Using devmem for Linux Kernel Debugging¶

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>

#define BASE_ADDRESS 0x12345678  // 替换为你要访问的基地址
#define REGISTER_OFFSET 0x04      // 替换为你要访问的寄存器相对于基地址的偏移量

int main() {
    int mem_fd;
    void *mapped_base, *mapped_dev_base;
    off_t dev_base = BASE_ADDRESS;

    // 打开 /dev/mem 设备文件
    mem_fd = open("/dev/mem", O_RDWR | O_SYNC);
    if (mem_fd == -1) {
        perror("Error opening /dev/mem");
        return EXIT_FAILURE;
    }

    // 映射物理地址到用户空间
    mapped_base = mmap(0, getpagesize(), PROT_READ | PROT_WRITE, MAP_SHARED, mem_fd, dev_base & ~(getpagesize() - 1));
    if (mapped_base == (void *)-1) {
        perror("Error mapping /dev/mem into user space");
        close(mem_fd);
        return EXIT_FAILURE;
    }

    // 计算相对于映射基地址的偏移量
    mapped_dev_base = mapped_base + (dev_base & (getpagesize() - 1));

    // 读取寄存器的值
    unsigned int reg_value = *((volatile unsigned int *)(mapped_dev_base + REGISTER_OFFSET));
    printf("Current value of the register: 0x%08X\n", reg_value);

    // 写入新的值到寄存器
    unsigned int new_value = 0xABCD;
    *((volatile unsigned int *)(mapped_dev_base + REGISTER_OFFSET)) = new_value;
    printf("New value written to the register: 0x%08X\n", new_value);

    // 解除映射并关闭文件
    if (munmap(mapped_base, getpagesize()) == -1) {
        perror("Error unmapping /dev/mem");
    }
    close(mem_fd);

    return EXIT_SUCCESS;
}