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1108 lines
51 KiB
Plaintext
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===============================================
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Release notes for the Genode OS Framework 18.11
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===============================================
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Genode Labs
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Our [https://genode.org/about/road-map - road map] for 2018 emphasized
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software quality and resilience as one of the major topics of the year.
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The release 18.11 pays tribute to this plan on multiple levels.
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First, by integrating *static code analysis* into Genode's build and packaging
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tools, we aim to cultivate rigid code analysis as a regular part of our work
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flows to catch bugs as early as possible - before running any code
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(Section [Static code analysis]).
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The second line of defense are intensive automated tests, which are steadily
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extended. The tests can roughly be classified into unit tests, component
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tests, and integration tests. By moving over 70 *component tests* from
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individual test scenarios (run scripts) to Genode packages, we became able to
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run all these tests as one big integration test. As described in
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Section [Automated test infrastructure hosted on top of Genode], the large
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batch of component tests, their orchestration, and the analysis of the results
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are performed directly on the target platform. This approach not only stresses
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the resilience of the base framework and the underlying kernels, but it also
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makes each individual test easily reproducible, e.g., on top of Sculpt OS.
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For unit tests, *coverage metrics* are a useful tool to aid the test
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development. The current release integrates the support of the gcov tool into
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the build system and test infrastructure so that these metrics become easy to
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obtain.
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To improve the resilience of Genode systems that contain parts that are
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known/expected to sometimes fail, e.g., because they depend on hugely complex
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software stacks, the new release features the ability to *monitor the health*
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of components (Section [Component health monitoring]). Using this new
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introspection mechanism, Genode systems become able to respond to such
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conditions by restarting the affected component or by logging the event.
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The most sophisticated integration test is certainly the interactive use of
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*Sculpt OS* on a daily basis. On that account, we are happy to introduce a few
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new toys to play with. By introducing a new window layouter and modularizing
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Sculpt's window-management packages, window decorators can now be swapped out
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at runtime, window layouts are preserved across reboots, and the layout rules
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can be edited on the fly (Section [Enhanced window-management flexibility]).
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Also outlined on our road map, we strive to apply Genode for network
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appliances and typical server applications. With the new ability to host
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MirageOS unikernels directly on Genode
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(Section [Genode as a platform for Mirage-OS unikernels]), MirageOS-based
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server applications can be readily integrated into Genode systems. Another
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key component for server use cases is the new SSH server described in
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Section [SSH terminal server], which allows for the friction-less remote
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administration of Genode-based servers.
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Further highlights of the current release are the improved network performance
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on Xilinx Zynq, the initial version of a Genode SDK, performance improvements
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of the base-hw kernel on NXP i.MX platforms, and the updated language support
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for Ada and Java.
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Raising the bar of quality assurance
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####################################
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Automated test infrastructure hosted on top of Genode
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=====================================================
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When it comes to testing, Genode's run tool provides a convenient way for
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building, configuring, executing, and evaluating system scenarios. Throughout
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the years, the base framework became equipped with a broad variety of run
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scripts, each dedicated to another aspect of Genode. Most of them support
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being integrated into a fully automated test infrastructure. For instance, all
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the tests listed in _tool/autopilot.list_ are automatically evaluated each
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night at Genode Labs for different platforms and kernels. This exposes the
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current state of development to a variety of base-system behavior (e.g.,
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scheduling) and quickly reveals regression bugs.
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[image depot_autopilot_before]
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However, the existing approach had its drawbacks:
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* As each test was realized through a run script executed individually,
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the target platform had to be booted over and over again. So, for larger
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lists of tests like _tool/autopilot.list_, boot times could sum up to a
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significant magnitude. Moreover, continuous on and off switching of
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hardware may have a negative effect on its lifetime.
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* Most of the mentioned run scripts neither needed more than a few minutes to
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finish nor did they include a lot of dynamics regarding, for instance, the
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creation and destruction of components. So the software system as a whole
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was stressed only to a very limited extent.
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* The description of the test scenarios could not be used for running tests
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from within an on-target Genode natively. But especially in the context of
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the ever growing use of the Sculpt desktop system, this becomes more and
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more desirable. The run script mechanism, however, is designed for a
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Linux-based host platform remote-controlling the target.
