Add helper to allow easier debugging of Throw

lib_standard_app/debug.c

@@ -0,0 +1,76 @@
+/*****************************************************************************
+ *   (c) 2020 Ledger SAS.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *****************************************************************************/
+
+#include <stdint.h>  // uint*_t
+#include <string.h>  // memset, explicit_bzero
+
+#include "os.h"
+#include "io.h"
+
+#ifdef HAVE_NBGL
+#include "nbgl_use_case.h"
+#endif
+
+#ifdef HAVE_DEBUG_THROWS
+static char errordata[20];
+
+WEAK void app_throw_info(unsigned int exception, unsigned int lr_val) {
+  snprintf(errordata,
+           sizeof(errordata),
+           "n%d, LR=0x%08X",
+           exception,
+           lr_val);
+}
+
+static void review_choice(bool confirm) {
+    UNUSED(confirm);
+    os_sched_exit(-1);
+}
+
+#ifdef HAVE_BAGL
+UX_STEP_CB(ux_error,
+           bnnn_paging,
+           review_choice(true),
+           {
+              .title = "App error",
+              .text = errordata,
+           });
+UX_FLOW(ux_error_flow, &ux_error);
+#endif
+
+WEAK void __attribute__((noreturn)) debug_display_throw_error(int exception) {
+    UNUSED(exception);
+
+#ifdef HAVE_BAGL
+    ux_flow_init(0, ux_error_flow, NULL);
+#endif
+
+#ifdef HAVE_NBGL
+    nbgl_useCaseChoice(&C_round_warning_64px,
+                       "App error",
+                       errordata,
+                       "Exit app",
+                       "Exit app",
+                       review_choice);
+#endif
+
+    // Block until the user approve and the app is quit
+    while (1) {
+        io_seproxyhal_io_heartbeat();
+    }
+}
+
+#endif

lib_standard_app/debug.h

@@ -0,0 +1,3 @@
+#pragma once
+
+WEAK void __attribute__((noreturn)) debug_display_throw_error(int exception);

lib_standard_app/main.c

@@ -19,6 +19,7 @@
 
 #include "os.h"
 #include "io.h"
+#include "debug.h"
 
 #ifdef HAVE_SWAP
 #include "swap.h"
@@ -62,6 +63,25 @@ static void standalone_app_main(void) {
         }
         CATCH_OTHER(e) {
             PRINTF("Exiting following exception: %d\n", e);
+
+#ifdef HAVE_DEBUG_THROWS
+            // Disable USB and BLE, the app have crashed and is going to be exited
+            // This is necessary to avoid device freeze while displaying throw error
+            // in a specific case:
+            // - the app receives an APDU
+            // - the app throws before replying
+            // - the app displays the error on screen
+            // - the user unplug the NanoX instead of confirming the screen
+            // - the NanoX goes on battery power and display the lock screen
+            // - the user plug the NanoX instead of entering its pin
+            // - the device is frozen, battery should be removed
+            USB_power(0);
+#ifdef HAVE_BLE
+            BLE_power(0, NULL);
+#endif
+            // Display crash info on screen for debug purpose
+            debug_display_throw_error(e);
+#endif
         }
         FINALLY {
         }

src/os.c

@@ -81,12 +81,29 @@ char os_secure_memcmp(const void *src1, const void* src2, size_t length) {
 }
 
 #ifndef HAVE_BOLOS
+#define MAIN_LINKER_SCRIPT_LOCATION 0xC0DE0000
+int main(void);
+
+// This function can be used to declare a callback to THROW in the application
+__attribute((weak)) void app_throw_info(unsigned int exception, unsigned int lr_val) {
+  UNUSED(exception);
+  UNUSED(lr_val);
+}
+
 void os_longjmp(unsigned int exception) {
-#ifdef HAVE_PRINTF
   unsigned int lr_val;
   __asm volatile("mov %0, lr" :"=r"(lr_val));
+
+  // Compute location before relocation (sort of anti PIC)
+  lr_val = lr_val - (unsigned int)main + MAIN_LINKER_SCRIPT_LOCATION;
+
+#ifdef HAVE_PRINTF
   PRINTF("exception[%d]: LR=0x%08X\n", exception, lr_val);
 #endif // HAVE_PRINTF
+
+  // Send to the app the info of exception and LR for debug purpose
+  app_throw_info(exception, lr_val);
+
   longjmp(try_context_get()->jmp_buf, exception);
 }
 #endif // HAVE_BOLOS