Merge remote-tracking branch 'remotes/stefanha-gitlab/tags/tracing-pull-request' into staging

Pull request

# gpg: Signature made Mon 12 Jul 2021 17:49:46 BST
# gpg: using RSA key 869

Merge remote-tracking branch 'remotes/stefanha-gitlab/tags/tracing-pull-request' into staging

Pull request

# gpg: Signature made Mon 12 Jul 2021 17:49:46 BST
# gpg: using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35 775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha-gitlab/tags/tracing-pull-request:
trace, lttng: require .pc files
trace/simple: add st_init_group
trace/simple: pass iter to st_write_event_mapping
trace: add trace_event_iter_init_group
trace: iter init tweaks
qemu-trace-stap: changing SYSTEMTAP_TAPSET considered harmful.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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qemu-trace-stap: changing SYSTEMTAP_TAPSET considered harmful.

Setting SYSTEMTAP_TAPSET to some value other than
/usr/share/systemtap/tapsets results in systemtap not finding the
standard tapset lib

qemu-trace-stap: changing SYSTEMTAP_TAPSET considered harmful.

Setting SYSTEMTAP_TAPSET to some value other than
/usr/share/systemtap/tapsets results in systemtap not finding the
standard tapset library any more, which in turn breaks tracing because
pid() and other standard systemtap functions are not available any more.

So using SYSTEMTAP_TAPSET to point systemtap to the qemu probes will
only work for the prefix=/usr installs because both qemu and system
tapsets in the same directory then. All other prefixes are broken.

Fix that by using the "-I $tapsetdir" command line switch instead.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20210601132414.432430-2-kraxel@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

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Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Pull request

# gpg: Signature made Tue 14 Jan 2020 09:29:11 GMT
# gpg: using RSA key 8695A8BFD3

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Pull request

# gpg: Signature made Tue 14 Jan 2020 09:29:11 GMT
# gpg: using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35 775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
trace: update qemu-trace-stap to Python 3

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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trace: update qemu-trace-stap to Python 3

qemu-trace-stap does not support Python 3 yet:

$ scripts/qemu-trace-stap list path/to/qemu-system-x86_64
Traceback (most recent call last):
File "s

trace: update qemu-trace-stap to Python 3

qemu-trace-stap does not support Python 3 yet:

$ scripts/qemu-trace-stap list path/to/qemu-system-x86_64
Traceback (most recent call last):
File "scripts/qemu-trace-stap", line 175, in <module>
main()
File "scripts/qemu-trace-stap", line 171, in main
args.func(args)
File "scripts/qemu-trace-stap", line 118, in cmd_list
print_probes(args.verbose, "*")
File "scripts/qemu-trace-stap", line 114, in print_probes
if line.startswith(prefix):
TypeError: startswith first arg must be bytes or a tuple of bytes, not str

Now that QEMU requires Python 3.5 or later we can switch to pure Python
3. Use Popen()'s universal_newlines=True argument to treat stdout as
text instead of binary.

Fixes: 62dd1048c0bd ("trace: add ability to do simple printf logging via systemtap")
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1787395
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20200107112438.383958-1-stefanha@redhat.com
Message-Id: <20200107112438.383958-1-stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Pull request

User-visible changes:
* The new qemu-trace-stap script makes it convenient to collect traces wit

Merge remote-tracking branch 'remotes/stefanha/tags/tracing-pull-request' into staging

Pull request

User-visible changes:
* The new qemu-trace-stap script makes it convenient to collect traces without
writing SystemTap scripts. See "man qemu-trace-stap" for details.

# gpg: Signature made Wed 30 Jan 2019 03:17:57 GMT
# gpg: using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg: aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35 775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/tracing-pull-request:
trace: rerun tracetool after ./configure changes
trace: improve runstate tracing
trace: add ability to do simple printf logging via systemtap
trace: forbid use of %m in trace event format strings
trace: enforce that every trace-events file has a final newline
display: ensure qxl log_buf is a nul terminated string

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

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trace: add ability to do simple printf logging via systemtap

The dtrace systemtap trace backend for QEMU is very powerful but it is
also somewhat unfriendly to users who aren't familiar with systemt

trace: add ability to do simple printf logging via systemtap

The dtrace systemtap trace backend for QEMU is very powerful but it is
also somewhat unfriendly to users who aren't familiar with systemtap,
or who don't need its power right now.

stap -e "....some strange script...."

