.SETFRAME

Article
06/05/2017

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The latest version of this topic can be found at .SETFRAME.

Fills in the frame register field and offset in the unwind information using the specified register (reg) and offset (offset). The offset must be a multiple of 16 and less than or equal to 240. This directive also generates a UWOP_SET_FPREG unwind code entry for the specified register using the current prologue offset.

Syntax

.SETFRAME reg, offset

Remarks

.SETFRAME allows ml64.exe users to specify how a frame function unwinds, and is only allowed within the prologue, which extends from the PROC FRAME declaration to the .ENDPROLOG directive. These directives do not generate code; they only generate .xdata and .pdata. .SETFRAME should be preceded by instructions that actually implement the actions to be unwound. It is a good practice to wrap both the unwind directives and the code they are meant to unwind in a macro to ensure agreement.

For more information, see MASM for x64 (ml64.exe).

Sample

Description

The following sample shows how to use a frame pointer:

Code

; ml64 frmex2.asm /link /entry:frmex2 /SUBSYSTEM:CONSOLE  
_text SEGMENT  
frmex2 PROC FRAME  
   push rbp  
.pushreg rbp  
   sub rsp, 010h  
.allocstack 010h  
   mov rbp, rsp  
.setframe rbp, 0  
.endprolog  
   ; modify the stack pointer outside of the prologue (similar to alloca)  
   sub rsp, 060h  
  
   ; we can unwind from the following AV because of the frame pointer     
   mov rax, 0  
   mov rax, [rax] ; AV!  
  
   add rsp, 060h  
   add rsp, 010h  
   pop rbp  
   ret  
frmex2 ENDP  
_text ENDS  
END

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