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*
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...
Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
---
Makefile | 3 +
Makefile.target | 11 +-
docs/devel/tracing.txt | 32 +++++
scripts/qemu-trace-stap | 167 +++++++++++++++++++++++++++
scripts/tracetool/format/log_stap.py | 127 ++++++++++++++++++++
5 files changed, 339 insertions(+), 1 deletion(-)
create mode 100755 scripts/qemu-trace-stap
create mode 100644 scripts/tracetool/format/log_stap.py
diff --git a/Makefile b/Makefile
index dccba1dca2..22e481e7ba 100644
--- a/Makefile
+++ b/Makefile
@@ -736,6 +736,9 @@ endif
ifneq ($(HELPERS-y),)
$(call install-prog,$(HELPERS-y),$(DESTDIR)$(libexecdir))
endif
+ifdef CONFIG_TRACE_SYSTEMTAP
+ $(INSTALL_PROG) "scripts/qemu-trace-stap" $(DESTDIR)$(bindir)
+endif
ifneq ($(BLOBS),)
set -e; for x in $(BLOBS); do \
$(INSTALL_DATA) $(SRC_PATH)/pc-bios/$$x
"$(DESTDIR)$(qemu_datadir)"; \
diff --git a/Makefile.target b/Makefile.target
index 39f72e81be..401dc1ea6f 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -45,7 +45,7 @@ config-target.h: config-target.h-timestamp
config-target.h-timestamp: config-target.mak
ifdef CONFIG_TRACE_SYSTEMTAP
-stap: $(QEMU_PROG).stp-installed $(QEMU_PROG).stp $(QEMU_PROG)-simpletrace.stp
+stap: $(QEMU_PROG).stp-installed $(QEMU_PROG).stp $(QEMU_PROG)-simpletrace.stp
$(QEMU_PROG)-log.stp
ifdef CONFIG_USER_ONLY
TARGET_TYPE=user
@@ -84,6 +84,14 @@ $(QEMU_PROG)-simpletrace.stp: $(BUILD_DIR)/trace-events-all
$(tracetool-y)
--probe-prefix=qemu.$(TARGET_TYPE).$(TARGET_NAME) \
$< > $@,"GEN","$(TARGET_DIR)$(QEMU_PROG)-simpletrace.stp")
+$(QEMU_PROG)-log.stp: $(BUILD_DIR)/trace-events-all $(tracetool-y)
+ $(call quiet-command,$(TRACETOOL) \
+ --group=all \
+ --format=log-stap \
+ --backends=$(TRACE_BACKENDS) \
+ --probe-prefix=qemu.$(TARGET_TYPE).$(TARGET_NAME) \
+ $< > $@,"GEN","$(TARGET_DIR)$(QEMU_PROG)-log.stp")
+
else
stap:
endif
@@ -227,6 +235,7 @@ ifdef CONFIG_TRACE_SYSTEMTAP
$(INSTALL_DIR) "$(DESTDIR)$(qemu_datadir)/../systemtap/tapset"
$(INSTALL_DATA) $(QEMU_PROG).stp-installed
"$(DESTDIR)$(qemu_datadir)/../systemtap/tapset/$(QEMU_PROG).stp"
$(INSTALL_DATA) $(QEMU_PROG)-simpletrace.stp
"$(DESTDIR)$(qemu_datadir)/../systemtap/tapset/$(QEMU_PROG)-simpletrace.stp"
+ $(INSTALL_DATA) $(QEMU_PROG)-log.stp
"$(DESTDIR)$(qemu_datadir)/../systemtap/tapset/$(QEMU_PROG)-log.stp"
endif
GENERATED_FILES += config-target.h
diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
index bc52f12485..53327cd35b 100644
--- a/docs/devel/tracing.txt
+++ b/docs/devel/tracing.txt
@@ -317,6 +317,38 @@ probes:
--target-name x86_64 \
<trace-events-all >qemu.stp
+To facilitate simple usage of systemtap where there merely needs to be printf
+logging of certain probes, a helper script "qemu-trace-stap" is provided
+
+This can list all probes available for a given QEMU emulator binary:
+
+ $ 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...
+
+Optionally restricted to a pattern prefix:
+
+ $ qemu-trace-stap list qemu-system-x86_64 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...
+
+It can then run a simple systemtap script which prints each requested probe
+
+ $ 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
+
== Trace event properties ==
Each event in the "trace-events-all" file can be prefixed with a
space-separated
diff --git a/scripts/qemu-trace-stap b/scripts/qemu-trace-stap
new file mode 100755
index 0000000000..2db7b1470c
--- /dev/null
+++ b/scripts/qemu-trace-stap
@@ -0,0 +1,167 @@
+#!/usr/bin/python
+# -*- python -*-
+#
+# Copyright (C) 2019 Red Hat, Inc
+#
+# QEMU SystemTap Trace Tool
+#
+# 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; under version 2 of the License.
