bootloader-fw-link: Use RAM to communicate

Instead of writing to non-volatile storage between mcu resets, write to
a well-known RAM location.

RAM is random after power cycling, but does not get cleared on MCU
reset.

Author: NickeZ

bootloader.ld

@@ -116,6 +116,7 @@ SECTIONS
     {
         . = ALIGN(4);
         _srtt = .;
+        *(.auto_enter);
         *(.segger_rtt);
         *(.segger_rtt_buf);
         _ertt = .;

firmware.ld

@@ -115,6 +115,7 @@ SECTIONS
     {
         . = ALIGN(4);
         _srtt = .;
+        *(.auto_enter);
         *(.segger_rtt);
         *(.segger_rtt_buf);
         _ertt = .;

src/bootloader/bootloader.c

@@ -51,6 +51,9 @@
 
 #include <assert.h>
 
+// Section is fixed in ram, so can be used to communicate between fw/bl
+volatile secbool_u32 auto_enter __attribute__((section(".auto_enter")));
+
 #define BOOT_OP_LEN 2u // 1 byte op code and 1 byte parameter
 #define BOOTLOADER_CMD (HID_VENDOR_FIRST + 0x03) // Hardware wallet command
 
@@ -845,12 +848,7 @@ static size_t _api_versions(uint8_t* output)
 
 static void _api_reboot(void)
 {
-    chunk_shared_t shared_data;
-    memory_read_shared_bootdata(&shared_data);
-    if (shared_data.fields.auto_enter == sectrue_u8) {
-        shared_data.fields.auto_enter = secfalse_u8;
-        _write_chunk(FLASH_SHARED_DATA_START, shared_data.bytes);
-    }
+    auto_enter = secfalse_u32;
     _reset_mcu();
 }
 
@@ -1076,7 +1074,7 @@ void bootloader_jump(void)
 
     UG_FontSelect(&font_font_a_9X9);
 
-    if (shared_data.fields.auto_enter != sectrue_u8) {
+    if (auto_enter != sectrue_u32) {
 #ifdef BOOTLOADER_DEVDEVICE
         if (!_devdevice_enter(_firmware_verified_jump(&bootdata, secfalse_u32))) {
             _binary_exec();

src/common_main.c

@@ -56,14 +56,14 @@ void common_main(void)
     mpu_bitbox02_init();
     if (!memory_setup(&_memory_interface_functions)) {
         // If memory setup failed, this also might fail, but can't hurt to try.
-        AbortAutoenter("memory_setup failed");
+        Abort("memory_setup failed");
     }
 
     /* Enable/configure SmartEEPROM. */
     smarteeprom_bb02_config();
 
     if (!securechip_init()) {
-        AbortAutoenter("Failed to detect securechip");
+        Abort("Failed to detect securechip");
     }
     // securechip_setup must come after memory_setup, so the io/auth keys to be
     // used are already initialized.
@@ -75,6 +75,6 @@ void common_main(void)
             sizeof(errmsg),
             "Securechip setup failed.\nError code: %i\nPlease contact support.",
             securechip_result);
-        AbortAutoenter(errmsg);
+        Abort(errmsg);
     }
 }

src/factorysetup.c

@@ -27,6 +27,7 @@
 #include "rust/rust.h"
 #include "screen.h"
 #include "securechip/securechip.h"
+#include "system.h"
 #include "uart.h"
 #include "usb/usb.h"
 #include "usb/usb_packet.h"
@@ -581,19 +582,8 @@ int main(void)
     screen_splash();
     common_main();
 
-    {
-        // Set to re-enter bootloader again, otherwise we are stuck with this
-        // firmware forever.
-        auto_enter_t auto_enter = {
-            .value = sectrue_u8,
-        };
-        upside_down_t upside_down = {
-            .value = false,
-        };
-        if (!memory_bootloader_set_flags(auto_enter, upside_down)) {
-            // Not much we can do here.
-        }
-    }
+    // After reset we prefer to stay in bootloader
+    auto_enter = sectrue_u32;
 
     if (memory_get_platform() == MEMORY_PLATFORM_BITBOX02_PLUS) {
         _ble_result = _setup_ble();

src/hardfault.c

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include "hardfault.h"
+#include "system.h"
 #include "util.h"
 #include "utils_assert.h"
 #include <driver_init.h>
@@ -27,6 +28,7 @@
 #endif
 
