linux 物理内存读写

使用mmap访问硬件内存

最新推荐文章于 2024-06-18 11:40:54 发布

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本文展示了一个通过/dev/mem文件映射特定物理地址范围到用户空间的例子，并演示了如何读写这些硬件寄存器。代码中利用mmap系统调用实现内存映射，通过对映射后的内存区域进行读写操作来与硬件交互。

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>

main()
{
    int   i, j;
    int   words = 10;
    int   devmem;
    off_t PageOffset, PageAddress;

    unsigned long *hw_addr = (unsigned long *) 0x20000000;
    unsigned long read_data;

    devmem = open("/dev/mem", O_RDWR | O_SYNC);
    PageOffset = (off_t) hw_addr % getpagesize();
    PageAddress = (off_t) (hw_addr - PageOffset);

    hw_addr = (unsigned long *) mmap(0, 4, PROT_READ|PROT_WRITE, MAP_SHARED, devmem, PageAddress);

    for (i = 0, j = 0; i < words; i++, j+=4)
    {
        printf("Writing to hardware model\n");

        *(hw_addr+j) = 0xabcd0000+j;

        read_data = *(hw_addr+j);

        printf("Read from hardware %x\n",read_data);

    }

}