xnu-3789.51.2.tar.gz

[apple/xnu.git] / bsd / kern / subr_log.c

/*
 * Copyright (c) 2000-2016 Apple, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1982, 1986, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)subr_log.c  8.3 (Berkeley) 2/14/95
 */

/*
 * Error log buffer for kernel printf's.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc_internal.h>
#include <sys/vnode.h>
#include <stdbool.h>
#include <firehose/tracepoint_private.h>
#include <firehose/chunk_private.h>
#include <firehose/ioctl_private.h>
#include <os/firehose_buffer_private.h>

#include <os/log_private.h>
#include <sys/ioctl.h>
#include <sys/msgbuf.h>
#include <sys/file_internal.h>
#include <sys/errno.h>
#include <sys/select.h>
#include <sys/kernel.h>
#include <kern/thread.h>
#include <kern/sched_prim.h>
#include <kern/simple_lock.h>
#include <sys/lock.h>
#include <sys/signalvar.h>
#include <sys/conf.h>
#include <sys/sysctl.h>
#include <sys/queue.h>
#include <kern/kalloc.h>
#include <pexpert/pexpert.h>
#include <mach/mach_port.h>
#include <mach/mach_vm.h>
#include <mach/vm_map.h>
#include <vm/vm_kern.h>
#include <kern/task.h>
#include <kern/locks.h>

/* XXX should be in a common header somewhere */
extern void logwakeup(void);
extern void oslogwakeup(void);
extern void oslog_streamwakeup(void);
static void oslog_streamwakeup_locked(void);
vm_offset_t kernel_firehose_addr = 0;

/* log message counters for streaming mode */
uint32_t oslog_s_streamed_msgcount = 0;
uint32_t oslog_s_dropped_msgcount  = 0;
extern uint32_t oslog_s_error_count;

#define LOG_RDPRI       (PZERO + 1)

#define LOG_NBIO        0x02
#define LOG_ASYNC       0x04
#define LOG_RDWAIT      0x08

#define MAX_UNREAD_CHARS (CONFIG_MSG_BSIZE/2)
/* All globals should be accessed under LOG_LOCK() */

/* logsoftc only valid while log_open=1 */
struct logsoftc {
        int     sc_state;               /* see above for possibilities */
        struct  selinfo sc_selp;        /* thread waiting for select */
        int     sc_pgid;                /* process/group for async I/O */
} logsoftc;

int     log_open;                       /* also used in log() */
char smsg_bufc[CONFIG_MSG_BSIZE]; /* static buffer */
char oslog_stream_bufc[FIREHOSE_CHUNK_SIZE]; /* static buffer */
struct firehose_chunk_s oslog_boot_buf = {
        .fc_pos = {
                .fcp_next_entry_offs = offsetof(struct firehose_chunk_s, fc_data),
                .fcp_private_offs = FIREHOSE_CHUNK_SIZE,
                .fcp_refcnt = 1, // indicate that there is a writer to this chunk
                .fcp_stream = firehose_stream_persist,
                .fcp_flag_io = 1, // for now, lets assume this is coming from the io bank
        },
}; /* static buffer */
firehose_chunk_t firehose_boot_chunk = &oslog_boot_buf;
struct msgbuf msgbuf = {MSG_MAGIC,sizeof(smsg_bufc),0,0,smsg_bufc};
struct msgbuf oslog_stream_buf = {MSG_MAGIC,0,0,0,NULL};
struct msgbuf *msgbufp __attribute__((used)) = &msgbuf;
struct msgbuf *oslog_streambufp __attribute__((used)) = &oslog_stream_buf;

// List entries for keeping track of the streaming buffer
static oslog_stream_buf_entry_t oslog_stream_buf_entries;

#define OSLOG_NUM_STREAM_ENTRIES        64
#define OSLOG_STREAM_BUF_SIZE           4096

int     oslog_open = 0;
int     os_log_wakeup = 0;
int     oslog_stream_open = 0;
int     oslog_stream_buf_size = OSLOG_STREAM_BUF_SIZE;
int     oslog_stream_num_entries = OSLOG_NUM_STREAM_ENTRIES;

/* oslogsoftc only valid while oslog_open=1 */
struct oslogsoftc {
        int     sc_state;               /* see above for possibilities */
        struct  selinfo sc_selp;        /* thread waiting for select */
        int     sc_pgid;                /* process/group for async I/O */
} oslogsoftc;

struct oslog_streamsoftc {
        int     sc_state;               /* see above for possibilities */
        struct  selinfo sc_selp;        /* thread waiting for select */
        int     sc_pgid;                /* process/group for async I/O */
}oslog_streamsoftc;

STAILQ_HEAD(, oslog_stream_buf_entry_s) oslog_stream_free_head =
                STAILQ_HEAD_INITIALIZER(oslog_stream_free_head);
STAILQ_HEAD(, oslog_stream_buf_entry_s) oslog_stream_buf_head =
                STAILQ_HEAD_INITIALIZER(oslog_stream_buf_head);

/* defined in osfmk/kern/printf.c  */
extern void oslog_lock_init(void);
extern void bsd_log_lock(void);
extern void bsd_log_unlock(void);

/* defined for osfmk/kern/printf.c */
void bsd_log_init(void);

/*
 * Ideally this file would define this lock, but bsd doesn't have the definition
 * for lock groups.
 */
decl_lck_spin_data(extern, oslog_stream_lock)

