ARM MOV指令传入一个立即数

ARM的MOV指令可以传入一个立即数作为操作数，立即数可以是十进制数、十六进制数或二进制数。

例如，MOV r0, #10 将立即数10传输到寄存器r0中，MOV r1, #0x20 将十六进制数0x20传输到寄存器r1中，MOV r2, #0b1010 将二进制数1010传输到寄存器r2中。

需要注意的是，立即数的范围是 -2^31 到 2^31-1，如果立即数超出了这个范围，就需要使用LDR指令从内存中读取数据到寄存器中。

相关问题

用ARM编写一个计算平方的代码

在ARM架构上编写一个计算平方的简单代码通常涉及使用Assembly语言，这是一种低级指令集语言，直接操作硬件。下面是一个基本的例子，假设我们有一个名为`square`的函数，它接受一个整数作为输入并返回它的平方：

.global square
.square:
    // 定义局部寄存器，r0用于保存输入值，r1用于保存结果
    MOV r0, #0   @ 将输入值传入r0
    LDR r1, [r0] @ 加载输入值到r1

    // 开始循环，将r1自加直到完成平方
    SQRTD r1, r1 @ 计算r1的平方根，实际上会得到r1的平方
    CMP r0, r1   @ 比较输入值是否等于结果
    BNE loop     @ 如果不相等，跳转回循环

loop:
    BX lr         @ 结束函数，返回结果

// 调用示例
.data
input_value EQU 5 @ 输入的整数值
.text
LDR R7, =square @ 获取square函数地址
LDR R0, =input_value
BLX R7           @ 调用函数，R0存放输入，结果存储在R1

// 结果会在R1中，可以进一步处理或保存

注意：这只是一个简化的示例，实际的ARM汇编可能会更复杂，并考虑异常处理、优化等因素。在现代嵌入式系统开发中，通常使用C语言配合编译器的内联汇编功能来编写这类代码。

arm64 的 rop 实现C代码

由于 ARM64 架构的指令集比较复杂，实现 ROP 需要理解 ARM64 的寄存器和指令的用途和操作，因此比较困难。以下是一个简单的示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

void gadget1() {
    asm("mov x0, 0x1\n"
        "mov x1, 0x2\n"
        "mov x2, 0x3\n"
        "mov x3, 0x4\n"
        "mov x4, 0x5\n"
        "mov x5, 0x6\n"
        "mov x6, 0x7\n"
        "mov x7, 0x8\n"
        "mov x8, 0x9\n"
        "mov x9, 0xa\n"
        "mov x10, 0xb\n"
        "mov x11, 0xc\n"
        "mov x12, 0xd\n"
        "mov x13, 0xe\n"
        "mov x14, 0xf\n"
        "mov x15, 0x10\n"
        "mov x16, 0x11\n"
        "mov x17, 0x12\n"
        "mov x18, 0x13\n"
        "mov x19, 0x14\n"
        "mov x20, 0x15\n"
        "mov x21, 0x16\n"
        "mov x22, 0x17\n"
        "mov x23, 0x18\n"
        "mov x24, 0x19\n"
        "mov x25, 0x1a\n"
        "mov x26, 0x1b\n"
        "mov x27, 0x1c\n"
        "mov x28, 0x1d\n"
        "mov x29, 0x1e\n"
        "mov x30, 0x1f\n"
        "ret");
}

void gadget2() {
    asm("mov x0, 0xdeadbeef\n"
        "mov x1, 0xcafebabe\n"
        "mov x2, 0xfeedface\n"
        "mov x3, 0xabcdef01\n"
        "mov x4, 0x12345678\n"
        "mov x5, 0x87654321\n"
        "mov x6, 0xabcdef01\n"
        "mov x7, 0xdeadbeef\n"
        "mov x8, 0xcafebabe\n"
        "mov x9, 0xfeedface\n"
        "mov x10, 0xabcdef01\n"
        "mov x11, 0x12345678\n"
        "mov x12, 0x87654321\n"
        "mov x13, 0xabcdef01\n"
        "mov x14, 0xdeadbeef\n"
        "mov x15, 0xcafebabe\n"
        "mov x16, 0xfeedface\n"
        "mov x17, 0xabcdef01\n"
        "mov x18, 0x12345678\n"
        "mov x19, 0x87654321\n"
        "mov x20, 0xabcdef01\n"
        "mov x21, 0xdeadbeef\n"
        "mov x22, 0xcafebabe\n"
        "mov x23, 0xfeedface\n"
        "mov x24, 0xabcdef01\n"
        "mov x25, 0x12345678\n"
        "mov x26, 0x87654321\n"
        "mov x27, 0xabcdef01\n"
        "mov x28, 0xdeadbeef\n"
        "mov x29, 0xcafebabe\n"
        "mov x30, 0xfeedface\n"
        "ret");
}

void gadget3() {
    asm("mov x0, 0x12345678\n"
        "mov x1, 0x87654321\n"
        "mov x2, 0xabcdef01\n"
        "mov x3, 0xdeadbeef\n"
        "mov x4, 0xcafebabe\n"
        "mov x5, 0xfeedface\n"
        "mov x6, 0x12345678\n"
        "mov x7, 0x87654321\n"
        "mov x8, 0xabcdef01\n"
        "mov x9, 0xdeadbeef\n"
        "mov x10, 0xcafebabe\n"
        "mov x11, 0xfeedface\n"
        "mov x12, 0x12345678\n"
        "mov x13, 0x87654321\n"
        "mov x14, 0xabcdef01\n"
        "mov x15, 0xdeadbeef\n"
        "mov x16, 0xcafebabe\n"
        "mov x17, 0xfeedface\n"
        "mov x18, 0x12345678\n"
        "mov x19, 0x87654321\n"
        "mov x20, 0xabcdef01\n"
        "mov x21, 0xdeadbeef\n"
        "mov x22, 0xcafebabe\n"
        "mov x23, 0xfeedface\n"
        "mov x24, 0x12345678\n"
        "mov x25, 0x87654321\n"
        "mov x26, 0xabcdef01\n"
        "mov x27, 0xdeadbeef\n"
        "mov x28, 0xcafebabe\n"
        "mov x29, 0xfeedface\n"
        "mov x30, 0x12345678\n"
        "ret");
}

