--- /dev/null
+/*
+ * 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.
+ */
+
+#define pr_fmt(fmt) "logger: " fmt
+
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/uaccess.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+#include <linux/vmalloc.h>
+#include <linux/aio.h>
+#include "logger.h"
+
+#include <asm/ioctls.h>
+
+/**
+ * struct logger_log - represents a specific log, such as 'main' or 'radio'
+ * @buffer: The actual ring buffer
+ * @misc: The "misc" device representing the log
+ * @wq: The wait queue for @readers
+ * @readers: This log's readers
+ * @mutex: The mutex that protects the @buffer
+ * @w_off: The current write head offset
+ * @head: The head, or location that readers start reading at.
+ * @size: The size of the log
+ * @logs: The list of log channels
+ *
+ * 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;
+ struct miscdevice misc;
+ wait_queue_head_t wq;
+ struct list_head readers;
+ struct mutex mutex;
+ size_t w_off;
+ size_t head;
+ size_t size;
+ struct list_head logs;
+};
+
+static LIST_HEAD(log_list);
+
+/**
+ * struct logger_reader - a logging device open for reading
+ * @log: The associated log
+ * @list: The associated entry in @logger_log's list
+ * @r_off: The current read head offset.
+ * @r_all: Reader can read all entries
+ * @r_ver: Reader ABI version
+ *
+ * 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;
+ struct list_head list;
+ size_t r_off;
+ bool r_all;
+ int r_ver;
+};
+
+/* logger_offset - returns index 'n' into the log via (optimized) modulus */
+static size_t logger_offset(struct logger_log *log, size_t n)
+{
+ return 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;
+ }
+ return file->private_data;
+}
+
+/*
+ * get_entry_header - returns a pointer to the logger_entry header within
+ * 'log' starting at offset 'off'. A temporary logger_entry 'scratch' must
+ * be provided. Typically the return value will be a pointer within
+ * 'logger->buf'. However, a pointer to 'scratch' may be returned if
+ * the log entry spans the end and beginning of the circular buffer.
+ */
+static struct logger_entry *get_entry_header(struct logger_log *log,
+ size_t off,
+ struct logger_entry *scratch)
+{
+ size_t len = min(sizeof(struct logger_entry), log->size - off);
+
+ if (len != sizeof(struct logger_entry)) {
+ memcpy(((void *)scratch), log->buffer + off, len);
+ memcpy(((void *)scratch) + len, log->buffer,
+ sizeof(struct logger_entry) - len);
+ return scratch;
+ }
+
+ return (struct logger_entry *) (log->buffer + off);
+}
+
+/*
+ * get_entry_msg_len - Grabs the length of the message of the entry
+ * starting from from 'off'.
+ *
+ * An entry length is 2 bytes (16 bits) in host endian order.
+ * In the log, the length does not include the size of the log entry structure.
+ * This function returns the size including the log entry structure.
+ *
+ * Caller needs to hold log->mutex.
+ */
+static __u32 get_entry_msg_len(struct logger_log *log, size_t off)
+{
+ struct logger_entry scratch;
+ struct logger_entry *entry;
+
+ entry = get_entry_header(log, off, &scratch);
+ return entry->len;
+}
+
+static size_t get_user_hdr_len(int ver)
+{
+ if (ver < 2)
+ return sizeof(struct user_logger_entry_compat);
+ return sizeof(struct logger_entry);
+}
+
+static ssize_t copy_header_to_user(int ver, struct logger_entry *entry,
+ char __user *buf)
+{
+ void *hdr;
+ size_t hdr_len;
+ struct user_logger_entry_compat v1;
+
+ if (ver < 2) {
+ v1.len = entry->len;
+ v1.__pad = 0;
+ v1.pid = entry->pid;
+ v1.tid = entry->tid;
+ v1.sec = entry->sec;
+ v1.nsec = entry->nsec;
+ hdr = &v1;
+ hdr_len = sizeof(struct user_logger_entry_compat);
+ } else {
+ hdr = entry;
+ hdr_len = sizeof(struct logger_entry);
+ }
+
+ return copy_to_user(buf, hdr, hdr_len);
+}
+
+/*
+ * 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)
+{
+ struct logger_entry scratch;
+ struct logger_entry *entry;
+ size_t len;
+ size_t msg_start;
+
+ /*
+ * First, copy the header to userspace, using the version of
+ * the header requested
+ */
+ entry = get_entry_header(log, reader->r_off, &scratch);
+ if (copy_header_to_user(reader->r_ver, entry, buf))
+ return -EFAULT;
+
+ count -= get_user_hdr_len(reader->r_ver);
+ buf += get_user_hdr_len(reader->r_ver);
+ msg_start = logger_offset(log,
+ reader->r_off + sizeof(struct logger_entry));
+
+ /*
+ * We read from the msg in two disjoint operations. First, we read from
+ * the current msg head offset up to 'count' bytes or to the end of
+ * the log, whichever comes first.