/* XXX wants a linker set so these can be static */
extern d_open_t         logopen;
extern d_close_t        logclose;
extern d_read_t         logread;
extern d_ioctl_t        logioctl;
extern d_select_t       logselect;

/* XXX wants a linker set so these can be static */
extern d_open_t         oslogopen;
extern d_close_t        oslogclose;
extern d_select_t       oslogselect;
extern d_ioctl_t        oslogioctl;

/* XXX wants a linker set so these can be static */
extern d_open_t         oslog_streamopen;
extern d_close_t        oslog_streamclose;
extern d_read_t         oslog_streamread;
extern d_ioctl_t        oslog_streamioctl;
extern d_select_t       oslog_streamselect;

void oslog_init(void);
void oslog_setsize(int size);
void oslog_streamwrite_locked(firehose_tracepoint_id_u ftid,
                uint64_t stamp, const void *pubdata, size_t publen);
void oslog_streamwrite_metadata_locked(oslog_stream_buf_entry_t m_entry);
static oslog_stream_buf_entry_t oslog_stream_find_free_buf_entry_locked(void);
static void oslog_streamwrite_append_bytes(const char *buffer, int buflen);

/*
 * Serialize log access.  Note that the log can be written at interrupt level,
 * so any log manipulations that can be done from, or affect, another processor
 * at interrupt level must be guarded with a spin lock.
 */

#define LOG_LOCK() bsd_log_lock()
#define LOG_UNLOCK() bsd_log_unlock()

#if DEBUG
#define LOG_SETSIZE_DEBUG(x...) kprintf(x)
#else
#define LOG_SETSIZE_DEBUG(x...) do { } while(0)
#endif

static int sysctl_kern_msgbuf(struct sysctl_oid *oidp,
                                void *arg1,
                                int arg2,
                                struct sysctl_req *req);

/*ARGSUSED*/
int
logopen(__unused dev_t dev, __unused int flags, __unused int mode, struct proc *p)
{
        LOG_LOCK();
        if (log_open) {
                LOG_UNLOCK();
                return (EBUSY);
        }
        logsoftc.sc_pgid = p->p_pid;            /* signal process only */
        log_open = 1;

        LOG_UNLOCK();

        return (0);
}

/*ARGSUSED*/
int
logclose(__unused dev_t dev, __unused int flag, __unused int devtype, __unused struct proc *p)
{
        LOG_LOCK();
        logsoftc.sc_state &= ~(LOG_NBIO | LOG_ASYNC);
        selwakeup(&logsoftc.sc_selp);
        selthreadclear(&logsoftc.sc_selp);
        log_open = 0;
        LOG_UNLOCK();
        return (0);
}


int
oslogopen(__unused dev_t dev, __unused int flags, __unused int mode, struct proc *p)
{
        LOG_LOCK();
        if (oslog_open) {
                LOG_UNLOCK();
                return(EBUSY);
        }
        oslogsoftc.sc_pgid = p->p_pid;          /* signal process only */
        oslog_open = 1;

        LOG_UNLOCK();
        return (0);
}

int
oslogclose(__unused dev_t dev, __unused int flag, __unused int devtype, __unused struct proc *p)
{
        LOG_LOCK();
        oslogsoftc.sc_state &= ~(LOG_NBIO | LOG_ASYNC);
        selwakeup(&oslogsoftc.sc_selp);
        selthreadclear(&oslogsoftc.sc_selp);
        oslog_open = 0;
        LOG_UNLOCK();
        return (0);
}

int
oslog_streamopen(__unused dev_t dev, __unused int flags, __unused int mode, struct proc *p)
{
        char *oslog_stream_msg_bufc = NULL;
        oslog_stream_buf_entry_t entries = NULL;

        lck_spin_lock(&oslog_stream_lock);
        if (oslog_stream_open) {
                lck_spin_unlock(&oslog_stream_lock);
                return EBUSY;
        }
        lck_spin_unlock(&oslog_stream_lock);

        // Allocate the stream buffer
        oslog_stream_msg_bufc = kalloc(oslog_stream_buf_size);
        if (!oslog_stream_msg_bufc) {
                return ENOMEM;
        }

        /* entries to support kernel logging in stream mode */
        entries = kalloc(oslog_stream_num_entries * sizeof(struct oslog_stream_buf_entry_s));
        if (!entries) {
                kfree(oslog_stream_msg_bufc, oslog_stream_buf_size);
                return ENOMEM;
        }

        lck_spin_lock(&oslog_stream_lock);
        if (oslog_stream_open) {
                lck_spin_unlock(&oslog_stream_lock);
                kfree(oslog_stream_msg_bufc, oslog_stream_buf_size);
                kfree(entries, oslog_stream_num_entries * sizeof(struct oslog_stream_buf_entry_s));
                return EBUSY;
        }

        assert(oslog_streambufp->msg_bufc == NULL);
        oslog_streambufp->msg_bufc = oslog_stream_msg_bufc;
        oslog_streambufp->msg_size = oslog_stream_buf_size;

        oslog_stream_buf_entries = entries;

