# Re: Buggy commit tracked to: "Re: \[PATCH 2/9\] iov\_iter: move rw\_copy\_check\_uvector() into lib/iov\_iter.c"

- From: Al Viro \<viro@zeniv.linux.org.uk\>
- Date: 2020-10-22 20:09:32 
- List: netdev
- Page: https://ratatoskr.run/netdev/2020/10/191050
- Thread: https://ratatoskr.run/linux-arm-kernel/2020/10/191046/t.md

```text
On Thu, Oct 22, 2020 at 09:06:29PM +0100, Al Viro wrote:
> On Thu, Oct 22, 2020 at 08:24:58PM +0100, Al Viro wrote:
> 
> > Depending upon the calling conventions, compiler might do truncation in caller or
> > in a callee, but it must be done _somewhere_.
> 
> Unless I'm misreading AAPCS64,
> 	"Unlike in the 32-bit AAPCS, named integral values must be narrowed by the callee
> 	 rather than the caller"
> in 6.4.2 means that callee must not _not_ expect the upper 32 bits of %x0..%x7 to contain

Sorry, artefact of editing - that's

"in 6.4.2 means that callee must _not_ expect the upper 32 bits of %x0..%x7 to contain"

obviously.
```