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This brought us to the idea of creating a new component that takes sets of
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tests that are described through Genode means only as input. It evaluates one
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after the other in a sandbox environment to, eventually, provide the user with
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an easy-to-read result list. When it came to choosing the test-description
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format, the already existing depot mechanism - as used within Sculpt OS - was
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an obvious candidate.
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Depot packages are designed to describe dynamically loadable sub trees for
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Genode's component hierarchy, i.e., exactly for what a test scenario should
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be in the context of the new component (plus some extra information about
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platform requirements and success conditions). Furthermore for managing
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package depots, Genode already provides a comprehensive set of well-tested
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tools, most noteworthy in this context the depot-query application. This
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component makes querying the contents of packages as easy as writing the
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package path to a report and awaiting an according blueprint through a ROM
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dataspace. That said, the choice of the back-end mechanism was clear and
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consequently, we named the new component _depot autopilot_.
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The depot autopilot
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-------------------
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As starting point for the development of the depot autopilot, the depot deploy
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component (introduced with the 17.08 release), served us well. Both components
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have the purpose of loading Genode scenarios from packages and start them
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inside a nicely separated instance of Genode's init runtime. For this reason,
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a good part of the depot autopilot configuration interface might look familiar
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to you, as shall be depicted by this example:
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! <config arch="x86_64" children_label_prefix="this is new">
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!
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! <static>
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! <parent-provides>
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! <service name="ROM"/>
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! <service name="CPU"/>
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! ...
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! </parent-provides>
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! </static>
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!
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! <common_routes>
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! <service name="ROM" label_last="init"> <parent/> </service>
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! <service name="CPU"> <parent/> </service>
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! ...
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! </common_routes>
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!
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! <start name="test-mmio" pkg="genodelabs/pkg/test-mmio/2018-10-30"/>
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! <start name="test-xml_node" pkg="genodelabs/pkg/test-xml_node/2018-10-30"/>
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! ...
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!
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! <previous-results ...> <!-- this is new --> </previous-results>
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!
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! </config>
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Like in depot deploy configurations, there are '<start>' nodes to declare,
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which scenarios to run and from which packages to load them, there is an
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'arch' attribute to select the packages architecture variant, and also the
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'<static>' and '<route>' nodes that install common parts of the configuration.
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The same goes for the 'runtime' files in the test packages. They are actually
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fully compatible with the depot deploy tool:
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! <runtime ram="32M" caps="1000" binary="init">
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!
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! <requires> <timer/> <nic/> </requires>
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!
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! <content>
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! <rom label="ld.lib.so"/>
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! <rom label="test-example"/>
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! </content>
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!
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! <config>
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! <parent-provides> ... </parent-provides>
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! <default-route> ... </default-route>
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! <start name="test-example" caps="500">
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! <resource name="RAM" quantum="10M"/>
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! </start>
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! </config>
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!
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! <events> <!-- this is new --> </events>
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!
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! </runtime>
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But there are also new things as you can see. We will explain them below.
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Roughly outlined, the concepts of the depot autopilot differs in three points
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from that of the depot deploy component:
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# The outcome of loaded scenarios is captured and interpreted in order
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to support failure detection and analysis,
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# Scenarios do not run in parallel but in a given order to mitigate
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interfering influences and make results reproducible, and
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# Scenarios must be considered to trigger bugs that
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may lead to situations where the scenario itself or even the whole system
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hangs or crashes.
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The first point is addressed by the new '<events>' tag in _runtime_ files. It
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allows for listing events that might trigger during a test and specify the
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reaction of the depot autopilot. Currently, two types of events, the '<log>'
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event and the '<timeout>' event, are available, which cover most of the use
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cases found in tests of the Genode main repositories. Here's a short example
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of how to use them:
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! <runtime>
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! <events>
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! <timeout meaning="failed" sec="20"/>
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! <log meaning="succeeded">[init -> test-example] Test succeeded!</log>
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! <log meaning="failed">Error: </log>
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! </events>
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! ...
