Mark J. Wielaard

The GNU Compiler Collection is making some great progress. Playing with the current development version I cannot wait till GCC6 is officially out. The new warnings look beautiful and are more useful because of the range tracking. Just found an embarrassing bug thanks to the new -Wmisleading-indentation

libebl/eblobjnote.c: In function ‘ebl_object_note’:
libebl/eblobjnote.c:135:5: error: statement is indented as if it were guarded by... [-Werror=misleading-indentation]
    switch (type)
    ^~~~~~

libebl/eblobjnote.c:45:3: note: ...this ‘if’ clause, but it is not
  if (! ebl->object_note (name, type, descsz, desc))
  ^~

And indeed, it should have been under the if, but wasn’t because of missing brackets. Woops. Thanks GCC.

Glad to see a little bit more copyleft being adopted by Android now that they are using parts of the OpenJDK class library. Even if the GNU Classpath Exception is probably the weakest form of copyleft there is. It is interesting how the GPL makes frenemies like Oracle and Google work together.

I support the Software Freedom Conservancy because they provide a virtual home for Free Software communities. In their own words:

Software Freedom Conservancy is a not-for-profit organization that helps promote, improve, develop, and defend Free, Libre, and Open Source Software (FLOSS) projects. Conservancy provides a non-profit home and infrastructure for FLOSS projects. This allows FLOSS developers to focus on what they do best — writing and improving FLOSS for the general public — while Conservancy takes care of the projects’ needs that do not relate directly to software development and documentation.

Some projects receive support from or are managed by companies or trade associations that benefit from the software the community produces. That is great as long as the community objectives and the company profit motives are aligned. Free Software is a good way for companies to work together. The services that the Conservancy provides allows projects to define their own terms and conditions for the community to work together. And companies can then join on equal terms. Making sure the project and community will work together for the public benefit.

Please support the Software Freedom Conservancy by donating so they will be able to provide a home to many more communities. A donation of 10 US dollars a month will make you an official sponsor. Or donate directly to one of their many member projects.

Software Freedom Conservancy Member Projects

Last weekend I did a talk on How to start hacking on Valgrind by example at Fosdem which contain some Easy hacks for valgrind. If If you always wanted to hack on Valgrind, but haven’t yet really looked at the code yet, then this might be a nice introduction. Make sure to also read the slides for all the other Valgrind devroom talks. Much thanks to the Fosdem organization for letting the Valgrind hackers meet. It was a great weekend.

Bradley M. Kuhn wrote an analysis on the recent Appeals Court Decision in Oracle v. Google. Pointing out who the real winners are and that it will now take years before we will have more clarity:

The case is remanded, so a new jury will first sit down and consider the fair use question. If that jury finds fair use and thus no infringement, Oracle’s next appeal will be quite weak, and the Appeals Court likely won’t reexamine the question in any detail. In that outcome, very little has changed overall: we’ll have certainty that API’s aren’t copyrightable, as long as any textual copying that occurs during reimplementation is easily called fair use. By contrast, if the new jury rejects Google’s fair use defense, I suspect Google will have to appeal all the way to SCOTUS. It’s thus going to be at least two years before anything definitive is decided, and the big winners will be wealthy litigation attorneys — as usual.

You will want to read the whole thing to know why from a copyleft perspective this decision will give that strange feeling of simultaneous annoyance and contentment.

There seems to be a nasty bug out there in some implementations of Java 7, including IcedTea7 and OpenJDK7. The bug is very public and being actively abused to circumvent security restrictions. Please upgrade to IcedTea 2.3.1 or build your packages using the patch as discussed on the OpenJDK mailinglists.

Note that if you are using the icedtea-web applet viewer then you are not directly vulnerable to the exploits as currently out there in the wild since those try to disable the SecurityManager completely and icedtea-web doesn’t allow that (some proprietary applet plugins do allow that though). But there are other ways to abuse this bug to circumvent security restrictions in a more subtle way, so patching is still very recommended.

Some classpath/icedtea servers changed networks/ip addresses on Sunday. Changes should propagate through DNS on Monday. This can cause connection errors to planet.classpath.org, builder.classpath.org (buildbot and jenkins) and icedtea.wildebeest.org (hg backups). Apologies for the late notice.

anyone is free under the Copyright Act to write his or her own code to carry out exactly the same function or specification of any methods used in the Java API

More on Groklaw.

commit 654443e20dfc0617231f28a07c96a979ee1a0239
Merge: 2c01e7b 9cba26e
Author: Linus Torvalds 
Date:   Thu May 24 11:39:34 2012 -0700

    Merge branch 'perf-uprobes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
    
    Pull user-space probe instrumentation from Ingo Molnar:
     "The uprobes code originates from SystemTap and has been used for years
      in Fedora and RHEL kernels.  This version is much rewritten, reviews
      from PeterZ, Oleg and myself shaped the end result.
    
      This tree includes uprobes support in 'perf probe' - but SystemTap
      (and other tools) can take advantage of user probe points as well.
    
      Sample usage of uprobes via perf, for example to profile malloc()
      calls without modifying user-space binaries.
    
      First boot a new kernel with CONFIG_UPROBE_EVENT=y enabled.
    
