From: Martin Schwidefsky <schwidefsky@de.ibm.com>
Date: Fri, 27 Apr 2018 05:36:54 +0000 (+0200)
Subject: s390: report spectre mitigation via syslog
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=4a51204f8b38e5533d0abf110dc922210b2b5f62;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git

s390: report spectre mitigation via syslog

[ Upstream commit bc035599718412cfba9249aa713f90ef13f13ee9 ]

Add a boot message if either of the spectre defenses is active.
The message is
    "Spectre V2 mitigation: execute trampolines."
or  "Spectre V2 mitigation: limited branch prediction."

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index daa36a38a8b7..7387ebace891 100644
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -33,6 +33,16 @@ static int __init nospec_setup_early(char *str)
 }
 early_param("nospec", nospec_setup_early);
 
+static int __init nospec_report(void)
+{
+	if (IS_ENABLED(CC_USING_EXPOLINE) && !nospec_disable)
+		pr_info("Spectre V2 mitigation: execute trampolines.\n");
+	if (__test_facility(82, S390_lowcore.alt_stfle_fac_list))
+		pr_info("Spectre V2 mitigation: limited branch prediction.\n");
+	return 0;
+}
+arch_initcall(nospec_report);
+
 #ifdef CONFIG_EXPOLINE
 
 int nospec_disable = IS_ENABLED(CONFIG_EXPOLINE_OFF);