64 bit calling convention

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cl0ckw0rkz14

Joined: 18 Feb 2014
Posts: 21

cl0ckw0rkz14 08 Jul 2014, 12:47

Hi,

Is it the calling function's responsibility to free the 32 bytes of 'shadow' space after the called function returns? I assumed yes because I disassembled some code from mingw and all the functions seemed to end with RET not RET 32. However, I have some programs ported from Linux that crash when I do ADD RSP, 32 after a function returns. Just wanted to rule out the possibility I've misunderstood something?

Thanks

08 Jul 2014, 12:47

tthsqe

Joined: 20 May 2009
Posts: 767

tthsqe 08 Jul 2014, 13:04

the shadow space in not necessarly only 32 bytes. If more than 4 integer arguments are passed to the function, then the shadow space is bigger. This is probably the source of your crash.

08 Jul 2014, 13:04

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20448
Location: In your JS exploiting you and your system

revolution 08 Jul 2014, 14:41

cl0ckw0rkz14 wrote:

Is it the calling function's responsibility to free the [...] 'shadow' space after the called function returns?

Yes.

08 Jul 2014, 14:41

cl0ckw0rkz14

Joined: 18 Feb 2014
Posts: 21

cl0ckw0rkz14 09 Jul 2014, 05:43

Thanks I have it working now. Smile

09 Jul 2014, 05:43

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