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]
Message-ID: <170673568564.398.16843749348991010106.tip-bot2@tip-bot2>
Date: Wed, 31 Jan 2024 21:14:45 -0000
From: "tip-bot2 for H. Peter Anvin (Intel)" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "H. Peter Anvin (Intel)" <hpa@...or.com>, Xin Li <xin3.li@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Shan Kang <shan.kang@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fred] x86/fred: Add a NMI entry stub for FRED

The following commit has been merged into the x86/fred branch of tip:

Commit-ID:     f8b8ee45f82b681606d288bcec89c9071b4079fc
Gitweb:        https://git.kernel.org/tip/f8b8ee45f82b681606d288bcec89c9071b4079fc
Author:        H. Peter Anvin (Intel) <hpa@...or.com>
AuthorDate:    Fri, 15 Dec 2023 22:31:39 -08:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Wed, 31 Jan 2024 22:02:20 +01:00

x86/fred: Add a NMI entry stub for FRED

On a FRED system, NMIs nest both with themselves and faults, transient
information is saved into the stack frame, and NMI unblocking only
happens when the stack frame indicates that so should happen.

Thus, the NMI entry stub for FRED is really quite small...

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Tested-by: Shan Kang <shan.kang@...el.com>
Link: https://lore.kernel.org/r/20231216063139.25567-1-xin3.li@intel.com
---
 arch/x86/kernel/nmi.c | 42 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 17e955a..3130a66 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -35,6 +35,7 @@
 #include <asm/nospec-branch.h>
 #include <asm/microcode.h>
 #include <asm/sev.h>
+#include <asm/fred.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nmi.h>
@@ -651,6 +652,47 @@ void nmi_backtrace_stall_check(const struct cpumask *btp)
 
 #endif
 
+#ifdef CONFIG_X86_FRED
+/*
+ * With FRED, CR2/DR6 is pushed to #PF/#DB stack frame during FRED
+ * event delivery, i.e., there is no problem of transient states.
+ * And NMI unblocking only happens when the stack frame indicates
+ * that so should happen.
+ *
+ * Thus, the NMI entry stub for FRED is really straightforward and
+ * as simple as most exception handlers. As such, #DB is allowed
+ * during NMI handling.
+ */
+DEFINE_FREDENTRY_NMI(exc_nmi)
+{
+	irqentry_state_t irq_state;
+
+	if (arch_cpu_is_offline(smp_processor_id())) {
+		if (microcode_nmi_handler_enabled())
+			microcode_offline_nmi_handler();
+		return;
+	}
+
+	/*
+	 * Save CR2 for eventual restore to cover the case where the NMI
+	 * hits the VMENTER/VMEXIT region where guest CR2 is life. This
+	 * prevents guest state corruption in case that the NMI handler
+	 * takes a page fault.
+	 */
+	this_cpu_write(nmi_cr2, read_cr2());
+
+	irq_state = irqentry_nmi_enter(regs);
+
+	inc_irq_stat(__nmi_count);
+	default_do_nmi(regs);
+
+	irqentry_nmi_exit(regs, irq_state);
+
+	if (unlikely(this_cpu_read(nmi_cr2) != read_cr2()))
+		write_cr2(this_cpu_read(nmi_cr2));
+}
+#endif
+
 void stop_nmi(void)
 {
 	ignore_nmis++;

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