linux-kernel - [PATCH 4/6] RTC/i.MX/DryIce: monitor a security violation at runtime

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Date:	Mon, 27 Apr 2015 15:59:50 +0200
From:	Juergen Borleis <jbe@...gutronix.de>
To:	linux-kernel@...r.kernel.org
Cc:	rtc-linux@...glegroups.com, kernel@...gutronix.de,
	Alessandro Zummo <a.zummo@...ertech.it>,
	linux-arm-kernel@...ts.infradead.org,
	Robert Schwebel <rsc@...gutronix.de>
Subject: [PATCH 4/6] RTC/i.MX/DryIce: monitor a security violation at runtime

Maybe the unit enters the hardware related state at runtime and not at
system boot time (after a power cycle).

Signed-off-by: Juergen Borleis <jbe@...gutronix.de>
Signed-off-by: Robert Schwebel <rsc@...gutronix.de>
[rsc: got NDA clearance from Freescale]
---
 drivers/rtc/rtc-imxdi.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-imxdi.c b/drivers/rtc/rtc-imxdi.c
index f0c8319..8890a62 100644
--- a/drivers/rtc/rtc-imxdi.c
+++ b/drivers/rtc/rtc-imxdi.c
@@ -665,6 +665,25 @@ static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
 	irqreturn_t rc = IRQ_NONE;
 
 	dier = readl(imxdi->ioaddr + DIER);
+	dsr = readl(imxdi->ioaddr + DSR);
+
+	/* handle the security violation event */
+	if (dier & DIER_SVIE) {
+		if (dsr & DSR_SVF) {
+			/*
+			 * Disable the interrupt when this kind of event has
+			 * happened.
+			 * There cannot be more than one event of this type,
+			 * because it needs a complex state change
+			 * including a main power cycle to get again out of
+			 * this state.
+			 */
+			di_int_disable(imxdi, DIER_SVIE);
+			/* report the violation */
+			di_report_tamper_info(imxdi, dsr);
+			rc = IRQ_HANDLED;
+		}
+	}
 
 	/* handle write complete and write error cases */
 	if (dier & DIER_WCIE) {
@@ -675,7 +694,6 @@ static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
 			return rc;
 
 		/* DSR_WCF clears itself on DSR read */
-		dsr = readl(imxdi->ioaddr + DSR);
 		if (dsr & (DSR_WCF | DSR_WEF)) {
 			/* mask the interrupt */
 			di_int_disable(imxdi, DIER_WCIE);
@@ -691,7 +709,6 @@ static irqreturn_t dryice_norm_irq(int irq, void *dev_id)
 	/* handle the alarm case */
 	if (dier & DIER_CAIE) {
 		/* DSR_WCF clears itself on DSR read */
-		dsr = readl(imxdi->ioaddr + DSR);
 		if (dsr & DSR_CAF) {
 			/* mask the interrupt */
 			di_int_disable(imxdi, DIER_CAIE);
-- 
2.1.4

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