保护模式(八):MmIsAddressValid逆向(PAE)

kd> u MmIsAddressValid l50h
nt!MmIsAddressValid:
80511980 8bff            mov     edi,edi
80511982 55              push    ebp
80511983 8bec            mov     ebp,esp
80511985 51              push    ecx
80511986 51              push    ecx
80511987 8b4d08          mov     ecx,dword ptr [ebp+8]  ;参数address
8051198a 56              push    esi
8051198b 8bc1            mov     eax,ecx
8051198d c1e812          shr     eax,12h                 ;eax>>18
80511990 bef83f0000      mov     esi,3FF8h          ;
80511995 23c6            and     eax,esi                 ;eax=(DPD)*8 
80511997 2d0000a03f      sub     eax,3FA00000h       ;eax+C0600000(PDT基址)
8051199c 8b10            mov     edx,dword ptr [eax]     ;edx=PDE后半段
8051199e 8b4004          mov     eax,dword ptr [eax+4]   ;eax=PDE前半段
805119a1 8945fc          mov     dword ptr [ebp-4],eax   
805119a4 8bc2            mov     eax,edx
805119a6 57              push    edi
805119a7 83e001          and     eax,1
805119aa 33ff            xor     edi,edi
805119ac 0bc7            or      eax,edi
805119ae 7461            je      nt!MmIsAddressValid+0x91 (80511a11)  ;判断P位是否有效,P=0跳转返回假
805119b0 bf80000000      mov     edi,80h
805119b5 23d7            and     edx,edi                   ;判断PS位
805119b7 6a00            push    0
805119b9 8955f8          mov     dword ptr [ebp-8],edx           
805119bc 58              pop     eax                      ;eax=0
805119bd 7404            je      nt!MmIsAddressValid+0x43 (805119c3)    ;PS=0跳转(小页)
805119bf 85c0            test    eax,eax
805119c1 7452            je      nt!MmIsAddressValid+0x95 (80511a15)    ;PS=1(大页)返回真
805119c3 c1e909          shr     ecx,9                    ;address>>9(取T)
805119c6 81e1f8ff7f00    and     ecx,7FFFF8h                 ;
805119cc 8b81040000c0    mov     eax,dword ptr [ecx-3FFFFFFCh]      ;[ecx+0xC0000004](eax为PTE前段)
805119d2 81e900000040    sub     ecx,40000000h                ;ecx=ecx+C0000000(页表基址)
805119d8 8b11            mov     edx,dword ptr [ecx]            ;edx为PTE后段
805119da 8945fc          mov     dword ptr [ebp-4],eax 
805119dd 53              push    ebx                      
805119de 8bc2            mov     eax,edx                   
805119e0 33db            xor     ebx,ebx
805119e2 83e001          and     eax,1
805119e5 0bc3            or      eax,ebx
805119e7 5b              pop     ebx
805119e8 7427            je      nt!MmIsAddressValid+0x91 (80511a11)    ;PTE,P=0,返回FALSE
805119ea 23d7            and     edx,edi                   ;PAT位
805119ec 6a00            push    0
805119ee 8955f8          mov     dword ptr [ebp-8],edx
805119f1 58              pop     eax                      ;eax=0
805119f2 7421            je      nt!MmIsAddressValid+0x95 (80511a15)     ;PAT=0返回TRUE
805119f4 85c0            test    eax,eax
805119f6 751d            jne     nt!MmIsAddressValid+0x95 (80511a15)   ;不会执行
805119f8 23ce            and     ecx,esi                                ;PAT=1时情况
805119fa 8b89000060c0    mov     ecx,dword ptr [ecx-3FA00000h]      ;不往下分析了
80511a00 b881000000      mov     eax,81h
80511a05 23c8            and     ecx,eax
80511a07 33d2            xor     edx,edx
80511a09 3bc8            cmp     ecx,eax
80511a0b 7508            jne     nt!MmIsAddressValid+0x95 (80511a15)
80511a0d 85d2            test    edx,edx
80511a0f 7504            jne     nt!MmIsAddressValid+0x95 (80511a15)
80511a11 32c0            xor     al,al                      //return FALSE
80511a13 eb02            jmp     nt!MmIsAddressValid+0x97 (80511a17)    
80511a15 b001            mov     al,1                       //return TRUE
80511a17 5f              pop     edi
80511a18 5e              pop     esi
80511a19 c9              leave
80511a1a c20400          ret     4
BOOLEAN MmIsAddressValid(
  PVOID VirtualAddress
);

 结论

PDE=[((VirtualAddress>>18)&0x3FF8)+0xC0600000]
PTE=[((VirtualAddress>>9)&0x7FFFF8)+0xC0000000]

 

posted @ 2020-12-24 20:21  Harmonica11  阅读(136)  评论(0编辑  收藏  举报