hello.ms

来自「这个是LINUX下的GDB调度工具的源码」· MS 代码 · 共 92 行

# output(): Hello, world.\n
# mach(): all

# Emit hello world while switching back and forth between arm/thumb.
# ??? Unfinished

	.macro invalid
# This is "undefined" but it's not properly decoded yet.
	.word 0x07ffffff
# This is stc which isn't recognized yet.
	stc 0,cr0,[r0]
	.endm

	.global _start
_start:
# Run some simple insns to confirm the engine is at least working.
	nop

# Skip over output text.

	bl skip_output

hello_text:
	.asciz "Hello, world.\n"

	.p2align 2
skip_output:

# Prime loop.

	mov r4, r14

output_next:

# Switch arm->thumb to output next chacter.
# At this point r4 must point to the next character to output.

	adr r0, into_thumb + 1
	bx r0

into_thumb:
	.thumb

# Output a character.

	mov r0,#3 @ writec angel call
	mov r1,r4
	swi 0xab @ ??? Confirm number.

# Switch thumb->arm.

	adr r5, back_to_arm
	bx r5

	.p2align 2
back_to_arm:
	.arm

# Load next character, see if done.

	add r4,r4,#1
	sub r3,r3,r3
	ldrb r5,[r4,r3]
	teq r5,#0
	beq done

# Output a character (in arm mode).

	mov r0,#3
	mov r1,r4
	swi #0x123456

# Load next character, see if done.

	add r4,r4,#1
	sub r3,r3,r3
	ldrb r5,[r4,r3]
	teq r5,#0
	bne output_next

done:
	mov r0,#0x18
	ldr r1,exit_code
	swi #0x123456

# If that fails, try to die with an invalid insn.

	invalid

exit_code:
	.word 0x20026