ErrNotExist) {
 		t.Fatalf("wanted ErrNotExist, got %s\n", err)
@@ -40,3 +40,36 @@ func TestForkExecInvalid(t *testing.T) {
 		t.Fatalf("wanted nil, got %v\n", proc)
 	}
 }
+
+func TestForkExecProcDir(t *testing.T) {
+	proc, err := StartProcess("/bin/echo", []string{"hello", "world"}, &ProcAttr{Dir: "dir"})
+	if !errors.Is(err, ErrNotImplementedDir) {
+		t.Fatalf("wanted ErrNotImplementedDir, got %v\n", err)
+	}
+
+	if proc != nil {
+		t.Fatalf("wanted nil, got %v\n", proc)
+	}
+}
+
+func TestForkExecProcSys(t *testing.T) {
+	proc, err := StartProcess("/bin/echo", []string{"hello", "world"}, &ProcAttr{Sys: &syscall.SysProcAttr{}})
+	if !errors.Is(err, ErrNotImplementedSys) {
+		t.Fatalf("wanted ErrNotImplementedSys, got %v\n", err)
+	}
+
+	if proc != nil {
+		t.Fatalf("wanted nil, got %v\n", proc)
+	}
+}
+
+func TestForkExecProcFiles(t *testing.T) {
+	proc, err := StartProcess("/bin/echo", []string{"hello", "world"}, &ProcAttr{Files: []*File{}})
+	if !errors.Is(err, ErrNotImplementedFiles) {
+		t.Fatalf("wanted ErrNotImplementedFiles, got %v\n", err)
+	}
+
+	if proc != nil {
+		t.Fatalf("wanted nil, got %v\n", proc)
+	}
+}

src/os/osexec.go

@@ -1,4 +1,4 @@
-//go:build linux && !baremetal && !darwin && !tinygo.wasm && !arm64
+//go:build linux && !baremetal && !tinygo.wasm && !arm64
 
 // arm64 does not have a fork syscall, so ignore it for now
 // TODO: add support for arm64 with clone or use musl implementation
@@ -10,15 +10,12 @@ import (
 	"unsafe"
 )
 
-func fork() (pid int, err error) {
-	ret, _, err := syscall.Syscall(syscall.SYS_FORK, 0, 0, 0)
-	if int(ret) != 0 {
-		errno := err.(syscall.Errno)
-		if int(errno) != 0 {
-			return -1, errno
-		}
+func fork() (pid int32, err error) {
+	pid = libc_fork()
+	if pid != 0 {
+		err = syscall.Errno(*libc_errno())
 	}
-	return int(ret), nil
+	return
 }
 
 // the golang standard library does not expose interfaces for execve and fork, so we define them here the same way via the libc wrapper
@@ -52,3 +49,11 @@ func cstring(s string) []byte {
 	// final byte should be zero from the initial allocation
 	return data
 }
+
+//export fork
+func libc_fork() int32
+
+// Internal musl function to get the C errno pointer.
+//
+//export __errno_location
+func libc_errno() *int32