[fasmg] Problem reading "byte" from "byte [imm]" in match

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alorent

Joined: 05 Dec 2005
Posts: 221

alorent 02 May 2023, 22:41

Hi,

I'm creating a macro for arm64 under fasmg like:

Code:

load x2, byte [0x11223344]

which should generate something like:

Code:

db 0xff, 0xff, 0xff
db (2 shl 5) | 1     ; 2 from x2 and last "1" from "[b]byte[/b] [mem"]

This is the current macro that I have. Most of the work from is not mine!

Code:

macro load a*, type_mem

    local size
    local address
    
    size=1
    address=0

    match = type [mem_addr], type_mem
   
        if type eq 'byte'
            size = 1
        else if type eq 'word'
            size = 2
        else if type eq 'dword'
            size = 3
        else if type eq 'qword'
            size = 4
        else 
            err 'invalid address prefix'
        end if 

        address=mem_addr
   
    end match

    aarch64.parse_operand @op0, a

    if (@op0.type and @type_xn_xsp) 
        
        db 0xFF, 0xFF, 0xFF 
        db 00 + (@op0.data shl 5) + size
        
        dd address

    end if

end macro

The problem is that I always get "invalid address prefix". It looks that the "type" variable is not loaded from "match = type [mem_addr], type_mem"

I'm a total noob in FASM macros Sad

Any help appreciated.

Thanks!

02 May 2023, 22:41

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8367
Location: Kraków, Poland

Tomasz Grysztar 03 May 2023, 07:28

To compare something to a quoted string, make it into such string, too:

Code:

        if `type eq 'byte'
            size = 1
        else if `type eq 'word'
            size = 2
        else if `type eq 'dword'
            size = 3
        else if `type eq 'qword'
            size = 4
        else 
            err 'invalid address prefix'
        end if

But I would recommend to use MATCH for everything, since EQ is more for computed values:

Code:

    match type [mem_addr], type_mem
   
        match =byte, type
            size = 1
        else match =word, type
            size = 2
        else match =dword, type
            size = 3
        else match =qword, type
            size = 4
        else 
            err 'invalid address prefix'
        end match

        address=mem_addr
   
    end match

Also "= " in your original MATCH seems completely unnecessary, it matches the space that you have after the comma, but this whitespace would be stripped anyway (the wildcard parameters need to be matched with non-whitespace tokens).

03 May 2023, 07:28

alorent

Joined: 05 Dec 2005
Posts: 221

alorent 03 May 2023, 09:01

Excellent Tomasz! This is better support than even big companies! Very Happy

Thanks a lot!

03 May 2023, 09:01

FlierMate2

Joined: 21 Mar 2023
Posts: 39

FlierMate2 03 May 2023, 13:08

alorent wrote:

This is better support than even big companies!

I agree 100%, Tomasz as maintainer for FASM and FASMG for over 20 years! And Tomasz and revolution always stand by on forum and on Discord server, giving prompt reply with answer.

03 May 2023, 13:08

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20516
Location: In your JS exploiting you and your system

revolution 03 May 2023, 13:13

I am not on any Discord server. If there is someone there named revolution then it isn't me.

03 May 2023, 13:13

FlierMate2

Joined: 21 Mar 2023
Posts: 39

FlierMate2 03 May 2023, 13:22

revolution wrote:

I am not on any Discord server. If there is someone there named revolution then it isn't me.

Oh I see! Thanks for your correction.

I thought "StaticSaga" is you.

03 May 2023, 13:22

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