Requirements for retpoline in Linux 4.15 (was: Re: Linux 4.15)
From: Martin Steigerwald
Date: Mon Jan 29 2018 - 04:47:26 EST
Hi Linus, hi everyone,
Linus Torvalds - 28.01.18, 22:52:
> details), and perhaps equally importantly, to actually get the biggest
> fix for the indirect branch mitigations, you need not just the kernel
> updates, you need to have a compiler with support for the "retpoline"
> indirect branch model.
> You can do
> cat /sys/devices/system/cpu/vulnerabilities/spectre_v2
> and if you don't have a compiler that supports the retpoline
> mitigations, you'll get:
> Vulnerable: Minimal generic ASM retpoline
> because only the assembly code (not the C code) will have the
> retpoline mitigation. So keep that in mind.
% cat /proc/version
Linux version 4.15.0-tp520-btrfstrim+ ([â]) (gcc version 7.3.0 (Debian
7.3.0-1)) #38 SMP PREEMPT Mon Jan 29 09:38:44 CET 2018
% grep RETPO /boot/config-4.15.0-tp520-btrfstrim+
% gcc --version | head -1
gcc (Debian 7.3.0-1) 7.3.0
% apt changelog gcc-7
gcc-7 (7.3.0-1) unstable; urgency=medium
* GCC 7.3.0 release.
* Ignore bootstrap comparison failures in gcc/d on alpha. Addresses:
-- Matthias Klose [â] Thu, 25 Jan 2018 12:07:10 +0100
% grep . /sys/devices/system/cpu/vulnerabilities/*
/sys/devices/system/cpu/vulnerabilities/spectre_v2:Vulnerable: Minimal generic
>From what I read gcc 7.3 was supposed to include back ported retpoline
patches. What am I missing here?