nintendoswitch: Fix invalid memory read / write in print calls

Author: racerxdl

src/runtime/runtime_nintendoswitch.go

@@ -40,21 +40,18 @@ func ticks() timeUnit {
 	return timeUnit(ticksToNanoseconds(timeUnit(getArmSystemTick())))
 }
 
-var stdoutBuffer = make([]byte, 0, 120)
+var stdoutBuffer = make([]byte, 120)
+var position = 0
 
 func putchar(c byte) {
-	if c == '\n' || len(stdoutBuffer)+1 >= 120 {
-		NxOutputString(string(stdoutBuffer))
-		stdoutBuffer = stdoutBuffer[:0]
+	if c == '\n' || position > len(stdoutBuffer) {
+		nxOutputString(&stdoutBuffer[0], uint64(position))
+		position = 0
 		return
 	}
 
-	stdoutBuffer = append(stdoutBuffer, c)
-}
-
-func usleep(usec uint) int {
-	sleepThread(uint64(usec) * 1000)
-	return 0
+	stdoutBuffer[position] = c
+	position++
 }
 
 func abort() {

src/runtime/runtime_nintendoswitch_heap.go

@@ -4,17 +4,11 @@
 
 package runtime
 
-import "unsafe"
-
 const heapSize = 0x2000000 * 16 // Default by libnx
 
-//go:extern _stack_top
-var stackTopSymbol [0]byte
-
 var (
 	heapStart = uintptr(0)
 	heapEnd   = uintptr(0)
-	stackTop  = uintptr(unsafe.Pointer(&stackTopSymbol))
 )
 
 //export setHeapSize
@@ -24,7 +18,7 @@ func preinit() {
 	setHeapSize(&heapStart, heapSize)
 
 	if heapStart == 0 {
-		panic("failed to allocate heap")
+		runtimePanic("failed to allocate heap")
 	}
 
 	heapEnd = heapStart + heapSize