Framebuffer access control

core/embed/trezorhal/mpu.h

@@ -20,6 +20,8 @@
 #ifndef TREZORHAL_MPU_H
 #define TREZORHAL_MPU_H
 
+#include <stddef.h>
+
 #ifdef KERNEL_MODE
 
 // The MPU driver can be set to on of the following modes.
@@ -66,6 +68,16 @@ mpu_mode_t mpu_reconfig(mpu_mode_t mode);
 // Same as `mpu_reconfig()`, but with a more descriptive name.
 void mpu_restore(mpu_mode_t mode);
 
+// Sets the MPU to allow unprivileged access to the
+// framebuffer at the given address and size.
+//
+// The changes are made effective after the next MPU reconfiguration
+// to the `MPU_MODE_APP` mode.
+//
+// Addr and size must be aligned to the 32-byte boundary.
+// If addr == 0, the framebuffer is not accessible in the unprivileged mode.
+void mpu_set_unpriv_fb(void* addr, size_t size);
+
 #endif  // KERNEL_MODE
 
 #endif  // TREZORHAL_MPU_H

core/embed/trezorhal/stm32f4/mpu.c

@@ -204,6 +204,10 @@ mpu_mode_t mpu_get_mode(void) {
   return drv->mode;
 }
 
+void mpu_set_unpriv_fb(void* addr, size_t size) {
+  // Not implemented on STM32F4
+}
+
 // STM32F4xx memory map
 //
 // 0x08000000  2MB    FLASH

core/embed/trezorhal/stm32f4/xdisplay/st-7789/display_driver.c

@@ -21,12 +21,12 @@
 
 #include <xdisplay.h>
 
+#include "backlight_pwm.h"
 #include "display_fb.h"
 #include "display_internal.h"
 #include "display_io.h"
 #include "display_panel.h"
-
-#include "backlight_pwm.h"
+#include "mpu.h"
 
 #ifndef BOARDLOADER
 #include "bg_copy.h"
@@ -98,6 +98,8 @@ void display_deinit(display_content_mode_t mode) {
 #endif
 #endif
 
+  mpu_set_unpriv_fb(NULL, 0);
+
   backlight_pwm_deinit(mode == DISPLAY_RESET_CONTENT ? BACKLIGHT_RESET
                                                      : BACKLIGHT_RETAIN);
 

core/embed/trezorhal/stm32f4/xdisplay/st-7789/display_fb.c

@@ -177,6 +177,8 @@ bool display_get_frame_buffer(display_fb_info_t *fb) {
 
   fb->ptr = get_fb_ptr(drv->queue.wix);
   fb->stride = DISPLAY_RESX * sizeof(uint16_t);
+  // Enable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(fb->ptr, PHYSICAL_FRAME_BUFFER_SIZE);
 
   return true;
 }
@@ -215,6 +217,9 @@ void display_refresh(void) {
     return;
   }
 
+  // Disable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(NULL, 0);
+
 #ifndef BOARDLOADER
   if (is_mode_exception()) {
     // Disable scheduling of any new background copying

core/embed/trezorhal/stm32f4/xdisplay/stm32f429i-disc1/display_driver.c

@@ -27,6 +27,7 @@
 
 #include "display_internal.h"
 #include "ili9341_spi.h"
+#include "mpu.h"
 #include "xdisplay.h"
 
 #if (DISPLAY_RESX != 240) || (DISPLAY_RESY != 320)
@@ -73,6 +74,8 @@ void display_init(display_content_mode_t mode) {
 void display_deinit(display_content_mode_t mode) {
   display_driver_t *drv = &g_display_driver;
 
+  mpu_set_unpriv_fb(NULL, 0);
+
   drv->initialized = false;
 }
 
@@ -133,12 +136,17 @@ bool display_get_frame_buffer(display_fb_info_t *fb) {
   } else {
     fb->ptr = (void *)drv->framebuf;
     fb->stride = DISPLAY_RESX * sizeof(uint16_t);
+    // Enable access to the frame buffer from the unprivileged code
+    mpu_set_unpriv_fb(fb->ptr, FRAME_BUFFER_SIZE);
     return true;
   }
 }
 
 void display_refresh(void) {
   // Do nothing as using just a single frame buffer
+
+  // Disable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(NULL, 0);
 }
 
 void display_fill(const gfx_bitblt_t *bb) {

core/embed/trezorhal/stm32f4/xdisplay/ug-2828/display_driver.c

@@ -23,6 +23,7 @@
 #include TREZOR_BOARD
 #include STM32_HAL_H
 
+#include "mpu.h"
 #include "xdisplay.h"
 
