proc: uid: Adds accounting for the cputimes per uid.

Adds proc files /proc/uid_cputime/show_uid_stat and
/proc/uid_cputime/remove_uid_range.

show_uid_stat lists the total utime and stime for the active as well as
terminated processes for each of the uids.

Writing a range of uids to remove_uid_range will delete the accounting
for all the uids within that range.

Change-Id: I21d9210379da730b33ddc1a0ea663c8c9d2ac15b

drivers/misc/Kconfig

@@ -666,6 +666,12 @@ config BU52031NVX_POUCHDETECT
 	help
 	  depends on BU52031NVX
 
+config UID_CPUTIME
+	tristate "Per-UID cpu time statistics"
+	default n
+	help
+	  Per UID based cpu time statistics exported to /proc/uid_cputime
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"

drivers/misc/Makefile

@@ -72,3 +72,4 @@ obj-$(CONFIG_QFP_FUSE) += qfp_fuse.o
 obj-y += tspdrv/
 obj-$(CONFIG_BU52031NVX) += pm8xxx-cradle.o
 obj-$(CONFIG_SLIMPORT_ANX7808)	+= slimport_anx7808/
+obj-$(CONFIG_UID_CPUTIME) += uid_cputime.o

drivers/misc/uid_cputime.c

@@ -0,0 +1,253 @@
+/* drivers/misc/uid_cputime.c
+ *
+ * Copyright (C) 2014 - 2015 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <asm/thread_notify.h>
+
+#include <linux/atomic.h>
+#include <linux/err.h>
+#include <linux/hashtable.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/proc_fs.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#define UID_HASH_BITS	10
+DECLARE_HASHTABLE(hash_table, UID_HASH_BITS);
+
+static DEFINE_SPINLOCK(uid_lock);
+static struct proc_dir_entry *parent;
+
+struct uid_entry {
+	uid_t uid;
+	cputime_t utime;
+	cputime_t stime;
+	cputime_t active_utime;
+	cputime_t active_stime;
+	struct hlist_node hash;
+};
+
+static struct uid_entry *find_uid_entry(uid_t uid)
+{
+	struct uid_entry *uid_entry;
+	struct hlist_node *node;
+
+	hash_for_each_possible(hash_table, uid_entry, node, hash, uid) {
+		if (uid_entry->uid == uid)
+			return uid_entry;
+	}
+	return NULL;
+}
+
+static struct uid_entry *find_or_register_uid(uid_t uid)
+{
+	struct uid_entry *uid_entry;
+
+	uid_entry = find_uid_entry(uid);
+	if (uid_entry)
+		return uid_entry;
+
+	uid_entry = kzalloc(sizeof(struct uid_entry), GFP_ATOMIC);
+	if (!uid_entry)
+		return NULL;
+
+	uid_entry->uid = uid;
+
+	hash_add(hash_table, &uid_entry->hash, uid);
+
+	return uid_entry;
+}
+
+static int uid_stat_show(struct seq_file *m, void *v)
+{
+	struct uid_entry *uid_entry;
+	struct task_struct *task;
+	struct hlist_node *node;
+	cputime_t utime;
+	cputime_t stime;
+	unsigned long bkt;
+
+	spin_lock(&uid_lock);
+
+	hash_for_each(hash_table, bkt, node, uid_entry, hash) {
+		uid_entry->active_stime = 0;
+		uid_entry->active_utime = 0;
+	}
+
+	read_lock(&tasklist_lock);
+	for_each_process(task) {
+		uid_entry = find_or_register_uid(task_uid(task));
+		if (!uid_entry) {
+			read_unlock(&tasklist_lock);
+			spin_unlock(&uid_lock);
+			pr_err("%s: failed to find the uid_entry for uid %d\n",
+						__func__, task_uid(task));
+			return -ENOMEM;
+		}
+		task_times(task, &utime, &stime);
+		uid_entry->active_utime += utime;
+		uid_entry->active_stime += stime;
+	}
+	read_unlock(&tasklist_lock);
+
+	hash_for_each(hash_table, bkt, node, uid_entry, hash) {