        STAILQ_INIT(&oslog_stream_free_head);
        STAILQ_INIT(&oslog_stream_buf_head);

        for (int i = 0; i < oslog_stream_num_entries; i++) {
                oslog_stream_buf_entries[i].type = oslog_stream_link_type_log;
                oslog_stream_buf_entries[i].offset = 0;
                oslog_stream_buf_entries[i].size = 0;
                oslog_stream_buf_entries[i].timestamp = 0;
                STAILQ_INSERT_TAIL(&oslog_stream_free_head, &oslog_stream_buf_entries[i], buf_entries);
        }

        /* there should be no pending entries in the stream */
        assert(STAILQ_EMPTY(&oslog_stream_buf_head));
        assert(oslog_streambufp->msg_bufx == 0);
        assert(oslog_streambufp->msg_bufr == 0);

        oslog_streambufp->msg_bufx = 0;
        oslog_streambufp->msg_bufr = 0;
        oslog_streamsoftc.sc_pgid = p->p_pid; /* signal process only */
        oslog_stream_open = 1;
        lck_spin_unlock(&oslog_stream_lock);

        return 0;
}

int
oslog_streamclose(__unused dev_t dev, __unused int flag, __unused int devtype, __unused struct proc *p)
{
        oslog_stream_buf_entry_t next_entry = NULL;
        char *oslog_stream_msg_bufc = NULL;
        oslog_stream_buf_entry_t entries = NULL;

        lck_spin_lock(&oslog_stream_lock);

        if (oslog_stream_open == 0) {
                lck_spin_unlock(&oslog_stream_lock);
                return EBADF;
        }

        // Consume all log lines
        while (!STAILQ_EMPTY(&oslog_stream_buf_head)) {
                next_entry = STAILQ_FIRST(&oslog_stream_buf_head);
                STAILQ_REMOVE_HEAD(&oslog_stream_buf_head, buf_entries);
        }
        oslog_streamwakeup_locked();
        oslog_streamsoftc.sc_state &= ~(LOG_NBIO | LOG_ASYNC);
        selwakeup(&oslog_streamsoftc.sc_selp);
        selthreadclear(&oslog_streamsoftc.sc_selp);
        oslog_stream_open = 0;
        oslog_streambufp->msg_bufr = 0;
        oslog_streambufp->msg_bufx = 0;
        oslog_stream_msg_bufc = oslog_streambufp->msg_bufc;
        oslog_streambufp->msg_bufc = NULL;
        entries = oslog_stream_buf_entries;
        oslog_stream_buf_entries = NULL;
        oslog_streambufp->msg_size = 0;

        lck_spin_unlock(&oslog_stream_lock);

        // Free the stream buffer
        kfree(oslog_stream_msg_bufc, oslog_stream_buf_size);
        // Free the list entries
        kfree(entries, oslog_stream_num_entries * sizeof(struct oslog_stream_buf_entry_s));

        return 0;
}

/*ARGSUSED*/
int
logread(__unused dev_t dev, struct uio *uio, int flag)
{
        int l;
        int error = 0;

        LOG_LOCK();
        while (msgbufp->msg_bufr == msgbufp->msg_bufx) {
                if (flag & IO_NDELAY) {
                        error = EWOULDBLOCK;
                        goto out;
                }
                if (logsoftc.sc_state & LOG_NBIO) {
                        error = EWOULDBLOCK;
                        goto out;
                }
                logsoftc.sc_state |= LOG_RDWAIT;
                LOG_UNLOCK();
                /*
                 * If the wakeup is missed 
                 * then wait for 5 sec and reevaluate 
                 */
                if ((error = tsleep((caddr_t)msgbufp, LOG_RDPRI | PCATCH,
                                "klog", 5 * hz)) != 0) {
                        /* if it times out; ignore */
                        if (error != EWOULDBLOCK)
                                return (error);
                }
                LOG_LOCK();
        }
        logsoftc.sc_state &= ~LOG_RDWAIT;

        while (uio_resid(uio) > 0) {
                int readpos;

                l = msgbufp->msg_bufx - msgbufp->msg_bufr;
                if (l < 0)
                        l = msgbufp->msg_size - msgbufp->msg_bufr;
                l = min(l, uio_resid(uio));
                if (l == 0)
                        break;

                readpos = msgbufp->msg_bufr;
                LOG_UNLOCK();
                error = uiomove((caddr_t)&msgbufp->msg_bufc[readpos],
                        l, uio);
                LOG_LOCK();
                if (error)
                        break;
                msgbufp->msg_bufr = readpos + l;
                if (msgbufp->msg_bufr >= msgbufp->msg_size)
                        msgbufp->msg_bufr = 0;
        }
out:
        LOG_UNLOCK();
        return (error);
}