 #if (DISPLAY_RESX != 128) || (DISPLAY_RESY != 128)
@@ -35,12 +36,16 @@
 // This type of displayed was used on some preliminary dev kits for T3T1 (Trezor
 // TS3)
 
+#define FRAME_BUFFER_SIZE (DISPLAY_RESX * DISPLAY_RESY)
+
+__attribute__((section(".fb1"))) uint8_t g_framebuf[FRAME_BUFFER_SIZE];
+
 // Display driver context.
 typedef struct {
   // Set if the driver is initialized
   bool initialized;
   // Frame buffer (8-bit Mono)
-  uint8_t framebuf[DISPLAY_RESX * DISPLAY_RESY];
+  uint8_t *framebuf;
   // Current display orientation (0 or 180)
   int orientation_angle;
   // Current backlight level ranging from 0 to 255
@@ -307,6 +312,7 @@ void display_init(display_content_mode_t mode) {
   }
 
   memset(drv, 0, sizeof(display_driver_t));
+  drv->framebuf = g_framebuf;
 
   if (mode == DISPLAY_RESET_CONTENT) {
     // Initialize GPIO & FSMC controller
@@ -321,6 +327,8 @@ void display_init(display_content_mode_t mode) {
 void display_deinit(display_content_mode_t mode) {
   display_driver_t *drv = &g_display_driver;
 
+  mpu_set_unpriv_fb(NULL, 0);
+
   drv->initialized = false;
 }
 
@@ -400,6 +408,8 @@ bool display_get_frame_buffer(display_fb_info_t *fb) {
   } else {
     fb->ptr = &drv->framebuf[0];
     fb->stride = DISPLAY_RESX;
+    // Enable access to the frame buffer from the unprivileged code
+    mpu_set_unpriv_fb(fb->ptr, FRAME_BUFFER_SIZE);
     return true;
   }
 }
@@ -411,6 +421,10 @@ void display_refresh(void) {
     return NULL;
   }
 
+  // Disable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(NULL, 0);
+
+  // Copy the frame buffer to the display
   display_sync_with_fb();
 }
 

core/embed/trezorhal/stm32f4/xdisplay/vg-2864/display_driver.c

@@ -25,6 +25,7 @@
 #include TREZOR_BOARD
 #include STM32_HAL_H
 
+#include "mpu.h"
 #include "xdisplay.h"
 
 #ifdef USE_CONSUMPTION_MASK
@@ -41,7 +42,9 @@
 //
 // This type of display is used with T3B1 model (Trezor TS3)
 
-__attribute__((section(".fb1"))) uint8_t framebuf[DISPLAY_RESX * DISPLAY_RESY];
+#define FRAME_BUFFER_SIZE (DISPLAY_RESX * DISPLAY_RESY)
+
+__attribute__((section(".fb1"))) uint8_t g_framebuf[FRAME_BUFFER_SIZE];
 
 // Display driver context.
 typedef struct {
@@ -236,7 +239,7 @@ void display_init(display_content_mode_t mode) {
 
   memset(drv, 0, sizeof(display_driver_t));
   drv->backlight_level = 255;
-  drv->framebuf = framebuf;
+  drv->framebuf = g_framebuf;
 
   if (mode == DISPLAY_RESET_CONTENT) {
     OLED_DC_CLK_ENA();
@@ -308,6 +311,8 @@ void display_init(display_content_mode_t mode) {
 void display_deinit(display_content_mode_t mode) {
   display_driver_t *drv = &g_display_driver;
 
+  mpu_set_unpriv_fb(NULL, 0);
+
   drv->initialized = false;
 }
 
@@ -369,6 +374,8 @@ bool display_get_frame_buffer(display_fb_info_t *fb) {
   } else {
     fb->ptr = &drv->framebuf[0];
     fb->stride = DISPLAY_RESX;
+    // Enable access to the frame buffer from the unprivileged code
+    mpu_set_unpriv_fb(fb->ptr, FRAME_BUFFER_SIZE);
     return true;
   }
 }
@@ -386,7 +393,10 @@ void display_refresh(void) {
   consumption_mask_randomize();
 #endif
 
