How to check that value stored in register is a valid address in the code segment

Question

I'm writing a small x86 Assembly program on a Windows machine. At one point I want to check if the value stored in the EDX register is a valid address pointing to the code segment of the same program. Can anyone please tell me how and if this can be done?

Answer 1

At the start of your program, put a label like this...

 The_Code_Starts_Here:

At the end of your program, put a label like this...

 The_Code_Ends_Here:

In your section where you want to question the validity of that address, do something like this...

 Cmp    Edx, The_Code_Starts_Here   ; Is it in the code segment ?
 Jb     Bombs_Away                  ; No, bomb out

 Cmp    Edx, The_Code_Ends_Here     ; Is it in the code segment ?
 Jae    Bombs_Away                  ; No, bomb out

                                    ; Else, good stuff, go on

If I screwed up on the Jb and Ja nomenclature, then just switch them.