/*ARGSUSED*/
int
oslog_streamread(__unused dev_t dev, struct uio *uio, int flag)
{
        int error = 0;
        int copy_size = 0;
        static char logline[FIREHOSE_CHUNK_SIZE];

        lck_spin_lock(&oslog_stream_lock);

        if (!oslog_stream_open) {
                lck_spin_unlock(&oslog_stream_lock);
                return EBADF;
        }

        while (STAILQ_EMPTY(&oslog_stream_buf_head)) {
                if (flag & IO_NDELAY || oslog_streamsoftc.sc_state & LOG_NBIO) {
                        lck_spin_unlock(&oslog_stream_lock);
                        return EWOULDBLOCK;
                }

                oslog_streamsoftc.sc_state |= LOG_RDWAIT;
                wait_result_t wr = assert_wait((event_t)oslog_streambufp,
                        THREAD_INTERRUPTIBLE);
                if (wr == THREAD_WAITING) {
                        lck_spin_unlock(&oslog_stream_lock);
                        wr = thread_block(THREAD_CONTINUE_NULL);
                        lck_spin_lock(&oslog_stream_lock);
                }

                switch (wr) {
                        case THREAD_AWAKENED:
                        case THREAD_TIMED_OUT:
                                break;
                        default:
                                lck_spin_unlock(&oslog_stream_lock);
                                return EINTR;
                }
        }

        if (!oslog_stream_open) {
                lck_spin_unlock(&oslog_stream_lock);
                return EBADF;
        }

        int logpos = 0;
        oslog_stream_buf_entry_t read_entry = NULL;
        uint16_t rec_length;

        read_entry = STAILQ_FIRST(&oslog_stream_buf_head);
        assert(read_entry != NULL);
        STAILQ_REMOVE_HEAD(&oslog_stream_buf_head, buf_entries);

        // Copy the timestamp first
        memcpy(logline + logpos, &read_entry->timestamp, sizeof(uint64_t));
        logpos += sizeof(uint64_t);

        switch (read_entry->type) {
                /* Handle metadata messages */
                case oslog_stream_link_type_metadata:
                {
                        memcpy(logline + logpos,
                                (read_entry->metadata), read_entry->size);
                        logpos += read_entry->size;

                        lck_spin_unlock(&oslog_stream_lock);

                        // Free the list entry
                        kfree(read_entry, (sizeof(struct oslog_stream_buf_entry_s) + read_entry->size));
                        break;
                }
                /* Handle log messages */
                case oslog_stream_link_type_log:
                {
                        /* ensure that the correct read entry was dequeued */
                        assert(read_entry->offset == oslog_streambufp->msg_bufr);
                        rec_length = read_entry->size;

                        // If the next log line is contiguous in the buffer, copy it out.
                        if(read_entry->offset + rec_length <= oslog_streambufp->msg_size) {
                                memcpy(logline + logpos,
                                        oslog_streambufp->msg_bufc + read_entry->offset, rec_length);

                                oslog_streambufp->msg_bufr += rec_length;
                                if (oslog_streambufp->msg_bufr == oslog_streambufp->msg_size) {
                                        oslog_streambufp->msg_bufr = 0;
                                }
                                logpos += rec_length;
                        } else {
                                // Otherwise, copy until the end of the buffer, and
                                // copy the remaining bytes starting at index 0.
                                int bytes_left = oslog_streambufp->msg_size - read_entry->offset;
                                memcpy(logline + logpos,
                                        oslog_streambufp->msg_bufc + read_entry->offset, bytes_left);
                                logpos += bytes_left;
                                rec_length -= bytes_left;

                                memcpy(logline + logpos, (const void *)oslog_streambufp->msg_bufc,
                                        rec_length);
                                oslog_streambufp->msg_bufr = rec_length;
                                logpos += rec_length;
                        }
                        assert(oslog_streambufp->msg_bufr < oslog_streambufp->msg_size);
                        STAILQ_INSERT_TAIL(&oslog_stream_free_head, read_entry, buf_entries);

                        lck_spin_unlock(&oslog_stream_lock);
                        break;
                }
                default:
                {
                        panic("Got unexpected log entry type: %hhu\n", read_entry->type);
                }
        }

        copy_size = min(logpos, uio_resid(uio));
        if (copy_size != 0) {
                error = uiomove((caddr_t)logline, copy_size, uio);
        }
        (void)hw_atomic_add(&oslog_s_streamed_msgcount, 1);

        return error;
}

/*ARGSUSED*/
int
logselect(__unused dev_t dev, int rw, void * wql, struct proc *p)
{
        switch (rw) {

        case FREAD:
                LOG_LOCK();     
                if (msgbufp->msg_bufr != msgbufp->msg_bufx) {
                        LOG_UNLOCK();
                        return (1);
                }
                selrecord(p, &logsoftc.sc_selp, wql);
                LOG_UNLOCK();
                break;
        }
        return (0);
}

int
oslogselect(__unused dev_t dev, int rw, void * wql, struct proc *p)
{
        switch (rw) {

        case FREAD:
                LOG_LOCK();
                if (os_log_wakeup) {
                        LOG_UNLOCK();
                        return (1);
                }
                selrecord(p, &oslogsoftc.sc_selp, wql);
                LOG_UNLOCK();
                break;
        }
        return (0);
}

int
oslog_streamselect(__unused dev_t dev, int rw, void * wql, struct proc *p)
{
        int ret = 0;

        lck_spin_lock(&oslog_stream_lock);

        switch (rw) {
        case FREAD:
                if (STAILQ_EMPTY(&oslog_stream_buf_head)) {
                        selrecord(p, &oslog_streamsoftc.sc_selp, wql);
                } else {
                        ret = 1;
                }
                break;
        }

        lck_spin_unlock(&oslog_stream_lock);
        return ret;
}

void
logwakeup(void)
{
        int pgid;

        /* cf. r24974766 & r25201228*/
        if (oslog_is_safe() == FALSE) {
                return;
        }

