stub "kernel"/makefile that boots in qemu

.gitignore

@@ -0,0 +1,4 @@
+*.o
+kernel7.elf
+kernel7.img
+

Makefile

@@ -0,0 +1,25 @@
+PREFIX ?= arm-none-eabi-
+AS = $(PREFIX)as
+CC = $(PREFIX)gcc
+LD = $(PREFIX)ld
+OBJCOPY = $(PREFIX)objcopy
+
+CFLAGS = -Wall -Werror -ffreestanding -march=armv7-a
+LDFLAGS = -nostdlib
+
+KERNELBASE=0x8000
+
+kernel7.img: kernel7.elf
+	$(OBJCOPY) $< -O binary $@
+
+kernel7.elf: entry.o main.o
+	$(LD) $(LDFLAGS) -o $@ -Ttext=$(KERNELBASE) $^
+
+clean::
+	$(RM) kernel7.elf kernel7.img *.o
+
+debug:	kernel7.img kernel7.elf
+	qemu-system-arm -M raspi2 -nographic -bios $< -gdb tcp:127.0.0.1:1234 -S & \
+	QEMUPID=$$! \
+	$(PREFIX)gdb --symbols=kernel7.elf -ex 'target remote :1234' \
+	kill $$QEMUPID

entry.S

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+        .section .text
+        .global _start
+
+_start:
+        ldr     sp, =stack_top
+        b       main
+
+        .section .bss
+        .align 3 // 8-byte alignment
+stack_end:
+        .skip 0x4000
+stack_top:

main.c

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+void __attribute__((noreturn))
+main(void)
+{
+    while (1) {}
+}