removing MPU Hal - details in desc

since it impossible for me to debug NULL pointer dereference without flipper, blind developing went to its end

firmware/targets/f7/Inc/FreeRTOSConfig.h

@@ -32,7 +32,7 @@ extern uint32_t SystemCoreClock;
 #define configUSE_16_BIT_TICKS 0
 #define configUSE_MUTEXES 1
 #define configQUEUE_REGISTRY_SIZE 0
-#define configCHECK_FOR_STACK_OVERFLOW 0
+#define configCHECK_FOR_STACK_OVERFLOW 2
 #define configUSE_RECURSIVE_MUTEXES 1
 #define configUSE_COUNTING_SEMAPHORES 1
 #define configENABLE_BACKWARD_COMPATIBILITY 0
@@ -145,7 +145,3 @@ standard names. */
 #define USE_CUSTOM_SYSTICK_HANDLER_IMPLEMENTATION 1
 #define configOVERRIDE_DEFAULT_TICK_CONFIGURATION \
     1 /* required only for Keil but does not hurt otherwise */
-
-#define traceTASK_SWITCHED_IN()                                     \
-    extern void furi_hal_mpu_set_stack_protection(uint32_t* stack); \
-    furi_hal_mpu_set_stack_protection((uint32_t*)pxCurrentTCB->pxStack)

firmware/targets/f7/furi_hal/furi_hal.c

@@ -1,5 +1,4 @@
 #include <furi_hal.h>
-#include <furi_hal_mpu.h>
 
 #include <stm32wbxx_ll_cortex.h>
 
@@ -36,7 +35,6 @@ void furi_hal_deinit_early() {
 }
 
 void furi_hal_init() {
-    furi_hal_mpu_init();
     furi_hal_clock_init();
     furi_hal_console_init();
     furi_hal_rtc_init();
@@ -82,6 +80,17 @@ void furi_hal_init() {
     // FatFS driver initialization
     MX_FATFS_Init();
     FURI_LOG_I(TAG, "FATFS OK");
+
+    // Partial null pointer dereference protection
+    LL_MPU_Disable();
+    LL_MPU_ConfigRegion(
+        LL_MPU_REGION_NUMBER0,
+        0x00,
+        0x0,
+        LL_MPU_REGION_SIZE_1MB | LL_MPU_REGION_PRIV_RO_URO | LL_MPU_ACCESS_BUFFERABLE |
+            LL_MPU_ACCESS_CACHEABLE | LL_MPU_ACCESS_SHAREABLE | LL_MPU_TEX_LEVEL1 |
+            LL_MPU_INSTRUCTION_ACCESS_ENABLE);
+    LL_MPU_Enable(LL_MPU_CTRL_PRIVILEGED_DEFAULT);
 }
 
 void furi_hal_switch(void* address) {

firmware/targets/f7/furi_hal/furi_hal_interrupt.c

@@ -6,7 +6,6 @@
 #include <stm32wbxx.h>
 #include <stm32wbxx_ll_tim.h>
 #include <stm32wbxx_ll_rcc.h>
-#include <stm32wbxx_ll_cortex.h>
 
 #define TAG "FuriHalInterrupt"
 
@@ -96,10 +95,6 @@ void furi_hal_interrupt_init() {
     LL_SYSCFG_DisableIT_FPU_IDC();
     LL_SYSCFG_DisableIT_FPU_IXC();
 
-    LL_HANDLER_EnableFault(LL_HANDLER_FAULT_USG);
-    LL_HANDLER_EnableFault(LL_HANDLER_FAULT_BUS);
-    LL_HANDLER_EnableFault(LL_HANDLER_FAULT_MEM);
-
     FURI_LOG_I(TAG, "Init OK");
 }
 
