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 <wrapper/vmalloc.h>
  32 #include <lttng-events.h>
  33
  34 #define TP_MODULE_NOAUTOLOAD
  35 #define LTTNG_PACKAGE_BUILD
  36 #define CREATE_TRACE_POINTS
  37 #define TRACE_INCLUDE_PATH instrumentation/events/lttng-module
  38 #define TRACE_INCLUDE_FILE lttng
  39 #define LTTNG_INSTRUMENTATION
  40
  41 #include <instrumentation/events/lttng-module/lttng.h>
  42
  43 /* Events written through logger are truncated at 1024 bytes */
  44 #define LTTNG_LOGGER_COUNT_MAX  1024
  45 #define LTTNG_LOGGER_FILE       "lttng-logger"
  46
  47 DEFINE_TRACE(lttng_logger);
  48
  49 static struct proc_dir_entry *lttng_logger_dentry;
  50
  51 /**
  52  * lttng_logger_write - write a userspace string into the trace system
  53  * @file: file pointer
  54  * @user_buf: user string
  55  * @count: length to copy
  56  * @ppos: file position
  57  *
  58  * Copy a userspace string into a trace event named "lttng:logger".
  59  * Copies at most @count bytes into the event "msg" dynamic array.
  60  * Truncates the count at LTTNG_LOGGER_COUNT_MAX. Returns the number of
  61  * bytes copied from the source.
  62  * Return -1 on error, with EFAULT errno.
  63  */
  64 static
  65 ssize_t lttng_logger_write(struct file *file, const char __user *user_buf,
  66                     size_t count, loff_t *ppos)
  67 {
  68         int nr_pages = 1, i;
  69         unsigned long uaddr = (unsigned long) user_buf;
  70         struct page *pages[2];
  71         ssize_t written;
  72         int ret;
  73
  74         /* Truncate count */
  75         if (unlikely(count > LTTNG_LOGGER_COUNT_MAX))
  76                 count = LTTNG_LOGGER_COUNT_MAX;
  77
  78         /* How many pages are we dealing with ? */
  79         if (unlikely((uaddr & PAGE_MASK) != ((uaddr + count) & PAGE_MASK)))
  80                 nr_pages = 2;
  81
  82         /* Pin userspace pages */
  83         ret = get_user_pages_fast(uaddr, nr_pages, 0, pages);
  84         if (unlikely(ret < nr_pages)) {
  85                 if (ret > 0) {
  86                         BUG_ON(ret != 1);
  87                         put_page(pages[0]);
  88                 }
  89                 written = -EFAULT;
  90                 goto end;
  91         }
  92
  93         /* Trace the event */
  94         trace_lttng_logger(user_buf, count);
  95         written = count;
  96         *ppos += written;
  97
  98         for (i = 0; i < nr_pages; i++)
  99                 put_page(pages[i]);
 100 end:
 101         return written;
 102 }
 103
 104 static const struct file_operations lttng_logger_operations = {
 105         .write = lttng_logger_write,
 106 };
 107
 108 int __init lttng_logger_init(void)
 109 {
 110         int ret = 0;
 111
 112         wrapper_vmalloc_sync_all();
 113         lttng_logger_dentry = proc_create_data(LTTNG_LOGGER_FILE,
 114                                 S_IRUGO | S_IWUGO, NULL,
 115                                 &lttng_logger_operations, NULL);
 116         if (!lttng_logger_dentry) {
 117                 printk(KERN_ERR "Error creating LTTng logger file\n");
 118                 ret = -ENOMEM;
 119                 goto error;
 120         }
 121         ret = __lttng_events_init__lttng();
 122         if (ret)
 123                 goto error_events;
 124         return ret;
 125
 126 error_events:
 127         remove_proc_entry("lttng-logger", NULL);
 128 error:
 129         return ret;
 130 }
 131
 132 void lttng_logger_exit(void)
 133 {
 134         __lttng_events_exit__lttng();
 135         if (lttng_logger_dentry)
 136                 remove_proc_entry("lttng-logger", NULL);
 137 }