遍历VISTA/WIN 7 缓存VACB

标题：遍历VISTA/WIN 7 缓存VACB
作者：Sysnap
时间：2010-08-25 17:29:36
链接：http://bbs.pediy.com/showthread.php?t=119195

PS:好久没在看雪发东西，这里有我大学的记忆。。。。
有时候系统缓慢，被占很多缓存，所以想知道哪些文件占据了缓存。缓存的结构在XP和VISTA下有些区别，为了了解VISTA的结构，XP比较简单就不说了。
IDA+WINDBG开始摸索，下面就是过程和结果。
很多文件没缓存，所以为了方便找出缓存的FILLE_OBJECT，我选择对nt!CcMapData下断
kd> bp nt!CcMapData "!fileobj poi(@esp + 4)"
kd> g

\$Directory

Device Object: 0x86579c08   \Driver\volmgr
Vpb: 0x8616d0d0
Access: Read Write SharedRead SharedWrite SharedDelete

Flags: 0x40100
Stream File
Handle Created

FsContext: 0x890740f8 FsContext2: 0x00000000
Private Cache Map: 0x873ff0e0
CurrentByteOffset: 0
Cache Data:
Section Object Pointers: 86a1c2c4
Shared Cache Map: 873ff008         File Offset: 0 in VACB number 0
Vacb: 84b6df10
Your data is at: 8ae40000

kd> dt _SECTION_OBJECT_POINTERS 86a1c2c4
ntdll!_SECTION_OBJECT_POINTERS
   +0x000 DataSectionObject : 0x86b8ddb8 Void
   +0x004 SharedCacheMap   : 0x873ff008 Void
   +0x008 ImageSectionObject : (null)

kd> dt _SHARED_CACHE_MAP 0x873ff008 InitialVacbs
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] 0x84b6df10 _VACB

查看VACB在什么内核池中：
kd> !pool 0x84b6df10
Pool page 84b6df10 region is Nonpaged pool
*84b6d000 : large page allocation, Tag is CcVa, size is 0x20000 bytes
   Pooltag CcVa : Cache Manager Initial array of Vacbs, Binary : nt!cc

可见这个VACB是落在TAG为 CcVa 的POOL中，那是谁分配了这个POOL

kd> ed nt!poolhittag 'aVcC'
kd> g
Break instruction exception - code 80000003 (first chance)
nt!DbgBreakPoint:
8186e954 cc              int     3
kd> kv
ChildEBP RetAddr Args to Child
80599b74 818592c9 61566343 00020000 00000000 nt!DbgBreakPoint
80599bd0 8190a4cd 00000000 00000000 00020000 nt!ExpAllocateBigPool+0x216
80599c30 8181e282 00000000 00020000 61566343 nt!ExAllocatePoolWithTag+0x116
80599c4c 81b6c0a0 80599c5c 00000001 00000000 nt!CcAllocateInitializeVacbArray+0x19
80599c60 81b6bf8d 8085b010 00010000 00000000 nt!CcInitializeVacbs+0x82
80599c98 81b7ca0a 84b34540 84b34218 00000000 nt!CcInitializeCacheManager+0x3b5
80599d74 81975af1 80599dc0 819f2a1c 8085b010 nt!Phase1InitializationDiscard+0x8dd
80599d7c 819f2a1c 8085b010 3d3a5762 00000000 nt!Phase1Initialization+0xd
80599dc0 8184ba3e 81975ae4 8085b010 00000000 nt!PspSystemThreadStartup+0x9d
00000000 00000000 00000000 00000000 00000000 nt!KiThreadStartup+0x16

