Process Environment Block
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In computing the Process Environment Block is a data structure in Win32 on x86 that stores information about the currently running process.
This is pointed to by the Thread Information Block at address 0x30.
It can be accessed using fs:30h
Contents of the PEB
+0x000 InheritedAddressSpace : UChar +0x001 ReadImageFileExecOptions : UChar +0x002 BeingDebugged : UChar +0x003 BitField : UChar +0x003 ImageUsesLargePages : Pos 0, 1 Bit +0x003 IsProtectedProcess : Pos 1, 1 Bit +0x003 IsLegacyProcess : Pos 2, 1 Bit +0x003 IsImageDynamicallyRelocated : Pos 3, 1 Bit +0x003 SkipPatchingUser32Forwarders : Pos 4, 1 Bit +0x003 SpareBits : Pos 5, 3 Bits +0x004 Mutant : Ptr32 Void +0x008 ImageBaseAddress : Ptr32 Void +0x00c Ldr : Ptr32 _PEB_LDR_DATA +0x010 ProcessParameters : Ptr32 _RTL_USER_PROCESS_PARAMETERS +0x014 SubSystemData : Ptr32 Void +0x018 ProcessHeap : Ptr32 Void +0x01c FastPebLock : Ptr32 _RTL_CRITICAL_SECTION +0x020 AtlThunkSListPtr : Ptr32 Void +0x024 IFEOKey : Ptr32 Void +0x028 CrossProcessFlags : Uint4B +0x028 ProcessInJob : Pos 0, 1 Bit +0x028 ProcessInitializing : Pos 1, 1 Bit +0x028 ProcessUsingVEH : Pos 2, 1 Bit +0x028 ProcessUsingVCH : Pos 3, 1 Bit +0x028 ReservedBits0 : Pos 4, 28 Bits +0x02c KernelCallbackTable : Ptr32 Void +0x02c UserSharedInfoPtr : Ptr32 Void +0x030 SystemReserved : [1] Uint4B +0x034 SpareUlong : Uint4B +0x038 SparePebPtr0 : Uint4B +0x03c TlsExpansionCounter : Uint4B +0x040 TlsBitmap : Ptr32 Void +0x044 TlsBitmapBits : [2] Uint4B +0x04c ReadOnlySharedMemoryBase : Ptr32 Void +0x050 HotpatchInformation : Ptr32 Void +0x054 ReadOnlyStaticServerData : Ptr32 Ptr32 Void +0x058 AnsiCodePageData : Ptr32 Void +0x05c OemCodePageData : Ptr32 Void +0x060 UnicodeCaseTableData : Ptr32 Void +0x064 NumberOfProcessors : Uint4B +0x068 NtGlobalFlag : Uint4B +0x070 CriticalSectionTimeout : _LARGE_INTEGER +0x078 HeapSegmentReserve : Uint4B +0x07c HeapSegmentCommit : Uint4B +0x080 HeapDeCommitTotalFreeThreshold : Uint4B +0x084 HeapDeCommitFreeBlockThreshold : Uint4B +0x088 NumberOfHeaps : Uint4B +0x08c MaximumNumberOfHeaps : Uint4B +0x090 ProcessHeaps : Ptr32 Ptr32 Void +0x094 GdiSharedHandleTable : Ptr32 Void +0x098 ProcessStarterHelper : Ptr32 Void +0x09c GdiDCAttributeList : Uint4B +0x0a0 LoaderLock : Ptr32 _RTL_CRITICAL_SECTION +0x0a4 OSMajorVersion : Uint4B +0x0a8 OSMinorVersion : Uint4B +0x0ac OSBuildNumber : Uint2B +0x0ae OSCSDVersion : Uint2B +0x0b0 OSPlatformId : Uint4B +0x0b4 ImageSubsystem : Uint4B +0x0b8 ImageSubsystemMajorVersion : Uint4B +0x0bc ImageSubsystemMinorVersion : Uint4B +0x0c0 ActiveProcessAffinityMask : Uint4B +0x0c4 GdiHandleBuffer : [34] Uint4B +0x14c PostProcessInitRoutine : Ptr32 void +0x150 TlsExpansionBitmap : Ptr32 Void +0x154 TlsExpansionBitmapBits : [32] Uint4B +0x1d4 SessionId : Uint4B +0x1d8 AppCompatFlags : _ULARGE_INTEGER +0x1e0 AppCompatFlagsUser : _ULARGE_INTEGER +0x1e8 pShimData : Ptr32 Void +0x1ec AppCompatInfo : Ptr32 Void +0x1f0 CSDVersion : _UNICODE_STRING +0x1f8 ActivationContextData : Ptr32 _ACTIVATION_CONTEXT_DATA +0x1fc ProcessAssemblyStorageMap : Ptr32 _ASSEMBLY_STORAGE_MAP +0x200 SystemDefaultActivationContextData : Ptr32 _ACTIVATION_CONTEXT_DATA +0x204 SystemAssemblyStorageMap : Ptr32 _ASSEMBLY_STORAGE_MAP +0x208 MinimumStackCommit : Uint4B +0x20c FlsCallback : Ptr32 _FLS_CALLBACK_INFO +0x210 FlsListHead : _LIST_ENTRY +0x218 FlsBitmap : Ptr32 Void +0x21c FlsBitmapBits : [4] Uint4B +0x22c FlsHighIndex : Uint4B +0x230 WerRegistrationData : Ptr32 Void +0x234 WerShipAssertPtr : Ptr32 Void