systemtap release 2.1

From: Serguei Makarov
Date: Wed Feb 13 2013 - 13:59:59 EST

The systemtap team announces release 2.1!

perf event probe improvements, dyninst backend improvements,
error:: and warning:: man pages, bundled emacs/vim editor modes,
customizable aggregate array sorting, optional time limit suppression,
experimental compiled regex support


= Where to get it

http://sourceware.org/systemtap/ - our project page
http://sourceware.org/systemtap/ftp/releases/systemtap-2.1.tar.gz
http://koji.fedoraproject.org/koji/packageinfo?packageID=615
git tag release-2.1 (commit addec81)

There have been over 400 commits since the last release.
There have been over 40 bugs/features fixed since the last release.


= How to build it

See the README and NEWS files at
http://sourceware.org/git/?p=systemtap.git;a=tree
Further information at http://sourceware.org/systemtap/wiki/


= Systemtap frontend (stap) changes

- EMACS and VIM editor modes for systemtap source files are included / updated.

- The translator now eliminates duplicate tapset files between its
preferred directory (as configured during the build with --prefix=/
or specified with the -I /path option), and files it may find under
$XDG_DATA_DIRS. This should eliminate a class of conflicts between
parallel system- and hand-built systemtap installations.

- The translator accepts a --suppress-time-limits option, which defeats
time-related constraints, to allows probe handlers to run for indefinite
periods. It requires the guru mode (-g) flag to work. Add the earlier
--suppress-handler-errors flag for a gung-ho "just-keep-going" attitude.

- Some error messages and warnings now refer to additional information
that is found in man pages. These are generally named
error::FOO or warning::BAR (in the 7stap man page section)
and may be read via
% man error::FOO
% man warning::BAR


= Systemtap script language changes

- Perf event probes may now be read on demand. The counter probe is
defined using the counter-name part:
probe perf.type(0).config(0).counter("NAME"). The counter is
read in a user space probe using @perf("NAME"), e.g.
process("PROCESS").statement("func@file") {stat <<< @perf("NAME")}

- Perf event probes may now be bound to a specific task using the
process-name part: probe perf.type(0).config(0).process("NAME") { }
If the probed process name is not specified, then it is inferred
from the -c CMD argument.

- The foreach looping construct can now sort aggregate arrays by the user's
choice of aggregating function. Previously, @count was implied. e.g.:
foreach ([x,y] in array @sum +) { println(@sum(array[x,y])) }

- Proof of concept support for regular expression matching has been added:
if ("aqqqqqb" =~ "q*b") { ... }
if ("abc" !~ "q*b") { ... }

The eventual aim is to support roughly the same functionality as
the POSIX Extended Regular Expressions implemented by glibc.
Currently missing features include extraction of the matched string
and subexpressions, and named character classes ([:alpha:], [:digit:], &c).

Special thanks go to the re2c project, whose public domain code this
functionality has been based on. For more info on re2c, see:
http://sourceforge.net/projects/re2c/


= Systemtap runtime changes

- The dyninst backend has improved in several aspects:
- The runtime now allows much more concurrency when probing multithreaded
processes, and will also follow probes across forks.
- Several new probe types are now supported, including timers, function
return, and process.begin/end and process.thread.begin/end.
- Semaphores for SDT probes are now set properly.
- Attaching to existing processes with -x PID now works.


= Systemtap tapset changes

- New tapsets:
choose_defined.stpm add @choose_defined() macro

- Added/changed tapsets for dyninst:
ctime.stp ctime() returns "<invalid time>" when an error occurs
context.stp add support for print_regs()

- Changed tapsets:
nfs_proc.stp account for separate nfsv2/3/4 kernel modules
context.stp add ppfunc() to parse the function name from pp()
netfilter.stp fix error in decoding of ar_tha and ar_tpa fields

- The folowing tapset variables are deprecated in release 2.1 and may
be removed in a future version:
- The 'send2queue' variable in the 'signal.send' probe.
- The 'oldset_addr' and 'regs' variables in the 'signal.handle' probe.

- The following tapset probes are deprecated in release 2.1 and may
be removed in a future version:
- signal.send.return
- signal.handle.return


= Systemtap sample scripts

- Tracing examples were updated to use ppfunc() instead of probefunc().

