ARM汇编指令裸板操作LEDrisc-v操作系统risc-v中文社区

joe 发表于 2022-10-10 11:28:00

ARM汇编指令裸板操作LED

//https://blog.csdn.net/szm1234/article/details/109764869
.global _start @全局标号

_start:
/* 使能所有外设时钟 */
ldr r0, = 0x020c4068 @CCGR0
ldr r1, = 0xffffffff @要向CCGR0写入的数据
str r1,       @将0xffffffff写入到CCGR0

ldr r0, = 0x020c406c @CCGR1
str r1,       @将0xffffffff写入到CCGR1

ldr r0, = 0x020c4070 @CCGR2
str r1,       @将0xffffffff写入到CCGR2

ldr r0, = 0x020c4074 @CCGR3
str r1,       @将0xffffffff写入到CCGR3

ldr r0, = 0x020c4078 @CCGR4
str r1,       @将0xffffffff写入到CCGR4

ldr r0, = 0x020c407c @CCGR5
str r1,       @将0xffffffff写入到CCGR5

ldr r0, = 0x020c4080 @CCGR6
str r1,       @将0xffffffff写入到CCGR6

/* IO复用配置GPIO1_IO03 PIN的复用为GPIO，也就是设置寄存器
* IOMUXC_SW_MUX_CTL_PAD_GPIO03 = 5
* IOMUXC_SW_MUX_CTL_PAD_GPIO03 地址为0x20e022ch
*/

ldr r0, = 0x20e022c @IOMUXC_SW_MUX_CTL_PAD_GPIO03
ldr r1, = 0x00000101 @要向IOMUXC_SW_MUX_CTL_PAD_GPIO03写入的数据
str r1,       @将0x00000101 = 5写入到IOMUXC_SW_MUX_CTL_PAD_GPIO03

/* 配置GPIO01_IO3的电气属性也就是寄存器：
* IOMUXC_SW_PAD_CTL_PAD_GPIO03
* IOMUXC_SW_MUX_CTL_PAD_GPIO03 寄存器地址为0x20e05fch
*
* bit0:    0 低速率
* bit5:3    110 R0/6驱动能力
* bit7:6    10 100MHz速度
* bit11:    0 关闭开路输出
* bit12:    1 使能pull/kepper
* bit15:14: 00 默认100K下拉
* bit16:    0 关闭hys
*/

ldr r0, = 0x20e05fc
ldr r1, = 0x10b0
str r1,       @将0x0x10b0写入到IOMUXC_SW_PAD_CTL_PAD_GPIO03

/* 设置GPIO
* 设置GPIO1_GDIR寄存器，设置GPIO1_GPIO03为输出
* GPIO1_GDIR寄存器地址为209c004，设置GPIO1_GDIR寄存器bit3为1
* 也就是设置GPIO1_IO03为输出
*/

ldr r0, = 0x209c004
ldr r1, = 0x8
str r1,

/* 设置GPIO1_IO03 为1
   * GPIO1_DR寄存器地址为0x0209c000
   */

   ldr r0, = 0x0209c00
   ldr r1, = 1
   str r1,

loop:                   @b loop 在73 74行死循环
b loop

在makefile文件中：
imx6led:imx6led.o
arm-none-eabi-ld -Ttext=0x7000 -Map imx6led.map -o imx6led.elf $^
arm-none-eabi-objcopy -O binary imx6led.elf imx6led.bin

（注意上在红色字体，后面反汇编之后可以看到这个基址值）
arm-none-eabi-objdump -D imx6led.elf >> im6leddisasm.dis
im6leddisasm.dis内容如下：

imx6led.elf: file format elf32-littlearm

Disassembly of section .text:

00007000 <_start>:
7000: e59f0068 ldr r0, ; 7070 <loop+0x4>
7004: e3e01000 mvn r1, #0
7008: e5801000 str r1,
700c: e59f0060 ldr r0, ; 7074 <loop+0x8>
7010: e5801000 str r1,
7014: e59f005c ldr r0, ; 7078 <loop+0xc>
7018: e5801000 str r1,
701c: e59f0058 ldr r0, ; 707c <loop+0x10>
7020: e5801000 str r1,
7024: e59f0054 ldr r0, ; 7080 <loop+0x14>
7028: e5801000 str r1,
702c: e59f0050 ldr r0, ; 7084 <loop+0x18>
7030: e5801000 str r1,
7034: e59f004c ldr r0, ; 7088 <loop+0x1c>
7038: e5801000 str r1,
703c: e59f0048 ldr r0, ; 708c <loop+0x20>
7040: e59f1048 ldr r1, ; 7090 <loop+0x24>
7044: e5801000 str r1,
7048: e59f0044 ldr r0, ; 7094 <loop+0x28>
704c: e59f1044 ldr r1, ; 7098 <loop+0x2c>
7050: e5801000 str r1,
7054: e59f0040 ldr r0, ; 709c <loop+0x30>
7058: e3a01008 mov r1, #8
705c: e5801000 str r1,
7060: e59f0038 ldr r0, ; 70a0 <loop+0x34>
7064: e3a01001 mov r1, #1
7068: e5801000 str r1,

0000706c <loop>:
706c: eafffffe b 706c <loop>
7070: 020c4068 andeq r4, ip, #104 ; 0x68
7074: 020c406c andeq r4, ip, #108 ; 0x6c
7078: 020c4070 andeq r4, ip, #112 ; 0x70
707c: 020c4074 andeq r4, ip, #116 ; 0x74
7080: 020c4078 andeq r4, ip, #120 ; 0x78
7084: 020c407c andeq r4, ip, #124 ; 0x7c
7088: 020c4080 andeq r4, ip, #128 ; 0x80
708c: 020e022c andeq r0, lr, #44, 4 ; 0xc0000002
7090: 00000101 andeq r0, r0, r1, lsl #2
7094: 020e05fc andeq r0, lr, #252, 10 ; 0x3f000000
7098: 000010b0 strheq r1, , -r0
709c: 0209c004 andeq ip, r9, #4
70a0: 00209c00 eoreq r9, r0, r0, lsl #24

Disassembly of section .debug_aranges:

00000000 <.debug_aranges>:
0: 0000001c andeq r0, r0, ip, lsl r0
4: 00000002 andeq r0, r0, r2
8: 00040000 andeq r0, r4, r0
c: 00000000 andeq r0, r0, r0
10: 00007000 andeq r7, r0, r0
14: 000000a4 andeq r0, r0, r4, lsr #1
...

Disassembly of section .debug_info:

00000000 <.debug_info>:
0: 0000004c andeq r0, r0, ip, asr #32
4: 00000002 andeq r0, r0, r2
8: 01040000 mrseq r0, (UNDEF: 4)
c: 00000000 andeq r0, r0, r0
10: 00007000 andeq r7, r0, r0
14: 000070a4 andeq r7, r0, r4, lsr #1
18: 36786d69 ldrbtcc r6, , -r9, ror #26
1c: 2e64656c cdpcs 5, 6, cr6, cr4, cr12, {3}
20: 3a480073 bcc 12001f4 <_stack+0x11801f4>
24: 504d545c subpl r5, sp, ip, asr r4
28: 7074665c rsbsvc r6, r4, ip, asr r6
2c: 76726573 ; <UNDEFINED> instruction: 0x76726573
30: 6f727265 svcvs 0x00727265
34: 615c746f cmpvs ip, pc, ror #8
38: 62396d72 eorsvs r6, r9, #7296 ; 0x1c80
3c: 00657261 rsbeq r7, r5, r1, ror #4
40: 20554e47 subscs r4, r5, r7, asr #28
44: 32205341 eorcc r5, r0, #67108865 ; 0x4000001
48: 2e36322e cdpcs 2, 3, cr3, cr6, cr14, {1}
4c: 80010030 andhi r0, r1, r0, lsr r0

Disassembly of section .debug_abbrev:

00000000 <.debug_abbrev>:
0: 10001101 andne r1, r0, r1, lsl #2
4: 12011106 andne r1, r1, #-2147483647 ; 0x80000001
8: 1b080301 blne 200c14 <_stack+0x180c14>
c: 13082508 movwne r2, #34056 ; 0x8508
10: 00000005 andeq r0, r0, r5

