From 01c9b17bf673b05bb401b76ec763e9730ccf1376 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 5 Jan 2018 09:44:36 -0800 Subject: x86/Documentation: Add PTI description Add some details about how PTI works, what some of the downsides are, and how to debug it when things go wrong. Also document the kernel parameter: 'pti/nopti'. Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Reviewed-by: Randy Dunlap Reviewed-by: Kees Cook Cc: Moritz Lipp Cc: Daniel Gruss Cc: Michael Schwarz Cc: Richard Fellner Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Hugh Dickins Cc: Andi Lutomirsky Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180105174436.1BC6FA2B@viggo.jf.intel.com --- Documentation/admin-guide/kernel-parameters.txt | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 520fdec..9059917 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2685,8 +2685,6 @@ steal time is computed, but won't influence scheduler behaviour - nopti [X86-64] Disable kernel page table isolation - nolapic [X86-32,APIC] Do not enable or use the local APIC. nolapic_timer [X86-32,APIC] Do not use the local APIC timer. @@ -3255,11 +3253,20 @@ pt. [PARIDE] See Documentation/blockdev/paride.txt. - pti= [X86_64] - Control user/kernel address space isolation: - on - enable - off - disable - auto - default setting + pti= [X86_64] Control Page Table Isolation of user and + kernel address spaces. Disabling this feature + removes hardening, but improves performance of + system calls and interrupts. + + on - unconditionally enable + off - unconditionally disable + auto - kernel detects whether your CPU model is + vulnerable to issues that PTI mitigates + + Not specifying this option is equivalent to pti=auto. + + nopti [X86_64] + Equivalent to pti=off pty.legacy_count= [KNL] Number of legacy pty's. Overwrites compiled-in -- cgit v1.1