+#
+# 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, see <http://www.gnu.org/licenses/>.
+
+from __future__ import print_function
+
+import argparse
+import copy
+import os.path
+import re
+import subprocess
+import sys
+
+
+def probe_prefix(binary):
+ dirname, filename = os.path.split(binary)
+ return re.sub("-", ".", filename) + ".log"
+
+
+def which(binary):
+ for path in os.environ["PATH"].split(os.pathsep):
+ if os.path.exists(os.path.join(path, binary)):
+ return os.path.join(path, binary)
+
+ print("Unable to find '%s' in $PATH" % binary)
+ sys.exit(1)
+
+
+def tapset_dir(binary):
+ dirname, filename = os.path.split(binary)
+ if dirname == '':
+ thisfile = which(binary)
+ else:
+ thisfile = os.path.realpath(binary)
+ if not os.path.exists(thisfile):
+ print("Unable to find '%s'" % thisfile)
+ sys.exit(1)
+
+ basedir = os.path.split(thisfile)[0]
+ tapset = os.path.join(basedir, "..", "share", "systemtap", "tapset")
+ return os.path.realpath(tapset)
+
+
+def tapset_env(tapset_dir):
+ tenv = copy.copy(os.environ)
+ tenv["SYSTEMTAP_TAPSET"] = tapset_dir
+ return tenv
+
+def cmd_run(args):
+ prefix = probe_prefix(args.binary)
+ tapsets = tapset_dir(args.binary)
+
+ if args.verbose:
+ print("Using tapset dir '%s' for binary '%s'" % (tapsets, args.binary))
+
+ probes = []
+ for probe in args.probes:
+ probes.append("probe %s.%s {}" % (prefix, probe))
+ if len(probes) == 0:
+ probes.append("probe %s.* {}" % prefix)
+
+ script = " ".join(probes)
+ if args.verbose:
+ print("Compiling script '%s'" % script)
+ script = """probe begin { print("Running script, <Ctrl>-c to quit\\n")
} """ + script
+ subprocess.call(["stap", "-e", script],
+ env=tapset_env(tapsets))
+
+
+def cmd_list(args):
+ tapsets = tapset_dir(args.binary)
+
+ if args.verbose:
+ print("Using tapset dir '%s' for binary '%s'" % (tapsets, args.binary))
+
+ def print_probes(verbose, name):
+ prefix = probe_prefix(args.binary)
+ offset = len(prefix) + 1
+ script = prefix + "." + name
+
+ if verbose:
+ print("Listing probes with name '%s'" % script)
+ proc = subprocess.Popen(["stap", "-l", script],
+ stdout=subprocess.PIPE,
env=tapset_env(tapsets))
+ out, err = proc.communicate()
+ if proc.returncode != 0:
+ print("No probes found, are the tapsets installed in %s" %
tapset_dir(args.binary))
+ sys.exit(1)
+
+ for line in out.splitlines():
+ if line.startswith(prefix):
+ print("%s" % line[offset:])
+
+ if len(args.probes) == 0:
+ print_probes(args.verbose, "*")
+ else:
+ for probe in args.probes:
+ print_probes(args.verbose, probe)
+
+
+def main():
+ parser = argparse.ArgumentParser(description="QEMU SystemTap trace tool")
+
+ subparser = parser.add_subparsers(help="commands")
+ subparser.required = True
+ subparser.dest = "command"
+
+ runparser = subparser.add_parser("run", help="Run a trace session",
+
formatter_class=argparse.RawDescriptionHelpFormatter,
+ epilog="""
+
+To watch all trace points on the qemu-system-x86_64 binary:
+
+ %(argv0)s run qemu-system-x86_64
+
+To only watch the trace points matching the qio* and qcrypto* patterns
+
+ %(argv0)s run qemu-system-x86_64 qio* qcrypto*
+""" % {"argv0": sys.argv[0]})
+ runparser.set_defaults(func=cmd_run)
+ runparser.add_argument("-v", "--verbose", help="Print verbose progress
info",
+ action='store_true')
+ runparser.add_argument("binary", help="QEMU system or user emulator
binary")
+ runparser.add_argument("probes", help="Probe names or wildcards",
+ nargs=argparse.REMAINDER)
+
+ listparser = subparser.add_parser("list", help="List probe points",
+
formatter_class=argparse.RawDescriptionHelpFormatter,
+ epilog="""
+
+To list all trace points on the qemu-system-x86_64 binary:
+
+ %(argv0)s list qemu-system-x86_64
+
+To only list the trace points matching the qio* and qcrypto* patterns
+
+ %(argv0)s list qemu-system-x86_64 qio* qcrypto*
+""" % {"argv0": sys.argv[0]})
+ listparser.set_defaults(func=cmd_list)
+ listparser.add_argument("-v", "--verbose", help="Print verbose progress
info",
+ action='store_true')
+ listparser.add_argument("binary", help="QEMU system or user emulator
binary")
+ listparser.add_argument("probes", help="Probe names or wildcards",
+ nargs=argparse.REMAINDER)
+
+ args = parser.parse_args()
+
+ args.func(args)
+ sys.exit(0)
+
+if __name__ == '__main__':
+ main()
diff --git a/scripts/tracetool/format/log_stap.py
b/scripts/tracetool/format/log_stap.py
new file mode 100644
index 0000000000..3ccbc09d61
--- /dev/null
+++ b/scripts/tracetool/format/log_stap.py
@@ -0,0 +1,127 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"""
+Generate .stp file that printfs log messages (DTrace with SystemTAP only).
