Staging: android: add logging driver

	tristate "Android Binder IPC Driver"

	default y

config ANDROID_LOGGER

	tristate "Android log driver"

	default n

endmenu

obj-$(CONFIG_ANDROID)			+= android.o

obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o

obj-$(CONFIG_ANDROID_LOGGER)		+= logger.o

/*

 * drivers/misc/logger.c

 *

 * A Logging Subsystem

 *

 * Copyright (C) 2007-2008 Google, Inc.

 *

 * Robert Love <rlove@google.com>

 *

 * 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 <linux/module.h>

#include <linux/fs.h>

#include <linux/miscdevice.h>

#include <linux/uaccess.h>

#include <linux/poll.h>

#include <linux/time.h>

#include "logger.h"

#include <asm/ioctls.h>

/*

 * struct logger_log - represents a specific log, such as 'main' or 'radio'

 *

 * This structure lives from module insertion until module removal, so it does

 * not need additional reference counting. The structure is protected by the

 * mutex 'mutex'.

 */

struct logger_log {

	unsigned char *		buffer;	/* the ring buffer itself */

	struct miscdevice	misc;	/* misc device representing the log */

	wait_queue_head_t	wq;	/* wait queue for readers */

	struct list_head	readers; /* this log's readers */

	struct mutex		mutex;	/* mutex protecting buffer */

	size_t			w_off;	/* current write head offset */

	size_t			head;	/* new readers start here */

	size_t			size;	/* size of the log */

};

/*

 * struct logger_reader - a logging device open for reading

 *

 * This object lives from open to release, so we don't need additional

 * reference counting. The structure is protected by log->mutex.

 */

struct logger_reader {

	struct logger_log *	log;	/* associated log */

	struct list_head	list;	/* entry in logger_log's list */

	size_t			r_off;	/* current read head offset */

};

/* logger_offset - returns index 'n' into the log via (optimized) modulus */

#define logger_offset(n)	((n) & (log->size - 1))

/*

 * file_get_log - Given a file structure, return the associated log

 *

 * This isn't aesthetic. We have several goals:

 *

 * 	1) Need to quickly obtain the associated log during an I/O operation

 * 	2) Readers need to maintain state (logger_reader)

 * 	3) Writers need to be very fast (open() should be a near no-op)

 *

 * In the reader case, we can trivially go file->logger_reader->logger_log.

 * For a writer, we don't want to maintain a logger_reader, so we just go

 * file->logger_log. Thus what file->private_data points at depends on whether

 * or not the file was opened for reading. This function hides that dirtiness.

 */

static inline struct logger_log * file_get_log(struct file *file)

{

	if (file->f_mode & FMODE_READ) {

		struct logger_reader *reader = file->private_data;

		return reader->log;

	} else

		return file->private_data;

}

/*

 * get_entry_len - Grabs the length of the payload of the next entry starting

 * from 'off'.

 *

 * Caller needs to hold log->mutex.

 */

static __u32 get_entry_len(struct logger_log *log, size_t off)

{

	__u16 val;

	switch (log->size - off) {

	case 1:

		memcpy(&val, log->buffer + off, 1);

		memcpy(((char *) &val) + 1, log->buffer, 1);

		break;

	default:

		memcpy(&val, log->buffer + off, 2);

	}

	return sizeof(struct logger_entry) + val;

}

/*

 * do_read_log_to_user - reads exactly 'count' bytes from 'log' into the

 * user-space buffer 'buf'. Returns 'count' on success.

 *

 * Caller must hold log->mutex.

 */

static ssize_t do_read_log_to_user(struct logger_log *log,

				   struct logger_reader *reader,

				   char __user *buf,

				   size_t count)

{

	size_t len;

	/*

	 * We read from the log in two disjoint operations. First, we read from

	 * the current read head offset up to 'count' bytes or to the end of

	 * the log, whichever comes first.

	 */

	len = min(count, log->size - reader->r_off);

	if (copy_to_user(buf, log->buffer + reader->r_off, len))

		return -EFAULT;

	/*

	 * Second, we read any remaining bytes, starting back at the head of

	 * the log.

	 */

	if (count != len)

		if (copy_to_user(buf + len, log->buffer, count - len))

			return -EFAULT;

	reader->r_off = logger_offset(reader->r_off + count);

	return count;

}

/*

 * logger_read - our log's read() method

 *

 * Behavior:

 *

 * 	- O_NONBLOCK works

 * 	- If there are no log entries to read, blocks until log is written to

 * 	- Atomically reads exactly one log entry

 *

 * Optimal read size is LOGGER_ENTRY_MAX_LEN. Will set errno to EINVAL if read

 * buffer is insufficient to hold next entry.

