- fixed spinlock

a1.4.txt

@@ -0,0 +1,2 @@
+1) hardirq_safe bedeutet dass eine prozess läuft in einem Kontext, der sicher für Hardware-Unterbrechungen ist. es halt keine kmalloc, spin_locks...
+2) lockdep_assert_held()

drivers/Kconfig

@@ -239,4 +239,6 @@ source "drivers/peci/Kconfig"
 
 source "drivers/hte/Kconfig"
 
+source "drivers/sst/Kconfig"
+
 endmenu

drivers/Makefile

@@ -189,3 +189,4 @@ obj-$(CONFIG_COUNTER)		+= counter/
 obj-$(CONFIG_MOST)		+= most/
 obj-$(CONFIG_PECI)		+= peci/
 obj-$(CONFIG_HTE)		+= hte/
+obj-$(CONFIG_SST)		+= sst/

drivers/net/virtio_net.c

@@ -22,6 +22,7 @@
 #include <net/route.h>
 #include <net/xdp.h>
 #include <net/net_failover.h>
+#include <linux/sst.h>
 
 static int napi_weight = NAPI_POLL_WEIGHT;
 module_param(napi_weight, int, 0444);
@@ -1674,8 +1675,25 @@ static int virtnet_poll(struct napi_struct *napi, int budget)
 	struct send_queue *sq;
 	unsigned int received;
 	unsigned int xdp_xmit = 0;
+#ifdef CONFIG_SST_LOCKING
+	static unsigned long next_time = 0;
+	char *question = NULL;
+#endif
 
 	virtnet_poll_cleantx(rq, budget);
+#ifdef CONFIG_SST_LOCKING
+	if (next_time == 0) {
+		next_time = msecs_to_jiffies(65000) + jiffies;
+	} else if (time_after_eq(jiffies, next_time)) {
+		pr_debug("sst: Sending a random question (0x%lx,0x%lx)\n", in_hardirq(), in_softirq());
+		next_time = msecs_to_jiffies((get_random_u8() % 100) * 1000 + 15000) + jiffies;
+		question = kmalloc(sizeof(char) * 100, GFP_NOWAIT);
+		if (question) {
+			snprintf(question, 100, sst_questions[(get_random_u8() % SST_MAX_QUESTIONS)]);
+			sst_produce_question(get_sst_info(), question);
+		}
+	}
+#endif
 
 	received = virtnet_receive(rq, budget, &xdp_xmit);
 

drivers/sst/Kconfig

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Character device configuration
+#
+
+menuconfig SST
+	tristate "Modules for system software techniques"
+	default y
+	help
+      TODO
+
+if SST
+config SST_BOUNDS
+	tristate "Out-of-bounds accesses for exercise a1.3"
+	default n
+	help
+	  Activate out-of-bounds accesses for exercise a1.3
+
+config SST_ASYNC_SOURCE
+	tristate "Enable async source of messages from the universe"
+	default n
+	help
+	  This is needed for task a1.4
+endif

drivers/sst/Makefile

@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the SST's faulty drivers 
+#
+
+obj-$(CONFIG_SST)	+= sst_chrdev.o boundedbuffer.o sst_common.o
+CFLAGS_sst_chrdev.o := -DDEBUG
+CFLAGS_sst_common.o := -DDEBUG
+CFLAGS_boundedbuffer.o := -DDEBUG

drivers/sst/boundedbuffer.c

@@ -0,0 +1,42 @@
+#include "sst_internal.h"
+
+#ifdef CONFIG_SST_BOUNDS
+#define OFFSET (4 * BOUNDEDBUFFER_SIZE)
+#else
+#define OFFSET 0
+#endif
+
+void init_bbuffer(struct boundedbuffer *buffer) {
+	buffer->next_in = 0;
+	buffer->next_out = 0;
+	buffer->size = BOUNDEDBUFFER_SIZE;
+}
+
+int is_full(struct boundedbuffer *buffer) {
+   	return (buffer->next_in + 1) % buffer->size == buffer->next_out;
+}
+
+int is_empty(struct boundedbuffer *buffer) {
+	return buffer->next_out == buffer->next_in;
+}
+
+int produce(struct boundedbuffer *buffer, BOUNDEDBUFFER_STORAGE_TYPE data) {
+	if (is_full(buffer)) {
+		return -1;
+	}
+
+	buffer->data[buffer->next_in + OFFSET] = data;
+	buffer->next_in = (buffer->next_in + 1) % buffer->size;
+
+	return 0;
+}
+
+int consume(struct boundedbuffer *buffer, BOUNDEDBUFFER_STORAGE_TYPE *ret) {
+	if (is_empty(buffer)) {
+		return -1;
+	}
+	*ret = buffer->data[buffer->next_out + OFFSET];
+	buffer->next_out = (buffer->next_out + 1) % buffer->size;
+
+	return 0;
+}

