diff --git a/SConscript.bootloader b/SConscript.bootloader
index 1d7953765..ec0ba8462 100644
--- a/SConscript.bootloader
+++ b/SConscript.bootloader
@@ -83,6 +83,7 @@ SOURCE_TREZORHAL = [
     'embed/trezorhal/image.c',
     'embed/trezorhal/flash.c',
     'embed/trezorhal/mini_printf.c',
+    'embed/trezorhal/mpu.c',
     'embed/trezorhal/rng.c',
     'embed/trezorhal/stm32.c',
     'embed/trezorhal/touch.c',
diff --git a/embed/bootloader/main.c b/embed/bootloader/main.c
index 61fa8df1c..f48d72cdd 100644
--- a/embed/bootloader/main.c
+++ b/embed/bootloader/main.c
@@ -21,6 +21,7 @@
 #include <sys/types.h>
 
 #include "common.h"
+#include "mpu.h"
 #include "image.h"
 #include "flash.h"
 #include "display.h"
@@ -224,6 +225,8 @@ static void check_bootloader_version(void)
 
 int main(void)
 {
+    mpu_config_bootloader();
+
 main_start:
     display_clear();
 
@@ -379,9 +382,10 @@ main_start:
         ui_fadeout();
     }
 
-    // mpu_config();
+    // mpu_config_firmware();
     // jump_to_unprivileged(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);
 
+    mpu_config_off();
     jump_to(FIRMWARE_START + vhdr.hdrlen + IMAGE_HEADER_SIZE);
 
     return 0;
diff --git a/embed/firmware/main.c b/embed/firmware/main.c
index 5d517fcc0..e0b5f2caf 100644
--- a/embed/firmware/main.c
+++ b/embed/firmware/main.c
@@ -54,7 +54,7 @@ int main(void)
 #if TREZOR_MODEL == T
     check_and_replace_bootloader();
     // Enable MPU
-    mpu_config();
+    mpu_config_firmware();
 #endif
 
     // Init peripherals
diff --git a/embed/trezorhal/common.c b/embed/trezorhal/common.c
index c3afd9261..d0dc28f8d 100644
--- a/embed/trezorhal/common.c
+++ b/embed/trezorhal/common.c
@@ -29,7 +29,8 @@
 
 #include "stm32f4xx_ll_utils.h"
 
-void shutdown(void);
+// from util.s
+extern void shutdown(void);
 
 #define COLOR_FATAL_ERROR RGB16(0x7F, 0x00, 0x00)
 
@@ -115,6 +116,24 @@ void hal_delay(uint32_t ms)
     HAL_Delay(ms);
 }
 
+void delay_random(void)
+{
+    int wait = rng_get() & 0xff;
+    volatile int i = 0;
+    volatile int j = wait;
+    while (i < wait) {
+        if (i + j != wait) {
+            shutdown();
+        }
+        ++i;
+        --j;
+    }
+    // Double-check loop completion.
+    if (i != wait || j != 0) {
+        shutdown();
+    }
+}
+
 // reference RM0090 section 35.12.1 Figure 413
 #define USB_OTG_HS_DATA_FIFO_RAM  (USB_OTG_HS_PERIPH_BASE + 0x20000U)
 #define USB_OTG_HS_DATA_FIFO_SIZE (4096U)
diff --git a/embed/trezorhal/common.h b/embed/trezorhal/common.h
index f886739e0..3fac1dec6 100644
--- a/embed/trezorhal/common.h
+++ b/embed/trezorhal/common.h
@@ -26,11 +26,14 @@
 #define XSTR(s) STR(s)
 #define STR(s) #s
 
+#ifndef MIN_8bits
+#define MIN_8bits(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); _a < _b ? (_a & 0xFF) : (_b & 0xFF); })
+#endif
 #ifndef MIN
-#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#define MIN(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); _a < _b ? _a : _b; })
 #endif
 #ifndef MAX
-#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#define MAX(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); _a > _b ? _a : _b; })
 #endif
 
 void __attribute__((noreturn)) __fatal_error(const char *expr, const char *msg, const char *file, int line, const char *func);
@@ -40,6 +43,8 @@ void __attribute__((noreturn)) error_shutdown(const char *line1, const char *lin
 
 void hal_delay(uint32_t ms);
 
+void delay_random(void);
+
 void clear_otg_hs_memory(void);
 
 extern uint32_t __stack_chk_guard;
diff --git a/embed/trezorhal/mpu.c b/embed/trezorhal/mpu.c
index 17fc68cc2..05e045335 100644
--- a/embed/trezorhal/mpu.c
+++ b/embed/trezorhal/mpu.c
@@ -27,10 +27,61 @@
 
 #define MPU_SUBREGION_DISABLE(X) ((X) << MPU_RASR_SRD_Pos)
 
