test: run ESP32 programs in QEMU

.github/workflows/linux.yml

@@ -196,6 +196,10 @@ jobs:
           cat /proc/cpuinfo
           sudo apt-get update
           sudo apt-get install --no-install-recommends \
+              libgcrypt20 \
+              libpixman-1-0 \
+              libsdl2-2.0-0 \
+              libslirp0 \
               qemu-system-arm \
               qemu-system-riscv32 \
               qemu-user \
@@ -216,6 +220,14 @@ jobs:
           version: "29.0.1"
       - name: Setup `wasm-tools`
         uses: bytecodealliance/actions/wasm-tools/setup@v1
+      - name: Install Espressif QEMU
+        run: |
+          release=esp-develop-9.2.2-20260417
+          archive=qemu-xtensa-softmmu-${release//-/_}-x86_64-linux-gnu.tar.xz
+          curl -fL --retry 3 -o "$RUNNER_TEMP/$archive" \
+            "https://github.com/espressif/qemu/releases/download/$release/$archive"
+          tar -xJf "$RUNNER_TEMP/$archive" -C "$RUNNER_TEMP"
+          echo "$RUNNER_TEMP/qemu/bin" >> "$GITHUB_PATH"
       - name: Restore LLVM source cache
         uses: actions/cache/restore@v5
         id: cache-llvm-source

builder/esp.go

@@ -111,9 +111,6 @@ func makeESPFirmwareImage(infile, outfile, format string) error {
 		// Compute the size of the RAM portion of the image (everything the ROM
 		// bootloader loads, up to and including the appended SHA256 hash).
 		ramImageSize := 0
-		if makeImage {
-			ramImageSize += 4096
-		}
 		ramImageSize += 24 // image header (8) + trailer fields (16)
 		for _, seg := range segments {
 			ramImageSize += 8 + len(seg.data) // segment header + data (4-aligned)
@@ -284,6 +281,9 @@ func makeESPFirmwareImage(infile, outfile, format string) error {
 		dromSize := 0
 		if len(dromSegs) > 0 {
 			targetImageOffset := int(dromFlashAddr - flashBase)
+			if makeImage {
+				targetImageOffset = int(dromFlashAddr)
+			}
 			if outf.Len() > targetImageOffset {
 				return fmt.Errorf("ESP32: RAM segments too large (%d bytes), overlap DROM at flash 0x%x", outf.Len(), dromFlashAddr)
 			}
@@ -304,6 +304,9 @@ func makeESPFirmwareImage(infile, outfile, format string) error {
 			}
 			iromFlashAddr := dromFlashAddr + uint32(dromPages)*pageSize
 			targetImageOffset := int(iromFlashAddr - flashBase)
+			if makeImage {
+				targetImageOffset = int(iromFlashAddr)
+			}
 			if outf.Len() > targetImageOffset {
 				return fmt.Errorf("ESP32: DROM too large, overlaps IROM at flash 0x%x", iromFlashAddr)
 			}

main_test.go

@@ -261,6 +261,21 @@ func TestTimerStopResetRace(t *testing.T) {
 	runTest("timer_stop_reset_race.go", optionsFromTarget("", sema), t, nil, nil)
 }
 
+func TestESP32QEMU(t *testing.T) {
+	t.Parallel()
+
+	options := optionsFromTarget("esp32-qemu", sema)
+	emuCheck(t, options)
+	machines, err := exec.Command("qemu-system-xtensa", "-machine", "help").Output()
+	if err != nil {
+		t.Fatal("failed to list qemu-system-xtensa machines:", err)
+	}
+	if !regexp.MustCompile(`(?m)^esp32\s`).Match(machines) {
+		t.Skip("qemu-system-xtensa does not support the ESP32 machine")
+	}
+	runTest("print.go", options, t, nil, nil)
+}
+
 func runPlatTests(options compileopts.Options, tests []string, t *testing.T) {
 	emuCheck(t, options)
 
@@ -539,6 +554,9 @@ func runTestWithConfig(name string, t *testing.T, options compileopts.Options, c
 	if config.EmulatorName() == "simavr" {
 		actual = cleanSimAVRTestOutput(actual)
 	}
+	if config.EmulatorName() == "qemu-system-xtensa" {
+		actual = cleanESP32QEMUOutput(actual)
+	}
 	if name == "testing.go" {
 		// Strip actual time.
 		re := regexp.MustCompile(`\([0-9]\.[0-9][0-9]s\)`)
@@ -564,6 +582,18 @@ func runTestWithConfig(name string, t *testing.T, options compileopts.Options, c
 	}
 }
 
+func cleanESP32QEMUOutput(output []byte) []byte {
+	entryLine := bytes.Index(output, []byte("\nentry "))
+	if entryLine < 0 {
+		return output
+	}
+	entryLineEnd := bytes.IndexByte(output[entryLine+1:], '\n')
+	if entryLineEnd < 0 {
+		return output
+	}
+	return output[entryLine+1+entryLineEnd+1:]
+}
+
 func cleanSimAVRTestOutput(output []byte) []byte {
 	output = bytes.ReplaceAll(output, []byte{0x1b, '[', '3', '2', 'm'}, nil)
 	output = bytes.ReplaceAll(output, []byte{0x1b, '[', '0', 'm'}, nil)

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()
+}

targets/esp32-qemu.json

@@ -0,0 +1,5 @@
+{
+	"inherits": ["esp32-generic"],
+	"build-tags": ["qemu"],
+	"emulator": "qemu-system-xtensa -machine esp32 -nographic -semihosting -drive file={img},if=mtd,format=raw"
+}

targets/esp32.json

@@ -25,6 +25,5 @@
 	],
 	"binary-format": "esp32",
 	"flash-method": "esp32flash",
-	"emulator": "qemu-system-xtensa -machine esp32 -nographic -drive file={img},if=mtd,format=raw",
 	"gdb": ["xtensa-esp32-elf-gdb"]
 }

targets/esp32s3.json

@@ -25,6 +25,5 @@
 	],
 	"binary-format": "esp32s3",
 	"flash-method": "esp32jtag",
-	"emulator": "qemu-system-xtensa -machine esp32 -nographic -drive file={img},if=mtd,format=raw",
 	"gdb": ["xtensa-esp32-elf-gdb"]
 }