上面的栈比较清晰地看到nt!CcAllocateInitializeVacbArray创建了 CcVa 的POOL，第三个参数61566343其实就是CcVa

看下nt!CcAllocateInitializeVacbArray
.text:004013A0 014                 call    esi ; KeReleaseQueuedSpinLock(x,x) ; KeReleaseQueuedSpinLock(x,x)
.text:004013A2 00C                 push    61566343h       ; Tag
.text:004013A7 010                 mov     edi, 20000h
.text:004013AC 010                 push    edi             ; NumberOfBytes
.text:004013AD 014                 push    0               ; PoolType
.text:004013AF 018                 call    _ExAllocatePoolWithTag@12 ; ExAllocatePoolWithTag(x,x,x)
.text:004013B4 00C                 mov     ebx, eax

.text:004013C6 00C                 lea     eax, [ebx+28h]
.text:004013C9 00C                 mov     ecx, 0FFFh
.text:004013CE
.text:004013CE     loc_4013CE:                             ; CODE XREF: CcAllocateInitializeVacbArray()+66 j
.text:004013CE 00C                 mov     [eax], ebx
.text:004013D0 00C                 add     eax, 20h @@@@@@@@@@@@@@@重要，VACB大小是0X18，但我们需要0X20才能访问
.text:004013D3 00C                 dec     ecx
.text:004013D4 00C                 jnz     short loc_4013CE
.text:004013D6 00C                 jmp     short loc_4013EE

分配的这片内存进行初始化，每隔0X20，都会填一个指向该内存的指针

kd> !list "-t _LIST_ENTRY.Flink -e -x \"dt _VACB_ARRAY_HEADER @$extret\" poi(CcVacbArrays)"
dt _VACB_ARRAY_HEADER @$extret
nt!_VACB_ARRAY_HEADER
   +0x000 Links            : _LIST_ENTRY [ 0x819530c8 - 0x819530c8 ]
   +0x008 MappingCount     : 0x2e0
   +0x00c Reserved         : 0

kd> dd 0x819530c8 l2
819530c8 84b6d000 84b6d000

84b6d000 就是 ExAllocatePoolWithTag（ NonPagedPool,0x20000, 'aVcC') 分配的内存

kd> dd 84b6d000 l16
/*84b6d000*/ 819530c8 819530c8 000002e0 00000000
84b6d010 83440000 00000000 00000000 00000000
84b6d020 84b6d040 819530b0 /*84b6d000*/ 00000000
84b6d030 83480000 00000000 00000000 00000000
84b6d040 84b6d060 84b6d020 /*84b6d000*/ 00000000
84b6d050 834c0000 00000000
就是上面代码初始化的原因

也就是nt!_VACB_ARRAY_HEADER的Links其实就是指向的内存第一个指针就是BigPool的指针

目前的话

测试下VACB在内存的位置

kd> bp nt!CcMapData " dt _SHARED_CACHE_MAP poi((poi((poi(@esp + 4) + 0x14)) + 0x4 )) InitialVacbs Vacbs ; g"
kd> g
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] (null)
   +0x040 Vacbs        : 0x86830df8 -> 0x86824910 _VACB
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] 0x84b6f8b0 _VACB
   +0x040 Vacbs        : 0x8690bd78 -> 0x84b6f8b0 _VACB
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] 0x84b6f8b0 _VACB
   +0x040 Vacbs        : 0x8690bd78 -> 0x84b6f8b0 _VACB
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] (null)
   +0x040 Vacbs        : 0x86830df8 -> 0x86824910 _VACB
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] 0x84b6f910 _VACB
   +0x040 Vacbs        : 0x86a50430 -> 0x84b6f910 _VACB
nt!_SHARED_CACHE_MAP
   +0x030 InitialVacbs : [4] 0x84b6f910 _VACB
   +0x040 Vacbs        : 0x86a50430 -> 0x84b6f910 _VACB

kd> dt _VACB 0x84b6f8b0
nt!_VACB
   +0x000 BaseAddress      : 0x8ebc0000 Void
   +0x004 SharedCacheMap   : 0x8690bd48 _SHARED_CACHE_MAP
   +0x008 Overlay          : <unnamed-tag>
   +0x010 LruList          : _LIST_ENTRY [ 0x84b715c0 - 0x84b72e60 ]
   +0x018 ArrayHead        : 0x84b6d000 _VACB_ARRAY_HEADER