        LOG_LOCK();     
        if (!log_open) {
                LOG_UNLOCK();
                return;
        }
        selwakeup(&logsoftc.sc_selp);
        if (logsoftc.sc_state & LOG_ASYNC) {
                pgid = logsoftc.sc_pgid;
                LOG_UNLOCK();
                if (pgid < 0)
                        gsignal(-pgid, SIGIO); 
                else 
                        proc_signal(pgid, SIGIO);
                LOG_LOCK();
        }
        if (logsoftc.sc_state & LOG_RDWAIT) {
                wakeup((caddr_t)msgbufp);
                logsoftc.sc_state &= ~LOG_RDWAIT;
        }
        LOG_UNLOCK();
}

void
oslogwakeup(void)
{
        LOG_LOCK();
        if (!oslog_open) {
                LOG_UNLOCK();
                return;
        }
        selwakeup(&oslogsoftc.sc_selp);
        os_log_wakeup = 1;
        LOG_UNLOCK();
}

static void
oslog_streamwakeup_locked(void)
{
        lck_spin_assert(&oslog_stream_lock, LCK_ASSERT_OWNED);
        if (!oslog_stream_open) {
                return;
        }
        selwakeup(&oslog_streamsoftc.sc_selp);
        if (oslog_streamsoftc.sc_state & LOG_RDWAIT) {
                wakeup((caddr_t)oslog_streambufp);
                oslog_streamsoftc.sc_state &= ~LOG_RDWAIT;
        }
}

void
oslog_streamwakeup(void)
{
        /* cf. r24974766 & r25201228*/
        if (oslog_is_safe() == FALSE) {
                return;
        }

        lck_spin_lock(&oslog_stream_lock);
        oslog_streamwakeup_locked();
        lck_spin_unlock(&oslog_stream_lock);
}

/*ARGSUSED*/
int
logioctl(__unused dev_t dev, u_long com, caddr_t data, __unused int flag, __unused struct proc *p)
{
        int l;

        LOG_LOCK();
        switch (com) {

        /* return number of characters immediately available */
        case FIONREAD:
                l = msgbufp->msg_bufx - msgbufp->msg_bufr;
                if (l < 0)
                        l += msgbufp->msg_size;
                *(off_t *)data = l;
                break;

        case FIONBIO:
                if (*(int *)data)
                        logsoftc.sc_state |= LOG_NBIO;
                else
                        logsoftc.sc_state &= ~LOG_NBIO;
                break;

        case FIOASYNC:
                if (*(int *)data)
                        logsoftc.sc_state |= LOG_ASYNC;
                else
                        logsoftc.sc_state &= ~LOG_ASYNC;
                break;

        case TIOCSPGRP:
                logsoftc.sc_pgid = *(int *)data;
                break;

        case TIOCGPGRP:
                *(int *)data = logsoftc.sc_pgid;
                break;

        default:
                LOG_UNLOCK();
                return (-1);
        }
        LOG_UNLOCK();
        return (0);
}

/*ARGSUSED*/
int
oslogioctl(__unused dev_t dev, u_long com, caddr_t data, __unused int flag, __unused struct proc *p)
{
        int ret = 0;
        mach_vm_size_t buffer_size = (FIREHOSE_BUFFER_KERNEL_CHUNK_COUNT * FIREHOSE_CHUNK_SIZE);
        firehose_buffer_map_info_t map_info = {0, 0};
        firehose_buffer_t kernel_firehose_buffer = NULL;
        mach_vm_address_t user_addr = 0;
        mach_port_t mem_entry_ptr = MACH_PORT_NULL;

        switch (com) {

        /* return number of characters immediately available */

        case LOGBUFFERMAP:
                kernel_firehose_buffer = kernel_firehose_addr;

                ret = mach_make_memory_entry_64(kernel_map,
                                                &buffer_size,
                                                (mach_vm_offset_t) kernel_firehose_buffer,
                                                ( MAP_MEM_VM_SHARE | VM_PROT_READ ),
                                                &mem_entry_ptr,
                                                MACH_PORT_NULL);
                if (ret == KERN_SUCCESS) {
                        ret = mach_vm_map(get_task_map(current_task()),
                                          &user_addr,
                                          buffer_size,
                                          0, /*  mask */
                                          VM_FLAGS_ANYWHERE,
                                          mem_entry_ptr,
                                          0, /* offset */
                                          FALSE, /* copy */
                                          VM_PROT_READ,
                                          VM_PROT_READ,
                                          VM_INHERIT_SHARE);
                }

                if (ret == KERN_SUCCESS) {
                        map_info.fbmi_addr = (uint64_t) (user_addr);
                        map_info.fbmi_size = buffer_size;
                        bcopy(&map_info, data, sizeof(firehose_buffer_map_info_t));
                }
                break;
        case LOGFLUSHED:
                LOG_LOCK();
                os_log_wakeup = 0;
                LOG_UNLOCK();
                __firehose_merge_updates(*(firehose_push_reply_t *)(data));
                break;
        default:
                return (-1);
        }
        return (0);
}

