syscall: mark arguments to Syscall as noescape

Heap arguments to "async" syscalls will break when/if we have moving GC anyway.
With this change is must not break until moving GC, because a user must
reference the object in Go to preserve liveness. Otherwise the code is broken already.
Reduces number of leaked params from 125 to 36 on linux.

R=golang-codereviews, mikioh.mikioh, bradfitz
CC=cshapiro, golang-codereviews, khr, rsc
https://golang.org/cl/45930043

src/cmd/gc/esc.c

@@ -1135,7 +1135,12 @@ esctag(EscState *e, Node *func)
 	if(func->nbody == nil) {
 		if(func->noescape) {
 			for(t=getinargx(func->type)->type; t; t=t->down)
-				if(haspointers(t->type))
+				// Mark all arguments, not only pointers,
+				// to support the following use case.
+				// Syscall package converts all pointers to uintptr
+				// when calls asm-implemented Syscall function:
+				// 
+				//   Syscall(SYS_FOO, uintptr(unsafe.Pointer(p)), 0, 0)
 				t->note = mktag(EscNone);
 		}
 		return;

src/pkg/syscall/dll_windows.go

@@ -20,11 +20,31 @@ type DLLError struct {
 func (e *DLLError) Error() string { return e.Msg }
 
 // Implemented in ../runtime/syscall_windows.goc.
+
+// Pointers passed to syscalls must not escape (be accessed by OS after the syscall returns).
+// For heap objects this will break when/if we have moving GC.
+// And for other objects (global, C allocated) go:noescape has no effect.
+
+//go:noescape
+
 func Syscall(trap, nargs, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func Syscall6(trap, nargs, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func Syscall9(trap, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func Syscall12(trap, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func Syscall15(trap, nargs, a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, a11, a12, a13, a14, a15 uintptr) (r1, r2 uintptr, err Errno)
+
 func loadlibrary(filename *uint16) (handle uintptr, err Errno)
 func getprocaddress(handle uintptr, procname *uint8) (proc uintptr, err Errno)
 

src/pkg/syscall/syscall_linux_386.go

@@ -169,7 +169,16 @@ const (
 	_SENDMMSG    = 20
 )
 
+// Pointers passed to syscalls must not escape (be accessed by OS after the syscall returns).
+// For heap objects this will break when/if we have moving GC.
+// And for other objects (global, C allocated) go:noescape has no effect.
+
+//go:noescape
+
 func socketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err Errno)
+
+//go:noescape
+
 func rawsocketcall(call int, a0, a1, a2, a3, a4, a5 uintptr) (n int, err Errno)
 
 func accept(s int, rsa *RawSockaddrAny, addrlen *_Socklen) (fd int, err error) {

src/pkg/syscall/syscall_plan9.go

@@ -51,9 +51,24 @@ var (
 // creation of IPv6 sockets to return EAFNOSUPPORT.
 var SocketDisableIPv6 bool
 
+// Pointers passed to syscalls must not escape (be accessed by OS after the syscall returns).
+// For heap objects this will break when/if we have moving GC.
+// And for other objects (global, C allocated) go:noescape has no effect.
+
+//go:noescape
+
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err ErrorString)
+
+//go:noescape
+
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err ErrorString)
+
+//go:noescape
+
 func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2, err uintptr)
+
+//go:noescape
+
 func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
 
 func atoi(b []byte) (n uint) {

src/pkg/syscall/syscall_unix.go

@@ -23,9 +23,24 @@ const (
 	netbsd32Bit = runtime.GOOS == "netbsd" && sizeofPtr == 4
 )
 
+// Pointers passed to syscalls must not escape (be accessed by OS after the syscall returns).
+// For heap objects this will break when/if we have moving GC.
+// And for other objects (global, C allocated) go:noescape has no effect.
+
+//go:noescape
+
 func Syscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func Syscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func RawSyscall(trap, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
+
+//go:noescape
+
 func RawSyscall6(trap, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2 uintptr, err Errno)
 
 // Mmap manager, for use by operating system-specific implementations.