-void mpu_config(void)
+void mpu_config_off(void)
 {
     // Disable MPU
     HAL_MPU_Disable();
+}
+
+void mpu_config_bootloader(void)
+{
+    // Disable MPU
+    HAL_MPU_Disable();
+
+    // Note: later entries overwrite previous ones
+
+    // Flash (0x08000000 - 0x081FFFFF, 2 MiB, read-write)
+    MPU->RBAR = FLASH_BASE | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER0;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_FLASH | LL_MPU_REGION_SIZE_2MB | LL_MPU_REGION_PRIV_RO_URO;
+
+    // Flash (0x0800C000 - 0x0800FFFF, 16 KiB, no access)
+    MPU->RBAR = FLASH_BASE | 0xC000 | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER1;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_FLASH | LL_MPU_REGION_SIZE_16KB | LL_MPU_REGION_NO_ACCESS;
+
+    // Flash (0x0810C000 - 0x0810FFFF, 16 KiB, no access)
+    MPU->RBAR = FLASH_BASE | 0x10C000 | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER2;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_FLASH | LL_MPU_REGION_SIZE_16KB | LL_MPU_REGION_NO_ACCESS;
+
+    // SRAM (0x20000000 - 0x2002FFFF, 192 KiB = 256 KiB except 2/8 at end, read-write, execute never)
+    MPU->RBAR = SRAM_BASE | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER3;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_SRAM | LL_MPU_REGION_SIZE_256KB | LL_MPU_REGION_FULL_ACCESS | MPU_RASR_XN_Msk | MPU_SUBREGION_DISABLE(0xC0);
+
+    // Peripherals (0x40000000 - 0x5FFFFFFF, read-write, execute never)
+    // External RAM (0x60000000 - 0x7FFFFFFF, read-write, execute never)
+    MPU->RBAR = PERIPH_BASE | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER4;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_PERIPH | LL_MPU_REGION_SIZE_1GB | LL_MPU_REGION_FULL_ACCESS | MPU_RASR_XN_Msk;
+
+#ifdef STM32F427xx
+    // CCMRAM (0x10000000 - 0x1000FFFF, read-write, execute never)
+    MPU->RBAR = CCMDATARAM_BASE | MPU_RBAR_VALID_Msk | MPU_REGION_NUMBER5;
+    MPU->RASR = MPU_RASR_ENABLE_Msk | MPU_RASR_ATTR_SRAM | LL_MPU_REGION_SIZE_64KB | LL_MPU_REGION_FULL_ACCESS | MPU_RASR_XN_Msk;
+#elif STM32F405xx
+    // no CCMRAM
+#else
+#error Unsupported MCU
+#endif
+
+    // Enable MPU
+    HAL_MPU_Enable(LL_MPU_CTRL_HARDFAULT_NMI);
+}
+
+
+void mpu_config_firmware(void)
+{
+    // Disable MPU
+    HAL_MPU_Disable();
+
+    // Note: later entries overwrite previous ones
 
 /*
     // Boardloader (0x08000000 - 0x0800FFFF, 64 KiB, read-only, execute never)
@@ -77,5 +128,5 @@ void mpu_config(void)
 #endif
 
     // Enable MPU
-    HAL_MPU_Enable(0);
+    HAL_MPU_Enable(LL_MPU_CTRL_HARDFAULT_NMI);
 }
diff --git a/embed/trezorhal/mpu.h b/embed/trezorhal/mpu.h
index 2a7ccf6fc..c7c136849 100644
--- a/embed/trezorhal/mpu.h
+++ b/embed/trezorhal/mpu.h
@@ -20,6 +20,8 @@
 #ifndef __MPU_H__
 #define __MPU_H__
 
-void mpu_config(void);
+void mpu_config_off(void);
+void mpu_config_bootloader(void);
+void mpu_config_firmware(void);
 
 #endif
diff --git a/embed/trezorhal/stm32.c b/embed/trezorhal/stm32.c
index 41de13aaf..5c74fd350 100644
--- a/embed/trezorhal/stm32.c
+++ b/embed/trezorhal/stm32.c
@@ -79,7 +79,8 @@ void SysTick_Handler(void)
     uwTick++;
 }
 
