tegrakernel/kernel/kernel-4.9/rt-patches/0275-random-Make-it-work-on-rt.patch

From 009c283c062765f56233edb87df368fe351ffecf Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 21 Aug 2012 20:38:50 +0200
Subject: [PATCH 275/365] random: Make it work on rt

Delegate the random insertion to the forced threaded interrupt
handler. Store the return IP of the hard interrupt handler in the irq
descriptor and feed it into the random generator as a source of
entropy.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/char/random.c   | 11 +++++------
 drivers/hv/vmbus_drv.c  |  5 ++++-
 include/linux/irqdesc.h |  1 +
 include/linux/random.h  |  2 +-
 kernel/irq/handle.c     |  8 +++++++-
 kernel/irq/manage.c     |  6 ++++++
 6 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index f1fb82b3e66c..3777a8ff637e 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1183,28 +1183,27 @@ static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 	return *ptr;
 }
 
-void add_interrupt_randomness(int irq, int irq_flags)
+void add_interrupt_randomness(int irq, int irq_flags, __u64 ip)
 {
 	struct entropy_store	*r;
 	struct fast_pool	*fast_pool = this_cpu_ptr(&irq_randomness);
-	struct pt_regs		*regs = get_irq_regs();
 	unsigned long		now = jiffies;
 	cycles_t		cycles = random_get_entropy();
 	__u32			c_high, j_high;
-	__u64			ip;
 	unsigned long		seed;
 	int			credit = 0;
 
 	if (cycles == 0)
-		cycles = get_reg(fast_pool, regs);
+		cycles = get_reg(fast_pool, NULL);
 	c_high = (sizeof(cycles) > 4) ? cycles >> 32 : 0;
 	j_high = (sizeof(now) > 4) ? now >> 32 : 0;
 	fast_pool->pool[0] ^= cycles ^ j_high ^ irq;
 	fast_pool->pool[1] ^= now ^ c_high;
-	ip = regs ? instruction_pointer(regs) : _RET_IP_;
+	if (!ip)
+		ip = _RET_IP_;
 	fast_pool->pool[2] ^= ip;
 	fast_pool->pool[3] ^= (sizeof(ip) > 4) ? ip >> 32 :
-		get_reg(fast_pool, regs);
+		get_reg(fast_pool, NULL);
 
 	fast_mix(fast_pool);
 	add_interrupt_bench(cycles);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 9a0d0d0ad6d0..ca93cfa43f64 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -43,6 +43,7 @@
 #include <linux/kdebug.h>
 #include <linux/efi.h>
 #include <linux/random.h>
+#include <asm/irq_regs.h>
 #include "hyperv_vmbus.h"
 
 static struct acpi_device  *hv_acpi_dev;
@@ -781,6 +782,8 @@ static void vmbus_isr(void)
 	void *page_addr;
 	struct hv_message *msg;
 	union hv_synic_event_flags *event;
+	struct pt_regs *regs = get_irq_regs();
+	u64 ip = regs ? instruction_pointer(regs) : 0;
 	bool handled = false;
 
 	page_addr = hv_context.synic_event_page[cpu];
@@ -828,7 +831,7 @@ static void vmbus_isr(void)
 			tasklet_schedule(hv_context.msg_dpc[cpu]);
 	}
 
-	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR, 0);
+	add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR, 0, ip);
 }
 
 
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index bb5547a83daf..529da7ef55e3 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -67,6 +67,7 @@ struct irq_desc {
 	unsigned int		irqs_unhandled;
 	atomic_t		threads_handled;
 	int			threads_handled_last;
+	u64			random_ip;
 	raw_spinlock_t		lock;
 	struct cpumask		*percpu_enabled;
 	const struct cpumask	*percpu_affinity;
diff --git a/include/linux/random.h b/include/linux/random.h
index 15cd75454468..a50fcce24354 100644
--- a/include/linux/random.h
+++ b/include/linux/random.h
@@ -31,7 +31,7 @@ static inline void add_latent_entropy(void) {}
 
 extern void add_input_randomness(unsigned int type, unsigned int code,
 				 unsigned int value) __latent_entropy;
-extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy;
+extern void add_interrupt_randomness(int irq, int irq_flags, __u64 ip) __latent_entropy;
 
 extern void get_random_bytes(void *buf, int nbytes);
 extern int add_random_ready_callback(struct random_ready_callback *rdy);
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index d3f24905852c..f87aa8fdcc51 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -181,10 +181,16 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
 {
 	irqreturn_t retval;
 	unsigned int flags = 0;
+	struct pt_regs *regs = get_irq_regs();
+	u64 ip = regs ? instruction_pointer(regs) : 0;
 
 	retval = __handle_irq_event_percpu(desc, &flags);
 
-	add_interrupt_randomness(desc->irq_data.irq, flags);
+#ifdef CONFIG_PREEMPT_RT_FULL
+	desc->random_ip = ip;
+#else
+	add_interrupt_randomness(desc->irq_data.irq, flags, ip);
+#endif
 
 	if (!noirqdebug)
 		note_interrupt(desc, retval);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 491ceca98798..5a217c230dee 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1032,6 +1032,12 @@ static int irq_thread(void *data)
 		if (action_ret == IRQ_WAKE_THREAD)
 			irq_wake_secondary(desc, action);
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+		migrate_disable();
+		add_interrupt_randomness(action->irq, 0,
+				 desc->random_ip ^ (unsigned long) action);
+		migrate_enable();
+#endif
 		wake_threads_waitq(desc);
 	}
 
-- 
2.28.0