【Linux系统编程】—— 虚拟内存与进程地址空间的管理：操作系统如何实现内存保护与高效分配

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

int g_unval;
int g_val = 100;

int main(int argc, char *argv[], char *env[])
{
	 const char *str = "helloworld";
	 printf("code addr: %p\n", main);
	 printf("init global addr: %p\n", &g_val);
	 printf("uninit global addr: %p\n", &g_unval);
	 static int test = 10;
	 char *heap_mem = (char*)malloc(10);
	 char *heap_mem1 = (char*)malloc(10);
	 char *heap_mem2 = (char*)malloc(10);
	 char *heap_mem3 = (char*)malloc(10);
	 printf("heap addr: %p\n", heap_mem); //heap_mem(0), &heap_mem(1)
	 printf("heap addr: %p\n", heap_mem1); //heap_mem(0), &heap_mem(1)
	 printf("heap addr: %p\n", heap_mem2); //heap_mem(0), &heap_mem(1)
	 printf("heap addr: %p\n", heap_mem3); //heap_mem(0), &heap_mem(1)
	 printf("test static addr: %p\n", &test); //heap_mem(0), &heap_mem(1)
	 printf("stack addr: %p\n", &heap_mem); //heap_mem(0), &heap_mem(1)
	 printf("stack addr: %p\n", &heap_mem1); //heap_mem(0), &heap_mem(1)
	 printf("stack addr: %p\n", &heap_mem2); //heap_mem(0), &heap_mem(1)
	 printf("stack addr: %p\n", &heap_mem3); //heap_mem(0), &heap_mem(1)
	 printf("read only string addr: %p\n", str);
	 for(int i = 0 ;i < argc; i++)
	 {
	 	printf("argv[%d]: %p\n", i, argv[i]);
	 }
	 for(int i = 0; env[i]; i++)
	 {
	 	printf("env[%d]: %p\n", i, env[i]);
	 }
	 return 0;
}

code addr: 0x40055d
init global addr: 0x601034
uninit global addr: 0x601040
heap addr: 0x1791010
heap addr: 0x1791030
heap addr: 0x1791050
heap addr: 0x1791070
test static addr: 0x601038
stack addr: 0x7ffd0f9a4368
stack addr: 0x7ffd0f9a4360
stack addr: 0x7ffd0f9a4358
stack addr: 0x7ffd0f9a4350
read only string addr: 0x400800
argv[0]: 0x7ffd0f9a4811
env[0]: 0x7ffd0f9a4819
env[1]: 0x7ffd0f9a482e
env[2]: 0x7ffd0f9a4845
env[3]: 0x7ffd0f9a4850
env[4]: 0x7ffd0f9a4860
env[5]: 0x7ffd0f9a486e
env[6]: 0x7ffd0f9a4892
env[7]: 0x7ffd0f9a48a5
env[8]: 0x7ffd0f9a48ae
env[9]: 0x7ffd0f9a48f1
env[10]: 0x7ffd0f9a4e8d
env[11]: 0x7ffd0f9a4ea6
env[12]: 0x7ffd0f9a4f00
env[13]: 0x7ffd0f9a4f13
env[14]: 0x7ffd0f9a4f24
env[15]: 0x7ffd0f9a4f3b
env[16]: 0x7ffd0f9a4f43
env[17]: 0x7ffd0f9a4f52
env[18]: 0x7ffd0f9a4f5e
env[19]: 0x7ffd0f9a4f93
env[20]: 0x7ffd0f9a4fb6
env[21]: 0x7ffd0f9a4fd5
env[22]: 0x7ffd0f9a4fdf

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int g_val = 0;
int main()
{
	pid_t id = fork();
	if(id < 0)
	{
		perror("fork");
		return 0;
	}
	else if(id == 0)
	{ //child
		printf("child[%d]: %d : %p\n", getpid(), g_val, &g_val);
	}
	else
	{ //parent
		printf("parent[%d]: %d : %p\n", getpid(), g_val, &g_val);
	}
	sleep(1);
	return 0;
}

parent[2995]: 0 : 0x80497d8
child[2996]: 0 : 0x80497d8

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
int g_val = 0;
int main()
{
	pid_t id = fork();
	if(id < 0){
	perror("fork");
	return 0;
}
else if(id == 0)
{ //child,⼦进程肯定先跑完，也就是⼦进程先修改，完成之后，⽗进程再读取
	g_val=100;
	printf("child[%d]: %d : %p\n", getpid(), g_val, &g_val);
}
else
{ //parent
	sleep(3);
	printf("parent[%d]: %d : %p\n", getpid(), g_val, &g_val);
}
	sleep(1);
	return 0;
}

child[3046]: 100 : 0x80497e8
parent[3045]: 0 : 0x80497e8

struct mm_struct {
    struct vm_area_struct *mmap;
    struct rb_root mm_rb;
    unsigned long task_size;
    unsigned long start_code, end_code;
    unsigned long start_data, end_data;
    unsigned long start_brk, brk;
    unsigned long start_stack;
    unsigned long arg_start, arg_end;
    unsigned long env_start, env_end;
};