diff options
Diffstat (limited to 'drivers/staging/android/logger.c')
| -rw-r--r-- | drivers/staging/android/logger.c | 756 |
1 files changed, 756 insertions, 0 deletions
diff --git a/drivers/staging/android/logger.c b/drivers/staging/android/logger.c new file mode 100644 index 000000000000..3e09d57dc6d9 --- /dev/null +++ b/drivers/staging/android/logger.c @@ -0,0 +1,756 @@ +/* + * 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/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 "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 */ + bool r_all; /* reader can read all entries */ + int r_ver; /* reader ABI version */ +}; + +/* 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_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'. + * + * 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); + else + 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(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(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, uid_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 (entry->euid == euid) + return off; + + next_len = sizeof(struct logger_entry) + entry->len; + off = logger_offset(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) { + 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); + + 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(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.euid = current_euid(); + header.len = min_t(size_t, iocb->ki_left, LOGGER_ENTRY_MAX_PAYLOAD); + 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); + + 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; + 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; + 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 (!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; + } + 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, + .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, and greater than + * (LOGGER_ENTRY_MAX_PAYLOAD + sizeof(struct logger_entry)). + */ +#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, 256*1024) +DEFINE_LOGGER_DEVICE(log_events, LOGGER_LOG_EVENTS, 256*1024) +DEFINE_LOGGER_DEVICE(log_radio, LOGGER_LOG_RADIO, 256*1024) +DEFINE_LOGGER_DEVICE(log_system, LOGGER_LOG_SYSTEM, 256*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; + if (log_system.misc.minor == minor) + return &log_system; + 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; + + ret = init_log(&log_system); + if (unlikely(ret)) + goto out; + +out: + return ret; +} +device_initcall(logger_init); |