Re: [PATCH v12 1/8] x86/cet/ibt: Add Kconfig option for user-mode Indirect Branch Tracking

From: Dave Hansen
Date: Mon Sep 21 2020 - 18:41:52 EST

On 9/21/20 3:30 PM, Yu, Yu-cheng wrote:
> + prompt "Intel Indirect Branch Tracking for user-mode"

Take the "Intel " and "INTEL_" out, please. It will only cause us all
pain later if some of our x86 compatriots decide to implement this.

> If the kernel is to be used only on older systems that do not support
> IBT, and the size of the binary is important, you can save 900 KB by
> disabling this feature.
> Otherwise, if unsure, say Y.

900k seems like a *lot*. Where the heck does that come from?

Also, comments like that don't age very well. Consider:

Support for this feature is only known to be present on Intel
processors released in 2020 or later. This feature is also
known to increase kernel text size substantially.

If unsure, say N.

The 900KB is probably wrong today in a lot of configurations, and will;
only get *more* wrong over time.