powerpc/speculation: Support 'mitigations=' cmdline option

Configure powerpc CPU runtime speculation bug mitigations in accordance
with the 'mitigations=' cmdline option.  This affects Meltdown, Spectre
v1, Spectre v2, and Speculative Store Bypass.

The default behavior is unchanged.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
Reviewed-by: Jiri Kosina <jkosina@suse.cz>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tyler Hicks <tyhicks@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Phil Auld <pauld@redhat.com>
Link: https://lkml.kernel.org/r/245a606e1a42a558a310220312d9b6adb9159df6.1555085500.git.jpoimboe@redhat.com
CVE-2017-5715
CVE-2017-5753
CVE-2017-5754
CVE-2018-3639

(backported from commit 782e69efb3dfed6e8360bc612e8c7827a901a8f9 https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git)
[tyhicks: Backport to 4.15:
 - include <linux/cpu.h> from security.c]
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 399f3cca28953a7b7c579d8d70ceb83e993e2e43..4f1a3b3f87fd825d879f7b0e0f09eff84831b8a4 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2424,7 +2424,7 @@
                        http://repo.or.cz/w/linux-2.6/mini2440.git
 
        mitigations=
-                       [X86] Control optional mitigations for CPU
+                       [X86,PPC] Control optional mitigations for CPU
                        vulnerabilities.  This is a set of curated,
                        arch-independent options, each of which is an
                        aggregation of existing arch-specific options.
@@ -2433,10 +2433,11 @@
                                Disable all optional CPU mitigations.  This
                                improves system performance, but it may also
                                expose users to several CPU vulnerabilities.
-                               Equivalent to: nopti [X86]
-                                              nospectre_v2 [X86]
+                               Equivalent to: nopti [X86,PPC]
+                                              nospectre_v1 [PPC]
+                                              nospectre_v2 [X86,PPC]
                                               spectre_v2_user=off [X86]
-                                              spec_store_bypass_disable=off [X86]
+                                              spec_store_bypass_disable=off [X86,PPC]
                                               l1tf=off [X86]
 
                        auto (default)

diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index 1341325599a7ac10818b04a0a0623db76b8a14d3..70568ccbd9fd5eae17014473aa415d9b472b7d86 100644 (file)
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -4,6 +4,7 @@
 //
 // Copyright 2018, Michael Ellerman, IBM Corporation.
 
+#include <linux/cpu.h>
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/seq_buf.h>
@@ -56,7 +57,7 @@ void setup_barrier_nospec(void)
        enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
                 security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
 
-       if (!no_nospec)
+       if (!no_nospec && !cpu_mitigations_off())
                enable_barrier_nospec(enable);
 }
 
@@ -115,7 +116,7 @@ static int __init handle_nospectre_v2(char *p)
 early_param("nospectre_v2", handle_nospectre_v2);
 void setup_spectre_v2(void)
 {
-       if (no_spectrev2)
+       if (no_spectrev2 || cpu_mitigations_off())
                do_btb_flush_fixups();
        else
                btb_flush_enabled = true;
@@ -299,7 +300,7 @@ void setup_stf_barrier(void)
 
        stf_enabled_flush_types = type;
 
-       if (!no_stf_barrier)
+       if (!no_stf_barrier && !cpu_mitigations_off())
                stf_barrier_enable(enable);
 }
 

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index 78a71b4fd646f59d116ba1e80f150ebdc7fdb359..fe30b2d8e280fb60c24507c2208875b6e75068f4 100644 (file)
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -900,7 +900,7 @@ void setup_rfi_flush(enum l1d_flush_type types, bool enable)
 
        enabled_flush_types = types;
 
-       if (!no_rfi_flush)
+       if (!no_rfi_flush && !cpu_mitigations_off())
                rfi_flush_enable(enable);
 }