windows – MEMORY_BASIC_INFORMATION结构中的BaseAddress和AllocationBase有什么区别？

Windows上的虚拟内存分配的粒度为64千字节,即SYstem_INFO.dwAllocationGranularity的值.但虚拟内存页面为4096字节,SYstem_INFO.dwPageSize的值.

使用VirtualAlloc分配虚拟内存时,您将始终获得一个BaseAddress等于AllocationBase的块.但是,如果您随后更改了此块中一个或多个页面的页面保护,那么您可以观察到此块被细分为不同的BaseAddress.使用示例程序最佳显示,在MSVC上运行：

#include "stdafx.h"
#include <Windows.h>
#include <stdio.h>
#include <conio.h>

void showmem(void* mem) {
    MEMORY_BASIC_informatION info = {};
    VirtualQuery(mem,&info,sizeof info);
    printf("Alloc = %p,base = %p,size = %d,protect = %d\n",info.AllocationBase,info.BaseAddress,info.RegionSize,info.Protect);
}


int main() {
    BYTE* mem = (BYTE*)VirtualAlloc(0,65536,MEM_COMMIT,PAGE_READWRITE);
    printf("%s","Initial allocation:\n");
    showmem(mem);

    DWORD oldprotect;
    BOOL ok = VirtualProtect(mem + 4096,4096,PAGE_NOACCESS,&oldprotect);
    printf("%s","\nAfter protection changes:\n");
    showmem(mem);
    showmem(mem + 4096);
    showmem(mem + 4096 + 4096);

    _getch();
    return 0;
}

该程序的示例输出：

Initial allocation:
Alloc = 00ED0000,base = 00ED0000,size = 65536,protect = 4

After protection changes:
Alloc = 00ED0000,size = 4096,protect = 4
Alloc = 00ED0000,base = 00ED1000,protect = 1
Alloc = 00ED0000,base = 00ED2000,size = 57344,protect = 4

并注意VirtualProtect()调用如何要求原始块在具有不同BaseAddress但具有相同AllocationBase的3个区域中分割.