Add KASAN support for detecting heap memory safety bugs (buffer
overflows, underflows, use-after-free) at runtime using compiler
instrumentation and shadow memory. Gated behind
CONFIG_IDF_EXPERIMENTAL_FEATURES, with touch points kept to esp_system
and heap so other components stay untouched.
- Core runtime (esp_system/kasan.c, esp_kasan.h): nibble-based shadow
memory in DRAM, poison/unpoison, per-access validation, and __asan_*
stubs; hot-path stubs in IRAM so they stay valid with the flash cache
off. Shadow init runs before heap bring-up.
- Heap integration (heap/heap_kasan*.c): alloc/free hooks add redzones,
a quarantine FIFO, and shadow updates.
- Panic handling: disable checks once at the panic handler entry so
backtrace and stack dumps can read redzones without nested reports.
- Build system: -fsanitize=kernel-address for app code, with HAL, SoC,
esp_rom, SPI flash, esp_hw_support, bootloader_support, FreeRTOS, and
heap internals excluded from instrumentation.
- Test app (tools/test_apps/system/kasan_test): Unity tests for
overflow, underflow, use-after-free, and all sized __asan_* stubs,
with halt and no-halt configurations.
- Docs: document KASAN in the heap memory debugging guide (EN and CN).
