读/写特定的内存地址(非常简单的memtest) - >分段错误

Question

我创建了一个简单的memtest程序.

但是,当我尝试运行它时(当然使用sudo)它会在以下行崩溃:

main - > test_all - > test_running - > for(j = 0; j <= memsize; j ++)p [j] = 1-value; //(第一次分配操作)

它没有指定错误.我在考虑两种可能性:

1)错误的内存范围,应该选择另一个(哪个？)

2)我的代码有问题(在哪里？)

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define MEM_start 0xFD002000
#define MEM_end 0xFDFFFFFF
#define MEM_size 16769023

int test_running(int value) {
    int i, j;
    int flag=0;
    int *p = (int *)MEM_start;
    int memsize = (int)MEM_size;
    for (i=0; i<=memsize; i++) {
        for (j=0; j<=memsize; j++) p[j]=1-value;
        p[i]=value;
        if (p[i]!=value) { printf("Error at address: %p\n", &p[i]); flag++; }
        for (j=0; j<=memsize; j++) {
            if ((j!=i)&&(p[j]==value)) {
                printf("Error at address: %p\n", &p[j]);
                flag++;
            }
        }
    }
    return flag;
}

int test_chess() {
        int i;
        int flag=0;
        int *p = (int *)MEM_start;
        int memsize = (int)MEM_size;
        for (i=0; i<=memsize; i++) p[i]=i%2;
        for (i=0; i<=memsize; i++) if (p[i]!=i%2) { printf("Error at address: %p\n", &p[i]); flag++; }
        for (i=0; i<=memsize; i++) p[i]=(i+1)%2;
        for (i=0; i<=memsize; i++) if (p[i]!=(i+1)%2) { printf("Error at address: %p\n", &p[i]); flag++; }
        return flag;
    }

int test_random() {
    int i, j;
    int flag=0;
    int *p = (int *)MEM_start;
    int memsize = (int)MEM_size;
    int buffer[32];
    int buffer_size=32;
    for (i=0; i<=memsize; i=i+buffer_size) {
        for (j=0; j<=buffer_size; j++) buffer[j]=(0==(rand()%2));
        for (j=0; j<=buffer_size; j++) p[i+j]=buffer[j];
        for (j=0; j<=buffer_size; j++) if (p[i+j]!=buffer[i]) { printf("Error at address: %p\n", &p[i+j]); flag++; }
    }
    return flag;
}

int test_all() {
    int test=0;
    int flag;
    flag=test_running(1);
    if (flag) { test++; printf("Running 1 - FAIL\n"); }
    else printf("Running 1 - SUCCESS\n");
    flag=test_running(0);
    if (flag) { test++; printf("Running 0 - FAIL"); }
    else printf("Running 0 - SUCCESS\n");
    flag=test_chess();
    if (flag) { test++; printf("Chess - FAIL\n"); }
    else printf("Chess - SUCCESS\n");
    flag=test_chess();
    if (flag) { test++; printf("Random - FAIL\n"); }
    else printf("Random - SUCCESS\n");
    if (test!=0) { printf("SOME TESTS FAILED: %i", test); return 1; }
    else { printf("ALL TESTS PASSED!!!"); return 0; }
}

int main() {
    srand(time(NULL));
    test_all();
    return 0;
}

更新:以下链接非常有用:1)FixUnix:在已知物理地址写入设备

2)DesignSomething:从用户空间读取/写入物理地址的简单代码

Answer 1

0xFD002000 您尝试读取/写入的地址未在您的进程中映射.它对您的访问进程无效.这就是为什么在第一次访问它时会出现分段错误的原因.

另外,请注意(在Windows,Linux,Mac等主流桌面操作系统中),进程中的地址是虚拟地址,而不是实际的物理地址.更多虚拟地址空间