LTTng logger ABI

[lttng-modules.git] / probes / lttng.c

diff --git a/probes/lttng.c b/probes/lttng.c
new file mode 100644 (file)
index 0000000..8025687
--- /dev/null
+++ b/probes/lttng.c
@@ -0,0 +1,134 @@
+/*
+ * lttng.c
+ *
+ * LTTng logger ABI
+ *
+ * Copyright (C) 2008-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <linux/tracepoint.h>
+#include <linux/uaccess.h>
+#include <linux/gfp.h>
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include "../wrapper/vmalloc.h"
+#include "../lttng-events.h"
+
+#define TP_MODULE_NOAUTOLOAD
+#define LTTNG_PACKAGE_BUILD
+#define CREATE_TRACE_POINTS
+#define TRACE_INCLUDE_PATH ../instrumentation/events/lttng-module
+#define TRACE_INCLUDE_FILE lttng
+
+#include "../instrumentation/events/lttng-module/lttng.h"
+
+/* Events written through logger are truncated at 1024 bytes */
+#define LTTNG_LOGGER_COUNT_MAX 1024
+#define LTTNG_LOGGER_FILE      "lttng-logger"
+
+static struct proc_dir_entry *lttng_logger_dentry;
+
+/**
+ * lttng_logger_write - write a userspace string into the trace system
+ * @file: file pointer
+ * @user_buf: user string
+ * @count: length to copy
+ * @ppos: file position
+ *
+ * Copy a userspace string into a trace event named "lttng:logger".
+ * Copies at most @count bytes into the event "msg" dynamic array.
+ * Truncates the count at LTTNG_LOGGER_COUNT_MAX. Returns the number of
+ * bytes copied from the source.
+ * Return -1 on error, with EFAULT errno.
+ */
+static
+ssize_t lttng_logger_write(struct file *file, const char __user *user_buf,
+                   size_t count, loff_t *ppos)
+{
+       unsigned int nr_pages = 1, i;
+       unsigned long uaddr = (unsigned long) user_buf;
+       struct page *pages[2];
+       ssize_t written;
+       int ret;
+
+       /* Truncate count */
+       if (unlikely(count > LTTNG_LOGGER_COUNT_MAX))
+               count = LTTNG_LOGGER_COUNT_MAX;
+
+       /* How many pages are we dealing with ? */
+       if (unlikely((uaddr & PAGE_MASK) != ((uaddr + count) & PAGE_MASK)))
+               nr_pages = 2;
+
+       /* Pin userspace pages */
+       ret = get_user_pages_fast(uaddr, nr_pages, 0, pages);
+       if (unlikely(ret < nr_pages)) {
+               if (ret > 0) {
+                       BUG_ON(ret != 1);
+                       put_page(pages[0]);
+               }
+               written = -EFAULT;
+               goto end;
+       }
+
+       /* Trace the event */
+       trace_lttng_logger(user_buf, count);
+       written = count;
+       *ppos += written;
+
+       for (i = 0; i < nr_pages; i++)
+               put_page(pages[i]);
+end:
+       return written;
+}
+
+static const struct file_operations lttng_logger_operations = {
+       .write = lttng_logger_write,
+};
+
+int __init lttng_logger_init(void)
+{
+       int ret = 0;
+
+       wrapper_vmalloc_sync_all();
+       lttng_logger_dentry = proc_create_data(LTTNG_LOGGER_FILE,
+                               S_IRUGO | S_IWUGO, NULL,
+                               &lttng_logger_operations, NULL);
+       if (!lttng_logger_dentry) {
+               printk(KERN_ERR "Error creating LTTng logger file\n");
+               ret = -ENOMEM;
+               goto error;
+       }
+       ret = __lttng_events_init__lttng();
+       if (ret)
+               goto error_events;
+       return ret;
+
+error_events:
+       remove_proc_entry("lttng-logger", NULL);
+error:
+       return ret;
+}
+
+void __exit lttng_logger_exit(void)
+{
+       __lttng_events_exit__lttng();
+       if (lttng_logger_dentry)
+               remove_proc_entry("lttng-logger", NULL);
+}