On Mon, Feb 11, 2019 at 5:08 PM igor.stoppa@xxxxxxxxx
On Tue, 12 Feb 2019, 4.47 Kees Cook <keescook@xxxxxxxxxxxx wrote:
On Mon, Feb 11, 2019 at 4:37 PM Igor Stoppa <igor.stoppa@xxxxxxxxx> wrote:
On 12/02/2019 02:09, Kees Cook wrote:
On Mon, Feb 11, 2019 at 3:28 PM Igor Stoppa <igor.stoppa@xxxxxxxxx> wrote:
It looked like only the memset() needed architecture support. Is there
a reason for not being able to implement memset() in terms of an
inefficient put_user() loop instead? That would eliminate the need for
per-arch support, yes?
So far, yes, however from previous discussion about power arch, I
understood this implementation would not be so easy to adapt.
Lacking other examples where the extra mapping could be used, I did not
want to add code without a use case.
Probably both arm and x86 32 bit could do, but I would like to first get
to the bitter end with memory protection (the other 2 thirds).
Mostly, I hated having just one arch and I also really wanted to have arm64.
Right, I meant, if you implemented the _memset() case with put_user()
in this version, you could drop the arch-specific _memset() and shrink
the patch series. Then you could also enable this across all the
architectures in one patch. (Would you even need the Kconfig patches,
i.e. won't this "Just Work" on everything with an MMU?)
I had similar thoughts, but this answer  deflated my hopes (if I understood it correctly).
It seems that each arch needs to be massaged in separately.
True, but I think x86_64, x86, arm64, and arm will all be "normal".
power may be that way too, but they always surprise me. :)
Anyway, series looks good, but since nothing uses _memset(), it might
make sense to leave it out and put all the arch-enabling into a single
patch to cover the 4 archs above, in an effort to make the series even