@@ -246,20 +241,6 @@ void HardFault_Handler() {
 }
 
 void MemManage_Handler() {
-    if(FURI_BIT(SCB->CFSR, SCB_CFSR_MMARVALID_Pos)) {
-        uint32_t memfault_address = SCB->MMFAR;
-        if(memfault_address < (1024 * 1024)) {
-            // from 0x00 to 1MB, see FuriHalMpuRegionNULL
-            furi_crash("NULL pointer dereference");
-        } else {
-            // write or read of MPU region 1 (FuriHalMpuRegionStack)
-            furi_crash("MPU fault, possibly stack overflow");
-        }
-    } else if(FURI_BIT(SCB->CFSR, SCB_CFSR_MSTKERR_Pos)) {
-        // push to stack on MPU region 1 (FuriHalMpuRegionStack)
-        furi_crash("MemManage fault, possibly stack overflow");
-    }
-
     furi_crash("MemManage");
 }
 

firmware/targets/f7/furi_hal/furi_hal_mpu.c

@@ -1,66 +0,0 @@
-#include <furi_hal_mpu.h>
-#include <stm32wbxx_ll_cortex.h>
-
-#define FURI_HAL_MPU_ATTRIBUTES                                                     \
-    (LL_MPU_ACCESS_BUFFERABLE | LL_MPU_ACCESS_CACHEABLE | LL_MPU_ACCESS_SHAREABLE | \
-     LL_MPU_TEX_LEVEL1 | LL_MPU_INSTRUCTION_ACCESS_ENABLE)
-
-#define FURI_HAL_MPU_STACK_PROTECT_REGION FuriHalMPURegionSize32B
-
-void furi_hal_mpu_init() {
-    furi_hal_mpu_enable();
-
-    // NULL pointer dereference protection
-    furi_hal_mpu_protect_no_access(FuriHalMpuRegionNULL, 0x00, FuriHalMPURegionSize1MB);
-}
-
-void furi_hal_mpu_enable() {
-    LL_MPU_Enable(LL_MPU_CTRL_PRIVILEGED_DEFAULT);
-}
-
-void furi_hal_mpu_disable() {
-    LL_MPU_Disable();
-}
-
-void furi_hal_mpu_protect_no_access(
-    FuriHalMpuRegion region,
-    uint32_t address,
-    FuriHalMPURegionSize size) {
-    uint32_t size_ll = size;
-    size_ll = size_ll << MPU_RASR_SIZE_Pos;
-
-    furi_hal_mpu_disable();
-    LL_MPU_ConfigRegion(
-        region, 0x00, address, FURI_HAL_MPU_ATTRIBUTES | LL_MPU_REGION_NO_ACCESS | size_ll);
-    furi_hal_mpu_enable();
-}
-
-void furi_hal_mpu_protect_read_only(
-    FuriHalMpuRegion region,
-    uint32_t address,
-    FuriHalMPURegionSize size) {
-    uint32_t size_ll = size;
-    size_ll = size_ll << MPU_RASR_SIZE_Pos;
-
-    furi_hal_mpu_disable();
-    LL_MPU_ConfigRegion(
-        region, 0x00, address, FURI_HAL_MPU_ATTRIBUTES | LL_MPU_REGION_PRIV_RO_URO | size_ll);
-    furi_hal_mpu_enable();
-}
-
-void furi_hal_mpu_protect_disable(FuriHalMpuRegion region) {
-    furi_hal_mpu_disable();
-    LL_MPU_DisableRegion(region);
-    furi_hal_mpu_enable();
-}
-
-void furi_hal_mpu_set_stack_protection(uint32_t* stack) {
-    // Protection area address must be aligned to region size
-    uint32_t stack_ptr = (uint32_t)stack;
-    uint32_t mask = ((1 << (FURI_HAL_MPU_STACK_PROTECT_REGION + 2)) - 1);
-    stack_ptr &= ~mask;
-    if(stack_ptr < (uint32_t)stack) stack_ptr += (mask + 1);
-
-    furi_hal_mpu_protect_read_only(
-        FuriHalMpuRegionStack, stack_ptr, FURI_HAL_MPU_STACK_PROTECT_REGION);
-}