+ */
+ len = min(count, log->size - msg_start);
+ if (copy_to_user(buf, log->buffer + msg_start, 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(log, reader->r_off +
+ sizeof(struct logger_entry) + count);
+
+ return count + get_user_hdr_len(reader->r_ver);
+}
+
+/*
+ * get_next_entry_by_uid - Starting at 'off', returns an offset into
+ * 'log->buffer' which contains the first entry readable by 'euid'
+ */
+static size_t get_next_entry_by_uid(struct logger_log *log,
+ size_t off, kuid_t euid)
+{
+ while (off != log->w_off) {
+ struct logger_entry *entry;
+ struct logger_entry scratch;
+ size_t next_len;
+
+ entry = get_entry_header(log, off, &scratch);
+
+ if (uid_eq(entry->euid, euid))
+ return off;
+
+ next_len = sizeof(struct logger_entry) + entry->len;
+ off = logger_offset(log, off + next_len);
+ }
+
+ return off;
+}
+
+/*
+ * 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
+ *
+ * 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) {
+ mutex_lock(&log->mutex);
+
+ prepare_to_wait(&log->wq, &wait, TASK_INTERRUPTIBLE);
+
+ 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);
+
+ if (!reader->r_all)
+ reader->r_off = get_next_entry_by_uid(log,
+ reader->r_off, current_euid());
+
+ /* 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_user_hdr_len(reader->r_ver) +
+ get_entry_msg_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 = sizeof(struct logger_entry) +
+ get_entry_msg_len(log, off);
+ off = logger_offset(log, off + nr);
+ count += nr;
+ } while (count < len);
+
+ return off;
+}
+
+/*
+ * is_between - is a < c < b, accounting for wrapping of a, b, and c
+ * positions in the buffer
+ *
+ * That is, if a<b, check for c between a and b
+ * and if a>b, check for c outside (not between) a and b
+ *
+ * |------- a xxxxxxxx b --------|
+ * c^
+ *
+ * |xxxxx b --------- a xxxxxxxxx|
+ * c^
+ * or c^
+ */
+static inline int is_between(size_t a, size_t b, size_t c)
+{
+ if (a < b) {
+ /* is c between a and b? */
+ if (a < c && c <= b)
+ return 1;
+ } else {
+ /* is c outside of b through a? */
+ if (c <= b || a < 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(log, old + len);
+ struct logger_reader *reader;
+
+ if (is_between(old, new, log->head))
+ log->head = get_next_entry(log, log->head, len);
+
+ list_for_each_entry(reader, &log->readers, list)
+ if (is_between(old, new, reader->r_off))
+ reader->r_off = get_next_entry(log, reader->r_off, len);
+}
+
+/*
+ * logger_write_iter - 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.