 */

static ssize_t logger_read(struct file *file, char __user *buf,

			   size_t count, loff_t *pos)

{

	struct logger_reader *reader = file->private_data;

	struct logger_log *log = reader->log;

	ssize_t ret;

	DEFINE_WAIT(wait);

start:

	while (1) {

		prepare_to_wait(&log->wq, &wait, TASK_INTERRUPTIBLE);

		mutex_lock(&log->mutex);

		ret = (log->w_off == reader->r_off);

		mutex_unlock(&log->mutex);

		if (!ret)

			break;

		if (file->f_flags & O_NONBLOCK) {

			ret = -EAGAIN;

			break;

		}

		if (signal_pending(current)) {

			ret = -EINTR;

			break;

		}

		schedule();

	}

	finish_wait(&log->wq, &wait);

	if (ret)

		return ret;

	mutex_lock(&log->mutex);

	/* is there still something to read or did we race? */

	if (unlikely(log->w_off == reader->r_off)) {

		mutex_unlock(&log->mutex);

		goto start;

	}

	/* get the size of the next entry */

	ret = get_entry_len(log, reader->r_off);

	if (count < ret) {

		ret = -EINVAL;

		goto out;

	}

	/* get exactly one entry from the log */

	ret = do_read_log_to_user(log, reader, buf, ret);

out:

	mutex_unlock(&log->mutex);

	return ret;

}

/*

 * get_next_entry - return the offset of the first valid entry at least 'len'

 * bytes after 'off'.

 *

 * Caller must hold log->mutex.

 */

static size_t get_next_entry(struct logger_log *log, size_t off, size_t len)

{

	size_t count = 0;

	do {

		size_t nr = get_entry_len(log, off);

		off = logger_offset(off + nr);

		count += nr;

	} while (count < len);

	return off;

}

/*

 * clock_interval - is a < c < b in mod-space? Put another way, does the line

 * from a to b cross c?

 */

static inline int clock_interval(size_t a, size_t b, size_t c)

{

	if (b < a) {

		if (a < c || b >= c)

			return 1;

	} else {

		if (a < c && b >= c)

			return 1;

	}

	return 0;

}

/*

 * fix_up_readers - walk the list of all readers and "fix up" any who were

 * lapped by the writer; also do the same for the default "start head".

 * We do this by "pulling forward" the readers and start head to the first

 * entry after the new write head.

 *

 * The caller needs to hold log->mutex.

 */

static void fix_up_readers(struct logger_log *log, size_t len)

{

	size_t old = log->w_off;

	size_t new = logger_offset(old + len);

	struct logger_reader *reader;

	if (clock_interval(old, new, log->head))

		log->head = get_next_entry(log, log->head, len);

	list_for_each_entry(reader, &log->readers, list)

		if (clock_interval(old, new, reader->r_off))

			reader->r_off = get_next_entry(log, reader->r_off, len);

}

/*

 * do_write_log - writes 'len' bytes from 'buf' to 'log'

 *

 * The caller needs to hold log->mutex.

 */

static void do_write_log(struct logger_log *log, const void *buf, size_t count)

{

	size_t len;

	len = min(count, log->size - log->w_off);

	memcpy(log->buffer + log->w_off, buf, len);

	if (count != len)

		memcpy(log->buffer, buf + len, count - len);

	log->w_off = logger_offset(log->w_off + count);

}

/*

 * do_write_log_user - writes 'len' bytes from the user-space buffer 'buf' to

 * the log 'log'

 *

 * The caller needs to hold log->mutex.

 *

 * Returns 'count' on success, negative error code on failure.

 */

static ssize_t do_write_log_from_user(struct logger_log *log,

				      const void __user *buf, size_t count)

{

	size_t len;

	len = min(count, log->size - log->w_off);

	if (len && copy_from_user(log->buffer + log->w_off, buf, len))

		return -EFAULT;

	if (count != len)

		if (copy_from_user(log->buffer, buf + len, count - len))

			return -EFAULT;

	log->w_off = logger_offset(log->w_off + count);

	return count;

}

/*

 * logger_aio_write - our write method, implementing support for write(),

 * writev(), and aio_write(). Writes are our fast path, and we try to optimize

 * them above all else.

 */

ssize_t logger_aio_write(struct kiocb *iocb, const struct iovec *iov,

			 unsigned long nr_segs, loff_t ppos)

{

	struct logger_log *log = file_get_log(iocb->ki_filp);

	size_t orig = log->w_off;

	struct logger_entry header;

	struct timespec now;

	ssize_t ret = 0;

	now = current_kernel_time();

	header.pid = current->tgid;

	header.tid = current->pid;

	header.sec = now.tv_sec;

	header.nsec = now.tv_nsec;

	header.len = min_t(size_t, iocb->ki_left, LOGGER_ENTRY_MAX_PAYLOAD);

	/* null writes succeed, return zero */

	if (unlikely(!header.len))

		return 0;

	mutex_lock(&log->mutex);

	/*

	 * Fix up any readers, pulling them forward to the first readable

	 * entry after (what will be) the new write offset. We do this now

	 * because if we partially fail, we can end up with clobbered log

	 * entries that encroach on readable buffer.