firmware/targets/furi_hal_include/furi_hal_mpu.h

@@ -1,86 +0,0 @@
-/**
- * @file furi_hal_light.h
- * Light control HAL API
- */
-
-#pragma once
-
-#include <stdbool.h>
-#include <stdint.h>
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-typedef enum {
-    FuriHalMpuRegionNULL = 0x00, // region 0 used to protect null pointer dereference
-    FuriHalMpuRegionStack = 0x01, // region 1 used to protect stack
-    FuriHalMpuRegion2 = 0x02,
-    FuriHalMpuRegion3 = 0x03,
-    FuriHalMpuRegion4 = 0x04,
-    FuriHalMpuRegion5 = 0x05,
-    FuriHalMpuRegion6 = 0x06,
-    FuriHalMpuRegion7 = 0x07,
-} FuriHalMpuRegion;
-
-typedef enum {
-    FuriHalMPURegionSize32B = 0x04U,
-    FuriHalMPURegionSize64B = 0x05U,
-    FuriHalMPURegionSize128B = 0x06U,
-    FuriHalMPURegionSize256B = 0x07U,
-    FuriHalMPURegionSize512B = 0x08U,
-    FuriHalMPURegionSize1KB = 0x09U,
-    FuriHalMPURegionSize2KB = 0x0AU,
-    FuriHalMPURegionSize4KB = 0x0BU,
-    FuriHalMPURegionSize8KB = 0x0CU,
-    FuriHalMPURegionSize16KB = 0x0DU,
-    FuriHalMPURegionSize32KB = 0x0EU,
-    FuriHalMPURegionSize64KB = 0x0FU,
-    FuriHalMPURegionSize128KB = 0x10U,
-    FuriHalMPURegionSize256KB = 0x11U,
-    FuriHalMPURegionSize512KB = 0x12U,
-    FuriHalMPURegionSize1MB = 0x13U,
-    FuriHalMPURegionSize2MB = 0x14U,
-    FuriHalMPURegionSize4MB = 0x15U,
-    FuriHalMPURegionSize8MB = 0x16U,
-    FuriHalMPURegionSize16MB = 0x17U,
-    FuriHalMPURegionSize32MB = 0x18U,
-    FuriHalMPURegionSize64MB = 0x19U,
-    FuriHalMPURegionSize128MB = 0x1AU,
-    FuriHalMPURegionSize256MB = 0x1BU,
-    FuriHalMPURegionSize512MB = 0x1CU,
-    FuriHalMPURegionSize1GB = 0x1DU,
-    FuriHalMPURegionSize2GB = 0x1EU,
-    FuriHalMPURegionSize4GB = 0x1FU,
-} FuriHalMPURegionSize;
-
-/**
- * @brief Initialize memory protection unit
- */
-void furi_hal_mpu_init();
-
-/**
-* @brief Enable memory protection unit
-*/
-void furi_hal_mpu_enable();
-
-/**
-* @brief Disable memory protection unit
-*/
-void furi_hal_mpu_disable();
-
-void furi_hal_mpu_protect_no_access(
-    FuriHalMpuRegion region,
-    uint32_t address,
-    FuriHalMPURegionSize size);
-
-void furi_hal_mpu_protect_read_only(
-    FuriHalMpuRegion region,
-    uint32_t address,
-    FuriHalMPURegionSize size);
-
-void furi_hal_mpu_protect_disable(FuriHalMpuRegion region);
-
-#ifdef __cplusplus
-}
-#endif

furi/core/memmgr.c

@@ -36,8 +36,10 @@ void* calloc(size_t count, size_t size) {
 }
 
 char* strdup(const char* s) {
-    // arg s marked as non-null, so we need hack to check for NULL
+    const char* s_null = s;
-    furi_check(((uint32_t)s << 2) != 0);
+    if(s_null == NULL) {
+        return NULL;
+    }
 
     size_t siz = strlen(s) + 1;
     char* y = pvPortMalloc(siz);