+ */
+static ssize_t logger_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+ struct logger_log *log = file_get_log(iocb->ki_filp);
+ struct logger_entry header;
+ struct timespec now;
+ size_t len, count, w_off;
+
+ count = min_t(size_t, iocb->ki_nbytes, LOGGER_ENTRY_MAX_PAYLOAD);
+
+ now = current_kernel_time();
+
+ header.pid = current->tgid;
+ header.tid = current->pid;
+ header.sec = now.tv_sec;
+ header.nsec = now.tv_nsec;
+ header.euid = current_euid();
+ header.len = count;
+ header.hdr_size = sizeof(struct logger_entry);
+
+ /* 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);
+
+ len = min(sizeof(header), log->size - log->w_off);
+ memcpy(log->buffer + log->w_off, &header, len);
+ memcpy(log->buffer, (char *)&header + len, sizeof(header) - len);
+
+ /* Work with a copy until we are ready to commit the whole entry */
+ w_off = logger_offset(log, log->w_off + sizeof(struct logger_entry));
+
+ len = min(count, log->size - w_off);
+
+ if (copy_from_iter(log->buffer + w_off, len, from) != len) {
+ /*
+ * Note that by not updating log->w_off, this abandons the
+ * portion of the new entry that *was* successfully
+ * copied, just above. This is intentional to avoid
+ * message corruption from missing fragments.
+ */
+ mutex_unlock(&log->mutex);
+ return -EFAULT;
+ }
+
+ if (copy_from_iter(log->buffer, count - len, from) != count - len) {
+ mutex_unlock(&log->mutex);
+ return -EFAULT;
+ }
+
+ log->w_off = logger_offset(log, w_off + count);
+ mutex_unlock(&log->mutex);
+
+ /* wake up any blocked readers */
+ wake_up_interruptible(&log->wq);
+
+ return len;
+}
+
+static struct logger_log *get_log_from_minor(int minor)
+{
+ struct logger_log *log;
+
+ list_for_each_entry(log, &log_list, logs)
+ if (log->misc.minor == minor)
+ return log;
+ return NULL;
+}
+
+/*
+ * 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;
+ reader->r_ver = 1;
+ reader->r_all = in_egroup_p(inode->i_gid) ||
+ capable(CAP_SYSLOG);
+
+ 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;
+ struct logger_log *log = reader->log;
+
+ mutex_lock(&log->mutex);
+ list_del(&reader->list);
+ mutex_unlock(&log->mutex);
+
+ 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 (!reader->r_all)
+ reader->r_off = get_next_entry_by_uid(log,
+ reader->r_off, current_euid());
+
+ if (log->w_off != reader->r_off)
+ ret |= POLLIN | POLLRDNORM;
+ mutex_unlock(&log->mutex);
+
+ return ret;
+}
+
+static long logger_set_version(struct logger_reader *reader, void __user *arg)
+{
+ int version;
+
+ if (copy_from_user(&version, arg, sizeof(int)))
+ return -EFAULT;
+
+ if ((version < 1) || (version > 2))
+ return -EINVAL;
+
+ reader->r_ver = version;
+ return 0;
+}
+
+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 = -EINVAL;
+ void __user *argp = (void __user *)arg;
+
+ 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 (!reader->r_all)
+ reader->r_off = get_next_entry_by_uid(log,
+ reader->r_off, current_euid());
+
+ if (log->w_off != reader->r_off)
+ ret = get_user_hdr_len(reader->r_ver) +
+ get_entry_msg_len(log, reader->r_off);
+ else
+ ret = 0;
+ break;
+ case LOGGER_FLUSH_LOG:
+ if (!(file->f_mode & FMODE_WRITE)) {
+ ret = -EBADF;
+ break;
+ }
+ if (!(in_egroup_p(file_inode(file)->i_gid) ||
+ capable(CAP_SYSLOG))) {
+ ret = -EPERM;
+ break;
+ }
+ list_for_each_entry(reader, &log->readers, list)
+ reader->r_off = log->w_off;
+ log->head = log->w_off;
+ ret = 0;
+ break;
+ case LOGGER_GET_VERSION:
+ if (!(file->f_mode & FMODE_READ)) {
+ ret = -EBADF;
+ break;
+ }
+ reader = file->private_data;
+ ret = reader->r_ver;
+ break;
+ case LOGGER_SET_VERSION:
+ if (!(file->f_mode & FMODE_READ)) {
+ ret = -EBADF;
+ break;
+ }
+ reader = file->private_data;
+ ret = logger_set_version(reader, argp);
+ break;
+ }
+
+ mutex_unlock(&log->mutex);
+
+ return ret;
+}
+
+static const struct file_operations logger_fops = {
+ .owner = THIS_MODULE,
+ .read = logger_read,
+ .write_iter = logger_write_iter,
+ .poll = logger_poll,
+ .unlocked_ioctl = logger_ioctl,
+ .compat_ioctl = logger_ioctl,
+ .open = logger_open,
+ .release = logger_release,
+};
+
+/*
+ * Log size must must be a power of two, and greater than
+ * (LOGGER_ENTRY_MAX_PAYLOAD + sizeof(struct logger_entry)).
