test: run ESP32 programs in QEMU

src/runtime/runtime_esp32.go

@@ -78,12 +78,6 @@ var _ebss [0]byte
 //go:extern _vector_table
 var _vector_table [0]uintptr
 
-func abort() {
-	for {
-		device.Asm("waiti 0")
-	}
-}
-
 // interruptInit installs the Xtensa vector table by writing its address
 // to the VECBASE special register and ensures all CPU interrupts are
 // initially disabled.

src/runtime/runtime_esp32_abort.go

@@ -0,0 +1,11 @@
+//go:build esp32 && !qemu
+
+package runtime
+
+import "device"
+
+func abort() {
+	for {
+		device.Asm("waiti 0")
+	}
+}

src/runtime/runtime_esp32_qemu.go

@@ -0,0 +1,28 @@
+//go:build esp32 && qemu
+
+package runtime
+
+import "device"
+
+func exit(code int) {
+	qemuExit(code)
+}
+
+func abort() {
+	qemuExit(1)
+}
+
+func qemuExit(code int) {
+	// QEMU semihosting expects a2 = SYS_exit (1) and a3 = the exit code.
+	// AsmFull cannot declare these clobbers, so no Go code may run afterward.
+	device.AsmFull(
+		"mov a3, {code}\n"+
+			"movi a2, 1\n"+
+			"simcall",
+		map[string]interface{}{"code": code},
+	)
+	// This loop ensures the clobbered registers are never used again.
+	for {
+		device.Asm("waiti 0")
+	}
+}

src/runtime/runtime_esp32xx.go

@@ -55,10 +55,6 @@ func ticksToNanoseconds(ticks timeUnit) int64 {
 	return int64(ticks) * 25
 }
 
-func exit(code int) {
-	abort()
-}
-
 func putchar(c byte) {
 	machine.Serial.WriteByte(c)
 }

src/runtime/runtime_esp32xx_exit.go

@@ -0,0 +1,7 @@
+//go:build (esp32 && !qemu) || esp32c3 || esp32c6
+
+package runtime
+
+func exit(code int) {
+	abort()
+}