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! </runtime>
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The content of each '<log>' node is matched continuously against the output of
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each LOG client of a test. The first tag whose content matches completely
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decides on the tests result through its 'meaning' attribute and causes the
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depot autopilot to replace the current test scenario with its successor. In
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order to be able to do the matching, the depot autopilot acts as LOG session
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server to all components of a test scenario, given that incoming LOG session
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requests can be correlated to these components. This behavior leads to the
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requirement that the depot autopilot receives the session-label prefix of the
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runtime init through the new 'children_label_prefix' attribute of its
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configuration:
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! <config ... children_label_prefix="test_init_runtime -> ">
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As soon as the '<log>' event matching is done, the test output is incorporated
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into the autopilot's LOG output, so, later debugging may benefit from it as
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well.
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A '<timeout>' node, on the other hand, causes the autopilot to set a timeout
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according to the 'sec' attribute when starting the test. Should the timeout
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trigger before the test terminated in another way, it's up to the '<timeout>'
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node to define the test's result and terminate the test.
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The second point, regarding the scheduling of tests, is an easy one. While for
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the depot deploy tool, the order of '<start>' nodes is irrelevant, for the
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depot autopilot, it defines the order in which tests shall be executed.
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The last point raised the question of what to do when a test gets stuck or,
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even worse, compromises the whole system. The former is already handled by
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using the above mentioned '<timeout>' events. The latter, on the other hand,
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brings the '<previous-results>' node of the autopilot configuration into play.
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With this node, the depot autopilot instance can be equipped with the results
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of a previously running instance. This way, the target platform can be
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rebooted when a system crash is detected and can proceed with the remaining
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tests without losing the information gathered during earlier boot cycles. This
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is a short example:
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! <config>
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! <previous-results time_sec="15"
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! failed="1"
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! succeeded="1"
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!
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! > test-1 ok 0.563 log "Succeeded"
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! test-2 failed 20.000 reboot</previous-results>
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! ...
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! </config>
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The so configured depot-autopilot instance will put the content string of
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the '<previous-results>' node at the top of its result list. The values of the
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attributes of the tag ('succeeded', 'failed', ...), at the other hand, are
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relevant for result statistics.
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Once all tests are evaluated, the depot autopilot outputs a result overview
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comprising a list of single test results and some statistical data:
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! --- Finished after 1207.154 sec ---
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!
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! test-init failed 300.015 timeout 300 sec
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! test-init_loop ok 57.228 log "child "test-init_loop" exited wi ..."
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! test-ldso ok 1.779 log "[init -> test-ldso] Lib_2_global ..."
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!
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! succeeded: 2 failed: 1 skipped: 0
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For a comprehensive description of all the features of the depot autopilot,
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please have a look at _repos/gems/src/app/depot_autopilot/README_.
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The run script
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--------------
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With the depot autopilot component, testing becomes more independent from a
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non-Genode host system that executes run scripts. However, we did not intend
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to port all existing tests at once nor do we know yet if this is desirable.
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In our nightly testing infrastructure, tasks like powering on and off the
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target platform or managing the log archives are still bound to Linux and the
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time-tested run mechanism. Thus, a mediation between the depot autopilot and
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the existing test infrastructure is required.
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[image depot_autopilot_after]
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The solution is the new run script _gems/run/depot_autopilot.run_. This run
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script contains a scenario that combines a TAR VFS, a depot query component,
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the depot autopilot, and an init runtime resulting in a fully automated meta
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test-unit for the run mechanism. Inside the script, you have a convenient and
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small set of configuration variables. Normally, you just list the names of the
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test packages to evaluate and define platform incompatibilities through
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optional 'skip_test_pkg' variables:
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! set avail_test_pkgs {
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! test-lx_block
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! test-log
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! test-tcp_bulk_lwip
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! test-mmio
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! ... }
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!
