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>

applications/plugins/dap_link/gui/scenes/dap_scene_help.c

@@ -72,13 +72,13 @@ void dap_scene_help_on_enter(void* context) {
         if(config->uart_swap == DapUartTXRXNormal) {
             furi_string_cat(
                 string,
-                "    TX: 15 [С1]\r\n"
+                "    TX: 15 [C1]\r\n"
-                "    RX: 16 [С0]\r\n");
+                "    RX: 16 [C0]\r\n");
         } else {
             furi_string_cat(
                 string,
-                "    RX: 15 [С1]\r\n"
+                "    RX: 15 [C1]\r\n"
-                "    TX: 16 [С0]\r\n");
+                "    TX: 16 [C0]\r\n");
         }
         break;
     default:

applications/services/rpc/rpc.c

@@ -148,7 +148,8 @@ size_t
     rpc_session_feed(RpcSession* session, uint8_t* encoded_bytes, size_t size, TickType_t timeout) {
     furi_assert(session);
     furi_assert(encoded_bytes);
-    furi_assert(size > 0);
+
+    if(!size) return 0;
 
     size_t bytes_sent = furi_stream_buffer_send(session->stream, encoded_bytes, size, timeout);
 

firmware/targets/f7/api_symbols.csv

@@ -1,5 +1,5 @@
 entry,status,name,type,params
-Version,+,4.0,,
+Version,+,5.0,,
 Header,+,applications/services/bt/bt_service/bt.h,,
 Header,+,applications/services/cli/cli.h,,
 Header,+,applications/services/cli/cli_vcp.h,,
@@ -2843,7 +2843,6 @@ Variable,+,I_update_10px,const Icon,
 Variable,-,MSIRangeTable,const uint32_t[16],
 Variable,-,SmpsPrescalerTable,const uint32_t[4][6],
 Variable,+,SystemCoreClock,uint32_t,
-Variable,+,__furi_check_message,const char*,
 Variable,+,_ctype_,const char[],
 Variable,+,_global_impure_ptr,_reent*,
 Variable,+,_impure_ptr,_reent*,

furi/core/check.c

@@ -14,6 +14,28 @@
 PLACE_IN_SECTION("MB_MEM2") const char* __furi_check_message = NULL;
 PLACE_IN_SECTION("MB_MEM2") uint32_t __furi_check_registers[12] = {0};
 
+/** Load r12 value to __furi_check_message and store registers to __furi_check_registers */
+#define GET_MESSAGE_AND_STORE_REGISTERS()               \
+    asm volatile("ldr r11, =__furi_check_message    \n" \
+                 "str r12, [r11]                    \n" \
+                 "ldr r12, =__furi_check_registers  \n" \
+                 "stm r12, {r0-r11}                 \n" \
+                 :                                      \
+                 :                                      \
+                 : "memory");
+
+// Restore registers and halt MCU
+#define RESTORE_REGISTERS_AND_HALT_MCU()                \
+    asm volatile("ldr r12, =__furi_check_registers  \n" \
+                 "ldm r12, {r0-r11}                 \n" \
+                 "loop%=:                           \n" \
+                 "bkpt 0x00                         \n" \
+                 "wfi                               \n" \
+                 "b loop%=                          \n" \
+                 :                                      \
+                 :                                      \
+                 : "memory");
+
 extern size_t xPortGetTotalHeapSize(void);
 extern size_t xPortGetFreeHeapSize(void);
 extern size_t xPortGetMinimumEverFreeHeapSize(void);
@@ -55,32 +77,11 @@ static void __furi_print_name(bool isr) {
     }
 }
 
-static FURI_NORETURN void __furi_halt_mcu() {
-    register const void* r12 asm ("r12") = (void*)__furi_check_registers;
-    asm volatile(
-        "ldm r12, {r0-r11} \n"
-#ifdef FURI_DEBUG
-        "bkpt 0x00  \n"
-#endif
-        "loop%=:    \n"
-        "wfi        \n"
-        "b loop%=   \n"
-        :
-        : "r" (r12)
-        : "memory");
-    __builtin_unreachable();
-}
-
 FURI_NORETURN void __furi_crash() {
-    register const void* r12 asm ("r12") = (void*)__furi_check_registers;
-    asm volatile(
-        "stm r12, {r0-r11} \n"
-        :
-        : "r" (r12)
-        : "memory");
-
-    bool isr = FURI_IS_ISR();
     __disable_irq();
+    GET_MESSAGE_AND_STORE_REGISTERS();
+
+    bool isr = FURI_IS_IRQ_MODE();
 
     if(__furi_check_message == NULL) {
         __furi_check_message = "Fatal Error";
@@ -98,7 +99,7 @@ FURI_NORETURN void __furi_crash() {
 #ifdef FURI_DEBUG
     furi_hal_console_puts("\r\nSystem halted. Connect debugger for more info\r\n");
     furi_hal_console_puts("\033[0m\r\n");
-    __furi_halt_mcu();
+    RESTORE_REGISTERS_AND_HALT_MCU();
 #else
     furi_hal_rtc_set_fault_data((uint32_t)__furi_check_message);
     furi_hal_console_puts("\r\nRebooting system.\r\n");
@@ -109,15 +110,10 @@ FURI_NORETURN void __furi_crash() {
 }
 
 FURI_NORETURN void __furi_halt() {
-    register const void* r12 asm ("r12") = (void*)__furi_check_registers;
-    asm volatile(
-        "stm r12, {r0-r11} \n"
-        :
-        : "r" (r12)
-        : "memory");
-
-    bool isr = FURI_IS_ISR();
     __disable_irq();
+    GET_MESSAGE_AND_STORE_REGISTERS();
+
+    bool isr = FURI_IS_IRQ_MODE();
 
     if(__furi_check_message == NULL) {
         __furi_check_message = "System halt requested.";
@@ -128,5 +124,6 @@ FURI_NORETURN void __furi_halt() {
     furi_hal_console_puts(__furi_check_message);
     furi_hal_console_puts("\r\nSystem halted. Bye-bye!\r\n");
     furi_hal_console_puts("\033[0m\r\n");
-    __furi_halt_mcu();
+    RESTORE_REGISTERS_AND_HALT_MCU();
+    __builtin_unreachable();
 }

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();
 
@@ -20,21 +30,23 @@ FURI_NORETURN void __furi_halt();
 /** Crash system with message. Show message after reboot. */
 #define furi_crash(message)                                   \
     do {                                                      \
-        __furi_check_message = message; \
+        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; \
+        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) {                           \
+        if((__e) == 0) {                         \
             furi_crash("furi_check failed\r\n"); \
         }                                        \
     } while(0)
@@ -43,7 +55,7 @@ FURI_NORETURN void __furi_halt();
 #ifdef FURI_DEBUG
 #define furi_assert(__e)                          \
     do {                                          \
-        if ((__e) == 0) {                           \
+        if((__e) == 0) {                          \
             furi_crash("furi_assert failed\r\n"); \
         }                                         \
     } while(0)