Add ARM basic bootloader build

arm/bootloader.ld

@@ -0,0 +1,32 @@
+MEMORY
+{
+    ICTM (rwx) : ORIGIN = 0x00000000, LENGTH = 16384
+}
+
+SECTIONS
+{
+    .text :
+    {
+        KEEP(vector_table.o(.vector_table))
+
+        *(.text*)
+        *(.rodata*)
+    } > ICTM
+
+    .bss (NOLOAD) :
+    {
+        _bss_begin = .;
+        *(.bss*)
+        *(COMMON)
+        _bss_end = .;
+    } > ICTM
+
+    .data :
+    {
+        *(.data*)
+
+        __exidx_start = .;
+        *(.exidx*)
+        __exidx_end = .;
+    } > ICTM
+}

arm/main.cc

@@ -0,0 +1,13 @@
+#include <cstdint>
+
+struct Gpio {
+    volatile uint32_t data;
+};
+
+#define gpio0 ((Gpio*) 0x40000000)
+
+int main() {
+    gpio0->data = 42;
+
+    while (true) {}
+}

arm/makefile

@@ -0,0 +1,25 @@
+CC = arm-none-eabi-gcc
+LD = arm-none-eabi-gcc
+CXX = arm-none-eabi-g++
+OBJCOPY = arm-none-eabi-objcopy
+
+linker_script = bootloader.ld
+
+CFLAGS = -march=armv6-m -g -ffunction-sections -fdata-sections -O2
+CXXFLAGS = $(CFLAGS) -std=c++20 -fno-exceptions
+LDFLAGS = -march=armv6-m -g --specs=nano.specs --specs=nosys.specs -Wl,--gc-sections -Wl,-T$(linker_script) -O2
+
+all: bootloader.bin
+
+%.bin: %.elf
+	$(OBJCOPY) -O binary $< $@
+
+bootloader.elf: main.o vector_table.o
+
+%.elf:
+	$(LD) $(LDFLAGS) -o $@ $^
+
+.PHONY: clean
+
+clean:
+	rm -rf *.elf *.bin *.o

arm/vector_table.cc

@@ -0,0 +1,30 @@
+#include <cstdint>
+
+extern "C" uint32_t _bss_begin, _bss_end;
+extern "C" int main();
+
+namespace {
+
+enum VectorTableEntry {
+    StackPointer = 0,
+    Reset = 1,
+};
+
+void ResetHandler() {
+    // clear .bss
+    for (uint32_t* ptr = &_bss_begin; ptr < &_bss_end; ptr++) {
+        *ptr = 0;
+    }
+
+    main();
+
+    while(true) {}
+}
+
+}  // namespace
+
+__attribute__((section(".vector_table")))
+uint32_t vector_table[16] = {
+    [StackPointer] = 0x00010000,
+    [Reset] = reinterpret_cast<uint32_t>(ResetHandler),
+};