SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

type ProcAttr struct {
	Dir   string    // Current working directory.
	Env   []string  // Environment.
	Files []uintptr // File descriptors.
	Sys   *SysProcAttr
}

type SysProcAttr struct {
	Rfork int // additional flags to pass to rfork
}

var zeroProcAttr ProcAttr
var zeroSysProcAttr SysProcAttr

func forkExec(argv0 string, argv []string, attr *ProcAttr) (pid int, err error) {
	var (
		p      [2]int
		n      int

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

	const (
		PR_CAP_AMBIENT       = 0x2f
		PR_CAP_AMBIENT_RAISE = 0x2
	)

	// vfork requires that the child not touch any of the parent's
	// active stack frames. Hence, the child does all post-fork
	// processing in this stack frame and never returns, while the
	// parent returns immediately from this frame and does all
	// post-fork processing in the outer frame.
	//
	// Declare all variables at top in case any

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

//
//go:nowritebarrier
func newosproc(mp *m) {
	if false {
		print("newosproc mp=", mp, " ostk=", &mp, "\n")
	}
	pid := rfork(_RFPROC | _RFMEM | _RFNOWAIT)
	if pid < 0 {
		throw("newosproc: rfork failed")
	}
	if pid == 0 {
		tstart_plan9(mp)
	}
}

func exitThread(wait *atomic.Uint32) {
	// We should never reach exitThread on Plan 9 because we let

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }

	SYS_CAP_ENTER                = 516 // { int cap_enter(void); }
	SYS_CAP_GETMODE              = 517 // { int cap_getmode(u_int *modep); }
	SYS_PDFORK                   = 518 // { int pdfork(int *fdp, int flags); }
	SYS_PDKILL                   = 519 // { int pdkill(int fd, int signum); }
	SYS_PDGETPID                 = 520 // { int pdgetpid(int fd, pid_t *pidp); }