void gadget4() {
    asm("mov x0, 0xdeadbeef\n"
        "mov x1, 0xcafebabe\n"
        "mov x2, 0xfeedface\n"
        "mov x3, 0xabcdef01\n"
        "mov x4, 0x12345678\n"
        "mov x5, 0x87654321\n"
        "mov x6, 0xabcdef01\n"
        "mov x7, 0xdeadbeef\n"
        "mov x8, 0xcafebabe\n"
        "mov x9, 0xfeedface\n"
        "mov x10, 0xabcdef01\n"
        "mov x11, 0x12345678\n"
        "mov x12, 0x87654321\n"
        "mov x13, 0xabcdef01\n"
        "mov x14, 0xdeadbeef\n"
        "mov x15, 0xcafebabe\n"
        "mov x16, 0xfeedface\n"
        "mov x17, 0xabcdef01\n"
        "mov x18, 0x12345678\n"
        "mov x19, 0x87654321\n"
        "mov x20, 0xabcdef01\n"
        "mov x21, 0xdeadbeef\n"
        "mov x22, 0xcafebabe\n"
        "mov x23, 0xfeedface\n"
        "mov x24, 0xabcdef01\n"
        "mov x25, 0x12345678\n"
        "mov x26, 0x87654321\n"
        "mov x27, 0xabcdef01\n"
        "mov x28, 0xdeadbeef\n"
        "mov x29, 0xcafebabe\n"
        "mov x30, 0xfeedface\n"
        "ret");
}

void gadget5() {
    asm("mov x0, 0xdeadbeef\n"
        "mov x1, 0xcafebabe\n"
        "mov x2, 0xfeedface\n"
        "mov x3, 0xabcdef01\n"
        "mov x4, 0x12345678\n"
        "mov x5, 0x87654321\n"
        "mov x6, 0xabcdef01\n"
        "mov x7, 0xdeadbeef\n"
        "mov x8, 0xcafebabe\n"
        "mov x9, 0xfeedface\n"
        "mov x10, 0xabcdef01\n"
        "mov x11, 0x12345678\n"
        "mov x12, 0x87654321\n"
        "mov x13, 0xabcdef01\n"
        "mov x14, 0xdeadbeef\n"
        "mov x15, 0xcafebabe\n"
        "mov x16, 0xfeedface\n"
        "mov x17, 0xabcdef01\n"
        "mov x18, 0x12345678\n"
        "mov x19, 0x87654321\n"
        "mov x20, 0xabcdef01\n"
        "mov x21, 0xdeadbeef\n"
        "mov x22, 0xcafebabe\n"
        "mov x23, 0xfeedface\n"
        "mov x24, 0xabcdef01\n"
        "mov x25, 0x12345678\n"
        "mov x26, 0x87654321\n"
        "mov x27, 0xabcdef01\n"
        "mov x28, 0xdeadbeef\n"
        "mov x29, 0xcafebabe\n"
        "mov x30, 0xfeedface\n"
        "ret");
}

void vuln(char *str) {
    char buf[128];
    strcpy(buf, str);
    printf("buf=%s\n", buf);
}

int main(int argc, char **argv) {
    char buf[128];
    memset(buf, 0, sizeof(buf));
    fgets(buf, sizeof(buf), stdin);
    if (argc > 1) {
        if (strcmp(argv[1], "1") == 0) {
            gadget1();
        } else if (strcmp(argv[1], "2") == 0) {
            gadget2();
        } else if (strcmp(argv[1], "3") == 0) {
            gadget3();
        } else if (strcmp(argv[1], "4") == 0) {
            gadget4();
        } else if (strcmp(argv[1], "5") == 0) {
            gadget5();
        }
    }
    vuln(buf);
    return 0;
}

该代码包含了 5 个 gadget 函数，每个函数都会将一些值存入寄存器中，然后返回。vuln 函数中使用了 strcpy 函数，可以用来实现栈溢出。在 main 函数中，根据命令行参数选择使用哪个 gadget 函数，在调用 vuln 函数前先调用相应的 gadget 函数，然后传入用户输入的字符串。

使用 ROP 实现的过程如下：

1. 找到一个能够跳转到某个 gadget 的地址，例如 main 函数中的 fgets 函数。

2. 找到一个能够将参数传递到寄存器中的地址，例如 main 函数中的 strcmp 函数。

3. 找到能够将控制流跳转到指定地址的 gadget，例如 gadget2 函数。

4. 将第 2 步中得到的地址和参数传递到第 3 步中得到的 gadget 中，使其执行返回操作时跳转到指定地址，例如跳转到 gadget2 函数。

5. 在第 4 步中的 gadget 中设置相应的寄存器，使得在返回到 vuln 函数时执行指定的代码，例如将 x0 寄存器设置为 system 函数的地址，x1 寄存器设置为 "/bin/sh" 字符串的地址。

6. 调用 vuln 函数，使其执行第 5 步中设置的代码，例如执行 system("/bin/sh")。

具体实现过程详见代码。