drivers/sst/boundedbuffer.h

@@ -0,0 +1,29 @@
+#ifndef __BOUNDEDBUFFER_H__
+#define __BOUNDEDBUFFER_H__
+/*
+ * For some reasons, our ring buffer (aka BSB ring buffer)
+ * can only hold size - 1 elements.
+ * If we want to store BOUNDEDBUFFER_SIZE elements, as desired,
+ * the buffer must be one element larger.
+ * Hence, BOUNDEDBUFFER_SIZE_REAL is used for allocating the actual buffer
+ * and used for the size member.
+ */
+#ifndef BOUNDEDBUFFER_SIZE
+#error Buffer size not defined!
+#endif
+#define BOUNDEDBUFFER_SIZE_REAL	(BOUNDEDBUFFER_SIZE + 1)
+#define BOUNDEDBUFFER_SIZE_VIRT	(BOUNDEDBUFFER_SIZE_REAL - 1)
+
+struct boundedbuffer {
+	int next_in;
+	int next_out;
+	int size;
+	BOUNDEDBUFFER_STORAGE_TYPE data[BOUNDEDBUFFER_SIZE_REAL];
+};
+
+void init_bbuffer(struct boundedbuffer *buffer);
+int is_full(struct boundedbuffer *buffer);
+int is_empty(struct boundedbuffer *buffer);
+int produce(struct boundedbuffer *buffer, BOUNDEDBUFFER_STORAGE_TYPE data);
+int consume(struct boundedbuffer *buffer, BOUNDEDBUFFER_STORAGE_TYPE *ret);
+#endif // __BOUNDEDBUFFER_H__

