From 7935a206e8d88150f669f18e4330b467844cd374 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 21 Aug 2012 20:38:50 +0200
Subject: [PATCH 111/158] 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>
---
 arch/x86/kernel/cpu/mshyperv.c |    3 ++-
 drivers/char/random.c          |   11 +++++------
 drivers/hv/hyperv_vmbus.h      |    1 +
 drivers/hv/vmbus_drv.c         |    5 ++++-
 include/linux/irqdesc.h        |    1 +
 include/linux/random.h         |    2 +-
 kernel/irq/handle.c            |   10 ++++++++--
 kernel/irq/manage.c            |    6 ++++++
 8 files changed, 28 insertions(+), 11 deletions(-)

Index: linux-5.15/arch/x86/kernel/cpu/mshyperv.c
===================================================================
--- linux-5.15.orig/arch/x86/kernel/cpu/mshyperv.c
+++ linux-5.15/arch/x86/kernel/cpu/mshyperv.c
@@ -75,11 +75,12 @@ void hv_remove_vmbus_handler(void)
 DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_stimer0)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
+	u64 ip = regs ? instruction_pointer(regs) : 0;
 
 	inc_irq_stat(hyperv_stimer0_count);
 	if (hv_stimer0_handler)
 		hv_stimer0_handler();
-	add_interrupt_randomness(HYPERV_STIMER0_VECTOR, 0);
+	add_interrupt_randomness(HYPERV_STIMER0_VECTOR, 0, ip);
 	ack_APIC_irq();
 
 	set_irq_regs(old_regs);
Index: linux-5.15/drivers/char/random.c
===================================================================
--- linux-5.15.orig/drivers/char/random.c
+++ linux-5.15/drivers/char/random.c
@@ -1242,26 +1242,25 @@ static __u32 get_reg(struct fast_pool *f
 	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;
 
 	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);
Index: linux-5.15/drivers/hv/hyperv_vmbus.h
===================================================================
--- linux-5.15.orig/drivers/hv/hyperv_vmbus.h
+++ linux-5.15/drivers/hv/hyperv_vmbus.h
@@ -19,6 +19,7 @@
 #include <linux/atomic.h>
 #include <linux/hyperv.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 
 #include "hv_trace.h"
 
Index: linux-5.15/drivers/hv/vmbus_drv.c
===================================================================
--- linux-5.15.orig/drivers/hv/vmbus_drv.c
+++ linux-5.15/drivers/hv/vmbus_drv.c
@@ -22,6 +22,7 @@
 #include <linux/clockchips.h>
 #include <linux/cpu.h>
 #include <linux/sched/task_stack.h>
+#include <linux/irq.h>
 
 #include <linux/delay.h>
 #include <linux/notifier.h>
@@ -1337,6 +1338,8 @@ static void vmbus_isr(void)
 	void *page_addr = hv_cpu->synic_event_page;
 	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;
 
 	if (unlikely(page_addr == NULL))
@@ -1381,7 +1384,7 @@ static void vmbus_isr(void)
 			tasklet_schedule(&hv_cpu->msg_dpc);
 	}
 
-	add_interrupt_randomness(vmbus_interrupt, 0);
+	add_interrupt_randomness(vmbus_interrupt, 0, ip);
 }
 
 static irqreturn_t vmbus_percpu_isr(int irq, void *dev_id)
Index: linux-5.15/include/linux/irqdesc.h
===================================================================
--- linux-5.15.orig/include/linux/irqdesc.h
+++ linux-5.15/include/linux/irqdesc.h
@@ -68,6 +68,7 @@ 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;
Index: linux-5.15/include/linux/random.h
===================================================================
--- linux-5.15.orig/include/linux/random.h
+++ linux-5.15/include/linux/random.h
@@ -35,7 +35,7 @@ static inline void add_latent_entropy(vo
 
 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 wait_for_random_bytes(void);
Index: linux-5.15/kernel/irq/handle.c
===================================================================
--- linux-5.15.orig/kernel/irq/handle.c
+++ linux-5.15/kernel/irq/handle.c
@@ -190,12 +190,18 @@ irqreturn_t __handle_irq_event_percpu(st
 
 irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
 {
-	irqreturn_t retval;
+	struct pt_regs *regs = get_irq_regs();
+	u64 ip = regs ? instruction_pointer(regs) : 0;
 	unsigned int flags = 0;
+	irqreturn_t retval;
 
 	retval = __handle_irq_event_percpu(desc, &flags);
 
-	add_interrupt_randomness(desc->irq_data.irq, flags);
+#ifdef CONFIG_PREEMPT_RT
+	desc->random_ip = ip;
+#else
+	add_interrupt_randomness(desc->irq_data.irq, flags, ip);
+#endif
 
 	if (!irq_settings_no_debug(desc))
 		note_interrupt(desc, retval);
Index: linux-5.15/kernel/irq/manage.c
===================================================================
--- linux-5.15.orig/kernel/irq/manage.c
+++ linux-5.15/kernel/irq/manage.c
@@ -1281,6 +1281,12 @@ static int irq_thread(void *data)
 		if (action_ret == IRQ_WAKE_THREAD)
 			irq_wake_secondary(desc, action);
 
+		if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+			migrate_disable();
+			add_interrupt_randomness(action->irq, 0,
+				 desc->random_ip ^ (unsigned long) action);
+			migrate_enable();
+		}
 		wake_threads_waitq(desc);
 	}