fix(core/prodtest): fix failing optiga communication

[no changelog]

core/embed/prodtest/main.c

@@ -35,6 +35,7 @@
 #include "sbu.h"
 #include "sdcard.h"
 #include "secbool.h"
+#include "supervise.h"
 #include "touch.h"
 #include "usb.h"
 
@@ -666,4 +667,28 @@ int main(void) {
   return 0;
 }
 
+void SVC_C_Handler(uint32_t *stack) {
+  uint8_t svc_number = ((uint8_t *)stack[6])[-2];
+  switch (svc_number) {
+    case SVC_GET_SYSTICK_VAL: {
+      systick_val_copy = SysTick->VAL;
+    } break;
+    default:
+      stack[0] = 0xffffffff;
+      break;
+  }
+}
+
+__attribute__((naked)) void SVC_Handler(void) {
+  __asm volatile(
+      " tst lr, #4    \n"  // Test Bit 3 to see which stack pointer we should
+      // use.
+      " ite eq        \n"  // Tell the assembler that the nest 2 instructions
+      // are if-then-else
+      " mrseq r0, msp \n"    // Make R0 point to main stack pointer
+      " mrsne r0, psp \n"    // Make R0 point to process stack pointer
+      " b SVC_C_Handler \n"  // Off to C land
+  );
+}
+
 void HardFault_Handler(void) { error_shutdown("INTERNAL ERROR!", "(HF)"); }