The 'log' backend for QEMU by comparison is very crude but incredibly
easy to use:

$ qemu -d trace:qio* ...some args...
23266@1547735759.137292:qio_channel_socket_new Socket new ioc=0x563a8a39d400
23266@1547735759.137305:qio_task_new Task new task=0x563a891d0570 source=0x563a8a39d400 func=0x563a86f1e6c0 opaque=0x563a89078000
23266@1547735759.137326:qio_task_thread_start Task thread start task=0x563a891d0570 worker=0x563a86f1ce50 opaque=0x563a891d9d90
23273@1547735759.137491:qio_task_thread_run Task thread run task=0x563a891d0570
23273@1547735759.137503:qio_channel_socket_connect_sync Socket connect sync ioc=0x563a8a39d400 addr=0x563a891d9d90
23273@1547735759.138108:qio_channel_socket_connect_fail Socket connect fail ioc=0x563a8a39d400

This commit introduces a way to do simple printf style logging of probe
points using systemtap. In particular it creates another set of tapsets,
one per emulator:

/usr/share/systemtap/tapset/qemu-*-log.stp

These pre-define probe functions which simply call printf() on their
arguments. The printf() format string is taken from the normal
trace-events files, with a little munging to the format specifiers
to cope with systemtap's more restrictive syntax.

With this you can now do

$ stap -e 'probe qemu.system.x86_64.log.qio*{}'
22806@1547735341399856820 qio_channel_socket_new Socket new ioc=0x56135d1d7c00
22806@1547735341399862570 qio_task_new Task new task=0x56135cd66eb0 source=0x56135d1d7c00 func=0x56135af746c0 opaque=0x56135bf06400
22806@1547735341399865943 qio_task_thread_start Task thread start task=0x56135cd66eb0 worker=0x56135af72e50 opaque=0x56135c071d70
22806@1547735341399976816 qio_task_thread_run Task thread run task=0x56135cd66eb0

We go one step further though and introduce a 'qemu-trace-stap' tool to
make this even easier

$ qemu-trace-stap run qemu-system-x86_64 'qio*'
22806@1547735341399856820 qio_channel_socket_new Socket new ioc=0x56135d1d7c00
22806@1547735341399862570 qio_task_new Task new task=0x56135cd66eb0 source=0x56135d1d7c00 func=0x56135af746c0 opaque=0x56135bf06400
22806@1547735341399865943 qio_task_thread_start Task thread start task=0x56135cd66eb0 worker=0x56135af72e50 opaque=0x56135c071d70
22806@1547735341399976816 qio_task_thread_run Task thread run task=0x56135cd66eb0

This tool is clever in that it will automatically change the
SYSTEMTAP_TAPSET env variable to point to the directory containing the
right set of probes for the QEMU binary path you give it. This is useful
if you have QEMU installed in /usr but are trying to test and trace a
binary in /home/berrange/usr/qemu-git. In that case you'd do

$ qemu-trace-stap run /home/berrange/usr/qemu-git/bin/qemu-system-x86_64 'qio*'

And it'll make sure /home/berrange/usr/qemu-git/share/systemtap/tapset
is used for the trace session

The 'qemu-trace-stap' script takes a verbose arg so you can understand
what it is running

$ qemu-trace-stap run /home/berrange/usr/qemu-git/bin/qemu-system-x86_64 'qio*'
Using tapset dir '/home/berrange/usr/qemu-git/share/systemtap/tapset' for binary '/home/berrange/usr/qemu-git/bin/qemu-system-x86_64'
Compiling script 'probe qemu.system.x86_64.log.qio* {}'
Running script, <Ctrl>-c to quit
...trace output...

It can enable multiple probes at once

$ qemu-trace-stap run qemu-system-x86_64 'qio*' 'qcrypto*' 'buffer*'

By default it monitors all existing running processes and all future
launched proceses. This can be restricted to a specific PID using the
--pid arg

$ qemu-trace-stap run --pid 2532 qemu-system-x86_64 'qio*'

Finally if you can't remember what probes are valid it can tell you

$ qemu-trace-stap list qemu-system-x86_64
ahci_check_irq
ahci_cmd_done
ahci_dma_prepare_buf
ahci_dma_prepare_buf_fail
ahci_dma_rw_buf
ahci_irq_lower
...snip...

Or list just those matching a prefix pattern

$ qemu-trace-stap list -v qemu-system-x86_64 'qio*'
Using tapset dir '/home/berrange/usr/qemu-git/share/systemtap/tapset' for binary '/home/berrange/usr/qemu-git/bin/qemu-system-x86_64'
Listing probes with name 'qemu.system.x86_64.log.qio*'
qio_channel_command_abort
qio_channel_command_new_pid
qio_channel_command_new_spawn
qio_channel_command_wait
qio_channel_file_new_fd
...snip...

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20190123120016.4538-5-berrange@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...