	 */

	fix_up_readers(log, sizeof(struct logger_entry) + header.len);

	do_write_log(log, &header, sizeof(struct logger_entry));

	while (nr_segs-- > 0) {

		size_t len;

		ssize_t nr;

		/* figure out how much of this vector we can keep */

		len = min_t(size_t, iov->iov_len, header.len - ret);

		/* write out this segment's payload */

		nr = do_write_log_from_user(log, iov->iov_base, len);

		if (unlikely(nr < 0)) {

			log->w_off = orig;

			mutex_unlock(&log->mutex);

			return nr;

		}

		iov++;

		ret += nr;

	}

	mutex_unlock(&log->mutex);

	/* wake up any blocked readers */

	wake_up_interruptible(&log->wq);

	return ret;

}

static struct logger_log * get_log_from_minor(int);

/*

 * logger_open - the log's open() file operation

 *

 * Note how near a no-op this is in the write-only case. Keep it that way!

 */

static int logger_open(struct inode *inode, struct file *file)

{

	struct logger_log *log;

	int ret;

	ret = nonseekable_open(inode, file);

	if (ret)

		return ret;

	log = get_log_from_minor(MINOR(inode->i_rdev));

	if (!log)

		return -ENODEV;

	if (file->f_mode & FMODE_READ) {

		struct logger_reader *reader;

		reader = kmalloc(sizeof(struct logger_reader), GFP_KERNEL);

		if (!reader)

			return -ENOMEM;

		reader->log = log;

		INIT_LIST_HEAD(&reader->list);

		mutex_lock(&log->mutex);

		reader->r_off = log->head;

		list_add_tail(&reader->list, &log->readers);

		mutex_unlock(&log->mutex);

		file->private_data = reader;

	} else

		file->private_data = log;

	return 0;

}

/*

 * logger_release - the log's release file operation

 *

 * Note this is a total no-op in the write-only case. Keep it that way!

 */

static int logger_release(struct inode *ignored, struct file *file)

{

	if (file->f_mode & FMODE_READ) {

		struct logger_reader *reader = file->private_data;

		list_del(&reader->list);

		kfree(reader);

	}

	return 0;

}

/*

 * logger_poll - the log's poll file operation, for poll/select/epoll

 *

 * Note we always return POLLOUT, because you can always write() to the log.

 * Note also that, strictly speaking, a return value of POLLIN does not

 * guarantee that the log is readable without blocking, as there is a small

 * chance that the writer can lap the reader in the interim between poll()

 * returning and the read() request.

 */

static unsigned int logger_poll(struct file *file, poll_table *wait)

{

	struct logger_reader *reader;

	struct logger_log *log;

	unsigned int ret = POLLOUT | POLLWRNORM;

	if (!(file->f_mode & FMODE_READ))

		return ret;

	reader = file->private_data;

	log = reader->log;

	poll_wait(file, &log->wq, wait);

	mutex_lock(&log->mutex);

	if (log->w_off != reader->r_off)

		ret |= POLLIN | POLLRDNORM;

	mutex_unlock(&log->mutex);

	return ret;

}

static long logger_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

{

	struct logger_log *log = file_get_log(file);

	struct logger_reader *reader;

	long ret = -ENOTTY;

	mutex_lock(&log->mutex);

	switch (cmd) {

	case LOGGER_GET_LOG_BUF_SIZE:

		ret = log->size;

		break;

	case LOGGER_GET_LOG_LEN:

		if (!(file->f_mode & FMODE_READ)) {

			ret = -EBADF;

			break;

		}

		reader = file->private_data;

		if (log->w_off >= reader->r_off)

			ret = log->w_off - reader->r_off;

		else

			ret = (log->size - reader->r_off) + log->w_off;

		break;

	case LOGGER_GET_NEXT_ENTRY_LEN:

		if (!(file->f_mode & FMODE_READ)) {

			ret = -EBADF;

			break;

		}

		reader = file->private_data;

		if (log->w_off != reader->r_off)

			ret = get_entry_len(log, reader->r_off);

		else

			ret = 0;

		break;

	case LOGGER_FLUSH_LOG:

		if (!(file->f_mode & FMODE_WRITE)) {

			ret = -EBADF;

			break;

