linux-kernel - [V3 PATCH 4/4] x86/apic: Introduce noextnmi boot option

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 06 Aug 2015 14:45:43 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	Jonathan Corbet <corbet@....net>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-doc@...r.kernel.org, x86@...nel.org,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Michal Hocko <mhocko@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: [V3 PATCH 4/4] x86/apic: Introduce noextnmi boot option

This patch introduces new boot option "noextnmi" which disables
external NMI.  This option is useful for the dump capture kernel
so that an HA application or administrator wouldn't mistakenly
shoot down the kernel by NMI.

Currently, only x86 supports this option.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Jonathan Corbet <corbet@....net>
---
 Documentation/kernel-parameters.txt |    4 ++++
 arch/x86/kernel/apic/apic.c         |   17 ++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 1d6f045..2cbd40b 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2364,6 +2364,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			noexec=on: enable non-executable mappings (default)
 			noexec=off: disable non-executable mappings
 
+	noextnmi	[X86]
+			Mask external NMI.  This option is useful for a
+			dump capture kernel to be shot down by NMI.
+
 	nosmap		[X86]
 			Disable SMAP (Supervisor Mode Access Prevention)
 			even if it is supported by processor.
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index dcb5285..a140410 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -82,6 +82,12 @@
 static unsigned int disabled_cpu_apicid __read_mostly = BAD_APICID;
 
 /*
+ * Don't enable external NMI via LINT1 on BSP.  This is useful for
+ * the dump capture kernel.
+ */
+static bool apic_noextnmi;
+
+/*
  * Map cpu index to physical APIC ID
  */
 DEFINE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid, BAD_APICID);
@@ -1150,6 +1156,8 @@ void __init init_bsp_APIC(void)
 	value = APIC_DM_NMI;
 	if (!lapic_is_integrated())		/* 82489DX */
 		value |= APIC_LVT_LEVEL_TRIGGER;
+	if (apic_noextnmi)
+		value |= APIC_LVT_MASKED;
 	apic_write(APIC_LVT1, value);
 }
 
@@ -1369,7 +1377,7 @@ void setup_local_APIC(void)
 	/*
 	 * only the BP should see the LINT1 NMI signal, obviously.
 	 */
-	if (!cpu)
+	if (!cpu && !apic_noextnmi)
 		value = APIC_DM_NMI;
 	else
 		value = APIC_DM_NMI | APIC_LVT_MASKED;
@@ -2537,3 +2545,10 @@ static int __init apic_set_disabled_cpu_apicid(char *arg)
 	return 0;
 }
 early_param("disable_cpu_apicid", apic_set_disabled_cpu_apicid);
+
+static int __init apic_set_noextnmi(char *arg)
+{
+	apic_noextnmi = true;
+	return 0;
+}
+early_param("noextnmi", apic_set_noextnmi);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/