+"""
+
+__author__ = "Daniel P. Berrange <berra...@redhat.com>"
+__copyright__ = "Copyright (C) 2014-2019, Red Hat, Inc."
+__license__ = "GPL version 2 or (at your option) any later version"
+
+__maintainer__ = "Daniel Berrange"
+__email__ = "berra...@redhat.com"
+
+import re
+
+from tracetool import out
+from tracetool.backend.dtrace import binary, probeprefix
+from tracetool.backend.simple import is_string
+from tracetool.format.stap import stap_escape
+
+def global_var_name(name):
+ return probeprefix().replace(".", "_") + "_" + name
+
+STATE_SKIP = 0
+STATE_LITERAL = 1
+STATE_MACRO = 2
+
+def c_macro_to_format(macro):
+ if macro.startswith("PRI"):
+ return macro[3]
+
+ if macro == "TARGET_FMT_plx":
+ return "%016x"
+
+ raise Exception("Unhandled macro '%s'" % macro)
+
+def c_fmt_to_stap(fmt):
+ state = 0
+ bits = []
+ literal = ""
+ macro = ""
+ escape = 0;
+ for i in range(len(fmt)):
+ if fmt[i] == '\\':
+ if escape:
+ escape = 0
+ else:
+ escape = 1
+ if state != STATE_LITERAL:
+ raise Exception("Unexpected escape outside string literal")
+ literal = literal + fmt[i]
+ elif fmt[i] == '"' and not escape:
+ if state == STATE_LITERAL:
+ state = STATE_SKIP
+ bits.append(literal)
+ literal = ""
+ else:
+ if state == STATE_MACRO:
+ bits.append(c_macro_to_format(macro))
+ state = STATE_LITERAL
+ elif fmt[i] == ' ' or fmt[i] == '\t':
+ if state == STATE_MACRO:
+ bits.append(c_macro_to_format(macro))
+ macro = ""
+ state = STATE_SKIP
+ elif state == STATE_LITERAL:
+ literal = literal + fmt[i]
+ else:
+ escape = 0
+ if state == STATE_SKIP:
+ state = STATE_MACRO
+
+ if state == STATE_LITERAL:
+ literal = literal + fmt[i]
+ else:
+ macro = macro + fmt[i]
+
+ if state == STATE_MACRO:
+ bits.append(c_macro_to_format(macro))
+ elif state == STATE_LITERAL:
+ bits.append(literal)
+
+ fmt = re.sub("%(\d*)z(x|u|d)", "%\\1\\2", "".join(bits))
+ return fmt
+
+def generate(events, backend, group):
+ out('/* This file is autogenerated by tracetool, do not edit. */',
+ '')
+
+ for event_id, e in enumerate(events):
+ if 'disable' in e.properties:
+ continue
+
+ out('probe %(probeprefix)s.log.%(name)s = %(probeprefix)s.%(name)s ?',
+ '{',
+ probeprefix=probeprefix(),
+ name=e.name)
+
+ # Get references to userspace strings
+ for type_, name in e.args:
+ name = stap_escape(name)
+ if is_string(type_):
+ out(' try {',
+ ' arg%(name)s_str = %(name)s ? ' +
+ 'user_string_n(%(name)s, 512) : "<null>"',
+ ' } catch {}',
+ name=name)
+
+ # Determine systemtap's view of variable names
+ fields = ["pid()", "gettimeofday_ns()"]
+ for type_, name in e.args:
+ name = stap_escape(name)
+ if is_string(type_):
+ fields.append("arg" + name + "_str")
+ else:
+ fields.append(name)
+
+ # Emit the entire record in a single SystemTap printf()
+ arg_str = ', '.join(arg for arg in fields)
+ fmt_str = "%d@%d " + e.name + " " + c_fmt_to_stap(e.fmt) + "\\n"
+ out(' printf("%(fmt_str)s", %(arg_str)s)',
+ fmt_str=fmt_str, arg_str=arg_str)
+
+ out('}')
+
+ out()
--
2.20.1