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! set skip_test_pkg(test-lx_block) [expr ![have_spec linux]]
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! set skip_test_pkg(test-tcp_bulk_lwip) [expr ![have_spec x86]]
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Together with the '--depot-user' run parameter, the run script composes an
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archive of a 'depot' directory containing the correct versions of all needed
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packages. As usual, the run modules manage the boot process of the target
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platform and the loading of the system image, thereby shipping the depot
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archive as Genode boot module. The archive can then be accessed by the depot
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query tool on target through the VFS server. The depot autopilot, on the other
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hand, gets configured to successively request the exact same packages from the
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depot query tool and evaluates them using the init runtime named "dynamic".
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[image depot_autopilot_arch]
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The run script can also handle system crashes. Through the depot autopilot's
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log output, it keeps track of every test started and its individual timeout.
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If a timeout goes by without the depot autopilot having terminated the current
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test, the run script intervenes. As it also records the individual test
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results printed by the depot autopilot up to this point, it can now reboot the
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system to continue testing. In this follow-up attempt, everything remains the
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same with two exceptions. First, the list of tests is pruned by the already
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evaluated tests plus the test that caused the reboot, and second, the
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'<previous-results>' node of the depot autopilot is used to pass on the
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findings of former attempts. This way, the final result list of the depot
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autopilot should always be reached and always be complete.
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Another feature of the run script is that it offers an alternate mode for
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debugging a single test without having to switch the scenario. Through three
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variables you can deactivate all but one test and apply source code changes
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without having to rebuild packages. For example:
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! set single_test_pkg "test-libc_vfs"
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! set single_test_build { server/ram_fs test/libc_vfs }
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! set single_test_modules { ram_fs vfs.lib.so }
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This would only run the _libc_vfs_ test and overlays the package contents with
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the _ram_fs_ and _vfs.lib.so_ images, which are freshly built from the local
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source repository.
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A more detailed documentation of the run script can be found at
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_repos/gems/src/app/depot_autopilot/README_ and inside the run script itself.
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The test packages
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-----------------
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Of course, the depot autopilot isn't worth much without any test packages in
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place and all of our tests existed solely in the format expected by the run
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tool. But we had the feeling that a significant amount of them should be
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portable without great difficulty. One potential limiting factor was that
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drivers should not be an individual part of test runtimes as, so far,
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restarting drivers causes problems in most cases. Therefore, they must be
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loaded by the surrounding system. However, holding drivers for all hardware
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available just in case that a test needs them would unnecessarily raise the
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scenario's complexity and disturb less demanding but more performance critical
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tests. Thus, we decided to let the depot-autopilot run script provide merely
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the timer driver as most of the component and unit tests are satisfied with
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this. As soon as we want to port tests using other drivers, like the
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network-bench suite, a dedicated depot-autopilot run script would be the way
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to go. Another noteworthy point is the rather basic feature set for doing
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result evaluation with the depot autopilot. As it turned out, most tests
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comply with this limitation because tricky success conditions aren't
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encouraged by the run mechanism either.
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All in all, we managed to port 75 tests from the repositories 'base', 'os',
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'libports', and 'ports' to the depot autopilot during this release cycle. To
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avoid redundancy, we removed the corresponding run scripts at the same time.
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Each package that represents a test is prefixed with "test-" so you can
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quickly receive an overview of all available tests by doing:
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! find <GENODE_DIR>/repos -type d -wholename *recipes/pkg/test-*
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New tooling for obtaining test-coverage metrics
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===============================================
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The [https://gcc.gnu.org/onlinedocs/gcc/Gcov.html - gcov] tool can analyze how
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often each source-code line of a test program has been executed.
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On POSIX-like systems the usual steps to use this tool are as follows:
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* When building a test program, special compiler flags add instrumentation code
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to the program and generate a gcov "note" file along with each object file.
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These note files are needed later on for the final analysis. The test
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program is also linked against the gcov library.
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* When the test program is running, it collects coverage data and writes it
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into a gcov "data" file for each object file when the program exits.
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* The gcov program uses the source, note, and data files to generate annotated
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source-code files with the number of times each line has been executed.
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We ported the gcov tool to Genode to use it with our native (non-libc) Genode
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tests and the 'depot_autopilot' run script. It is integrated in the following
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way:
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* When adding 'COVERAGE = yes' to a _target.mk_ file of a test program,
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the build system adds the gcov-specific compiler flags and links the
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program with the gcov library.
