Is it possible to detect label type (code or data)?

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seapoint

Joined: 25 May 2013
Posts: 8

seapoint 31 May 2013, 08:59

Code:

macro check l* {
if l is label pointing to code
something
else if l is label pointing to data
something2
end if
}

codelabel:
stillacodelabel:
mov eax, eax ;instruction

datalabel:
db 0 ;everything that is not a instruction, d*, r*, ...

So: a label is a code-label if it points to x86/amd64 instruction (generated by other macros possibly), it's a data-label otherwise.

My guess is, it's not possible, so I'm going to write a limited version in python, but with fasm macros you really never know Smile

31 May 2013, 08:59

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20343
Location: In your JS exploiting you and your system

revolution 31 May 2013, 09:21

When you use a colon (:) to define the label there is no type attached to the label. So in your example there is no way to know just from the label name whether the following lines are data or instructions.

If you use a data definition to define a label then it might be possible, although I haven't thought about how yet:

Code:

datalabel db 0 ;define datalabel without using a colon and the type "byte" is now part of the label

31 May 2013, 09:21

cod3b453

Joined: 25 Aug 2004
Posts: 618

cod3b453 31 May 2013, 16:13

You can override the dx's with struc's to define an internal marker:

Code:

struc db [x]
{
 common
        .__isdata = 1
 forward
       db x
}

macro isData id
{
        if defined id#.__isdata
                display 'DATA',0x0D,0x0A
        else
                display 'CODE?',0x0D,0x0A
        end if
}

test0:
xor eax,eax

test1 db 'blah',0,'blah'
test2:
db 'blah',0,'blah'

isData test0
isData test1
isData test2

Another option is to tag memory ranges and compare the address but this only works if data and code are separate. The fundamental problem is code is data Laughing

31 May 2013, 16:13

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