-  // Sends the current frame buffer to the display
+  // Disable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(NULL, 0);
+
+  // Copy the frame buffer to the display
   display_sync_with_fb(drv);
 }
 

core/embed/trezorhal/stm32u5/mpu.c

@@ -192,6 +192,11 @@ typedef struct {
   bool initialized;
   // Current mode
   mpu_mode_t mode;
+  // Address of the framebuffer visible to unprivileged code
+  // (if set to 0, the framebuffer is not accessible)
+  uint32_t unpriv_fb_addr;
+  // Size of the framebuffer in bytes
+  size_t unpriv_fb_size;
 
 } mpu_driver_t;
 
@@ -287,6 +292,17 @@ mpu_mode_t mpu_get_mode(void) {
   return drv->mode;
 }
 
+void mpu_set_unpriv_fb(void* addr, size_t size) {
+  mpu_driver_t* drv = &g_mpu_driver;
+
+  if (!drv->initialized) {
+    return;
+  }
+
+  drv->unpriv_fb_addr = (uint32_t)addr;
+  drv->unpriv_fb_size = size;
+}
+
 mpu_mode_t mpu_reconfig(mpu_mode_t mode) {
   mpu_driver_t* drv = &g_mpu_driver;
 
@@ -307,6 +323,13 @@ mpu_mode_t mpu_reconfig(mpu_mode_t mode) {
     case MPU_MODE_SAES:
       SET_REGION( 5, PERIPH_BASE_NS,           PERIPH_SIZE,  PERIPHERAL,  YES,    YES ); // Peripherals - SAES, TAMP
       break;
+    case MPU_MODE_APP:
+      if (drv->unpriv_fb_addr != 0) {
+        SET_REGION( 5, drv->unpriv_fb_addr, drv->unpriv_fb_size,   SRAM,  YES,    YES ); // Frame buffer
+      } else {
+        DIS_REGION( 5 );
+      }
+      break;
     default:
       SET_REGION( 5, GRAPHICS_START,           GRAPHICS_SIZE,      SRAM,  YES,    YES ); // Frame buffer or display interface
       break;

core/embed/trezorhal/stm32u5/xdisplay/stm32u5a9j-dk/display_driver.c

@@ -24,6 +24,7 @@
 #include STM32_HAL_H
 
 #include "display_internal.h"
+#include "mpu.h"
 #include "xdisplay.h"
 
 #if (DISPLAY_RESX != 240) || (DISPLAY_RESY != 240)
@@ -110,6 +111,8 @@ void display_deinit(display_content_mode_t mode) {
     BSP_LCD_DeInit(0);
   }
 
+  mpu_set_unpriv_fb(NULL, 0);
+
   drv->initialized = false;
 }
 

core/embed/trezorhal/stm32u5/xdisplay/stm32u5a9j-dk/display_fb.c

@@ -25,6 +25,7 @@
 
 #include <xdisplay.h>
 #include "display_internal.h"
+#include "mpu.h"
 
 #ifdef KERNEL_MODE
 
@@ -67,6 +68,9 @@ bool display_get_frame_buffer(display_fb_info_t *fb) {
   fb->ptr = (void *)addr;
   fb->stride = fb_stride;
 
+  // Enable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(fb->ptr, VIRTUAL_FRAME_BUFFER_SIZE);
+
   return true;
 }
 
@@ -77,6 +81,9 @@ void display_refresh(void) {
     return;
   }
 
+  // Disable access to the frame buffer from the unprivileged code
+  mpu_set_unpriv_fb(NULL, 0);
+
   if (current_frame_buffer == 0) {
     current_frame_buffer = 1;
     BSP_LCD_SetFrameBuffer(0, GFXMMU_VIRTUAL_BUFFER1_BASE_S);

core/embed/trezorhal/stm32u5/xdisplay/stm32u5a9j-dk/display_internal.h

@@ -45,6 +45,10 @@ extern display_driver_t g_display_driver;
 // Pitch (in pixels) of the virtual frame buffer
 #define FRAME_BUFFER_PIXELS_PER_LINE 768
 
+// Size of the virtual frame buffer in bytes
+#define VIRTUAL_FRAME_BUFFER_SIZE \
+  (FRAME_BUFFER_PIXELS_PER_LINE * DISPLAY_RESY * 4)
+
 // Physical frame buffers in internal SRAM memory
 //
 // Both frame buffers layes in the fixed addresses that