Re: [RFC PATCH v9 05/27] x86/cet/shstk: Add Kconfig option for user-mode Shadow Stack protection

Andy Lutomirski
2020-02-27T03:57:10Z

> On Feb 26, 2020, at 6:11 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>
> ﻿On Wed, Feb 26, 2020 at 5:16 PM Dave Hansen <dave.hansen@intel.com> wrote:
>>
>> On 2/26/20 5:02 PM, H.J. Lu wrote:
>>>> That way everybody with old toolchains can still build the kernel (and
>>>> run/test code with your config option on, btw...).
>>> CET requires a complete new OS image from kernel, toolchain, run-time.
>>> CET enabled kernel without the rest of updated OS won't give you CET
>>> at all.
>>
>> If you require a new toolchain, nobody even builds your fancy feature.
>> Probably including 0day and all of the lazy maintainers with crufty old
>> distros.
>
> GCC 8 or above is needed since vDSO must be compiled with
> --fcf-protection=branch.

Fair enough. I don’t particularly want to carry a gross hack to add the ENDBRANCHes without compiler support.