/*ARGSUSED*/
int
oslog_streamioctl(__unused dev_t dev, u_long com, caddr_t data, __unused int flag, __unused struct proc *p)
{
        int err = 0;

        lck_spin_lock(&oslog_stream_lock);

        switch (com) {
        case FIONBIO:
                if (data && *(int *)data)
                        oslog_streamsoftc.sc_state |= LOG_NBIO;
                else
                        oslog_streamsoftc.sc_state &= ~LOG_NBIO;
                break;
        case FIOASYNC:
                if (data && *(int *)data)
                        oslog_streamsoftc.sc_state |= LOG_ASYNC;
                else
                        oslog_streamsoftc.sc_state &= ~LOG_ASYNC;
                break;
        default:
                err = -1;
                break;
        }

        lck_spin_unlock(&oslog_stream_lock);
        return err;
}

void
bsd_log_init(void)
{
        /* After this point, we must be ready to accept characters */
}

void
oslog_init(void)
{
        kern_return_t kr;
        vm_size_t size = FIREHOSE_BUFFER_KERNEL_CHUNK_COUNT * FIREHOSE_CHUNK_SIZE;

        oslog_lock_init();

        kr = kmem_alloc_flags(kernel_map, &kernel_firehose_addr,
                size + (2 * PAGE_SIZE), VM_KERN_MEMORY_LOG,
                KMA_GUARD_FIRST | KMA_GUARD_LAST);
        if (kr != KERN_SUCCESS) {
                panic("Failed to allocate memory for firehose logging buffer");
        }
        kernel_firehose_addr += PAGE_SIZE;
        bzero(kernel_firehose_addr, size);
        /* register buffer with firehose */
        kernel_firehose_addr = __firehose_buffer_create((size_t *) &size);

        kprintf("oslog_init completed\n");
}

/*
 * log_putc_locked
 *
 * Decription:  Output a character to the log; assumes the LOG_LOCK() is held
 *              by the caller.
 *
 * Parameters:  c                               Character to output
 *
 * Returns:     (void)
 *
 * Notes:       This functions is used for multibyte output to the log; it
 *              should be used preferrentially where possible to ensure that
 *              log entries do not end up interspersed due to preemption or
 *              SMP reentrancy.
 */
void
log_putc_locked(char c)
{
        struct msgbuf *mbp;

        mbp = msgbufp; 
        mbp->msg_bufc[mbp->msg_bufx++] = c;
        if (mbp->msg_bufx >= msgbufp->msg_size)
                mbp->msg_bufx = 0;
}

static oslog_stream_buf_entry_t
oslog_stream_find_free_buf_entry_locked(void)
{
        struct msgbuf *mbp;
        oslog_stream_buf_entry_t buf_entry = NULL;

        lck_spin_assert(&oslog_stream_lock, LCK_ASSERT_OWNED);

        mbp = oslog_streambufp;

        buf_entry = STAILQ_FIRST(&oslog_stream_free_head);
        if (buf_entry) {
                STAILQ_REMOVE_HEAD(&oslog_stream_free_head, buf_entries);
        }
        else {
                // If no list elements are available in the free-list,
                // consume the next log line so we can free up its list element
                oslog_stream_buf_entry_t prev_entry = NULL;

                buf_entry = STAILQ_FIRST(&oslog_stream_buf_head);
                while (buf_entry->type == oslog_stream_link_type_metadata) {
                        prev_entry = buf_entry;
                        buf_entry = STAILQ_NEXT(buf_entry, buf_entries);
                }

                if (prev_entry == NULL) {
                        STAILQ_REMOVE_HEAD(&oslog_stream_buf_head, buf_entries);
                }
                else {
                        STAILQ_REMOVE_AFTER(&oslog_stream_buf_head, prev_entry, buf_entries);
                }

                mbp->msg_bufr += buf_entry->size;
                oslog_s_dropped_msgcount++;
                if (mbp->msg_bufr >= mbp->msg_size) {
                        mbp->msg_bufr = (mbp->msg_bufr % mbp->msg_size);
                }
        }

        return buf_entry;
}

void
oslog_streamwrite_metadata_locked(oslog_stream_buf_entry_t m_entry)
{
        lck_spin_assert(&oslog_stream_lock, LCK_ASSERT_OWNED);
        STAILQ_INSERT_TAIL(&oslog_stream_buf_head, m_entry, buf_entries);

        return;
}

static void oslog_streamwrite_append_bytes(const char *buffer, int buflen)
{
        struct msgbuf *mbp;

        lck_spin_assert(&oslog_stream_lock, LCK_ASSERT_OWNED);

        mbp = oslog_streambufp;
        // Check if we have enough space in the stream buffer to write the data
        if (mbp->msg_bufx + buflen <= mbp->msg_size) {
                memcpy((void *)(mbp->msg_bufc + mbp->msg_bufx), buffer, buflen);

                mbp->msg_bufx += buflen;
                if (mbp->msg_bufx == mbp->msg_size) {
                        mbp->msg_bufx = 0;
                }
        } else {
                // Copy part of the data until the end of the stream
                int bytes_left = mbp->msg_size - mbp->msg_bufx;
                memcpy((void *)(mbp->msg_bufc + mbp->msg_bufx), buffer, bytes_left);

                buflen -= bytes_left;
                buffer += bytes_left;