-void shutdown(void);
+// from util.s
+extern void shutdown(void);
 
 void PVD_IRQHandler(void)
 {
diff --git a/embed/trezorhal/usb.c b/embed/trezorhal/usb.c
index 57dff2b0f..03ac2cd5b 100644
--- a/embed/trezorhal/usb.c
+++ b/embed/trezorhal/usb.c
@@ -314,6 +314,7 @@ static uint8_t usb_class_deinit(USBD_HandleTypeDef *dev, uint8_t cfg_idx) {
 #define USB_WEBUSB_URL_SCHEME_HTTPS     1
 
 static uint8_t usb_class_setup(USBD_HandleTypeDef *dev, USBD_SetupReqTypedef *req) {
+    delay_random();
     if (((req->bmRequest & USB_REQ_TYPE_MASK) != USB_REQ_TYPE_CLASS) &&
         ((req->bmRequest & USB_REQ_TYPE_MASK) != USB_REQ_TYPE_STANDARD) &&
         ((req->bmRequest & USB_REQ_TYPE_MASK) != USB_REQ_TYPE_VENDOR)) {
@@ -330,7 +331,7 @@ static uint8_t usb_class_setup(USBD_HandleTypeDef *dev, USBD_SetupReqTypedef *re
                         USB_WEBUSB_URL_SCHEME_HTTPS,        // uint8_t bScheme
                         't', 'r', 'e', 'z', 'o', 'r', '.', 'i', 'o', '/', 's', 't', 'a', 'r', 't',  // char URL[]
                     };
-                    USBD_CtlSendData(dev, UNCONST(webusb_url), MIN(req->wLength, sizeof(webusb_url)));
+                    USBD_CtlSendData(dev, UNCONST(webusb_url), MIN_8bits(req->wLength, sizeof(webusb_url)));
                     return USBD_OK;
                 } else {
                     USBD_CtlError(dev, req);
@@ -354,7 +355,7 @@ static uint8_t usb_class_setup(USBD_HandleTypeDef *dev, USBD_SetupReqTypedef *re
                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // subCompatibleId
                         0x00, 0x00, 0x00, 0x00, 0x00, 0x00,             // reserved
                     };
-                    USBD_CtlSendData(dev, UNCONST(winusb_wcid), MIN(req->wLength, sizeof(winusb_wcid)));
+                    USBD_CtlSendData(dev, UNCONST(winusb_wcid), MIN_8bits(req->wLength, sizeof(winusb_wcid)));
                     return USBD_OK;
                 } else {
                     USBD_CtlError(dev, req);
@@ -380,7 +381,7 @@ static uint8_t usb_class_setup(USBD_HandleTypeDef *dev, USBD_SetupReqTypedef *re
                         0x50, 0x00, 0x00, 0x00, // dwPropertyDataLength
                         '{', 0x00, 'c', 0x00, '6', 0x00, 'c', 0x00, '3', 0x00, '7', 0x00, '4', 0x00, 'a', 0x00, '6', 0x00, '-', 0x00, '2', 0x00, '2', 0x00, '8', 0x00, '5', 0x00, '-', 0x00, '4', 0x00, 'c', 0x00, 'b', 0x00, '8', 0x00, '-', 0x00, 'a', 0x00, 'b', 0x00, '4', 0x00, '3', 0x00, '-', 0x00, '1', 0x00, '7', 0x00, '6', 0x00, '4', 0x00, '7', 0x00, 'c', 0x00, 'e', 0x00, 'a', 0x00, '5', 0x00, '0', 0x00, '3', 0x00, 'd', 0x00, '}', 0x00, 0x00, 0x00, 0x00, 0x00,  // propertyData
                     };
-                    USBD_CtlSendData(dev, UNCONST(winusb_guid), MIN(req->wLength, sizeof(winusb_guid)));
+                    USBD_CtlSendData(dev, UNCONST(winusb_guid), MIN_8bits(req->wLength, sizeof(winusb_guid)));
                     return USBD_OK;
                 } else {
                     USBD_CtlError(dev, req);
@@ -410,6 +411,7 @@ static uint8_t usb_class_setup(USBD_HandleTypeDef *dev, USBD_SetupReqTypedef *re
 }
 
 static uint8_t usb_class_data_in(USBD_HandleTypeDef *dev, uint8_t ep_num) {
+    delay_random();
     for (int i = 0; i < USBD_MAX_NUM_INTERFACES; i++) {
         switch (usb_ifaces[i].type) {
             case USB_IFACE_TYPE_HID:
@@ -429,6 +431,7 @@ static uint8_t usb_class_data_in(USBD_HandleTypeDef *dev, uint8_t ep_num) {
 }
 
 static uint8_t usb_class_data_out(USBD_HandleTypeDef *dev, uint8_t ep_num) {
+    delay_random();
     for (int i = 0; i < USBD_MAX_NUM_INTERFACES; i++) {
         switch (usb_ifaces[i].type) {
             case USB_IFACE_TYPE_HID:
@@ -448,6 +451,7 @@ static uint8_t usb_class_data_out(USBD_HandleTypeDef *dev, uint8_t ep_num) {
 }
 
 static uint8_t usb_class_sof(USBD_HandleTypeDef *dev) {
+    delay_random();
     for (int i = 0; i < USBD_MAX_NUM_INTERFACES; i++) {
         switch (usb_ifaces[i].type) {
             case USB_IFACE_TYPE_VCP:
diff --git a/embed/trezorhal/usb_hid-impl.h b/embed/trezorhal/usb_hid-impl.h
index 084342557..7b20c9bee 100644
--- a/embed/trezorhal/usb_hid-impl.h
+++ b/embed/trezorhal/usb_hid-impl.h
@@ -254,7 +254,6 @@ static void usb_hid_class_deinit(USBD_HandleTypeDef *dev, usb_hid_state_t *state
 }
 
 static int usb_hid_class_setup(USBD_HandleTypeDef *dev, usb_hid_state_t *state, USBD_SetupReqTypedef *req) {
-
     switch (req->bmRequest & USB_REQ_TYPE_MASK) {
 
