Re: [PATCH RFC v9 2/7] x86/entry: Add STACKLEAK erasing the kernel stack at the end of syscalls

[Peter Zijlstra]

On Mon, Mar 05, 2018 at 11:43:19AM -0800, Laura Abbott wrote:
> On 03/05/2018 08:41 AM, Dave Hansen wrote:
> > On 03/03/2018 12:00 PM, Alexander Popov wrote:
> > >   Documentation/x86/x86_64/mm.txt  |   2 +
> > >   arch/Kconfig                     |  27 ++++++++++
> > >   arch/x86/Kconfig                 |   1 +
> > >   arch/x86/entry/entry_32.S        |  88 +++++++++++++++++++++++++++++++
> > >   arch/x86/entry/entry_64.S        | 108 +++++++++++++++++++++++++++++++++++++++
> > >   arch/x86/entry/entry_64_compat.S |  11 ++++
> > 
> > This is a *lot* of assembly.  I wonder if you tried at all to get more
> > of this into C or whether you just inherited the assembly from the
> > original code?
> > 
> 
> This came up previously http://www.openwall.com/lists/kernel-hardening/2017/10/23/5
> there were concerns about trusting C to do the right thing as well as
> speed.

And therefore the answer to this obvious question should've been part of
the Changelog :-)

Dave is last in a long line of people asking this same question.