Disassembly of section .debug_line:

00000000 <.debug_line>:
0: 00000066 andeq r0, r0, r6, rrx
4: 00200002 eoreq r0, r0, r2
8: 01020000 mrseq r0, (UNDEF: 2)
c: 000d0efb strdeq r0, , -fp
10: 01010101 tsteq r1, r1, lsl #2
14: 01000000 mrseq r0, (UNDEF: 0)
18: 00010000 andeq r0, r1, r0
1c: 36786d69 ldrbtcc r6, , -r9, ror #26
20: 2e64656c cdpcs 5, 6, cr6, cr4, cr12, {3}
24: 00000073 andeq r0, r0, r3, ror r0
28: 05000000 streq r0,
2c: 00700002 rsbseq r0, r0, r2
30: 2f2f1700 svccs 0x002f1700
34: 2f302f30 svccs 0x00302f30
38: 2f302f30 svccs 0x00302f30
3c: 2f302f30 svccs 0x00302f30
40: 032f2f36 ; <UNDEFINED> instruction: 0x032f2f36
44: 2f2f2e0f svccs 0x002f2e0f
48: 342f2f36 strtcc r2, , #-3894 ; 50 <_start-0x6fb0>
4c: 03312f2f teqeq r1, #47, 30 ; 0xbc
50: 322e7fbc eorcc r7, lr, #188, 30 ; 0x2f0
54: 31313131 teqcc r1, r1, lsr r1
58: 2e090331 mcrcs 3, 0, r0, cr9, cr1, {1}
5c: 2e10032f cdpcs 3, 1, cr0, cr0, cr15, {1}
60: 2e09032f cdpcs 3, 0, cr0, cr9, cr15, {1}
64: 00020236 andeq r0, r2, r6, lsr r2
68: Address 0x00000068 is out of bounds.

Disassembly of section .ARM.attributes:

00000000 <_stack-0x80000>:
0: 00001341 andeq r1, r0, r1, asr #6
4: 61656100 cmnvs r5, r0, lsl #2
8: 01006962 tsteq r0, r2, ror #18
c: 00000009 andeq r0, r0, r9
10: 01080106 tsteq r8, r6, lsl #2

joe 发表于 2022-10-10 13:22:02

很明显可以看到，第一句汇编语句： ldr r0, = 0x020c4068，汇编之后的最终结果是：
7000:    e59f0068       ldr    r0,    ; 7070 <loop+0x4>
7004:    e3e01000       mvn    r1, #0对应原代码中的ldr r1,#0xffffffff (mvn指令将源按位取反再传送）
7008:    e5801000       str    r1,
同时，我们在这个.text节的末尾可以看到：
0000706c <loop>:
706c:    eafffffe       b    706c <loop>
7070:    020c4068       andeq    r4, ip, #104    ; 0x68
也就是说在原来的源码：
loop:
b loop
之后编译器自动放置了一些数据，实际上就是源代码中的立即数值0x020c4068等。

joe 发表于 2022-10-10 14:19:08

如果将源代码改为：
_start:
/* 使能所有外设时钟 */
ldr r0, =0x10 @ = 0x020c4068 @CCGR0
ldr r1, =0xff @= 0xffffffff @要向CCGR0写入的数据

反汇编之后可以看到如下代码：
00007000 <_start>:
7000: e3a00010 mov r0, #16
7004: e3a010ff mov r1, #255 ; 0xff
7008: e5801000 str r1,

joe 发表于 2022-10-11 11:14:11

注意，
7000: e59f0068 ldr r0, ; 7070 <loop+0x4>
和：
7070: 020c4068 andeq r4, ip, #104 ; 0x68
这二句可知，offset其实是0x70=112，并不是104，那为什么呢？
这是因为我的实验硬件平台满足:
ARM7的三级流水线，PC=PC+8，
ARM9的五级流水线，也是PC=PC+8，
根本的原因是，两者的流水线设计中，指令的Execute执行阶段，都是处于流水线的第三级
所以：104+8=112正确。

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ARM汇编指令裸板操作LED