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* The generated gcov note files get a symlink in the _build/.../bin/gcov_data_
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directory, which is added to the binary depot package of the test program.
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This way, the note files become available within the binary archives of the
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depot as used by the "depot_autopilot" system scenario described in
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Section [Automated test infrastructure hosted on top of Genode].
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* When the test program starts, it calls 'env.exec_static_constructors()'.
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Each instrumented object file registers itself at the gcov library from a
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static constructor (auto-generated with the gcov compiler flags).
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* The gcov library needs the Genode environment to write the collected data to
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a file system, so the test program also calls the 'gcov_init()' function
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with a reference to the environment.
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* When the test program has finished, it calls 'genode_exit()', which in turn
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calls an exit handler registered by the gcov library. The gcov library then
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writes the coverage data files to a RAM file system with a path that matches
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the path to the note files in the depot in the same file system.
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* When all tests have finished, the depot_autopilot scenario runs the gcov
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program, which scans the file system for the collected gcov data files and
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writes the final analysis for each file to the log. If the name of the test
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package is included in the 'avail_test_src_pkgs' list of the
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_depot_autopilot.run_ script, the source and API archives of the test are
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added to the depot and the source code is printed together with the counts
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and line numbers, otherwise only the counts and line numbers with the text
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'/*EOF*/' on each line are printed.
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So far, we enabled the code coverage analysis feature for the 'xml_generator'
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test and it can be seen in action by running the _depot_autopilot.run_ script.
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Static code analysis
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====================
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The static analyzer tool of [https://clang-analyzer.llvm.org] can analyze
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source code in C and C++ projects to find bugs at compile time.
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With this tool enabled, Genode users can check and ensure the quality of
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Genode components. The tool can be invoked during make invocations and during
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the creation of Genode packages.
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|
|
For the invocation of _make_ within a Genode build directory, the new
|
|
STATIC_ANALYZE variable on the command line will prompt the static analyzer to
|
|
run next to the actual build step.
|
|
|
|
! STATIC_ANALYZE=1 make -C build/x86_64 KERNEL=... run/...
|
|
|
|
For analyzing Genode packages, a new wrapper tool _tool/depot/static_analyze_
|
|
becomes handy. It can be combined with the existing _tool/depot/*_ tools to
|
|
take effect, e.g.:
|
|
|
|
! tool/depot/static_analyze tool/depot/create <user>/pkg/...
|
|
|
|
The results of the static-analyzer tool are generated in the form of html
|
|
pages and can be inspected afterwards. The following example output showcases
|
|
a run of the static analyzer tool:
|
|
|
|
!
|
|
! make: Entering directory '../genode/build/x86_64'
|
|
! checking library dependencies...
|
|
! scan-build: Using '/usr/lib/llvm-6.0/bin/clang' for static analysis
|
|
! ...
|
|
!
|
|
! LINK init
|
|
! scan-build: 0 bugs found.
|
|
! scan-build: The analyzer encountered problems on some source files.
|
|
! scan-build: Preprocessed versions of these sources were deposited in
|
|
! '/tmp/scan-build-2018-11-28-111203-20081-1/failures'.
|
|
|
|
During our enablement of this feature we used Clang 6.0 on Ubuntu 16.04. The
|
|
steps to provide the required tools on Linux are like follows.
|
|
|
|
! sudo apt install clang-tools-6.0
|
|
! cd $HOME/bin
|
|
! ln -s $(which scan-build-6.0) scan-build
|
|
|
|
|
|
Genode as a platform for Mirage-OS unikernels
|
|
#############################################
|
|
|
|
This year, we collaborated with [https://mirage.io - MirageOS]
|
|
at [https://bornhack.dk/bornhack-2018/ - Bornhack] and the MirageOS hack
|
|
retreat in Marrakesh to bring unikernel applications to Genode as native
|
|
components. MirageOS is an application framework that provides all necessary
|
|
OS abstractions for network applications as a library. A MirageOS unikernel
|
|
requires a machine operating system to provide a thread of execution, system
|
|
time, a network interface, and block storage. Higher-level OS facilities such
|
|
as multitasking, TCP/IP, and object storage are implemented as statically
|
|
linked libraries written in the same language as the application, OCaml in the
|
|
case of MirageOS. Relative to traditional applications that rely on a POSIX
|
|
runtime this allows for significant code pruning at compile-time and simple
|
|
and precise host environment requirements.
