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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 68 | daniel-mar | 1 | unit PatchU; |
| 2 | |||
| 3 | interface |
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| 4 | |||
| 5 | type |
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| 6 | pPatchEvent = ^TPatchEvent; |
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| 7 | |||
| 8 | // "Asm" opcode hack to patch an existing routine |
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| 9 | TPatchEvent = packed record |
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| 10 | Jump: Byte; |
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| 11 | Offset: Integer; |
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| 12 | end; |
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| 13 | |||
| 14 | TPatchMethod = class |
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| 15 | private |
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| 16 | PatchedMethod, OriginalMethod: TPatchEvent; |
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| 17 | PatchPositionMethod: pPatchEvent; |
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| 18 | FIsPatched: boolean; |
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| 19 | public |
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| 20 | property IsPatched: boolean read FIsPatched; |
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| 21 | constructor Create(const aSource, aDestination: Pointer); |
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| 22 | destructor Destroy; override; |
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| 23 | procedure Restore; |
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| 24 | procedure Hook; |
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| 25 | end; |
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| 26 | |||
| 27 | implementation |
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| 28 | |||
| 29 | uses |
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| 30 | Windows, Sysutils; |
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| 31 | |||
| 32 | { TPatchMethod } |
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| 33 | |||
| 34 | constructor TPatchMethod.Create(const aSource, aDestination: Pointer); |
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| 35 | var |
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| 36 | OldProtect: Cardinal; |
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| 37 | begin |
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| 38 | PatchPositionMethod := pPatchEvent(aSource); |
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| 39 | OriginalMethod := PatchPositionMethod^; |
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| 40 | PatchedMethod.Jump := $E9; |
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| 41 | PatchedMethod.Offset := Integer(PByte(aDestination)) - Integer(PByte(PatchPositionMethod)) - SizeOf(TPatchEvent); |
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| 42 | |||
| 43 | if not VirtualProtect(PatchPositionMethod, SizeOf(TPatchEvent), PAGE_EXECUTE_READWRITE, OldProtect) then |
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| 44 | RaiseLastOSError; |
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| 45 | |||
| 46 | Hook; |
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| 47 | end; |
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| 48 | |||
| 49 | destructor TPatchMethod.Destroy; |
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| 50 | begin |
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| 51 | Restore; |
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| 52 | inherited; |
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| 53 | end; |
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| 54 | |||
| 55 | procedure TPatchMethod.Hook; |
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| 56 | begin |
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| 57 | if FIsPatched then Exit; |
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| 58 | FIsPatched := true; |
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| 59 | PatchPositionMethod^ := PatchedMethod; |
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| 60 | end; |
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| 61 | |||
| 62 | procedure TPatchMethod.Restore; |
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| 63 | begin |
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| 64 | if not FIsPatched then Exit; |
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| 65 | FIsPatched := false; |
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| 66 | PatchPositionMethod^ := OriginalMethod; |
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| 67 | end; |
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| 68 | |||
| 69 | end. |
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| 70 |