Add userspace event support to LTTng. Simply has to write to : /debugfs/ltt/write_event E.g. : echo "Error X happened !" > /debugfs/ltt/write_event (assuming debugfs is mounted under /debugfs) Todo : Maybe use ltt_relay_user_blocking to block if channel is full rather than losing an event ? Be careful about effect of stopped tracing on userspace... Changelog : - Support correctly when multiple strings are sent to the same write. - Cut the strings at each \n or \0. - Made sure we never return a count value larger than the requested count. Count is counting the number of _source_ data used, not the number of trace bytes written. Signed-off-by: Mathieu Desnoyers --- ltt/Kconfig | 9 +++ ltt/Makefile | 1 ltt/ltt-userspace-event.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 141 insertions(+) Index: linux-2.6-lttng/ltt/Kconfig =================================================================== --- linux-2.6-lttng.orig/ltt/Kconfig 2009-03-05 16:09:08.000000000 -0500 +++ linux-2.6-lttng/ltt/Kconfig 2009-03-05 16:09:41.000000000 -0500 @@ -114,6 +114,15 @@ config LTT_DEBUG_EVENT_SIZE help Tracer-internal option to help debugging event type encoding problems. +config LTT_USERSPACE_EVENT + tristate "Support logging events from userspace" + depends on LTT_TRACER + depends on LTT_FAST_SERIALIZE + default m + help + This option lets userspace write text events in + /debugfs/ltt/write_event. + config LTT_VMCORE bool "Support trace extraction from crash dump" default y Index: linux-2.6-lttng/ltt/Makefile =================================================================== --- linux-2.6-lttng.orig/ltt/Makefile 2009-03-05 16:09:20.000000000 -0500 +++ linux-2.6-lttng/ltt/Makefile 2009-03-05 16:09:53.000000000 -0500 @@ -12,3 +12,4 @@ obj-$(CONFIG_LTT_SERIALIZE) += ltt-seri obj-$(CONFIG_LTT_STATEDUMP) += ltt-statedump.o obj-$(CONFIG_LTT_FAST_SERIALIZE) += ltt-type-serializer.o obj-$(CONFIG_LTT_TRACE_CONTROL) += ltt-trace-control.o +obj-$(CONFIG_LTT_USERSPACE_EVENT) += ltt-userspace-event.o Index: linux-2.6-lttng/ltt/ltt-userspace-event.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6-lttng/ltt/ltt-userspace-event.c 2009-03-05 16:09:41.000000000 -0500 @@ -0,0 +1,131 @@ +/* + * Copyright (C) 2008 Mathieu Desnoyers + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + */ + +#include +#include +#include +#include +#include +#include +#include + +#define LTT_WRITE_EVENT_FILE "write_event" + +DEFINE_MARKER(userspace, event, "string %s"); +static struct dentry *ltt_event_file; + +/** + * write_event - write a userspace string into the trace system + * @file: file pointer + * @user_buf: user string + * @count: length to copy, including the final NULL + * @ppos: unused + * + * Copy a string into a trace event, in channel "userspace", event "event". + * Copies until either \n or \0 is reached. + * On success, returns the number of bytes copied from the source, including the + * \n or \0 character (if there was one in the count range). It cannot return + * more than count. + * Inspired from tracing_mark_write implementation from Steven Rostedt and + * Ingo Molnar. + */ +static ssize_t write_event(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct marker *marker; + char *buf, *end; + long copycount; + ssize_t ret; + + buf = kmalloc(count + 1, GFP_KERNEL); + if (!buf) { + ret = -ENOMEM; + goto string_out; + } + copycount = strncpy_from_user(buf, user_buf, count); + if (copycount < 0) { + ret = -EFAULT; + goto string_err; + } + /* Cut from the first nil or newline. */ + buf[copycount] = '\0'; + end = strchr(buf, '\n'); + if (end) { + *end = '\0'; + copycount = end - buf; + } + /* Add final \0 to copycount */ + copycount++; + marker = &GET_MARKER(userspace, event); + ltt_specialized_trace(marker, marker->single.probe_private, + buf, copycount, sizeof(char)); + /* If there is no \0 nor \n in count, do not return a larger value */ + ret = min_t(size_t, copycount, count); +string_err: + kfree(buf); +string_out: + return ret; +} + +static const struct file_operations ltt_userspace_operations = { + .write = write_event, +}; + +static int __init ltt_userspace_init(void) +{ + struct dentry *ltt_root_dentry; + int err = 0; + + ltt_root_dentry = get_ltt_root(); + if (!ltt_root_dentry) { + err = -ENOENT; + goto err_no_root; + } + + ltt_event_file = debugfs_create_file(LTT_WRITE_EVENT_FILE, + S_IWUGO, + ltt_root_dentry, + NULL, + <t_userspace_operations); + if (IS_ERR(ltt_event_file) || !ltt_event_file) { + printk(KERN_ERR + "ltt_userspace_init: failed to create file %s\n", + LTT_WRITE_EVENT_FILE); + err = -EPERM; + goto err_no_file; + } + + return err; +err_no_file: + put_ltt_root(); +err_no_root: + return err; +} + +static void __exit ltt_userspace_exit(void) +{ + debugfs_remove(ltt_event_file); + put_ltt_root(); +} + +module_init(ltt_userspace_init); +module_exit(ltt_userspace_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Mathieu Desnoyers "); +MODULE_DESCRIPTION("Linux Trace Toolkit Userspace Event"); -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/