linux-kernel - [PATCH 2/3] x86, ras: Extend machine check recovery code to annotated ring0 areas

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Message-Id: <e916478b9587ef006b30255a7adbee6d84268d7c.1447093568.git.tony.luck@intel.com>
Date:	Fri, 6 Nov 2015 13:01:55 -0800
From:	Tony Luck <tony.luck@...el.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
	x86@...nel.org
Subject: [PATCH 2/3] x86, ras: Extend machine check recovery code to annotated
 ring0 areas

Extend the severity checking code to add a new context IN_KERN_RECOV
which is used to indicate that the machine check was triggered by code
in the kernel with a fixup entry.

Add code to check for this situation and respond by altering the return
IP to the fixup address and changing the regs->ax so that the recovery
code knows the physical address of the error. Note that we also set bit
63 because 0x0 is a legal physical address.

Signed-off-by: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mcheck/mce-severity.c | 19 +++++++++++++++++--
 arch/x86/kernel/cpu/mcheck/mce.c          | 13 ++++++++++---
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-severity.c b/arch/x86/kernel/cpu/mcheck/mce-severity.c
index 9c682c222071..1e83842310e8 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-severity.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-severity.c
@@ -12,6 +12,7 @@
 #include <linux/kernel.h>
 #include <linux/seq_file.h>
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/debugfs.h>
 #include <asm/mce.h>
 
@@ -29,7 +30,7 @@
  * panic situations)
  */
 
-enum context { IN_KERNEL = 1, IN_USER = 2 };
+enum context { IN_KERNEL = 1, IN_USER = 2, IN_KERNEL_RECOV = 3 };
 enum ser { SER_REQUIRED = 1, NO_SER = 2 };
 enum exception { EXCP_CONTEXT = 1, NO_EXCP = 2 };
 
@@ -48,6 +49,7 @@ static struct severity {
 #define MCESEV(s, m, c...) { .sev = MCE_ ## s ## _SEVERITY, .msg = m, ## c }
 #define  KERNEL		.context = IN_KERNEL
 #define  USER		.context = IN_USER
+#define  KERNEL_RECOV	.context = IN_KERNEL_RECOV
 #define  SER		.ser = SER_REQUIRED
 #define  NOSER		.ser = NO_SER
 #define  EXCP		.excp = EXCP_CONTEXT
@@ -87,6 +89,10 @@ static struct severity {
 		EXCP, KERNEL, MCGMASK(MCG_STATUS_RIPV, 0)
 		),
 	MCESEV(
+		PANIC, "In kernel and no restart IP",
+		EXCP, KERNEL_RECOV, MCGMASK(MCG_STATUS_RIPV, 0)
+		),
+	MCESEV(
 		DEFERRED, "Deferred error",
 		NOSER, MASK(MCI_STATUS_UC|MCI_STATUS_DEFERRED|MCI_STATUS_POISON, MCI_STATUS_DEFERRED)
 		),
@@ -123,6 +129,11 @@ static struct severity {
 		MCGMASK(MCG_STATUS_RIPV|MCG_STATUS_EIPV, MCG_STATUS_RIPV)
 		),
 	MCESEV(
+		AR, "Action required: data load error recoverable area of kernel",
+		SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
+		KERNEL_RECOV
+		),
+	MCESEV(
 		AR, "Action required: data load error in a user process",
 		SER, MASK(MCI_STATUS_OVER|MCI_UC_SAR|MCI_ADDR|MCACOD, MCI_UC_SAR|MCI_ADDR|MCACOD_DATA),
 		USER
@@ -183,7 +194,11 @@ static struct severity {
  */
 static int error_context(struct mce *m)
 {
-	return ((m->cs & 3) == 3) ? IN_USER : IN_KERNEL;
+	if ((m->cs & 3) == 3)
+		return IN_USER;
+	if (search_mcexception_tables(m->ip))
+		return IN_KERNEL_RECOV;
+	return IN_KERNEL;
 }
 
 /*
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 9d014b82a124..472d11150b7a 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -31,6 +31,7 @@
 #include <linux/types.h>
 #include <linux/slab.h>
 #include <linux/init.h>
+#include <linux/module.h>
 #include <linux/kmod.h>
 #include <linux/poll.h>
 #include <linux/nmi.h>
@@ -1132,9 +1133,15 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 		if (no_way_out)
 			mce_panic("Fatal machine check on current CPU", &m, msg);
 		if (worst == MCE_AR_SEVERITY) {
-			recover_paddr = m.addr;
-			if (!(m.mcgstatus & MCG_STATUS_RIPV))
-				flags |= MF_MUST_KILL;
+			if ((m.cs & 3) == 3) {
+				recover_paddr = m.addr;
+				if (!(m.mcgstatus & MCG_STATUS_RIPV))
+					flags |= MF_MUST_KILL;
+			} else if (fixup_mcexception(regs)) {
+				regs->ax = BIT(63) | m.addr;
+			} else
+				mce_panic("Failed kernel mode recovery",
+					  &m, NULL);
 		} else if (kill_it) {
 			force_sig(SIGBUS, current);
 		}
-- 
2.1.4

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