-/*
- * 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 / cascardo / linux.git / commitdiff