 #ifndef TESTING
+#define ABORT_COUNTDOWN 30
 void HardFault_Handler(void)
 {
     Abort("Unexpected error.\nPlease contact support.");
@@ -46,29 +48,18 @@ void Abort(const char* msg)
 #else
     util_log("%s", msg);
     screen_print_debug(msg, 0);
-    usb_stop();
-#if defined(BOOTLOADER)
-    bootloader_close_interfaces();
-#else
-    system_close_interfaces();
-#endif
     // Break the program if we are debugging
     ASSERT(false);
-    while (1) {
+    char buf[30] = {0};
+    for (int i = 0; i < ABORT_COUNTDOWN; i++) {
+        snprintf(buf, sizeof(buf), "Enter bootloader in %02d", ABORT_COUNTDOWN - i);
+        UG_PutStringCentered(0, 56, 128, 8, buf, false);
+        UG_SendBuffer();
+        delay_ms(1000);
     }
+    // Restart into bootloader
+    auto_enter = sectrue_u32;
+    _reset_mcu();
+    while (1);
 #endif
 }
-
-void AbortAutoenter(const char* msg)
-{
-    auto_enter_t auto_enter = {
-        .value = sectrue_u8,
-    };
-    upside_down_t upside_down = {
-        .value = screen_is_upside_down(),
-    };
-    if (!memory_bootloader_set_flags(auto_enter, upside_down)) {
-        // If this failed, we might not be able to reboot into the bootloader.
-    }
-    Abort(msg);
-}

src/hardfault.h

@@ -26,11 +26,4 @@ void HardFault_Handler(void) __attribute__((weak));
 // debugging.
 __attribute__((noreturn)) void Abort(const char* msg);
 
-// Abort is for manual calls to stop execution, providing a message for debugging. It also sets
-// autoenter to true, making sure that the device boots into the bootloader after reconnecting it.
-// This should be called for any Abort during firmware startup, so a firmware update can be
-// applied. Otherwise, if there is an Abort() during startup, there would no way to reboot into the
-// bootloader and the device would be bricked.
-__attribute__((noreturn)) void AbortAutoenter(const char* msg);
-
 #endif

src/memory/bitbox02_smarteeprom.c

@@ -110,7 +110,7 @@ void bitbox02_smarteeprom_init(void)
          */
         char msg[200] = {0};
         snprintf(msg, sizeof(msg), "Unrecognized SmartEEPROM version.\nGot %d", current_version);
-        AbortAutoenter(msg);
+        Abort(msg);
     }
 }
 

src/system.c

@@ -18,11 +18,14 @@
 #include <memory/memory.h>
 #include <memory/memory_shared.h>
 #include <screen.h>
+#include <stdint.h>
 #ifndef TESTING
 #include "uart.h"
 #include <driver_init.h>
 #endif
 
+volatile secbool_u32 auto_enter __attribute__((section(".auto_enter")));
+
 static void _ble_clear_product(void)
 {
     struct ringbuffer uart_queue;
@@ -43,16 +46,7 @@ void reboot_to_bootloader(void)
     if (memory_get_platform() == MEMORY_PLATFORM_BITBOX02_PLUS) {
         _ble_clear_product();
     }
-    auto_enter_t auto_enter = {
-        .value = sectrue_u8,
-    };
-    upside_down_t upside_down = {
-        .value = screen_is_upside_down(),
-    };
-    if (!memory_bootloader_set_flags(auto_enter, upside_down)) {
-        // If this failed, we might not be able to reboot into the bootloader.
-        // We will try anyway, no point in aborting here.
-    }
+    auto_enter = sectrue_u32;
 #ifndef TESTING
     _reset_mcu();
 #endif

src/system.h

@@ -15,6 +15,12 @@
 #ifndef _SYSTEM_H_
 #define _SYSTEM_H_
 
+#include "util.h"
+
+// Set this to `sectrue_u32` to stay in bootloader, or anything else to jump to firmware
+
+extern volatile secbool_u32 auto_enter;
+
 /**
  * Reboots the device to bootloader
  */