+		cputime_t total_utime = uid_entry->utime +
+							uid_entry->active_utime;
+		cputime_t total_stime = uid_entry->stime +
+							uid_entry->active_stime;
+		seq_printf(m, "%d: %u %u\n", uid_entry->uid,
+						cputime_to_usecs(total_utime),
+						cputime_to_usecs(total_stime));
+	}
+
+	spin_unlock(&uid_lock);
+	return 0;
+}
+
+static int uid_stat_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, uid_stat_show, PDE(inode)->data);
+}
+
+static const struct file_operations uid_stat_fops = {
+	.open		= uid_stat_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+static int uid_remove_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, NULL, NULL);
+}
+
+static ssize_t uid_remove_write(struct file *file,
+			const char __user *buffer, size_t count, loff_t *ppos)
+{
+	struct uid_entry *uid_entry;
+	struct hlist_node *node, *tmp;
+	char uids[128];
+	char *start_uid, *end_uid = NULL;
+	long int uid_start = 0, uid_end = 0;
+
+	if (count >= sizeof(uids))
+		count = sizeof(uids) - 1;
+
+	if (copy_from_user(uids, buffer, count))
+		return -EFAULT;
+
+	uids[count] = '\0';
+	end_uid = uids;
+	start_uid = strsep(&end_uid, "-");
+
+	if (!start_uid || !end_uid)
+		return -EINVAL;
+
+	if (kstrtol(start_uid, 10, &uid_start) != 0 ||
+		kstrtol(end_uid, 10, &uid_end) != 0) {
+		return -EINVAL;
+	}
+
+	spin_lock(&uid_lock);
+
+	for (; uid_start <= uid_end; uid_start++) {
+		hash_for_each_possible_safe(hash_table, uid_entry, node, tmp,
+							hash, uid_start) {
+			hash_del(&uid_entry->hash);
+			kfree(uid_entry);
+		}
+	}
+
+	spin_unlock(&uid_lock);
+	return count;
+}
+
+static const struct file_operations uid_remove_fops = {
+	.open		= uid_remove_open,
+	.release	= single_release,
+	.write		= uid_remove_write,
+};
+
+static void uid_task_exit(struct task_struct *task)
+{
+	struct uid_entry *uid_entry;
+	uid_t uid = task_uid(task);
+	cputime_t utime, stime;
+
+	spin_lock(&uid_lock);
+
+	uid_entry = find_or_register_uid(uid);
+	if (!uid_entry) {
+		pr_err("%s: failed to find uid %d\n", __func__, uid);
+		goto exit;
+	}
+
+	task_times(task, &utime, &stime);
+	uid_entry->utime += utime;
+	uid_entry->stime += stime;
+
+exit:
+	spin_unlock(&uid_lock);
+}
+
+static int process_notifier(struct notifier_block *self,
+			unsigned long cmd, void *v)
+{
+	struct thread_info *thread = v;
+	struct task_struct *task = v ? thread->task : NULL;
+
+	if (!task)
+		return NOTIFY_DONE;
+
+	switch (cmd) {
+	case THREAD_NOTIFY_EXIT:
+		uid_task_exit(task);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block process_notifier_block = {
+	.notifier_call	= process_notifier,
+};
+
+static int __init proc_uid_cputime_init(void)
+{
+	hash_init(hash_table);
+
+	parent = proc_mkdir("uid_cputime", NULL);
+	if (!parent) {
+		pr_err("%s: failed to create proc entry\n", __func__);
+		return -ENOMEM;
+	}
+
+	proc_create_data("remove_uid_range", S_IWUGO, parent, &uid_remove_fops,
+					NULL);
+
+	proc_create_data("show_uid_stat", S_IWUGO, parent, &uid_stat_fops,
+					NULL);
+
+	thread_register_notifier(&process_notifier_block);
+
+	return 0;
+}
+
+early_initcall(proc_uid_cputime_init);