startup: setup the stack protector for the stage before main function (#46)

embed/boardloader/main.c

@@ -122,7 +122,6 @@ static const uint8_t * const BOARDLOADER_KEYS[] = {
 
 int main(void)
 {
-    __stack_chk_guard = rng_get();
 
 #if PRODUCTION
     flash_set_option_bytes();

embed/boardloader/startup.s

@@ -47,6 +47,11 @@ reset_handler:
   ldr r2, =data_size    // size in bytes
   bl memcpy
 
+  // setup the stack protector (see build script "-fstack-protector-all") with an unpredictable value
+  bl rng_get
+  ldr r1, = __stack_chk_guard
+  str r0, [r1]
+
   // enter the application code
   bl main
 

embed/bootloader/main.c

@@ -183,7 +183,6 @@ void check_bootloader_version(void)
 
 int main(void)
 {
-    __stack_chk_guard = rng_get();
 
 #if PRODUCTION
     check_bootloader_version();

embed/bootloader/startup.s

@@ -22,6 +22,11 @@ reset_handler:
   ldr r2, =data_size    // size in bytes
   bl memcpy
 
+  // setup the stack protector (see build script "-fstack-protector-all") with an unpredictable value
+  bl rng_get
+  ldr r1, = __stack_chk_guard
+  str r0, [r1]
+
   // re-enable exceptions
   // according to "ARM Cortex-M Programming Guide to Memory Barrier Instructions" Application Note 321, section 4.7:
   // "If it is not necessary to ensure that a pended interrupt is recognized immediately before

embed/firmware/main.c

@@ -23,7 +23,6 @@
 
 int main(void)
 {
-    __stack_chk_guard = rng_get();
 
     periph_init();
 

embed/firmware/startup.s

@@ -22,6 +22,11 @@ reset_handler:
   ldr r2, =data_size    // size in bytes
   bl memcpy
 
+  // setup the stack protector (see build script "-fstack-protector-all") with an unpredictable value
+  bl rng_get
+  ldr r1, = __stack_chk_guard
+  str r0, [r1]
+
   // re-enable exceptions
   // according to "ARM Cortex-M Programming Guide to Memory Barrier Instructions" Application Note 321, section 4.7:
   // "If it is not necessary to ensure that a pended interrupt is recognized immediately before