probes/lttng.c

   1 /*
   2  * lttng.c
   3  *
   4  * LTTng logger ABI
   5  *
   6  * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/tracepoint.h>
  25 #include <linux/uaccess.h>
  26 #include <linux/gfp.h>
  27 #include <linux/fs.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/slab.h>
  30 #include <linux/mm.h>
  31 #include <linux/miscdevice.h>
  32 #include <wrapper/vmalloc.h>
  33 #include <lttng-events.h>
  34
  35 #define TP_MODULE_NOAUTOLOAD
  36 #define LTTNG_PACKAGE_BUILD
  37 #define CREATE_TRACE_POINTS
  38 #define TRACE_INCLUDE_PATH instrumentation/events/lttng-module
  39 #define TRACE_INCLUDE_FILE lttng
  40 #define LTTNG_INSTRUMENTATION
  41
  42 #include <instrumentation/events/lttng-module/lttng.h>
  43
  44 /* Events written through logger are truncated at 1024 bytes */
  45 #define LTTNG_LOGGER_COUNT_MAX  1024
  46 #define LTTNG_LOGGER_FILE       "lttng-logger"
  47
  48 DEFINE_TRACE(lttng_logger);
  49
  50 static struct proc_dir_entry *lttng_logger_dentry;
  51
  52 /**
  53  * lttng_logger_write - write a userspace string into the trace system
  54  * @file: file pointer
  55  * @user_buf: user string
  56  * @count: length to copy
  57  * @ppos: file position
  58  *
  59  * Copy a userspace string into a trace event named "lttng:logger".
  60  * Copies at most @count bytes into the event "msg" dynamic array.
  61  * Truncates the count at LTTNG_LOGGER_COUNT_MAX. Returns the number of
  62  * bytes copied from the source.
  63  * Return -1 on error, with EFAULT errno.
  64  */
  65 static
  66 ssize_t lttng_logger_write(struct file *file, const char __user *user_buf,
  67                     size_t count, loff_t *ppos)
  68 {
  69         int nr_pages = 1, i;
  70         unsigned long uaddr = (unsigned long) user_buf;
  71         struct page *pages[2];
  72         ssize_t written;
  73         int ret;
  74
  75         /* Truncate count */
  76         if (unlikely(count > LTTNG_LOGGER_COUNT_MAX))
  77                 count = LTTNG_LOGGER_COUNT_MAX;
  78
  79         /* How many pages are we dealing with ? */
  80         if (unlikely((uaddr & PAGE_MASK) != ((uaddr + count) & PAGE_MASK)))
  81                 nr_pages = 2;
  82
  83         /* Pin userspace pages */
  84         ret = get_user_pages_fast(uaddr, nr_pages, 0, pages);
  85         if (unlikely(ret < nr_pages)) {
  86                 if (ret > 0) {
  87                         BUG_ON(ret != 1);
  88                         put_page(pages[0]);
  89                 }
  90                 written = -EFAULT;
  91                 goto end;
  92         }
  93
  94         /* Trace the event */
  95         trace_lttng_logger(user_buf, count);
  96         written = count;
  97         *ppos += written;
  98
  99         for (i = 0; i < nr_pages; i++)
 100                 put_page(pages[i]);
 101 end:
 102         return written;
 103 }
 104
 105 static const struct file_operations lttng_logger_operations = {
 106         .write = lttng_logger_write,
 107 };
 108
 109 static struct miscdevice logger_dev = {
 110         .minor = MISC_DYNAMIC_MINOR,
 111         .name = "lttng-logger",
 112         .mode = 0666,
 113         .fops = &lttng_logger_operations
 114 };
 115
 116 int __init lttng_logger_init(void)
 117 {
 118         int ret = 0;
 119
 120         wrapper_vmalloc_sync_all();
 121
 122         /* /dev/lttng-logger */
 123         ret = misc_register(&logger_dev);
 124         if (ret) {
 125                 printk(KERN_ERR "Error creating LTTng logger device\n");
 126                 goto error;
 127         }
 128
 129         /* /proc/lttng-logger */
 130         lttng_logger_dentry = proc_create_data(LTTNG_LOGGER_FILE,
 131                                 S_IRUGO | S_IWUGO, NULL,
 132                                 &lttng_logger_operations, NULL);
 133         if (!lttng_logger_dentry) {
 134                 printk(KERN_ERR "Error creating LTTng logger proc file\n");
 135                 ret = -ENOMEM;
 136                 goto error_proc;
 137         }
 138
 139         /* Init */
 140         ret = __lttng_events_init__lttng();
 141         if (ret)
 142                 goto error_events;
 143         return ret;
 144
 145 error_events:
 146         remove_proc_entry("lttng-logger", NULL);
 147 error_proc:
 148         misc_deregister(&logger_dev);
 149 error:
 150         return ret;
 151 }
 152
 153 void lttng_logger_exit(void)
 154 {
 155         __lttng_events_exit__lttng();
 156         if (lttng_logger_dentry)
 157                 remove_proc_entry("lttng-logger", NULL);
 158         misc_deregister(&logger_dev);
 159 }