armcm_boot: Add get/set_bootup_code() helper functions

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/canboot_main.c

@@ -266,22 +266,20 @@ enter_bootloader(void)
 void
 canboot_main(void)
 {
-    uint32_t req_addr = *(uint32_t *)CONFIG_FLASH_START;
-    volatile uint64_t* boot_request_sig = (volatile uint64_t *)req_addr;
-
     // Enter the bootloader in the following conditions:
     // - The request signature is set in memory (request from app)
     // - No application code is present
-    if ((*boot_request_sig == REQUEST_SIG ) || !check_application_code()) {
+    uint64_t bootup_code = get_bootup_code();
-        *boot_request_sig = 0;
+    if (bootup_code == REQUEST_SIG || !check_application_code()) {
+        set_bootup_code(0);
         enter_bootloader();
     }
 
     // set request signature and delay for two seconds.  This enters the bootloader if
     // the reset button is double clicked
-    *boot_request_sig = REQUEST_SIG;
+    set_bootup_code(REQUEST_SIG);
     udelay(2000000);
-    *boot_request_sig = 0;
+    set_bootup_code(0);
     // No reset, read the key back out to clear it
 
     // jump to app

src/generic/armcm_boot.c

@@ -18,6 +18,20 @@ extern uint32_t _stack_end;
  * Basic interrupt handlers
  ****************************************************************/
 
+uint64_t
+get_bootup_code(void)
+{
+    uint64_t *req_code = (void*)&_stack_end;
+    return *req_code;
+}
+
+void
+set_bootup_code(uint64_t code)
+{
+    uint64_t *req_code = (void*)&_stack_end;
+    *req_code = code;
+}
+
 void __noreturn __visible
 reset_handler_stage_two(void)
 {

src/generic/misc.h

@@ -5,6 +5,8 @@
 #include <stdint.h> // uint8_t
 #include "autoconf.h" // CONFIG_MACH_STM32F0
 
+uint64_t get_bootup_code(void);
+void set_bootup_code(uint64_t code);
 void jump_to_application(void);
 
 // Timer Functions