kd> .printf"%x\n",poi(0x86a50430) ；dt _VACB poi(0x86a50430)
84b6f910
nt!_VACB
   +0x000 BaseAddress      : 0x8f840000 Void
   +0x004 SharedCacheMap   : 0x86a50400 _SHARED_CACHE_MAP
   +0x008 Overlay          : <unnamed-tag>
   +0x010 LruList          : _LIST_ENTRY [ 0x84b6e060 - 0x84b715c0 ]
   +0x018 ArrayHead        : 0x84b6d000 _VACB_ARRAY_HEADER

kd> ? 0x84b6f910 - 0x84b6f8b0
Evaluate expression: 96 = 00000060

kd> ? 0n96 / 0x20
Evaluate expression: 3 = 00000003

能被整除，俩个VACB中间隔了3个VACB

目前的话我们知道CcVa POOL的地址范围是 84b6d000 - 84b8d000 （ 84b6d000 + 0x20000 ）
这个范围内就有我们的VACB。。。下面是WINDBG的脚本
$t0 的值可以通过bp /1 nt!CcMapData "r $t0 = poi(@esp + 4); r $t10 = poi((poi(poi( @$t0 + 0x14 ) + 0x4) + 0x30))

; r $t11 = poi((poi(poi( @$t0 + 0x14 ) + 0x4) + 0x40)) ; r $t11 = poi(poi(@$t11)); r @$t10 ; r @$t11 "来获取

.expr /s masm;
r $t0 = 0x84b6f910; $$第一个VACB
r $t1 = poi(nt!CcVacbArrays);
r $t2 = @$t1 + 0x20000;

.printf"Hdr = 0x%x, end = 0x%x\n",@$t1,@$t2 ;

.printf"down --->\n";
.for( r $t3 = $t0 ; @$t3 < @$t2 ; r $t3 = @$t3 + 0x20)
{
        .if( poi(@$t3 + 0x04) == 0 )
        {
           .printf"VACB = 0x%x NULL SharedCacheMap \n",@$t3;
           .continue
         }

r $t4 = @$t3;
   r $t4 = poi(@$t4 + 0x18);
        r $t5 = poi((poi(@$t3 + 0x04) + 0x44 )) + 0x30;


.if( @$t4 == $t1)
{

   .printf"vacb = 0x%x fileobj 0x%x， %msu \n",@$t3, @$t5-0x30, @$t5;
}
}

.printf"up --->\n";
.for( r $t3 = $t0 ; @$t3 > @$t1 ; r $t3 = @$t3 - 0x20)
{
        .if( poi(@$t3 + 0x04) == 0 )
        {
           .printf"VACB = 0x%x NULL SharedCacheMap \n",@$t3;
           .continue
         }

r $t4 = @$t3;
   r $t4 = poi(@$t4 + 0x18);
        r $t5 = poi((poi(@$t3 + 0x04) + 0x44 )) + 0x30;

.if( @$t4 == $t1 & @$t3 + 0x04 != 0 )
{
   .printf"vacb = 0x%x fileobj 0x%x ,%msu\n",@$t3, @$t5-0x30, @$t5;
}
}

输出
kd> $$>a<c:\vacb.txt
Current expression evaluator: MASM - Microsoft Assembler expressions
Hdr = 0x84b6d000, end = 0x84b8d000
down --->
vacb = 0x84b6f910 fileobj 0x86a38300 ,\$Directory
vacb = 0x84b6f930 fileobj 0x86838f1f ,<Win32 error 0n30>
vacb = 0x84b6f950 fileobj 0x86980450 ,\$Directory
vacb = 0x84b6f970 fileobj 0x85287e70 ,\$Directory
vacb = 0x84b6f990 fileobj 0x85132250 ,\Windows\System32\catroot2\{127D0A1D-4EF2-11D1-8608-00C04FC295EE}\catdb
vacb = 0x84b6f9b0 fileobj 0x86b1ad00 ,\$Directory