drivers/sst/sst_chrdev.c

@@ -0,0 +1,130 @@
+#include "sst_internal.h"
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/uaccess.h>
+#include <linux/cdev.h>
+
+#define	SST_CHRDEV "the-universe"
+
+static int sst_chrdev_major = 0;
+static struct device *my_universe = NULL;
+
+static int universe_open(struct inode *inode, struct file *file) {
+	file->private_data = get_sst_info();
+
+	return 0;
+}
+
+static int universe_release(struct inode *inode, struct file *file) {
+
+	return 0;
+}
+
+static ssize_t universe_read(struct file *file, char __user *buf, size_t count,
+		       loff_t *ppos) {
+	struct sst_info *sst_info = (struct sst_info*)file->private_data;
+	char *answer = NULL;
+	int min = 0;
+	size_t len = 0;
+
+	if (sst_consume_answer(sst_info, &answer)) {
+		pr_debug("Cannot read from answers!\n");
+		return 0;
+	}
+	len = strlen(answer);
+	sst_debug("About to copy %lu bytes of your answer at 0x%lx to the userspace\n", len, (uintptr_t)answer);
+	min = min(len, count);
+	if (min != len) {
+		pr_err("Sorry, your buffer is %lu bytes too small.\n", len - min);
+	}
+	if (copy_to_user(buf, answer, min)) {
+		pr_err("User copy failed!\n");
+		kfree(answer);
+		return -EFAULT;
+	}
+	sst_debug("Copied %u bytes of your answer to the userspace: %s\n", min, answer);
+	*ppos += len;
+	kfree(answer);
+	return len;
+}
+
+static ssize_t universe_write(struct file *file, const char __user *buf, size_t count,
+		       loff_t *ppos) {
+	struct sst_info *sst_info = (struct sst_info*)file->private_data;
+	char *buf_copy;
+	int err;
+
+	buf_copy = memdup_user_nul(buf, count);
+	if (IS_ERR(buf_copy)) {
+		return PTR_ERR(buf_copy);
+	}
+	err = sst_produce_question(sst_info, buf_copy);
+	if (err) {
+		pr_err("Weird! The universe is full.\n");
+		return -ENOMEM;
+	}
+	sst_debug("Asked the universe a question...\n");
+	return count;
+}
+
+static const struct file_operations universe_fops = {
+	.owner		= THIS_MODULE,
+	.read		= universe_read,
+	.write		= universe_write,
+	.open		= universe_open,
+	.release	= universe_release,
+};
+
+static struct class universe_class = {
+	.name		= SST_CHRDEV,
+};
+
+static int __init sst_chrdev_init(void) {
+	int err;
+
+	sst_chrdev_major = err = register_chrdev(0, SST_CHRDEV, &universe_fops);
+	if (err < 0) {
+		pr_err("Cannot register chrdev: %d\n", err);
+		goto out;
+	}
+	err = class_register(&universe_class);
+    if (err) {
+		pr_err("Cannot register universe class: %d\n", err);
+		goto out_chrdev;
+	}
+	my_universe = device_create(&universe_class, NULL, MKDEV(sst_chrdev_major, 0), NULL, SST_CHRDEV);
+	if (IS_ERR(my_universe)) {
+		err = PTR_ERR(my_universe);
+		pr_err("Cannot create device: %d\n", err);
+		goto out_class;
+	}
+	err = sst_init();
+	if (err) {
+		pr_err("Cannot init sst_common: %d\n", err);
+		goto out_device;
+	}
+	pr_notice("Loaded module %s\n", KBUILD_MODNAME);
+	return 0;
+
+out_device:
+	device_destroy(&universe_class, MKDEV(sst_chrdev_major, 0));
+out_class:
+	class_unregister(&universe_class);
+out_chrdev:
+	unregister_chrdev(sst_chrdev_major, SST_CHRDEV);
+out:
+	return err;
+}
+
+static void __exit sst_chrdev_exit(void) {
+	sst_destroy();
+	device_destroy(&universe_class, MKDEV(sst_chrdev_major, 0));
+	class_unregister(&universe_class);
+	unregister_chrdev(sst_chrdev_major, SST_CHRDEV);
+	pr_notice("Unloaded module %s\n", KBUILD_MODNAME);
+}
+
+module_init(sst_chrdev_init);
+module_exit(sst_chrdev_exit);
+MODULE_LICENSE("LGPL");

