OSKRNL中的奇怪指令

  在NTOSKRNL中的函数里经常看到这个奇怪的指令
mov edi, edi
之所以奇怪是因为很多函数的第一条指令就是它。

有两个问题：
这是用什么编译器生成的？
这有什么用？或者说为什么要在开头生成这样的指令？

哪位能说说？

it is generated by visual C/C++ compiler
A 2 bytes nop for hotpatch (a near jmp)

great

引用第1楼Odyssey于2007-04-02 12:27发表的“”:
it is generated by visual C/C++ compiler
A 2 bytes nop for hotpatch (a near jmp)

需要什么选项吗？
我用VC6和VS2005都生成不了这样的代码

WIN2000DDK和VISTA DDK也生成不了

Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 14.00.50727.42 for 80x86
Copyright (C) Microsoft Corporation.  All rights reserved.

                         C/C++ COMPILER OPTIONS


                              -OPTIMIZATION-

/O1 minimize space                      /O2 maximize speed
/Ob<n> inline expansion (default n=0)   /Od disable optimizations (default)
/Og enable global optimization          /Oi[-] enable intrinsic functions
/Os favor code space                    /Ot favor code speed
/Ox maximum optimizations               /Oy[-] enable frame pointer omission

                             -CODE GENERATION-

/GF enable read-only string pooling     /Gm[-] enable minimal rebuild
/Gy[-] separate functions for linker    /GS[-] enable security checks
/GR[-] enable C++ RTTI                  /GX[-] enable C++ EH (same as /EHsc)
/EHs enable C++ EH (no SEH exceptions)  /EHa enable C++ EH (w/ SEH exceptions)
/EHc extern "C" defaults to nothrow
/fp:<except[-]|fast|precise|strict> choose floating-point model:
    except[-] - consider floating-point exceptions when generating code
    fast - "fast" floating-point model; results are less predictable
(press <return> to continue)
    precise - "precise" floating-point model; results are predictable
    strict - "strict" floating-point model (implies /fp:except)
/GL[-] enable link-time code generation /GA optimize for Windows Application
/Ge force stack checking for all funcs  /Gs[num] control stack checking calls
/Gh enable _penter function call        /GH enable _pexit function call
/GT generate fiber-safe TLS accesses    /RTC1 Enable fast checks (/RTCsu)
/RTCc Convert to smaller type checks    /RTCs Stack Frame runtime checking
/RTCu Uninitialized local usage checks
/clr[:option] compile for common language runtime, where option is:
    pure - produce IL-only output file (no native executable code)
    safe - produce IL-only verifiable output file
    oldSyntax - accept the Managed Extensions syntax from Visual C++ 2002/2003
    initialAppDomain - enable initial AppDomain behavior of Visual C++ 2002
    noAssembly - do not produce an assembly
/Gd __cdecl calling convention          /Gr __fastcall calling convention
/Gz __stdcall calling convention        /GZ Enable stack checks (/RTCs)
/QIfist[-] use FIST instead of ftol()
/hotpatch ensure function padding for hotpatchable images
/arch:<SSE|SSE2> minimum CPU architecture requirements, one of:
    SSE - enable use of instructions available with SSE enabled CPUs
    SSE2 - enable use of instructions available with SSE2 enabled CPUs

                              -OUTPUT FILES-

(press <return> to continue)

maybe you can use /hotpatch switch.  

花指令,相当于NOP

感谢感谢