Add an asan native_sim build

ports/zephyr-cp/Makefile

@@ -123,6 +123,21 @@ sim:
 clean-sim:
 	rm -rf $(wildcard build-native_*)
 
-test: build-native_native_sim/zephyr-cp/zephyr/zephyr.exe
+# Every board the test suite uses: native sim (non-asan + asan) and the bsim
+# boards (tests/bsim/conftest.py parametrizes over both). Zephyr samples for
+# bsim tests are built on demand by the zephyr_sample fixture.
+TEST_BOARDS := native_native_sim native_native_sim_asan native_nrf5340bsim native_nrf54lm20bsim
+
+# Delegate to a sub-make with BOARD set so the per-board build rule (and its
+# shield args + bsim prep) applies. The targets are phony: the west builds are
+# incremental, so this just keeps the test binaries fresh.
+define test_board_rule
+.PHONY: test-build-$(1)
+test-build-$(1):
+	+$$(MAKE) BOARD=$(1) BUILD=build-$(1) build-$(1)/zephyr-cp/zephyr/zephyr.elf
+endef
+$(foreach board,$(TEST_BOARDS),$(eval $(call test_board_rule,$(board))))
+
+test: $(TEST_BOARDS:%=test-build-%)
 	pytest cptools/tests
 	pytest tests/ -v

ports/zephyr-cp/boards/board_aliases.cmake

@@ -35,6 +35,7 @@ cp_board_alias(renesas_ek_ra6m5 ek_ra6m5)
 cp_board_alias(renesas_ek_ra8d1 ek_ra8d1)
 cp_board_alias(renesas_da14695_dk_usb da14695_dk_usb)
 cp_board_alias(native_native_sim native_sim/native)
+cp_board_alias(native_native_sim_asan native_sim/native)
 cp_board_alias(native_nrf5340bsim nrf5340bsim/nrf5340/cpuapp)
 cp_board_alias(native_nrf54lm20bsim nrf54lm20bsim/nrf54lm20a/cpuapp)
 cp_board_alias(nordic_nrf54l15dk nrf54l15dk/nrf54l15/cpuapp)

ports/zephyr-cp/boards/native/native_sim_asan/autogen_board_info.toml

@@ -0,0 +1,131 @@
+# This file is autogenerated when a board is built. Do not edit. Do commit it to git. Other scripts use its info.
+name = "zephyr Native simulator - native_sim"
+
+[modules]
+__future__ = true
+_bleio = false
+_eve = false
+_pew = false
+_pixelmap = false
+_stage = false
+adafruit_bus_device = true
+adafruit_pixelbuf = false
+aesio = true
+alarm = false
+analogbufio = false
+analogio = false
+atexit = false
+audiobusio = true # Zephyr board has audiobusio
+audiocore = true # Zephyr board has audiobusio
+audiodelays = true # Zephyr board has audiobusio
+audiofilewriter = false
+audiofilters = true # Zephyr board has audiobusio
+audiofreeverb = true # Zephyr board has audiobusio
+audioi2sin = false
+audioio = false
+audiomixer = true # Zephyr board has audiobusio
+audiomp3 = true # Zephyr board has audiobusio
+audiopwmio = false
+audiospeed = false
+aurora_epaper = false
+bitbangio = false
+bitmapfilter = true # Zephyr board has busio
+bitmaptools = true # Zephyr board has busio
+bitops = false
+board = false
+busdisplay = true # Zephyr board has busio
+busio = true # Zephyr board has busio
+camera = false
+canio = false
+codeop = false
+countio = false
+digitalio = true
+displayio = true # Zephyr board has displayio
+dotclockframebuffer = false
+dualbank = false
+emmcio = false
+epaperdisplay = true # Zephyr board has busio
+floppyio = false
+fontio = true # Zephyr board has busio
+fourwire = true # Zephyr board has busio
+framebufferio = true # Zephyr board has busio
+frequencyio = false
+getpass = true
+gifio = true # Zephyr board has busio
+gnss = false
+hashlib = true # Zephyr networking enabled
+hostnetwork = true # Zephyr board has hostnetwork
+i2cdisplaybus = true # Zephyr board has busio
+i2cioexpander = false
+i2ctarget = false
+imagecapture = false
+ipaddress = true # Zephyr networking enabled
+is31fl3741 = false
+jpegio = true # Zephyr board has busio
+keypad = false
+keypad_demux = false
+locale = false
+lvfontio = true # Zephyr board has busio
+math = true
+max3421e = false
+mcp4822 = false
+mdns = false
+memorymap = false
+memorymonitor = false
+microcontroller = true
+mipidsi = false
+msgpack = true
+neopixel_write = false
+nvm = true # Zephyr board has nvm
+onewireio = false
+os = true
+paralleldisplaybus = false
+picogame = false
+ps2io = false
+pulseio = false
+pwmio = false
+qrio = false
+qspibus = false
+rainbowio = true
+random = true
+rclcpy = false
+rgbmatrix = false
+rotaryio = true # Zephyr board has rotaryio
+rtc = false
+sdcardio = true # Zephyr board has busio
+sdioio = false
+sharpdisplay = true # Zephyr board has busio
+socketpool = true # Zephyr networking enabled
+spitarget = false
+ssl = false
+storage = true
+struct = true
+supervisor = true
+synthio = true # Zephyr board has audiobusio
+terminalio = true # Zephyr board has busio
+tilepalettemapper = true # Zephyr board has busio
+time = true
+touchio = false
+traceback = true
+uheap = false
+usb = false
+usb_audio = false
+usb_cdc = false
+usb_hid = false
+usb_host = false
+usb_midi = false
+usb_video = false
+ustack = false
+vectorio = true # Zephyr board has busio
+warnings = true
+watchdog = false
+wifi = false
+zephyr_display = true # Zephyr board has zephyr_display
+zephyr_kernel = false
+zlib = true
+# extmod modules shared with MicroPython
+asyncio = true
+binascii = true
+json = true
+re = true
+select = true

