Methods to solve program running address conflicts: static relocation technology

How static relocation technology solves the problem of address conflicts during program running requires specific code examples

Introduction:
During the running of computer programs, there are often Address conflicts occur, which may adversely affect the normal operation of the program. To solve this problem, static relocation technology was proposed and widely used. This article will introduce the principles of static relocation technology and give specific code examples.

1. What is static relocation technology
Static relocation technology is a process of changing the address in the program to the actual address of the executable file or library file loaded into the memory. It mainly solves the problem of address conflicts caused by different locations when the program is running. Through static relocation technology, we can ensure that the program can run correctly in any location.

2. Principle of static relocation technology
The core principle of static relocation technology is to use the base address register (Base Register) and the limit register (Limit Register) to solve the address conflict problem.

The base address register stores the starting address of the executable file or library file loaded into the memory, and the limit register stores the size of the area loaded into the memory. When the program is executed, the relative addresses in the program are converted into actual addresses through the base address register, thereby avoiding the problem of address conflicts.

3. Specific code examples
The following is a program written in C language. If static relocation technology is not used, address conflicts will occur.

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

int global_variable = 10;

int main() {
    int local_variable = 20;
    
    printf("global_variable: %p
", &global_variable);
    printf("local_variable: %p
", &local_variable);
    
    return 0;
}

In the above code, we declare a global variable global_variable and a local variable local_variable. In the main function, we print the addresses of these two variables through printf.

Run the above code, the result may be as follows:

global_variable: 0x60103c
local_variable: 0x7ffe12e4b9ac

You can see that the address of global_variable is 0x60103c, and local_variable The address of is 0x7ffe12e4b9ac.

Next, we will use static relocation technology to solve the address conflict problem.

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

int global_variable = 10;

int main() {
    // 静态重定位
    int* base_address = (int*)0x600000;
    
    int local_variable = 20;
    
    printf("global_variable: %p
", (void*)((int)&global_variable + (int)base_address));
    printf("local_variable: %p
", (void*)((int)&local_variable + (int)base_address));
    
    return 0;
}

In the above code, we implement static relocation by defining a base address register base_address. We set base_address to 0x600000 and then get the actual address by adding the relative address to the base address.

Run the above code, we can get the following results:

global_variable: 0x60003c
local_variable: 0x600778

You can see that by using static relocation technology, the address of global_variable becomes 0x60003c, the address of local_variable becomes 0x600778. In this way, we successfully solved the address conflict problem.

Conclusion:
Static relocation technology is an important technology to solve the problem of address conflict during program running. By using the base address register and the limit register to convert relative addresses in the program to real addresses, we can ensure that the program will run correctly at any location. This article demonstrates the practical application of static relocation technology by giving specific code examples.

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