Furi: smaller crash routine (#1912)

* Furi: smaller crash routine
* Furi: small fixes
* Furi: cleanup check routines, more assembly code, force inline of __furi_halt_mcu
* SubGhz: cleanup residual line mess
* Documentation
* Dap-link: fix help
* Furi: replace __furi_halt_mcu with HALT_MCU macros
* Furi: disable IRQ earlier in crash handler
* Furi: properly handle masked mode when detecting ISR
* Ble: allow 0 length feed in rpc_session_feed
* Format sources
* Furi: better crash logic explanation.
* Furi: some grammar in check.h

Co-authored-by: SG <who.just.the.doctor@gmail.com>

furi/core/check.h

@@ -1,3 +1,16 @@
+/**
+ * @file check.h
+ * 
+ * Furi crash and assert functions.
+ * 
+ * The main problem with crashing is that you can't do anything without disturbing registers,
+ * and if you disturb registers, you won't be able to see the correct register values in the debugger.
+ * 
+ * Current solution works around it by passing the message through r12 and doing some magic with registers in crash function.
+ * r0-r10 are stored in the ram2 on crash routine start and restored at the end.
+ * The only register that is going to be lost is r11.
+ * 
+ */
 #pragma once
 
 #ifdef __cplusplus
@@ -8,9 +21,6 @@ extern "C" {
 #define FURI_NORETURN noreturn
 #endif
 
-/** Pointer to pass message to __furi_crash and __furi_halt */
-extern const char* __furi_check_message;
-
 /** Crash system */
 FURI_NORETURN void __furi_crash();
 
@@ -18,39 +28,41 @@ FURI_NORETURN void __furi_crash();
 FURI_NORETURN void __furi_halt();
 
 /** Crash system with message. Show message after reboot. */
-#define furi_crash(message)             \
-    do {                                \
-        __furi_check_message = message; \
-        __furi_crash();                 \
+#define furi_crash(message)                                   \
+    do {                                                      \
+        register const void* r12 asm("r12") = (void*)message; \
+        asm volatile("sukima%=:" : : "r"(r12));               \
+        __furi_crash();                                       \
     } while(0)
 
 /** Halt system with message. */
-#define furi_halt(message)              \
-    do {                                \
-        __furi_check_message = message; \
-        __furi_halt();                  \
+#define furi_halt(message)                                    \
+    do {                                                      \
+        register const void* r12 asm("r12") = (void*)message; \
+        asm volatile("sukima%=:" : : "r"(r12));               \
+        __furi_halt();                                        \
     } while(0)
 
 /** Check condition and crash if check failed */
-#define furi_check(__e)                             \
-    do {                                            \
-        if ((__e) == 0) {                           \
-            furi_crash("furi_check failed\r\n");    \
-        }                                           \
+#define furi_check(__e)                          \
+    do {                                         \
+        if((__e) == 0) {                         \
+            furi_crash("furi_check failed\r\n"); \
+        }                                        \
     } while(0)
 
 /** Only in debug build: Assert condition and crash if assert failed  */
 #ifdef FURI_DEBUG
-#define furi_assert(__e)                            \
-    do {                                            \
-        if ((__e) == 0) {                           \
-            furi_crash("furi_assert failed\r\n");   \
-        }                                           \
+#define furi_assert(__e)                          \
+    do {                                          \
+        if((__e) == 0) {                          \
+            furi_crash("furi_assert failed\r\n"); \
+        }                                         \
     } while(0)
 #else
-#define furi_assert(__e)    \
-    do {                    \
-        ((void)(__e));      \
+#define furi_assert(__e) \
+    do {                 \
+        ((void)(__e));   \
     } while(0)
 #endif