replace raw syscall implementation with musl wrapper

Signed-off-by: leongross <[email protected]>

Author: leongross

builder/musl.go

@@ -136,6 +136,8 @@ var libMusl = Library{
 			"thread/*.c",
 			"time/*.c",
 			"unistd/*.c",
+			// "process/fork.c",
+			"process/*.c",
 		}
 		if arch == "arm" {
 			// These files need to be added to the start for some reason.

src/os/exec_linux.go

@@ -57,7 +57,9 @@ 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 {

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