Re: [PATCH] Syscall arguments are unsigned long (full registers)

[Andi Kleen <ak-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

On Mon, Jul 04, 2016 at 01:52:58PM +0000, Tautschnig, Michael wrote:
> All syscall arguments are passed in as types of the same byte size as
> unsigned long (width of full registers). Using a smaller type without a
> cast may result in losing bits of information. In all other instances
> apart from the ones fixed by the patch the code explicitly introduces
> type casts (using, e.g., SYSCALL_DEFINE1).
> 
> While goto-cc reported these problems at build time, it is noteworthy
> that the calling conventions specified in the System V AMD64 ABI do
> ensure that parameters 1-6 are passed via registers, thus there is no
> implied risk of misaligned stack access.

Does this actually fix anything?

It seems a big dangerous to me, potentially breaking some existing
binaries that rely on these arguments being truncated.

-Andi