+ */
+static int __init create_log(char *log_name, int size)
+{
+ int ret = 0;
+ struct logger_log *log;
+ unsigned char *buffer;
+
+ buffer = vmalloc(size);
+ if (buffer == NULL)
+ return -ENOMEM;
+
+ log = kzalloc(sizeof(struct logger_log), GFP_KERNEL);
+ if (log == NULL) {
+ ret = -ENOMEM;
+ goto out_free_buffer;
+ }
+ log->buffer = buffer;
+
+ log->misc.minor = MISC_DYNAMIC_MINOR;
+ log->misc.name = kstrdup(log_name, GFP_KERNEL);
+ if (log->misc.name == NULL) {
+ ret = -ENOMEM;
+ goto out_free_log;
+ }
+
+ log->misc.fops = &logger_fops;
+ log->misc.parent = NULL;
+
+ init_waitqueue_head(&log->wq);
+ INIT_LIST_HEAD(&log->readers);
+ mutex_init(&log->mutex);
+ log->w_off = 0;
+ log->head = 0;
+ log->size = size;
+
+ INIT_LIST_HEAD(&log->logs);
+ list_add_tail(&log->logs, &log_list);
+
+ /* finally, initialize the misc device for this log */
+ ret = misc_register(&log->misc);
+ if (unlikely(ret)) {
+ pr_err("failed to register misc device for log '%s'!\n",
+ log->misc.name);
+ goto out_free_misc_name;
+ }
+
+ pr_info("created %luK log '%s'\n",
+ (unsigned long)log->size >> 10, log->misc.name);
+
+ return 0;
+
+out_free_misc_name:
+ kfree(log->misc.name);
+
+out_free_log:
+ kfree(log);
+
+out_free_buffer:
+ vfree(buffer);
+ return ret;
+}
+
+static int __init logger_init(void)
+{
+ int ret;
+
+ ret = create_log(LOGGER_LOG_MAIN, 256*1024);
+ if (unlikely(ret))
+ goto out;
+
+ ret = create_log(LOGGER_LOG_EVENTS, 256*1024);
+ if (unlikely(ret))
+ goto out;
+
+ ret = create_log(LOGGER_LOG_RADIO, 256*1024);
+ if (unlikely(ret))
+ goto out;
+
+ ret = create_log(LOGGER_LOG_SYSTEM, 256*1024);
+ if (unlikely(ret))
+ goto out;
+
+out:
+ return ret;
+}
+
+static void __exit logger_exit(void)
+{
+ struct logger_log *current_log, *next_log;
+
+ list_for_each_entry_safe(current_log, next_log, &log_list, logs) {
+ /* we have to delete all the entry inside log_list */
+ misc_deregister(¤t_log->misc);
+ vfree(current_log->buffer);
+ kfree(current_log->misc.name);
+ list_del(¤t_log->logs);
+ kfree(current_log);
+ }
+}
+
+device_initcall(logger_init);
+module_exit(logger_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Robert Love, <rlove@google.com>");
+MODULE_DESCRIPTION("Android Logger");
projects / platform / kernel / linux-rpi.git / commitdiff