feat(core): introduce kernel event loop

[no changelog]

core/embed/projects/kernel/main.c

@@ -28,6 +28,7 @@
 #include <sys/applet.h>
 #include <sys/bootutils.h>
 #include <sys/mpu.h>
+#include <sys/sysevent.h>
 #include <sys/system.h>
 #include <sys/systick.h>
 #include <util/bl_check.h>
@@ -169,6 +170,19 @@ void drivers_init() {
 #endif
 }
 
+// Kernel task main loop
+//
+// Returns when the coreapp task is terminated
+static void kernel_loop(applet_t *coreapp) {
+  do {
+    sysevents_t awaited = {0};
+    sysevents_t signalled = {0};
+
+    sysevents_poll(&awaited, &signalled, 100);
+
+  } while (applet_is_alive(coreapp));
+}
+
 // defined in linker script
 extern uint32_t _codelen;
 
@@ -218,6 +232,10 @@ static void show_rsod(const systask_postmortem_t *pminfo) {
   if (applet_reset(&coreapp, 1, pminfo, sizeof(systask_postmortem_t))) {
     // Run the applet & wait for it to finish
     applet_run(&coreapp);
+    // Loop until the coreapp is terminated
+    kernel_loop(&coreapp);
+    // Release the coreapp resources
+    applet_stop(&coreapp);
 
     if (coreapp.task.pminfo.reason == TASK_TERM_REASON_EXIT) {
       // RSOD was shown successfully
@@ -277,8 +295,12 @@ int main(void) {
     error_shutdown("Cannot start coreapp");
   }
 
-  // Run the applet & wait for it to finish
+  // Run the applet
   applet_run(&coreapp);
+  // Loop until the coreapp is terminated
+  kernel_loop(&coreapp);
+  // Release the coreapp resources
+  applet_stop(&coreapp);
 
   // Coreapp crashed, show RSOD
   show_rsod(&coreapp.task.pminfo);

core/embed/sys/task/inc/sys/applet.h

@@ -90,6 +90,12 @@ bool applet_reset(applet_t* applet, uint32_t cmd, const void* arg,
 // Runs the applet and waits until it finishes.
 void applet_run(applet_t* applet);
 
+// Release all resources help by the applet
+void applet_stop(applet_t* applet);
+
+// Returns `true` if the applet task is alive.
+bool applet_is_alive(applet_t* applet);
+
 // Returns the currently active applet.
 //
 // Returns `NULL` if no applet is currently active.

core/embed/sys/task/inc/sys/systask.h

@@ -114,7 +114,7 @@ typedef struct {
   // Exception return value
   uint32_t exc_return;
   // Set to nonzero, if the task is killed
-  uint32_t killed;
+  volatile uint32_t killed;
 
   // Task id
   systask_id_t id;
@@ -147,6 +147,9 @@ void systask_yield_to(systask_t* task);
 bool systask_init(systask_t* task, uint32_t stack_ptr, uint32_t stack_size,
                   void* context);
 
+// Returns true if the task is alive (not terminated, killed or crashed)
+bool systask_is_alive(const systask_t* task);
+
 // Pushes data onto the stack of the task
 //
 // The task must be not be running when the function is called

core/embed/sys/task/stm32/applet.c

@@ -104,12 +104,18 @@ void applet_run(applet_t* applet) {
 #endif
 
   systask_yield_to(&applet->task);
+}
 
+void applet_stop(applet_t* applet) {
 #ifdef USE_TRUSTZONE
   applet_set_unpriv(applet, false);
 #endif
 }
 
+bool applet_is_alive(applet_t* applet) {
+  return systask_is_alive(&applet->task);
+}
+
 applet_t* applet_active(void) {
   systask_t* task = systask_active();
 

core/embed/sys/task/stm32/systask.c

@@ -255,6 +255,8 @@ static void systask_kill(systask_t* task) {
   }
 }
 
+bool systask_is_alive(const systask_t* task) { return !task->killed; }
+
 void systask_exit(systask_t* task, int exit_code) {
   systask_scheduler_t* scheduler = &g_systask_scheduler;
 

core/embed/upymod/modtrezorio/modtrezorio-poll.h

@@ -21,6 +21,7 @@
 #include <trezor_types.h>
 
 #include <io/display.h>
+#include <sys/sysevent.h>
 #include <sys/systick.h>
 
 #ifdef USE_BLE
@@ -84,6 +85,15 @@ STATIC mp_obj_t mod_trezorio_poll(mp_obj_t ifaces, mp_obj_t list_ref,
   const mp_uint_t deadline = mp_hal_ticks_ms() + timeout;
   mp_obj_iter_buf_t iterbuf = {0};
 
+  {
+    // This is just a dummy call to `sysevent_poll` to ensure cooperative
+    // multitasking works. Event polling is still performed in the loop below
+    // but will be replaced in the future.
+    sysevents_t awaited = {0};
+    sysevents_t signalled = {0};
+    sysevent_poll(&awaited, &signalled, 0);
+  }
+
   for (;;) {
     mp_obj_t iter = mp_getiter(ifaces, &iterbuf);
     mp_obj_t item = 0;