      If you don't know which function you want to probe you can pick one
      from 'perf top' or can get a list all functions that can be probed
      within libc (binaries can be specified as well):
    
    	$ perf probe -F -x /lib/libc.so.6
    
      To probe libc's malloc():
    
    	$ perf probe -x /lib64/libc.so.6 malloc
    	Added new event:
    	probe_libc:malloc    (on 0x7eac0)
    
      You can now use it in all perf tools, such as:
    
    	perf record -e probe_libc:malloc -aR sleep 1
    
      Make use of it to create a call graph (as the flat profile is going to
      look very boring):
    
    	$ perf record -e probe_libc:malloc -gR make
    	[ perf record: Woken up 173 times to write data ]
    	[ perf record: Captured and wrote 44.190 MB perf.data (~1930712
    
    	$ perf report | less
    
    	  32.03%            git  libc-2.15.so   [.] malloc
    	                    |
    	                    --- malloc
    
    	  29.49%            cc1  libc-2.15.so   [.] malloc
    	                    |
    	                    --- malloc
    	                       |
    	                       |--0.95%-- 0x208eb1000000000
    	                       |
    	                       |--0.63%-- htab_traverse_noresize
    
    	  11.04%             as  libc-2.15.so   [.] malloc
    	                     |
    	                     --- malloc
    	                        |
    
    	   7.15%             ld  libc-2.15.so   [.] malloc
    	                     |
    	                     --- malloc
    	                        |
    
    	   5.07%             sh  libc-2.15.so   [.] malloc
    	                     |
    	                     --- malloc
    	                        |
    	   4.99%  python-config  libc-2.15.so   [.] malloc
    	          |
    	          --- malloc
    	             |
    	   4.54%           make  libc-2.15.so   [.] malloc
    	                   |
    	                   --- malloc
    	                      |
    	                      |--7.34%-- glob
    	                      |          |
    	                      |          |--93.18%-- 0x41588f
    	                      |          |
    	                      |           --6.82%-- glob
    	                      |                     0x41588f
    
    	   ...
    
      Or:
    
    	$ perf report -g flat | less
    
    	# Overhead        Command  Shared Object      Symbol
    	# ........  .............  .............  ..........
    	#
    	  32.03%            git  libc-2.15.so   [.] malloc
    	          27.19%
    	              malloc
    
    	  29.49%            cc1  libc-2.15.so   [.] malloc
    	          24.77%
    	              malloc
    
    	  11.04%             as  libc-2.15.so   [.] malloc
    	          11.02%
    	              malloc
    
    	   7.15%             ld  libc-2.15.so   [.] malloc
    	           6.57%
    	              malloc
    
    	 ...
    
      The core uprobes design is fairly straightforward: uprobes probe
      points register themselves at (inode:offset) addresses of
      libraries/binaries, after which all existing (or new) vmas that map
      that address will have a software breakpoint injected at that address.
      vmas are COW-ed to preserve original content.  The probe points are
      kept in an rbtree.
    
      If user-space executes the probed inode:offset instruction address
      then an event is generated which can be recovered from the regular
      perf event channels and mmap-ed ring-buffer.
    
      Multiple probes at the same address are supported, they create a
      dynamic callback list of event consumers.
    
      The basic model is further complicated by the XOL speedup: the
      original instruction that is probed is copied (in an architecture
      specific fashion) and executed out of line when the probe triggers.
      The XOL area is a single vma per process, with a fixed number of
      entries (which limits probe execution parallelism).
    
      The API: uprobes are installed/removed via
      /sys/kernel/debug/tracing/uprobe_events, the API is integrated to
      align with the kprobes interface as much as possible, but is separate
      to it.
    
      Injecting a probe point is privileged operation, which can be relaxed
      by setting perf_paranoid to -1.
    
      You can use multiple probes as well and mix them with kprobes and
      regular PMU events or tracepoints, when instrumenting a task."
    
    Fix up trivial conflicts in mm/memory.c due to previous cleanup of
    unmap_single_vma().
    
    * 'perf-uprobes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
      perf probe: Detect probe target when m/x options are absent
      perf probe: Provide perf interface for uprobes
      tracing: Fix kconfig warning due to a typo
      tracing: Provide trace events interface for uprobes
      tracing: Extract out common code for kprobes/uprobes trace events
      tracing: Modify is_delete, is_return from int to bool
      uprobes/core: Decrement uprobe count before the pages are unmapped
      uprobes/core: Make background page replacement logic account for rss_stat counters
      uprobes/core: Optimize probe hits with the help of a counter
      uprobes/core: Allocate XOL slots for uprobes use
      uprobes/core: Handle breakpoint and singlestep exceptions
      uprobes/core: Rename bkpt to swbp
      uprobes/core: Make order of function parameters consistent across functions
      uprobes/core: Make macro names consistent
      uprobes: Update copyright notices
      uprobes/core: Move insn to arch specific structure
      uprobes/core: Remove uprobe_opcode_sz
      uprobes/core: Make instruction tables volatile
      uprobes: Move to kernel/events/
      uprobes/core: Clean up, refactor and improve the code
      ...

Were it grounded in reality, Oracle’s claim that copyright law gives them proprietary control over any software that uses a particular functional API would be terrible for free software and programmers everywhere. It is an unethical and greedy interpretation created with the express purpose of subjugating as many computer users as possible, and is particularly bad in this context because it comes at a time when the sun has barely set on the free software community’s celebration of Java as a language newly suitable for use in the free world. Fortunately, the claim is not yet reality, and we hope Judge Alsup will keep it that way.

John Sullivan, executive director of the Free Software Foundation