Postmortem Debugging to serial port (#20492)

Marlin/src/HAL/shared/cpu_exception/exception_hook.h

@@ -0,0 +1,54 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (c) 2021 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (c) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ */
+#pragma once
+
+/* Here is the expected behavior of a system producing a CPU exception with this hook installed:
+   1. Before the system is crashed
+     1.1 Upon validation (not done yet in this code, but we could be using DEBUG flags here to allow/disallow hooking)
+     1.2 Install the hook by overwriting the vector table exception handler with the hooked function
+   2. Upon system crash (for example, by a dereference of a NULL pointer or anything else)
+     2.1 The CPU triggers its exception and jump into the vector table for the exception type
+     2.2 Instead of finding the default handler, it finds the updated pointer to our hook
+     2.3 The CPU jumps into our hook function (likely a naked function to keep all information about crash point intact)
+     2.4 The hook (naked) function saves the important registers (stack pointer, program counter, current mode) and jumps to a common exception handler (in C)
+     2.5 The common exception handler dumps the registers on the serial link and perform a backtrace around the crashing point
+     2.6 Once the backtrace is performed the last resort function is called (platform specific).
+         On some platform with a LCD screen, this might display the crash information as a QR code or as text for the
+         user to capture by taking a picture
+     2.7 The CPU is reset and/or halted by triggering a debug breakpoint if a debugger is attached */
+
+// Hook into CPU exception interrupt table to call the backtracing code upon an exception
+// Most platform will simply do nothing here, but those who can will install/overwrite the default exception handler
+// with a more performant exception handler
+void hook_cpu_exceptions();
+
+// Some platform might deal without a hard fault handler, in that case, return 0 in your platform here or skip implementing it
+void * __attribute__((weak)) hook_get_hardfault_vector_address(unsigned base_address);
+// Some platform might deal without a memory management fault handler, in that case, return 0 in your platform here or skip implementing it
+void * __attribute__((weak)) hook_get_memfault_vector_address(unsigned base_address);
+// Some platform might deal without a bus fault handler, in that case, return 0 in your platform here or skip implementing it
+void * __attribute__((weak)) hook_get_busfault_vector_address(unsigned base_address);
+// Some platform might deal without a usage fault handler, in that case, return 0 in your platform here or skip implementing it
+void * __attribute__((weak)) hook_get_usagefault_vector_address(unsigned base_address);
+
+// Last resort function that can be called after the exception handler was called.
+void __attribute__((weak)) hook_last_resort_func();