WSL2-Linux-Kernel/tools/virtio/virtio-trace
Greg Kroah-Hartman b24413180f License cleanup: add SPDX GPL-2.0 license identifier to files with no license
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-11-02 11:10:55 +01:00
..
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
README tools: Add guest trace agent as a user tool 2012-09-28 15:05:13 +09:30
trace-agent-ctl.c tools: Add guest trace agent as a user tool 2012-09-28 15:05:13 +09:30
trace-agent-rw.c tools: Add guest trace agent as a user tool 2012-09-28 15:05:13 +09:30
trace-agent.c tools: Add guest trace agent as a user tool 2012-09-28 15:05:13 +09:30
trace-agent.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00

README

Trace Agent for virtio-trace
============================

Trace agent is a user tool for sending trace data of a guest to a Host in low
overhead. Trace agent has the following functions:
 - splice a page of ring-buffer to read_pipe without memory copying
 - splice the page from write_pipe to virtio-console without memory copying
 - write trace data to stdout by using -o option
 - controlled by start/stop orders from a Host

The trace agent operates as follows:
 1) Initialize all structures.
 2) Create a read/write thread per CPU. Each thread is bound to a CPU.
    The read/write threads hold it.
 3) A controller thread does poll() for a start order of a host.
 4) After the controller of the trace agent receives a start order from a host,
    the controller wake read/write threads.
 5) The read/write threads start to read trace data from ring-buffers and
    write the data to virtio-serial.
 6) If the controller receives a stop order from a host, the read/write threads
    stop to read trace data.


Files
=====

README: this file
Makefile: Makefile of trace agent for virtio-trace
trace-agent.c: includes main function, sets up for operating trace agent
trace-agent.h: includes all structures and some macros
trace-agent-ctl.c: includes controller function for read/write threads
trace-agent-rw.c: includes read/write threads function


Setup
=====

To use this trace agent for virtio-trace, we need to prepare some virtio-serial
I/Fs.

1) Make FIFO in a host
 virtio-trace uses virtio-serial pipe as trace data paths as to the number
of CPUs and a control path, so FIFO (named pipe) should be created as follows:
	# mkdir /tmp/virtio-trace/
	# mkfifo /tmp/virtio-trace/trace-path-cpu{0,1,2,...,X}.{in,out}
	# mkfifo /tmp/virtio-trace/agent-ctl-path.{in,out}

For example, if a guest use three CPUs, the names are
	trace-path-cpu{0,1,2}.{in.out}
and
	agent-ctl-path.{in,out}.

2) Set up of virtio-serial pipe in a host
 Add qemu option to use virtio-serial pipe.

 ##virtio-serial device##
     -device virtio-serial-pci,id=virtio-serial0\
 ##control path##
     -chardev pipe,id=charchannel0,path=/tmp/virtio-trace/agent-ctl-path\
     -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,\
      id=channel0,name=agent-ctl-path\
 ##data path##
     -chardev pipe,id=charchannel1,path=/tmp/virtio-trace/trace-path-cpu0\
     -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel0,\
      id=channel1,name=trace-path-cpu0\
      ...

If you manage guests with libvirt, add the following tags to domain XML files.
Then, libvirt passes the same command option to qemu.

	<channel type='pipe'>
	   <source path='/tmp/virtio-trace/agent-ctl-path'/>
	   <target type='virtio' name='agent-ctl-path'/>
	   <address type='virtio-serial' controller='0' bus='0' port='0'/>
	</channel>
	<channel type='pipe'>
	   <source path='/tmp/virtio-trace/trace-path-cpu0'/>
	   <target type='virtio' name='trace-path-cpu0'/>
	   <address type='virtio-serial' controller='0' bus='0' port='1'/>
	</channel>
	...
Here, chardev names are restricted to trace-path-cpuX and agent-ctl-path. For
example, if a guest use three CPUs, chardev names should be trace-path-cpu0,
trace-path-cpu1, trace-path-cpu2, and agent-ctl-path.

3) Boot the guest
 You can find some chardev in /dev/virtio-ports/ in the guest.


Run
===

0) Build trace agent in a guest
	$ make

1) Enable ftrace in the guest
 <Example>
	# echo 1 > /sys/kernel/debug/tracing/events/sched/enable

2) Run trace agent in the guest
 This agent must be operated as root.
	# ./trace-agent
read/write threads in the agent wait for start order from host. If you add -o
option, trace data are output via stdout in the guest.

3) Open FIFO in a host
	# cat /tmp/virtio-trace/trace-path-cpu0.out
If a host does not open these, trace data get stuck in buffers of virtio. Then,
the guest will stop by specification of chardev in QEMU. This blocking mode may
be solved in the future.

4) Start to read trace data by ordering from a host
 A host injects read start order to the guest via virtio-serial.
	# echo 1 > /tmp/virtio-trace/agent-ctl-path.in

5) Stop to read trace data by ordering from a host
 A host injects read stop order to the guest via virtio-serial.
	# echo 0 > /tmp/virtio-trace/agent-ctl-path.in