                // Copy the remainder of the data from the beginning of stream
                memcpy((void *)mbp->msg_bufc, buffer, buflen);
                mbp->msg_bufx = buflen;
        }
        return;
}


void
oslog_streamwrite_locked(firehose_tracepoint_id_u ftid,
                uint64_t stamp, const void *pubdata, size_t publen)
{
        struct msgbuf *mbp;
        int available_space = 0;
        oslog_stream_buf_entry_t buf_entry = NULL;
        oslog_stream_buf_entry_t next_entry = NULL;

        uint16_t ft_size = offsetof(struct firehose_tracepoint_s, ft_data);
        int ft_length = ft_size + publen;

        lck_spin_assert(&oslog_stream_lock, LCK_ASSERT_OWNED);

        mbp = oslog_streambufp;
        if (ft_length > mbp->msg_size) {
                (void)hw_atomic_add(&oslog_s_error_count, 1);
                return;
        }

        // Ensure that we have a list element for this record
        buf_entry = oslog_stream_find_free_buf_entry_locked();

        assert(buf_entry != NULL);

        // Ensure that we have space in the ring buffer for the current logline
        if (mbp->msg_bufr > mbp->msg_bufx) {
                available_space = mbp->msg_bufr - mbp->msg_bufx;
        } else {
                available_space = mbp->msg_size - mbp->msg_bufx + mbp->msg_bufr;
        }
        while(ft_length > available_space) {
                oslog_stream_buf_entry_t prev_entry = NULL;

                next_entry = STAILQ_FIRST(&oslog_stream_buf_head);
                assert(next_entry != NULL);
                while (next_entry->type == oslog_stream_link_type_metadata) {
                        prev_entry = next_entry;
                        next_entry = STAILQ_NEXT(next_entry, buf_entries);
                }

                if (prev_entry == NULL) {
                        STAILQ_REMOVE_HEAD(&oslog_stream_buf_head, buf_entries);
                }
                else {
                        STAILQ_REMOVE_AFTER(&oslog_stream_buf_head, prev_entry, buf_entries);
                }

                mbp->msg_bufr += next_entry->size;
                if (mbp->msg_bufr >= mbp->msg_size) {
                        mbp->msg_bufr = (mbp->msg_bufr % mbp->msg_size);
                }

                oslog_s_dropped_msgcount++;
                available_space += next_entry->size;

                STAILQ_INSERT_TAIL(&oslog_stream_free_head, next_entry, buf_entries);
        }

        assert(ft_length <= available_space);

        // Write the log line and update the list entry for this record
        buf_entry->offset = mbp->msg_bufx;
        buf_entry->size = ft_length;
        buf_entry->timestamp = stamp;
        buf_entry->type = oslog_stream_link_type_log;

        // Construct a tracepoint
        struct firehose_tracepoint_s fs = {
                .ft_thread = thread_tid(current_thread()),
                .ft_id.ftid_value = ftid.ftid_value,
                .ft_length = publen
        };

        oslog_streamwrite_append_bytes((char *)&fs, sizeof(fs));
        oslog_streamwrite_append_bytes(pubdata, publen);

        assert(mbp->msg_bufr < mbp->msg_size);
        // Insert the element to the buffer data list
        STAILQ_INSERT_TAIL(&oslog_stream_buf_head, buf_entry, buf_entries);

        return;
}



/*
 * log_putc
 *
 * Decription:  Output a character to the log; assumes the LOG_LOCK() is NOT
 *              held by the caller.
 *
 * Parameters:  c                               Character to output
 *
 * Returns:     (void)
 *
 * Notes:       This function is used for syingle byte output to the log.  It
 *              primarily exists to maintain binary backward compatibility.
 */
void
log_putc(char c)
{
        int unread_count = 0;
        LOG_LOCK();
        log_putc_locked(c);
        unread_count = msgbufp->msg_bufx - msgbufp->msg_bufr;
        LOG_UNLOCK();

        if (unread_count < 0)
                unread_count = 0 - unread_count;
        if (c == '\n' || unread_count >= MAX_UNREAD_CHARS)
                logwakeup();
}


/*
 * it is possible to increase the kernel log buffer size by adding
 *   msgbuf=n
 * to the kernel command line, and to read the current size using
 *   sysctl kern.msgbuf
 * If there is no parameter on the kernel command line, the buffer is
 * allocated statically and is CONFIG_MSG_BSIZE characters in size, otherwise
 * memory is dynamically allocated. Memory management must already be up.
 */
int
log_setsize(int size) {
        char *new_logdata;
        int new_logsize, new_bufr, new_bufx;
        char *old_logdata;
        int old_logsize, old_bufr, old_bufx;
        int i, count;
        char *p, ch;

        if (size > MAX_MSG_BSIZE)
                return (EINVAL);

        if (size <= 0)
                return (EINVAL);

        new_logsize = size;
        if (!(new_logdata = (char*)kalloc(size))) {
                printf("log_setsize: unable to allocate memory\n");
                return (ENOMEM);
        }
        bzero(new_logdata, new_logsize);

        LOG_LOCK();

        old_logsize = msgbufp->msg_size;
        old_logdata = msgbufp->msg_bufc;
        old_bufr = msgbufp->msg_bufr;
        old_bufx = msgbufp->msg_bufx;

        LOG_SETSIZE_DEBUG("log_setsize(%d): old_logdata %p old_logsize %d old_bufr %d old_bufx %d\n",
                                          size, old_logdata, old_logsize, old_bufr, old_bufx);