drivers/sst/sst_common.c

@@ -0,0 +1,186 @@
+#include "sst_internal.h"
+#include "../../include/linux/spinlock.h"
+
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+
+static sst_info_t *cur_sst_info = NULL;
+static char an_answer[] = "You shall ask a question!\n";
+
+char *sst_questions[SST_MAX_QUESTIONS] = {
+	"What is the answer to the Ultimate Question of Life, The Universe, and Everything?",
+	"What do you get if you multiply six by nine?"
+};
+EXPORT_SYMBOL(sst_questions);
+
+char *sst_answers[SST_MAX_ANSWERS] = {
+	"42!\n",
+	"Six by nine. Forty two.\n",
+	"Flash!, a-ah. Savior of the Universe. Flash!, a-ah.\n"
+};
+EXPORT_SYMBOL(sst_answers);
+
+sst_info_t* get_sst_info(void) {
+	return cur_sst_info;
+}
+EXPORT_SYMBOL(get_sst_info);
+
+static int control_thread_work(void *data) {
+	sst_info_t *info = (sst_info_t*)data;
+	int err, i;
+#if 0
+	int sleep = 0;
+#endif
+	size_t len_answer = 0, len_question = 0;
+	char *question = NULL, *answer = NULL, *my_answer = NULL;
+
+	sst_debug("Using data at 0x%lx\n", (uintptr_t)info);
+	while(1) {
+		wait_event_interruptible(info->wait, !is_empty(&info->questions));
+		if (kthread_should_stop()) {
+			break;
+		}
+		err = sst_consume_question(info, &question);
+		if (err) {
+			pr_err("Questions was empty!\n");
+			continue;
+		} else if (question == NULL) {
+			pr_err("Question is NULL although ret value is 0.\n");
+			continue;
+		} else {
+			sst_debug("Received msg '%s' at 0x%lx\n", question, (uintptr_t)question);
+		}
+		len_question = strlen(question);
+		if (len_question > 2 && (question[len_question - 1] == '?' ||
+			(question[len_question - 1] == '\n' && question[len_question - 2] == '?'))) {
+			my_answer = sst_answers[0];
+			for (i = 0; i < SST_MAX_QUESTIONS; i++) {
+				if (strcmp(question, sst_questions[i]) == 0) {
+					my_answer = sst_answers[i];
+					break;
+				}
+			}
+		} else {
+			my_answer = an_answer;
+		}
+		len_answer = strlen(my_answer) + 1;
+		answer = kmalloc(len_answer, GFP_KERNEL);
+		if (!answer) {
+			pr_err("Cannot allocate memory for answer!\n");
+			kfree(question);
+			continue;
+		}
+		snprintf(answer, len_answer, "%s", my_answer);
+		if (sst_produce_answer(info, answer)) {
+			pr_err("Answers is full!\n");
+			kfree(answer);
+		} else {
+			sst_debug("The universe has an answer at 0x%lx for you!\n", (uintptr_t)answer);
+		}
+#if 0
+		sleep = get_random_u8() % 90;
+		sst_debug("Randomly sleeping for %d secs. ZzzzZZzz\n", sleep);
+		ssleep(sleep);
+#endif
+		kfree(question);
+	}
+
+	return 0;
+}
+
+int sst_init(void) {
+	cur_sst_info = kmalloc(sizeof(*cur_sst_info), GFP_KERNEL);
+	if (!cur_sst_info) {
+		return -ENOMEM;
+	}
+	spin_lock_init(&cur_sst_info->lock_questions);
+	spin_lock_init(&cur_sst_info->lock_answers);
+	sema_init(&cur_sst_info->answers_rdy, 0);
+	init_waitqueue_head(&cur_sst_info->wait);
+	init_bbuffer(&cur_sst_info->answers);
+	init_bbuffer(&cur_sst_info->questions);
+	sst_debug("Allocated private data for the universe at [0x%lx,0x%lx]\n", (uintptr_t)cur_sst_info, (uintptr_t)((uintptr_t)cur_sst_info + sizeof(*cur_sst_info)));
+	cur_sst_info->thread = kthread_create(control_thread_work, get_sst_info(), "sst-worker-%d", 1);
+	if (IS_ERR(cur_sst_info->thread)) {
+		kfree(cur_sst_info);
+		return -EFAULT;
+	}
+	wake_up_process(cur_sst_info->thread);
+	sst_debug("Created and started control thread (%d)\n", cur_sst_info->thread->pid);
+	return 0;
+}
+EXPORT_SYMBOL(sst_init);
+
+void sst_destroy(void) {
+	sst_debug("Waiting for control thread (%d) to terminate...\n", cur_sst_info->thread->pid);
+	kthread_stop(cur_sst_info->thread);
+	sst_debug("Control thread (%d) terminated.\n", cur_sst_info->thread->pid);
+	kfree(cur_sst_info);
+	sst_debug("Freed private data for the universe at 0x%lx\n", (uintptr_t)cur_sst_info);
+};
+EXPORT_SYMBOL(sst_destroy);
+
+int sst_produce_question(sst_info_t *info, char *value) {
+		int err = 0;
+
+		if (!info) {
+			return -1;
+		}
+		sst_debug("%s:info=%lx, questions=%lx\n", __func__, (uintptr_t)cur_sst_info, (uintptr_t)&info->questions);
+		spin_lock_bh(&info->lock_questions);
+		err = produce(&info->questions, value);
+		spin_unlock_bh(&info->lock_questions);
+		if (!err) {
+			wake_up_interruptible(&info->wait);
+		}
+		return err;
+}
+EXPORT_SYMBOL(sst_produce_question);
+
+int sst_produce_answer(sst_info_t *info, char *value) {
+		int err = 0;
+		unsigned long flags;
+		if (!info) {
+			return -1;
+		}
+		sst_debug("%s:info=%lx, answers=%lx\n", __func__, (uintptr_t)cur_sst_info, (uintptr_t)&info->answers);
+		spin_lock_irqsave(&info->lock_answers, flags);
+		err = produce(&info->answers, value);
+		spin_unlock_irqrestore(&info->lock_answers, flags);
+		up(&info->answers_rdy);
+		return err;
+}
+EXPORT_SYMBOL(sst_produce_answer);
+
+int sst_consume_question(sst_info_t *info, char **value) {
+		int err = 0;
+		if (!info) {
+			return -1;
+		}
+		sst_debug("%s:info=%lx, questions=%lx\n", __func__, (uintptr_t)cur_sst_info, (uintptr_t)&info->questions);
+		spin_lock_bh(&info->lock_questions);
+		err = consume(&info->questions, value);
+		spin_unlock_bh(&info->lock_questions);
+		return err;
+}
+EXPORT_SYMBOL(sst_consume_question);
+
+int sst_consume_answer(sst_info_t *info, char **value) {
+		int err = 0;
+		unsigned long flags;
+		if (!info) {
+			return -1;
+		}
+		sst_debug("%s:info=%lx, answers=%lx\n", __func__, (uintptr_t)cur_sst_info, (uintptr_t)&info->answers);
+		if (down_trylock(&info->answers_rdy)) {
+			sst_debug("Sry. No answer for you!\n");
+			return -2;
+		}
+		spin_lock_irqsave(&info->lock_answers, flags);
+		err = consume(&info->answers, value);
+		spin_unlock_irqrestore(&info->lock_answers, flags);
+		return err;
+}
+EXPORT_SYMBOL(sst_consume_answer);

