IDA Pro编辑功能（Edit Function）

Action name:EditFunction

Here you can change function bounds,its name and flags.In order to change only the function end address,you can use FunctionEnd command.

If the current address does not belong to any function,IDA beeps.

This command allows you to change the function frame parameters too.You can change sizes of some parts of frame structure.

IDA considers the stack as the following structure:

+------------------------------+

|function arguments|

+------------------------------+

|return address|

+------------------------------+

|saved registers(SI,DI,etc)|

+------------------------------+<-BP

|local variables|

+------------------------------+<-SP

For some processors or functions,BP may be equal to SP.In other words,it can point to the bottom of the stack frame.

You may specify the number of bytes in each part of the stack frame.The size of the return address is calculated by IDA(possibly depending on the far function flag).

"Purged bytes"specifies the number of bytes added to SP upon function return.This value will be used to calculate the SP changes at call sites(used in some calling conventions,such as __stdcall in Windows 32-bit programs.)

"BP based frame"allows IDA to automatically convert[BP+xxx]operands to stack variables.

"BP equal to SP"means that the frame pointer points to the bottom of the stack.It is usually used for the processors which set up the stack frame with EBP and ESP both pointing to the bottom of the frame(for example MC6816,M32R).

If you presseven without changing any parameter,IDA will reanalyze the function.

Sometimes,EBP points to the middle of the stack frame.FPD(frame pointer delta)is used to handle such situations.FPD is the value substracted from the EBP before accessing variables.An example:

push ebp

lea ebp,[esp-78h]

sub esp,588h

push ebx

push esi

lea eax,[ebp+74h]

+------------------------------+

|function arguments|

+------------------------------+

|return address|

+------------------------------+

|saved registers(SI,DI,etc)|

+------------------------------+<-typical BP

||

||

||<-actual BP

|local variables|

||

||

||

+------------------------------+<-SP

In our example,the saved registers area is empty(since EBP has been initialized before saving EBX and ESI).The difference between the'typical BP'and'actual BP'is 0x78 and this is the value of FPD.

After specifying FPD=0x78 the last instruction of the example becomes

lea eax,[ebp+78h+var_4]

where var_4=-4

Most of the time,IDA calculates the FPD value automatically.If it fails,the user can specify the value manually.

If the value of the stack pointer is modified in an unpredictable way,(e.g."and esp,-16"),then IDA marks the function as"fuzzy-sp".

If this command is invoked for an imported function,then a simplified dialog box will appear on the screen.

以下为中文翻译：

Action name:EditFunction

这里您可以更改函数边界、其名称和标志。为了只更改函数结束地址，您可以使用FunctionEnd

命令。

如果当前地址不属于任何函数，IDA发出嘟嘟声。

此命令也允许您更改函数框架参数。您可以更改框架结构的某些部分的大小。

IDA将堆栈视为以下结构：+-------------------------------+|函数参数|+-------------------------------+|返回地址|+-----------------------------------+|保存的寄存器（SI、DI等）

|

+-------------------------------+<-

BP|局部变量|+-----------------------------------+<-SP

对于某些处理器或函数，BP可能等于SP。换句话说，它可以指向堆栈帧的底部。

您可以指定堆栈帧每个部分的字节数。返回地址的大小由IDA计算（可能取决于远函数标志）。

“清除的字节”指定函数返回时添加到SP的字节数。此值将用于计算调用站点的SP更改（用于某些调用约定，如Windows 32位程序中的__stdcall）。

“基于BP的帧”允许IDA自动将[BP+xxx]操作变量转换

为堆栈变量。

“BP等于SP”意味着帧指针指向堆栈的底部。它通常用于设置堆栈帧的处理器，其中EBP和ESP都指向帧的底部（例如MC6816、M32R）。

如果您在不更改任何参数的情况下按，IDA将重新分析函数。

有时，EBP指向堆栈帧的中间。PD（帧指针delta）用于处理此类情况。PD是在访问变量之前从EBP减去的值。

例如：push EBP

lea EBP，[esp-78h]

sub esp，588h

push ebx

push esi

lea eax，[ebp+74h]+-------------------------------+

|

函数参数|+-------------------------------+|返回地址|+-----------------------------------+|保存的寄存器（SI、DI等）|+---------------------------------

+<-典型BP|||||<-实际BP|局部变量||||||+------------------------------+<-SPI-

在我们的示例中，保存的寄存器区域是空的（因为在保存EBX和ESI之前已经初始化了EBP）。“典型BP”和“实际BP”之间的差值为0x78，这是FPD的值。

指定FPD=0x78后，示例的最后一条指令变为lea-eax，[ebp+78h+var_4]，

其中var_4=-4

大多数时间，IDA自动计算FPD值。如果失败，用户可以手动指定值。

如果堆栈指针的值以不可预测的方式修改（例如“and esp，-16”），则IDA将该函数标记为“fuzzy-sp”。

如果为导入的函数调用此命令，则屏幕上将显示

一个简化的对话框。