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

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