On 05.03.2018 23:25, Peter Zijlstra wrote: > 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.
Yes, actually the changelog in the cover letter contains that: After some experiments, kept the asm implementation of erase_kstack(), because it gives a full control over the stack for clearing it neatly and doesn't offend KASAN. Moreover, later erase_kstack() on x86_64 became different from one on x86_32. Best regards, Alexander