- New samples:
perf.stp use perf.counter to access performance counters
regex.stp report opened files whose names match a given regex
threadstacks.stp override default new-pthread stack sizes
mutex_contention.stp pthread mutex contention analysis
ltrace.stp uprobes-based ltrace demo
block.stp stapgames Breakout demo using input/output devices
eater.stp stapgames Snake demo using input/output devices
lifegame.stp stapgames Game of Life demo using input/output devices
pingpong.stp stapgames Pong demo using input/output devices

- Changed samples:
deviceseeks.stp switch to using ioblock_trace.request probe point


= Examples of tested kernel versions

3.8.0-rc (x86_64)
3.7.0 (x86_64, i686)
3.6.2 (x86_64)
3.4.0 (armv7l)
2.6.32 (x86_64, i686, ppc64, s390x)
2.6.18 (x86_64, i686, ia64)
2.6.9 (i686, ppc64)


= Known issues with this release

- The regular expression support is still experimental and incomplete; in particular:
+ Support for named character classes is missing. (PR15064)
+ Support for extracting matched strings and substrings is missing. (PR15065)

- Some kernel crashes continue to be reported when a script probes
broad kernel function wildcards. (PR2725)

- The dyninst backend is still a work in progress. Current issues:
+ lack of support for multiarch/cross-instrumentation
+ tapset functions are still incomplete relative to what is supported
when the kernel backend is active
+ exception handling becomes completely broken in programs
instrumented by the current version of dyninst (PR14702)
+ command line interrupts are slightly mishandled (PR15049)
+ not all registers are made available on 32-bit x86 (PR15136)

See dyninst/README and the systemtap/dyninst Bugzilla component
(http://tinyurl.com/stapdyn-PR-list) if you want all the gory
details about the state of the feature.


= Contributors for this release

Alexander Lochmann, Daniel Tschan*, Dave Brolley, David Smith,
Frank Ch. Eigler, Jiri Horky*, Josh Stone, JÃhann B. GuÃmundsson*,
Lukas Berk, LukÃÅ HejtmÃnek*, Mark Wielaard, Masami Hiramatsu,
Nathan Scott, Rich Megginson*, RÃdiger Sonderfeld*, Serguei Makarov,
Stan Cox, Tom Tromey, Tomoki Sekiyama*, William Cohen

Special thanks to new contributors, marked with '*' above.
Special thanks to the authors of the re2c project (http://re2c.sourceforge.net).


= Bugs fixed for this release <http://sourceware.org/PR#####>

1887 write emacs/vim editor mode for script language
6697 need more access_ok() checks in runtime/tapsets
11334 regular expression string matching
11576 per-process perf events
11955 signal tapsets don't match
12022 Allow foreach to order iterations for aggregates on @min @max and @avg operators
12231 reading perfctr events
12443 XDG_DATA_DIRS conflict between preinstalled and hand-built stap
12642 utrace: taskfinder misses events when main thread does not go through at least one quiesce
13022 probe module("*").function("*") does not work on arm
14178 Add a pure-userspace runtime mode
14245 Support debugfs mounted 0700
14390 separate process.**.return tests and mark UNSUPPORTED
14555 tolerate /proc/sys/kernel/kptr_restrict=2
14571 Make stapdyn multithreaded
14659 task_finder2 breaks ptrace apps
14701 stapdyn needs timer probe support
14705 stapdyn needs to set SDT semaphores
14707 Support stapdyn -x PID
14709 Support process.function.return in stapdyn
14712 VM_EXECUTABLE went to heaven
14714 stap flag for bigger --suppress-handler-errors hammer
14731 regression in buildok/thirty.stp
14735 stapdyn needs timing ('-t') support
14742 more complete dwz / DW_TAG_partial_unit support
14774 process.statement("*@file:*") probes don't match all functions
14781 kmem_cache conflict leads to panic & badness
14794 autoconf auto-enable dyninst if possible
14795 add stapgames
14804 Kernel panic when running hello world stap script
14820 hang when running semok/nodwf01.stp
14842 Old "-kelf" and "--ignore-dwarf" command line options should be removed
14883 let probefunc() not fail - or fail more informatively, on non-uprobes kernels
14900 collision between tapset locals and user globals: contexts
14929 staperrors man page
14949 cannot use systemtap on linux 3.7 intel x86_64
14957 foreach_aggrsort.exp test hangs on i686 rhel5 system
14997 DW_OP_rot mistranslation
15031 stapdyn needs a _stp_print_binary() runtime function
15059 session.print_error called frequently from listing_mode
15074 pthread_stacks.exp problems
15080 The kernel function 'signal_wake_up' is gone
15087 netfilter.arp tapset probes duplicate source/target addresses
15101 [PATCH] Stap sefaults when calling NSS_shutdown() which was not previously initialized
15112 Can't connect to stap-server via IPv6 raw hex addresses
15123 workaround for bad debuginfo for -mfentry
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