ports/zephyr-cp/boards/native/native_sim_asan/board.conf

@@ -0,0 +1,51 @@
+# Build with AddressSanitizer to catch memory errors in tests.
+CONFIG_ASAN=y
+
+# No Bluetooth hardware on native_sim
+CONFIG_BT=n
+
+CONFIG_EMUL=y
+CONFIG_GPIO=y
+CONFIG_NATIVE_SIM_SLOWDOWN_TO_REAL_TIME=n
+
+# So we can test safe mode
+CONFIG_NATIVE_SIM_REBOOT=y
+
+CONFIG_TRACING=y
+CONFIG_TRACING_PERFETTO=y
+CONFIG_TRACING_SYNC=y
+CONFIG_TRACING_BACKEND_POSIX=y
+CONFIG_TRACING_GPIO=y
+
+# I2C emulation for testing
+CONFIG_I2C_EMUL=y
+
+# Display emulation for display/terminal golden tests.
+CONFIG_DISPLAY=y
+CONFIG_SDL_DISPLAY=y
+# Don't require hardware acceleration so the software renderer can be used.
+CONFIG_SDL_DISPLAY_USE_HARDWARE_ACCELERATOR=n
+
+# EEPROM emulation for testing
+CONFIG_EEPROM=y
+CONFIG_EEPROM_AT24=y
+CONFIG_EEPROM_AT2X_EMUL=y
+
+# I2S SDL emulation for audio testing
+CONFIG_I2S_SDL=y
+
+CONFIG_NETWORKING=y
+CONFIG_NET_IPV4=y
+CONFIG_NET_TCP=y
+CONFIG_NET_SOCKETS=y
+CONFIG_ETH_NATIVE_TAP=n
+CONFIG_NET_DRIVERS=y
+CONFIG_NET_SOCKETS_OFFLOAD=y
+CONFIG_NET_NATIVE_OFFLOADED_SOCKETS=y
+CONFIG_HEAP_MEM_POOL_SIZE=1024
+
+CONFIG_NET_LOG=y
+
+CONFIG_MBEDTLS=y
+CONFIG_PSA_WANT_ALG_SHA_1=y
+CONFIG_PSA_WANT_ALG_SHA_256=y

ports/zephyr-cp/boards/native/native_sim_asan/board.overlay

@@ -0,0 +1,8 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Device tree overlay for CircuitPython on native_sim with AddressSanitizer.
+ * Identical hardware description to the non-asan board, so just reuse it.
+ */
+
+#include "../native_sim/board.overlay"

ports/zephyr-cp/boards/native/native_sim_asan/circuitpython.toml

@@ -0,0 +1 @@
+CIRCUITPY_BUILD_EXTENSIONS = ["exe"]

ports/zephyr-cp/supervisor/port.c

@@ -22,6 +22,7 @@
 
 #if defined(CONFIG_ARCH_POSIX)
 #include <limits.h>
+#include <stdio.h>
 #include <fcntl.h>
 
