Overridable ISRs

Makefile

@@ -9,7 +9,7 @@ CFLAGS += -std=c99 -g -Wall # -Os
 CC=clang
 CFLAGS += -target thumbv7em-unknown-eabi -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -ffreestanding
 
-objs := boot/crt0.o arch/stm32f429/registers/rcc.o arch/stm32f429/registers/gpio.o external/freertos/tasks.o external/freertos/list.o external/freertos/queue.o external/freertos/portable/GCC/ARM_CM4F/port.o external/freertos/portable/MemMang/heap_1.o external/newlib/libc/string/memset.o external/newlib/libc/string/memcpy.o
+objs := boot/crt0.o arch/stm32f429/isr.o arch/stm32f429/registers/rcc.o arch/stm32f429/registers/gpio.o external/freertos/tasks.o external/freertos/list.o external/freertos/queue.o external/freertos/portable/GCC/ARM_CM4F/port.o external/freertos/portable/MemMang/heap_1.o external/newlib/libc/string/memset.o external/newlib/libc/string/memcpy.o
 
 default: clean boot.elf
 

boot/crt0.c

@@ -1,57 +1,15 @@
 #include <stdint.h>
 #include <string.h>
-// FIXME: Use a libc, and memset, bzerto!
 
 extern const void * _data_section_start_flash;
 extern const void * _data_section_start_ram;
 extern const void * _data_section_end_ram;
 extern const void * _bss_section_start_ram;
 extern const void * _bss_section_end_ram;
-extern const void * _stack_start;
-extern const void * _stack_end;
-
-void _ResetServiceRoutine(void);
-void _NMIServiceRoutine(void);
-void _HardFaultServiceRoutine(void);
-void _MemManageServiceRoutine(void);
-void _BusFaultServiceRoutine(void);
-void _SVCallServiceRoutine(void);
-void _PendSVServiceRoutine(void);
-void _SystickServiceRoutine(void);
-
-/* Interrupt Service Routines are void->void functions */
-typedef void(*ISR)(void);
-
-/* Notice: The Cortex-M4 expects all jumps to be made at an odd address when
- * jumping to Thumb code. For example, if you want to execute Thumb code at
- * address 0x100, you'll have to jump to 0x101. Luckily, this idiosyncrasy is
- * properly handled by the C compiler that will generate proper addresses when
- * using function pointers. */
-
-#define INITIALISATION_VECTOR_SIZE 0x6B
-
-ISR InitialisationVector[INITIALISATION_VECTOR_SIZE]
-  __attribute__((section(".isr_vector_table")))
-  = {
-  (ISR)&_stack_start,
-  _ResetServiceRoutine,
-  _NMIServiceRoutine,
-  _HardFaultServiceRoutine,
-  _MemManageServiceRoutine,
-  _BusFaultServiceRoutine,
-  0, // UsageFault
-  0, // Reserved
-  _SVCallServiceRoutine,
-  0, // Debug Monitor
-  _PendSVServiceRoutine, // PendSV
-  _SystickServiceRoutine, // Systick
-  0
-};
-
 
 int main(int argc, char * argv[]);
 
-void _ResetServiceRoutine(void) {
+void _start(void) {
   // This is where execution starts after reset.
   // Many things are not initialized yet so the code here has to pay attention.
 
@@ -71,22 +29,7 @@ void _ResetServiceRoutine(void) {
   main(0, 0x0);
 }
 
-void _NMIServiceRoutine(void) {
-  while (1) {
-  }
-}
-
-void _HardFaultServiceRoutine(void) {
-  while (1) {
-  }
-}
-
-void _MemManageServiceRoutine(void) {
-  while (1) {
-  }
-}
-
-void _BusFaultServiceRoutine(void) {
+void _halt(void) {
   while (1) {
   }
 }

boot/stm32f429.ld

@@ -18,6 +18,7 @@ MEMORY {
 }
 
 SECTIONS {
+
   .isr_vector_table ORIGIN(FLASH) : {
     /* When booting, the STM32F42xx fetches the content of address 0x0, and
      * extracts from it various key infos: the initial value of the PC register
@@ -32,7 +33,24 @@ SECTIONS {
      * We're generating the ISR vector table in C, because it's very convenient:
      * using function pointers, we can easily point to the service routing for
      * each interrupt.
-     * See ST/RM0090/p70 for more infos. */
+     * See ST/RM0090/p70 for more infos.
+     *
+     * Last but not least, the ISR vector table contains pointer to functions
+     * that we may want to override depending on the binary we want to produce.
+     * The C implementation uses _NameServiceRoutine symbols. If those symbols
+     * are defined elsewhere, we'll use that version. If they aren't defined, we
+     * will provide here a default implementation (namely, calling crt0's _start
+     * on reset, and an infinite loop on HardFault). */
+
+    _ResetServiceRoutine = DEFINED(_ResetServiceRoutine) ? _ResetServiceRoutine : _start;
+    _NMIServiceRoutine = DEFINED(_NMIServiceRoutine) ? _NMIServiceRoutine : 0;
+    _HardFaultServiceRoutine = DEFINED(_HardFaultServiceRoutine) ? _HardFaultServiceRoutine : _halt;
+    _MemManageServiceRoutine = DEFINED(_MemManageServiceRoutine) ? _MemManageServiceRoutine : 0;
+    _BusFaultServiceRoutine = DEFINED(_BusFaultServiceRoutine) ? _BusFaultServiceRoutine : 0;
+    _SVCallServiceRoutine = DEFINED(_SVCallServiceRoutine) ? _SVCallServiceRoutine : 0;
+    _PendSVServiceRoutine = DEFINED(_PendSVServiceRoutine) ? _PendSVServiceRoutine : 0;
+    _SysTickServiceRoutine = DEFINED(_SysTickServiceRoutine) ? _SysTickServiceRoutine : 0;
+
     *(.isr_vector_table)
   } >FLASH
 

external/FreeRTOSConfig.h

@@ -166,7 +166,7 @@ header file. */
 standard names. */
 #define vPortSVCHandler _SVCallServiceRoutine
 #define xPortPendSVHandler _PendSVServiceRoutine
-#define xPortSysTickHandler _SystickServiceRoutine
+#define xPortSysTickHandler _SysTickServiceRoutine
 
 #endif /* FREERTOS_CONFIG_H */