        /* start "new_logsize" bytes before the write pointer */
        if (new_logsize <= old_bufx) {
                count = new_logsize;
                p = old_logdata + old_bufx - count;
        } else {
                /*
                 * if new buffer is bigger, copy what we have and let the
                 * bzero above handle the difference
                 */
                count = MIN(new_logsize, old_logsize);
                p = old_logdata + old_logsize - (count - old_bufx);
        }
        for (i = 0; i < count; i++) {
                if (p >= old_logdata + old_logsize)
                        p = old_logdata;

                ch = *p++;
                new_logdata[i] = ch;
        }

        new_bufx = i;
        if (new_bufx >= new_logsize)
                new_bufx = 0;
        msgbufp->msg_bufx = new_bufx;

        new_bufr = old_bufx - old_bufr; /* how much were we trailing bufx by? */
        if (new_bufr < 0)
                new_bufr += old_logsize;
        new_bufr = new_bufx - new_bufr; /* now relative to oldest data in new buffer */
        if (new_bufr < 0)
                new_bufr += new_logsize;
        msgbufp->msg_bufr = new_bufr;

        msgbufp->msg_size = new_logsize;
        msgbufp->msg_bufc = new_logdata;

        LOG_SETSIZE_DEBUG("log_setsize(%d): new_logdata %p new_logsize %d new_bufr %d new_bufx %d\n",
                                          size, new_logdata, new_logsize, new_bufr, new_bufx);

        LOG_UNLOCK();

        /* this memory is now dead - clear it so that it compresses better
           in case of suspend to disk etc. */
        bzero(old_logdata, old_logsize);
        if (old_logdata != smsg_bufc) {
                /* dynamic memory that must be freed */
                kfree(old_logdata, old_logsize);
        }

        printf("set system log size to %d bytes\n", new_logsize);

        return 0;
}

void oslog_setsize(int size)
{
        uint16_t scale = 0;
        // If the size is less than the default stream buffer
        // do nothing
        if (size <= OSLOG_STREAM_BUF_SIZE) {
                return;
        }

        scale = (uint16_t) (size / OSLOG_STREAM_BUF_SIZE);

        oslog_stream_buf_size = size;
        oslog_stream_num_entries = scale * OSLOG_NUM_STREAM_ENTRIES;
        printf("oslog_setsize: new buffer size = %d, new num entries= %d\n", oslog_stream_buf_size, oslog_stream_num_entries);
}

SYSCTL_PROC(_kern, OID_AUTO, msgbuf, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_LOCKED, 0, 0, sysctl_kern_msgbuf, "I", "");

static int sysctl_kern_msgbuf(struct sysctl_oid *oidp __unused,
                                                          void *arg1 __unused,
                                                          int arg2 __unused,
                                                          struct sysctl_req *req)
{
        int old_bufsize, bufsize;
        int error;

        LOG_LOCK();
        old_bufsize = bufsize = msgbufp->msg_size;
        LOG_UNLOCK();

        error = sysctl_io_number(req, bufsize, sizeof(bufsize), &bufsize, NULL);
        if (error)
                return (error);

        if (bufsize != old_bufsize) {
                error = log_setsize(bufsize);
        }

        return (error);
}


/*
 * This should be called by /sbin/dmesg only via libproc.
 * It returns as much data still in the buffer as possible.
 */
int
log_dmesg(user_addr_t buffer, uint32_t buffersize, int32_t * retval) {
        uint32_t i;
        uint32_t localbuff_size;
        int error = 0, newl, skip;
        char *localbuff, *p, *copystart, ch;
        size_t copysize;

        LOG_LOCK();
        localbuff_size = (msgbufp->msg_size + 2); /* + '\n' + '\0' */
        LOG_UNLOCK();

        /* Allocate a temporary non-circular buffer for copyout */
        if (!(localbuff = (char *)kalloc(localbuff_size))) {
                printf("log_dmesg: unable to allocate memory\n");
                return (ENOMEM);
        }

        /* in between here, the log could become bigger, but that's fine */
        LOG_LOCK();

        /*
         * The message buffer is circular; start at the write pointer, and
         * make one loop up to write pointer - 1.
         */
        p = msgbufp->msg_bufc + msgbufp->msg_bufx;
        for (i = newl = skip = 0; p != msgbufp->msg_bufc + msgbufp->msg_bufx - 1; ++p) {
                if (p >= msgbufp->msg_bufc + msgbufp->msg_size)
                        p = msgbufp->msg_bufc;
                ch = *p;
                /* Skip "\n<.*>" syslog sequences. */
                if (skip) {
                        if (ch == '>')
                                newl = skip = 0;
                        continue;
                }
                if (newl && ch == '<') {
                        skip = 1;
                        continue;
                }
                if (ch == '\0')
                        continue;
                newl = (ch == '\n');
                localbuff[i++] = ch;
                /* The original version of this routine contained a buffer
                 * overflow. At the time, a "small" targeted fix was desired
                 * so the change below to check the buffer bounds was made.
                 * TODO: rewrite this needlessly convoluted routine.
                 */
                if (i == (localbuff_size - 2))
                        break;
        }
        if (!newl)
                localbuff[i++] = '\n';
        localbuff[i++] = 0;

        if (buffersize >= i) {
                copystart = localbuff;
                copysize = i;
        } else {
                copystart = localbuff + i - buffersize;
                copysize = buffersize;
        }

        LOG_UNLOCK();

        error = copyout(copystart, buffer, copysize);
        if (!error)
                *retval = copysize;

        kfree(localbuff, localbuff_size);
        return (error);
}