 #include "cmdline.h"
@@ -280,7 +281,39 @@ uint32_t *port_stack_get_limit(void) {
 uint32_t *port_stack_get_top(void) {
     _thread_stack_info_t stack_info = k_current_get()->stack_info;
 
-    return (uint32_t *)(stack_info.start + stack_info.size - stack_info.delta);
+    uint32_t *top = (uint32_t *)(stack_info.start + stack_info.size - stack_info.delta);
+    #if defined(CONFIG_ARCH_POSIX)
+    // On hosted builds the thread stack is a pthread stack. pthread_getattr_np(),
+    // which the POSIX arch uses to fix up stack_info, can report a size larger
+    // than the real mapping (ASan intercepts it and inflates the size). The GC
+    // scans up to the returned top, so clamp it to the end of the mapping that
+    // contains the current stack pointer.
+    //
+    // Only ever clamp *downwards*: /proc/self/maps merges adjacent anonymous
+    // mappings with the same flags, so the line containing our stack pointer
+    // routinely covers several thread stacks at once (e.g. 0xf63c2000-0xf73c4000
+    // for two 8MB stacks). Taking its end as the top made the GC scan megabytes
+    // past this thread's stack, into the neighbouring thread's live stack -- and
+    // segfault whenever the range had an unmapped hole (a guard page, or a stack
+    // that has since been freed).
+    volatile uint32_t stack_probe;
+    uintptr_t sp = (uintptr_t)&stack_probe;
+    FILE *maps = fopen("/proc/self/maps", "r");
+    if (maps != NULL) {
+        char line[256];
+        unsigned long low, high;
+        while (fgets(line, sizeof(line), maps) != NULL) {
+            if (sscanf(line, "%lx-%lx", &low, &high) == 2 && low <= sp && sp < high) {
+                if (high < (uintptr_t)top) {
+                    top = (uint32_t *)high;
+                }
+                break;
+            }
+        }
+        fclose(maps);
+    }
+    #endif
+    return top;
 }
 
 uint64_t port_get_raw_ticks(uint8_t *subticks) {

ports/zephyr-cp/tests/conftest.py

@@ -149,14 +149,21 @@ def log_uart_trace_output(trace_file: Path) -> None:
             )
 
 
-@pytest.fixture
+# Native_sim boards each test runs against: the non-asan default and the
+# asan-enabled build, so memory errors fail tests.
+NATIVE_BOARDS = ["native_native_sim", "native_native_sim_asan"]
+
+
+@pytest.fixture(params=NATIVE_BOARDS)
 def board(request):
+    """Parametrized over both native_sim builds (non-asan and asan).
+
+    The bsim conftest overrides this fixture with its own bsim boards.
+    """
     board = request.node.get_closest_marker("circuitpython_board")
     if board is not None:
-        board = board.args[0]
-    else:
-        board = "native_native_sim"
-    return board
+        return board.args[0]
+    return request.param
 
 
 @pytest.fixture

ports/zephyr-cp/tests/test_basics.py

@@ -7,12 +7,12 @@
 
 
 @pytest.mark.circuitpy_drive(None)
-def test_blank_flash_hello_world(circuitpython):
+def test_blank_flash_hello_world(board, circuitpython):
     """Test that an erased flash shows code.py output header."""
     circuitpython.wait_until_done()
 
     output = circuitpython.serial.all_output
-    assert "Board ID:native_native_sim" in output
+    assert f"Board ID:{board}" in output
     assert "UID:" in output
     assert "code.py output:" in output
     assert "Hello World" in output

ports/zephyr-cp/zephyr_main.c

@@ -2,6 +2,20 @@
 
 extern int circuitpython_main(void);
 
+#if defined(__SANITIZE_ADDRESS__) || (defined(__has_feature) && __has_feature(address_sanitizer))
+// ASAN's stack-use-after-return detection (on by default in recent runtimes)
+// moves C locals into "fake stack" frames on the heap. The GC scans the real
+// machine stack for live object pointers, so with fake stacks enabled it misses
+// pointers held in C frames and collects still-referenced objects, corrupting
+// the heap. GCC's instrumentation consults this global at every instrumented
+// function entry, so clearing it from a constructor disables only that check;
+// all other ASAN checks stay enabled.
+extern char __asan_option_detect_stack_use_after_return;
+__attribute__((constructor)) static void cp_disable_asan_fake_stack(void) {
+    __asan_option_detect_stack_use_after_return = 0;
+}
+#endif
+
 int main(void) {
     // Use a unique name for CP main so that the linker needs to look in libcircuitpython.a
     return circuitpython_main();