/* * 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 <linux/vmalloc.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 list_head logs; /* list of log channels (myself)*/}; static LIST_HEAD(log_list); /* * 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 */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; } else return file->private_data;} /* * get_entry_len - Grabs the length of the payload of the next entry starting * 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_len(struct logger_log *log, size_t off){ __u16 val; /* copy 2 bytes from buffer, in memcpy order, */ /* handling possible wrap at end of buffer */ ((__u8 *)&val)[0] = log->buffer[off]; if (likely(off+1 < log->size)) ((__u8 *)&val)[1] = log->buffer[off+1]; else ((__u8 *)&val)[1] = log->buffer[0]; 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(log, 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) { 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); /* 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(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);} /* * 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, 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)) /* * Note that by not updating 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. */ return -EFAULT; log->w_off = logger_offset(log, 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. */static 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 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; 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;Lines 1–500 of 665. Load more
/* * 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 <linux/vmalloc.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 list_head logs; /* list of log channels (myself)*/ }; static LIST_HEAD(log_list); /* * 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 */ 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; } else return file->private_data; } /* * get_entry_len - Grabs the length of the payload of the next entry starting * 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_len(struct logger_log *log, size_t off) { __u16 val; /* copy 2 bytes from buffer, in memcpy order, */ /* handling possible wrap at end of buffer */ ((__u8 *)&val)[0] = log->buffer[off]; if (likely(off+1 < log->size)) ((__u8 *)&val)[1] = log->buffer[off+1]; else ((__u8 *)&val)[1] = log->buffer[0]; 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(log, 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) { 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); /* 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(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); } /* * 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, 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)) /* * Note that by not updating 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. */ return -EFAULT; log->w_off = logger_offset(log, 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. */ static 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 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; 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;