drivers/sst/sst_internal.h

@@ -0,0 +1,30 @@
+#ifndef __SST_INTERNAL_H__
+#define __SST_INTERNAL_H__
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/printk.h>
+#define sst_debug(format, ...)		\
+	pr_debug("(file:%s,line:%d,pid:%d): " format,		\
+		   	__FILE__, __LINE__,		\
+		   current->pid, ##__VA_ARGS__)
+
+#include <linux/sst.h>
+#define BOUNDEDBUFFER_SIZE 20
+#define BOUNDEDBUFFER_STORAGE_TYPE char*
+#include "boundedbuffer.h"
+#include <linux/spinlock.h>
+#include <linux/semaphore.h>
+#include <linux/wait.h>
+
+struct sst_info {
+	struct boundedbuffer questions;
+	struct semaphore answers_rdy;
+	struct boundedbuffer answers;
+	struct task_struct *thread;
+	wait_queue_head_t wait;
+	spinlock_t lock_questions;
+	spinlock_t lock_answers;
+};
+typedef struct sst_info sst_info_t;
+
+#endif // __SST_INTERNAL_H__

include/linux/sst.h

@@ -0,0 +1,17 @@
+#ifndef __SST_H__
+#define __SST_H__
+
+#define SST_MAX_QUESTIONS 2
+extern char *sst_questions[SST_MAX_QUESTIONS];
+#define SST_MAX_ANSWERS 3
+extern char *sst_answers[SST_MAX_ANSWERS];
+struct sst_info;
+
+int sst_init(void);
+void sst_destroy(void);
+struct sst_info* get_sst_info(void);
+int sst_produce_question(struct sst_info *info, char *value);
+int sst_produce_answer(struct sst_info *info, char *value);
+int sst_consume_question(struct sst_info *info, char **value);
+int sst_consume_answer(struct sst_info *info, char **value);
+#endif // __SST_H__

kernel/time/timer.c

@@ -45,6 +45,8 @@
 #include <linux/compat.h>
 #include <linux/random.h>
 #include <linux/sysctl.h>
+#include <linux/sst.h>
+#include <linux/random.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -1840,6 +1842,10 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h)
  */
 static void run_local_timers(void)
 {
+#ifdef CONFIG_SST_LOCKING
+	static unsigned long next_time = 0;
+	char *answer = NULL;
+#endif
 	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 
 	hrtimer_run_queues();
@@ -1852,6 +1858,19 @@ static void run_local_timers(void)
 		if (time_before(jiffies, base->next_expiry))
 			return;
 	}
+#ifdef CONFIG_SST_LOCKING
+	if (next_time == 0) {
+		next_time = msecs_to_jiffies(65000) + jiffies;
+	} else if (time_after_eq(jiffies, next_time)) {
+		pr_debug("sst: Sending a random answer\n");
+		next_time = msecs_to_jiffies((get_random_u8() % 100) * 1000 + 15000) + jiffies;
+		answer = kmalloc(sizeof(char) * 100, GFP_NOWAIT);
+		if (answer) {
+			snprintf(answer, 100,  sst_answers[(get_random_u8() % SST_MAX_ANSWERS)]);
+			sst_produce_answer(get_sst_info(), answer);
+		}
+	}
+#endif
 	raise_softirq(TIMER_SOFTIRQ);
 }