Added arm32-hello-world

arm32-hello-world/.gitignore

@@ -0,0 +1,2 @@
+*.o
+hello-world

arm32-hello-world/Makefile

@@ -0,0 +1,15 @@
+AS=arm-linux-gnueabihf-as
+ASFLAGS=-g
+LD=arm-linux-gnueabihf-gcc
+LDFLAGS=-nostdlib
+
+hello-world: main.o
+	$(LD) $(LDFLAGS) -o $@ $<
+
+%.o: %.s
+	$(AS) $(ASFLAGS) -o $@ $<
+
+.PHONY: clean
+
+clean:
+	rm -f *.o hello-world

arm32-hello-world/main.s

@@ -0,0 +1,44 @@
+.data
+msg: .asciz "Hello World!\n"
+
+.text
+.global _start
+_start:
+    ldr r0,=msg
+    bl print
+    mov r0,#0x0
+    bl exit
+
+exit: @ NORETURN void exit(int code)
+    @ code already in r0
+    mov r7,#0x1
+    svc #0x0
+
+print: @ void print(const char *str)
+    stmdb sp!,{r0,lr}
+
+    @ msg already in r0
+    bl strlen
+
+    mov r2,r0 @ len
+    ldr r1,[sp] @ msg
+    mov r7,#0x4 @ SYS_write
+    mov r0,#1 @ FD_stdout
+    svc #0x0
+
+    ldmia sp!,{r0,lr}
+    bx lr
+
+strlen: @ u32 strlen(const char *str)
+    stmdb sp!,{r0,lr}
+strlen_loop:
+    ldrb r1,[r0]
+    cmp r1,#0
+    beq strlen_end
+
+    add r0,r0,#1
+    b strlen_loop
+strlen_end:
+    ldmia sp!,{r1,lr}
+    sub r0,r0,r1
+    bx lr