Re: [PATCH v16 05/16] arm64: untag user pointers passed to memory syscalls

From: Catalin Marinas
Date: Mon Jun 10 2019 - 10:33:00 EST

On Mon, Jun 03, 2019 at 06:55:07PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends arm64 kernel ABI to allow to
> pass tagged user pointers (with the top byte set to something else other
> than 0x00) as syscall arguments.
> This patch allows tagged pointers to be passed to the following memory
> syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
> mremap, msync, munlock.
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

I would add in the commit log (and possibly in the code with a comment)
that mremap() and mmap() do not currently accept tagged hint addresses.
Architectures may interpret the hint tag as a background colour for the
corresponding vma. With this:

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>