		}

		list_for_each_entry(reader, &log->readers, list)

			reader->r_off = log->w_off;

		log->head = log->w_off;

		ret = 0;

		break;

	}

	mutex_unlock(&log->mutex);

	return ret;

}

static struct file_operations logger_fops = {

	.owner = THIS_MODULE,

	.read = logger_read,

	.aio_write = logger_aio_write,

	.poll = logger_poll,

	.unlocked_ioctl = logger_ioctl,

	.compat_ioctl = logger_ioctl,

	.open = logger_open,

	.release = logger_release,

};

/*

 * Defines a log structure with name 'NAME' and a size of 'SIZE' bytes, which

 * must be a power of two, greater than LOGGER_ENTRY_MAX_LEN, and less than

 * LONG_MAX minus LOGGER_ENTRY_MAX_LEN.

 */

#define DEFINE_LOGGER_DEVICE(VAR, NAME, SIZE) \

static unsigned char _buf_ ## VAR[SIZE]; \

static struct logger_log VAR = { \

	.buffer = _buf_ ## VAR, \

	.misc = { \

		.minor = MISC_DYNAMIC_MINOR, \

		.name = NAME, \

		.fops = &logger_fops, \

		.parent = NULL, \

	}, \

	.wq = __WAIT_QUEUE_HEAD_INITIALIZER(VAR .wq), \

	.readers = LIST_HEAD_INIT(VAR .readers), \

	.mutex = __MUTEX_INITIALIZER(VAR .mutex), \

	.w_off = 0, \

	.head = 0, \

	.size = SIZE, \

};

DEFINE_LOGGER_DEVICE(log_main, LOGGER_LOG_MAIN, 64*1024)

DEFINE_LOGGER_DEVICE(log_events, LOGGER_LOG_EVENTS, 256*1024)

DEFINE_LOGGER_DEVICE(log_radio, LOGGER_LOG_RADIO, 64*1024)

static struct logger_log * get_log_from_minor(int minor)

{

	if (log_main.misc.minor == minor)

		return &log_main;

	if (log_events.misc.minor == minor)

		return &log_events;

	if (log_radio.misc.minor == minor)

		return &log_radio;

	return NULL;

}

static int __init init_log(struct logger_log *log)

{

	int ret;

	ret = misc_register(&log->misc);

	if (unlikely(ret)) {

		printk(KERN_ERR "logger: failed to register misc "

		       "device for log '%s'!\n", log->misc.name);

		return ret;

	}

	printk(KERN_INFO "logger: created %luK log '%s'\n",

	       (unsigned long) log->size >> 10, log->misc.name);

	return 0;

}

static int __init logger_init(void)

{

	int ret;

	ret = init_log(&log_main);

	if (unlikely(ret))

		goto out;

	ret = init_log(&log_events);

	if (unlikely(ret))

		goto out;

	ret = init_log(&log_radio);

	if (unlikely(ret))

		goto out;

out:

	return ret;

}

device_initcall(logger_init);

/* include/linux/logger.h

 *

 * Copyright (C) 2007-2008 Google, Inc.

 * Author: Robert Love <rlove@android.com>

 *

 * 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.

 *

 */

#ifndef _LINUX_LOGGER_H

#define _LINUX_LOGGER_H

#include <linux/types.h>

#include <linux/ioctl.h>

struct logger_entry {

	__u16		len;	/* length of the payload */

	__u16		__pad;	/* no matter what, we get 2 bytes of padding */

	__s32		pid;	/* generating process's pid */

	__s32		tid;	/* generating process's tid */

	__s32		sec;	/* seconds since Epoch */

	__s32		nsec;	/* nanoseconds */

	char		msg[0];	/* the entry's payload */

};

#define LOGGER_LOG_RADIO	"log_radio"	/* radio-related messages */

#define LOGGER_LOG_EVENTS	"log_events"	/* system/hardware events */

#define LOGGER_LOG_MAIN		"log_main"	/* everything else */

#define LOGGER_ENTRY_MAX_LEN		(4*1024)

#define LOGGER_ENTRY_MAX_PAYLOAD	\

	(LOGGER_ENTRY_MAX_LEN - sizeof(struct logger_entry))

#define __LOGGERIO	0xAE

#define LOGGER_GET_LOG_BUF_SIZE		_IO(__LOGGERIO, 1) /* size of log */

#define LOGGER_GET_LOG_LEN		_IO(__LOGGERIO, 2) /* used log len */

#define LOGGER_GET_NEXT_ENTRY_LEN	_IO(__LOGGERIO, 3) /* next entry len */

#define LOGGER_FLUSH_LOG		_IO(__LOGGERIO, 4) /* flush log */

#endif /* _LINUX_LOGGER_H */