         // Class request
@@ -302,11 +301,11 @@ static int usb_hid_class_setup(USBD_HandleTypeDef *dev, usb_hid_state_t *state,
                     switch (req->wValue >> 8) {
 
                         case USB_DESC_TYPE_HID:
-                            USBD_CtlSendData(dev, UNCONST(&state->desc_block->hid), MIN(req->wLength, sizeof(state->desc_block->hid)));
+                            USBD_CtlSendData(dev, UNCONST(&state->desc_block->hid), MIN_8bits(req->wLength, sizeof(state->desc_block->hid)));
                             return USBD_OK;
 
                         case USB_DESC_TYPE_REPORT:
-                            USBD_CtlSendData(dev, UNCONST(state->report_desc), MIN(req->wLength, state->report_desc_len));
+                            USBD_CtlSendData(dev, UNCONST(state->report_desc), MIN_8bits(req->wLength, state->report_desc_len));
                             return USBD_OK;
 
                         default:
diff --git a/embed/trezorhal/usb_vcp-impl.h b/embed/trezorhal/usb_vcp-impl.h
index 28aa63875..9f8d81e2a 100644
--- a/embed/trezorhal/usb_vcp-impl.h
+++ b/embed/trezorhal/usb_vcp-impl.h
@@ -364,13 +364,13 @@ static int usb_vcp_class_setup(USBD_HandleTypeDef *dev, usb_vcp_state_t *state,
 
     if ((req->bmRequest & USB_REQ_DIR_MASK) == USB_REQ_DIR_D2H) {
         if (req->bRequest == USB_CDC_GET_LINE_CODING) {
-            USBD_CtlSendData(dev, UNCONST(&line_coding), MIN(req->wLength, sizeof(line_coding)));
+            USBD_CtlSendData(dev, UNCONST(&line_coding), MIN_8bits(req->wLength, sizeof(line_coding)));
         } else {
-            USBD_CtlSendData(dev, state->cmd_buffer, MIN(req->wLength, USB_CDC_MAX_CMD_PACKET_LEN));
+            USBD_CtlSendData(dev, state->cmd_buffer, MIN_8bits(req->wLength, USB_CDC_MAX_CMD_PACKET_LEN));
         }
     } else { // USB_REQ_DIR_H2D
         if (req->wLength > 0) {
-            USBD_CtlPrepareRx(dev, state->cmd_buffer, MIN(req->wLength, USB_CDC_MAX_CMD_PACKET_LEN));
+            USBD_CtlPrepareRx(dev, state->cmd_buffer, MIN_8bits(req->wLength, USB_CDC_MAX_CMD_PACKET_LEN));
         }
     }
 
diff --git a/embed/trezorhal/usbd_def.h b/embed/trezorhal/usbd_def.h
index d3c3e5b99..e3da6243d 100644
--- a/embed/trezorhal/usbd_def.h
+++ b/embed/trezorhal/usbd_def.h
@@ -263,9 +263,12 @@ typedef struct _USBD_HandleTypeDef
 
 #define LOBYTE(x)  ((uint8_t)(x & 0x00FF))
 #define HIBYTE(x)  ((uint8_t)((x & 0xFF00) >>8))
+#ifndef MIN
 #define MIN(a, b)  (((a) < (b)) ? (a) : (b))
+#endif
+#ifndef MAX
 #define MAX(a, b)  (((a) > (b)) ? (a) : (b))
-
+#endif
 
 #if  defined ( __GNUC__ )
   #ifndef __weak
diff --git a/embed/unix/common.h b/embed/unix/common.h
index fd6c95949..e0bc6dde8 100644
--- a/embed/unix/common.h
+++ b/embed/unix/common.h
@@ -27,10 +27,10 @@
 #define STR(s) #s
 
 #ifndef MIN
-#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#define MIN(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); _a < _b ? _a : _b; })
 #endif
 #ifndef MAX
-#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#define MAX(a, b) ({ typeof(a) _a = (a); typeof(b) _b = (b); _a > _b ? _a : _b; })
 #endif
 
 void __attribute__((noreturn)) __fatal_error(const char *expr, const char *msg, const char *file, int line, const char *func);