By writing to the file /proc/lttng_uevent, a user-space application creates a kernel event. The event's payload is by default UTF-8 text, but any data can be written. The maximum size of the data is at most the size of a packet defined for the trace session. Null-character is optional and is not enforced. The event uses sequence for space efficiency and to store any data as payload.
The feature is enabled when the module lttng-uevent is loaded. The module can be removed if no tracing sessions with lttng_uevent enabled is active. Signed-off-by: Francis Giraldeau <[email protected]> --- instrumentation/events/lttng-module/uevent.h | 33 +++++++++ probes/Makefile | 1 + probes/lttng-uevent.c | 97 ++++++++++++++++++++++++++ 3 files changed, 131 insertions(+) create mode 100644 instrumentation/events/lttng-module/uevent.h create mode 100644 probes/lttng-uevent.c diff --git a/instrumentation/events/lttng-module/uevent.h b/instrumentation/events/lttng-module/uevent.h new file mode 100644 index 0000000..f67d901 --- /dev/null +++ b/instrumentation/events/lttng-module/uevent.h @@ -0,0 +1,33 @@ +#undef TRACE_SYSTEM +#define TRACE_SYSTEM uevent + +#if !defined(UEVENT_H_) || defined(TRACE_HEADER_MULTI_READ) +#define UEVENT_H_ + +#include <linux/tracepoint.h> + +TRACE_EVENT(lttng_uevent, + + TP_PROTO(const char *str, size_t len), + + TP_ARGS(str, len), + + /* + * Uses sequence to hold variable size data, by default considered + * as text. Null-terminal character is optional and is not enforced. + */ + TP_STRUCT__entry( + __dynamic_array_text(char, text, len) + ), + + TP_fast_assign( + tp_memcpy_dyn_from_user(text, str) + ), + + TP_printk("") +) + +#endif /* UEVENT_H_ */ + +/* This part must be outside protection */ +#include "../../../probes/define_trace.h" diff --git a/probes/Makefile b/probes/Makefile index 698a9c9..3003535 100644 --- a/probes/Makefile +++ b/probes/Makefile @@ -14,6 +14,7 @@ obj-m += lttng-probe-sched.o obj-m += lttng-probe-irq.o obj-m += lttng-probe-signal.o obj-m += lttng-probe-timer.o +obj-m += lttng-uevent.o obj-m += lttng-probe-statedump.o diff --git a/probes/lttng-uevent.c b/probes/lttng-uevent.c new file mode 100644 index 0000000..65bac2a --- /dev/null +++ b/probes/lttng-uevent.c @@ -0,0 +1,97 @@ +/* + * probes/lttng-uevent.c + * + * Expose kernel tracer to user-space through /proc/lttng_uevent + * + * Copyright (C) 2009-2012 Mathieu Desnoyers <[email protected]> + * + * 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/proc_fs.h> + +/* + * Create lttng_uevent tracepoint probes. + */ + +#define TP_MODULE_NOAUTOLOAD +#define LTTNG_PACKAGE_BUILD +#define CREATE_TRACE_POINTS +#define TRACE_INCLUDE_PATH ../instrumentation/events/lttng-module +#include "../instrumentation/events/lttng-module/uevent.h" + +#define LTTNG_UEVENT_FILE "lttng_uevent" + +/** + * lttng_uevent_write - write user-space data into kernel trace + * @file: file pointer + * @user_buf: user string + * @count: length to copy + * @ppos: unused + * + * Copy count bytes into a trace event "lttng_uevent". + * + * Returns the number of bytes copied from the source. + * Notice that there is no guarantee that the event is + * actually written in a trace. This can occur in 3 + * situations: + * + * * Buffer overrun + * * No trace session are active + * * The data size is greater than a sub-buffer + */ + +ssize_t lttng_uevent_write(struct file *file, const char __user *ubuf, + size_t count, loff_t *fpos) +{ + trace_lttng_uevent(ubuf, count); + return count; +} + +static const struct file_operations uev_ops = { + .owner = THIS_MODULE, + .write = lttng_uevent_write +}; + +static int __init lttng_uevent_init(void) +{ + struct proc_dir_entry *uev_file; + + uev_file = create_proc_entry(LTTNG_UEVENT_FILE, 0444, NULL); + if (!uev_file) + return -ENOENT; + uev_file->proc_fops = &uev_ops; + uev_file->mode = S_IFREG | S_IWUGO; + uev_file->uid = 0; + uev_file->gid = 0; + /* register manually the probe */ + __lttng_events_init__uevent(); + return 0; +} + +static void __exit lttng_uevent_exit(void) +{ + /* unregister manually the probe */ + __lttng_events_exit__uevent(); + remove_proc_entry(LTTNG_UEVENT_FILE, NULL); +} + +module_init(lttng_uevent_init); +module_exit(lttng_uevent_exit); + +MODULE_LICENSE("GPL and additional rights"); +MODULE_AUTHOR("Francis Giraldeau <[email protected]>"); +MODULE_DESCRIPTION("Append custom events to kernel trace from user-space"); -- 1.7.9.5 _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
