os rework

Author: leongross

src/os/exec_linux.go

@@ -46,10 +46,6 @@ func (p *Process) release() error {
 // * 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")
 	}
@@ -58,40 +54,18 @@ func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error)
 		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)
+	pid, err = Fork()
 	if err != nil {
 		return 0, err
-	}
-
-	if (runtime.GOOS == "freebsd" || runtime.GOOS == "dragonfly") && len(argv) > 0 && len(argv[0]) > len(argv0) {
-		argvp[0] = argv0p
-	}
-
-	ret = syscall.Fork()
-	if int(ret) < 0 {
-		return 0, errors.New("fork failed")
-	}
-
-	if int(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 int(ret) != 0 {
+		err = Execve(argv0, argv, attr.Env)
+		if err != nil {
 			// exec failed
-			return int(ret), errors.New("exec failed")
+			return 0, err
 		}
 		// 3. TODO: use pipes to communicate back child status
-		return int(ret), nil
+		return pid, nil
 	}
 }
 

src/os/osexec.go

@@ -0,0 +1,56 @@
+//go:build linux
+// +build linux
+
+package os
+
+import (
+	"errors"
+	"syscall"
+	"unsafe"
+)
+
+func Fork() (pid int, err error) {
+	// ret := libc_fork()
+	// ret, _, _ := syscall.Syscall(syscall.SYS_FORK, 0, 0, 0)
+	ret, _, _ := syscall.Syscall(57, 0, 0, 0)
+	if ret < 0 {
+		// TODO: parse the syscall return codes
+		return 0, errors.New("fork failed")
+	}
+	return int(ret), nil
+}
+
+// the golang standard library does not expose interfaces for execve and fork, so we define them here the same way via the libc wrapper
+func Execve(pathname string, argv []string, envv []string) (err error) {
+	argv0 := cstring(pathname)
+
+	// transform argv and envv into the format expected by execve
+	argv1 := make([]*byte, len(argv)+1)
+	for i, arg := range argv {
+		argv1[i] = &cstring(arg)[0]
+	}
+	argv1[len(argv)] = nil
+
+	env1 := make([]*byte, len(envv)+1)
+	for i, env := range envv {
+		env1[i] = &cstring(env)[0]
+	}
+	env1[len(envv)] = nil
+
+	// fail := libc_execve(&argv0[0], &argv1[0], &env1[0])
+	// fail, _, _ := syscall.Syscall(syscall.SYS_EXECVE, uintptr(unsafe.Pointer(&argv0[0])), uintptr(unsafe.Pointer(&argv1[0])), uintptr(unsafe.Pointer(&env1[0])))
+	fail, _, _ := syscall.Syscall(59, uintptr(unsafe.Pointer(&argv0[0])), uintptr(unsafe.Pointer(&argv1[0])), uintptr(unsafe.Pointer(&env1[0])))
+	if fail < 0 {
+		// TODO: parse the syscall return codes
+		return errors.New("execve failed")
+	}
+
+	return nil
+}
+
+func cstring(s string) []byte {
+	data := make([]byte, len(s)+1)
+	copy(data, s)
+	// final byte should be zero from the initial allocation
+	return data
+}

src/syscall/syscall_unix.go

@@ -3,8 +3,6 @@
 
 package syscall
 
-import "errors"
-
 func Exec(argv0 string, argv []string, envv []string) (err error)
 
 // The two SockaddrInet* structs have been copied from the Go source tree.
@@ -22,53 +20,7 @@ type SockaddrInet6 struct {
 	raw    RawSockaddrInet6
 }
 
-func Fork() (err error) {
-	fail := int(libc_fork())
-	if fail < 0 {
-		// TODO: parse the syscall return codes
-		return errors.New("fork failed")
-	}
-	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
-func Execve(pathname string, argv []string, envv []string) (err error) {
-	argv0 := cstring(pathname)
-
-	// transform argv and envv into the format expected by execve
-	argv1 := make([]*byte, len(argv)+1)
-	for i, arg := range argv {
-		argv1[i] = &cstring(arg)[0]
-	}
-	argv1[len(argv)] = nil
-
-	env1 := make([]*byte, len(envv)+1)
-	for i, env := range envv {
-		env1[i] = &cstring(env)[0]
-	}
-	env1[len(envv)] = nil
-
-	fail := int(libc_execve(&argv0[0], &argv1[0], &env1[0]))
-	if fail < 0 {
-		// TODO: parse the syscall return codes
-		return errors.New("fork failed")
-	}
-	return
-}
-
-func cstring(s string) []byte {
-	data := make([]byte, len(s)+1)
-	copy(data, s)
-	// final byte should be zero from the initial allocation
-	return data
-}
-
-// pid_t fork(void);
-//
-//export fork
-func libc_fork() int32
-
-// int execve(const char *filename, char *const argv[], char *const envp[]);
-//
-//export execve
-func libc_execve(filename *byte, argv **byte, envp **byte) int
+const (
+	SYS_FORK   = 57
+	SYS_EXECVE = 59
+)