What is mean ? proc Main c audioMaster

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Roman

Joined: 21 Apr 2012
Posts: 1823

Roman 12 Oct 2022, 06:15

Fasmw 1.73
I found example, compile ok for 64 bits.

Code:

proc Main c audioMaster 
ret
endp

But what is c ?
I expected audioMaster is stack 8 bytes.

12 Oct 2022, 06:15

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20423
Location: In your JS exploiting you and your system

revolution 12 Oct 2022, 06:51

You can see the code in proc32.inc

Code:

;...
macro epiloguedef procname,flag,parmbytes,localbytes,reglist
 { irps reg, reglist \{ reverse pop reg \}
   if parmbytes | localbytes
    leave
   end if
   if flag and 10000b
    retn
   else
    retn parmbytes
   end if }

close@proc equ

macro define@proc name,statement
 { local params,flag,regs,parmbytes,localbytes,current
   if used name
   name:
   match =stdcall args, statement \{ params equ args
                                     flag = 11b \}
   match =stdcall, statement \{ params equ
                                flag = 11b \}
   match =c args, statement \{ params equ args
                               flag = 10001b \}
   match =c, statement \{ params equ
                          flag = 10001b \}
;...

c uses ccall semantics.

You can also do ...

Code:

proc Main stdcall audioMaster 
ret
endp

... and have stdcall semantics.

stdcall is the default if you don't have the specifier..

Code:

proc Main audioMaster 
ret
endp

Last edited by revolution on 12 Oct 2022, 07:04; edited 1 time in total

12 Oct 2022, 06:51

ProMiNick

Joined: 24 Mar 2012
Posts: 802
Location: Russian Federation, Sochi

ProMiNick 12 Oct 2022, 07:01

There is no C-calling convention for x64.
only fastcall calling convention. keyword C is ignored.
fastcall calling conventions only varies according to OS (windows:shadowregs, params via rcx,rdx,r8,r9,stack(stack cleared by callee) or linux:redzone , params via rdi,rsi,rcx,rdx,r8,r9, stack(stack cleared by caller))

12 Oct 2022, 07:01

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20423
Location: In your JS exploiting you and your system

revolution 12 Oct 2022, 08:21

I missed the 64-bit part.

In proc64.inc the same flag parameter is defined in define@proc but the epilogue ignores it. So it makes no difference in 64-bit mode, the binary code output will be exactly the same.

Code:

macro epiloguedef procname,flag,parmbytes,localbytes,reglist
 { irps reg, reglist \{ reverse pop reg \}
   leave
   retn }

12 Oct 2022, 08:21

macomics

Joined: 26 Jan 2021
Posts: 1014
Location: Russia

macomics 12 Oct 2022, 13:12

revolution wrote:

Code:

macro epiloguedef procname,flag,parmbytes,localbytes,reglist
 { irps reg, reglist \{ reverse pop reg \}
   leave
   retn }

Isn't it better to restore registers after leave. Accordingly, and save until enter. Otherwise, in case of a failure of the rsp value, garbage will be restored in the registers! At a minimum, it is necessary to reset the rsp value before irps.

12 Oct 2022, 13:12

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