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