利用 qemu user mode学习aarch64汇编

环境

x86-64 PC ubuntu 系统

工具准备

• aarch64-linux-gnu-gcc：可以通过下载 linaro 工具链  http://releases.linaro.org/components/toolchain/binaries/latest-7/aarch64-linux-gnu/
• qemu-aarch64 -  sudo apt install qemu-user

aarch64 汇编

创建文件head.S，其内容如下

 1 .global _start
 2 
 3 _start:
 4     ldr x0, loop
 5     adr x1, loop
 6     ldr x2, =loop
 7     adrl x3, loop
 8 
 9 loop:
10     nop
11     nop

然后编译并使用 qemu-aarch64 运行

1 aarch64-linux-gnu-gcc -nostdlib -nodefaultlibs -o head.elf head.S
2 
3 zhiwei@zhiwei-pc:~/work/qemu-aarch64/examples$ file head.elf
4 head.elf: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, BuildID[sha1]=33d5c1030ba8161948a56be12aa694853537acc7, not stripped

调试 运行：

qemu-aarch64 -g 1234 -cpu cortex-a53 head.elf

另外一个terminal 里面启动  aarch64-linux-gnu-gdb进行调试

 1 (gdb) target remote :1234
 2 0x00000000004000d8 in ?? ()
 3 (gdb) file head.elf
 4 
 5 (gdb) disass
 6 Dump of assembler code for function _start:
 7 => 0x00000000004000d8 <+0>:    ldr    x0, 0x4000e4 
 8    0x00000000004000dc <+4>:    adr    x1, 0x4000e4 
 9    0x00000000004000e0 <+8>:    ldr    x2, 0x4000e8 4>
10 End of assembler dump.
11 (gdb) si
12 0x00000000004000dc in _start ()
13 (gdb) info r
14 x0             0x4000e4d503201f    18015381335777311
15 x1             0x0                 0
16 x2             0x0                 0

附件：系统调用汇编示例：

 1 .section .text
 2 .global _start
 3 
 4 _start:
 5         /* syscall write(int fd, const void *buf, size_t count) */
 6         mov x0, #1
 7         ldr x1, =msg
 8         ldr x2, =len
 9         mov w8, #64
10         svc #0
11 
12         /* syscall exit(int status) */
13         mov x0, #0
14         mov w8, #93
15         svc #0
16 
17 msg:
18         .ascii "Hello, ARM64!"
19         len = . - msg