|
|
|
|
MirageOS was originally implemented with [https://xenproject.org/ - Xen] as
|
|
the machine OS but to port MirageOS to other hypervisors a general sandboxing
|
|
middleware library was created. This library is
|
|
[https://github.com/Solo5/solo5 - Solo5], which provides the simple
|
|
abstractions necessary for running a unikernel as paravirtualized guest or as
|
|
sandboxed process of another OS. After investigating both approaches, we chose
|
|
to implement a native Solo5 bindings library. This follows our belief that an
|
|
operating system can provide process isolation equal to and more efficiently
|
|
than hardware assisted virtualization. We share this belief with the unikernel
|
|
community and expect it as an
|
|
[https://dl.acm.org/citation.cfm?id=3267845 - inevitable trend]
|
|
in hosted computing. Furthermore, the burden of developing and maintaining a
|
|
unikernel support layer is trivial compared to a virtual machine monitor.
|
|
|
|
Building and deploying MirageOS with Genode requires coordination at both
|
|
sides. For this reason, Genode target support was added to the Mirage tooling
|
|
in the
|
|
[https://github.com/mirage/mirage/releases/tag/3.3.0 - 3.3.0 release].
|
|
The Genode platform layer of Solo5 and Mirage differs most from other targets
|
|
such as [https://muen.sk/articles.html#mirageos-unikernels - Muen] in that it
|
|
is dynamically linked. This allows a Mirage image to remain viable across
|
|
Genode API and ABI changes.
|
|
|
|
To compile Mirage code into a Genode compatible binary, one may follow the
|
|
standard build procedure using the _mirage_ tool just as one would for Muen or
|
|
Unix.
|
|
|
|
! # See https://mirage.io/docs/ for instructions
|
|
! # on building a MirageOS application.
|
|
!
|
|
! cd mirage-skeleton/tutorial/hello/
|
|
! mirage configure --target genode --dhcp=true
|
|
! make depends
|
|
! make build
|
|
|
|
The output is a Genode program dynamically linked to a Solo5 bindings library.
|
|
This library is built using the Genode tool chain and is available as a
|
|
[https://depot.genode.org/genodelabs/bin/x86_64/solo5 - depot package].
|
|
Finding a smooth workflow for deploying unikernels with Genode is a topic open
|
|
for discussion, but for now, we offer a run scenario for creating a standalone
|
|
x86_64 MirageOS boot image with an ethernet driver.
|
|
|
|
! # See https://genode.org/documentation/developer-resources/build_system
|
|
! # for instructions on preparing the Genode build system.
|
|
!
|
|
! cp mirage-skeleton/tutorial/hello/hello.genode \
|
|
! genode/build/x86_64/bin/mirage
|
|
! cd genode/build/x86_64
|
|
!
|
|
! # Build and run a minimal image (serial logging only):
|
|
! make run/mirage_net KERNEL=hw
|
|
!
|
|
! # Build and run an image with a graphical console:
|
|
! make run/mirage_pretty KERNEL=hw
|
|
!
|
|
! # To prepare a USB image for booting real hardware:
|
|
! sudo cp var/run/mirage_pretty.iso «your USB stick device file»
|
|
|
|
For a minimal network scenario, a Mirage instance requires only a handful of
|
|
components, time sources, a network driver, and an I/O hardware-access
|
|
multiplexer.
|
|
|
|
[image solo5_tcb] A minimum viable Genode system for hosting Mirage,
|
|
the trusted computing base is highlighted in red
|
|
|
|
A simple demo not withstanding, we can justify Genode as a unikernel hosting
|
|
platform by analyzing the complexity of a Genode host system by measuring the
|
|
lines of C++ code used to produce such an image. This yields an initial metric
|
|
for assessing the security of a system as well as its cost to develop and
|
|
maintain. By compiling each component with debugging symbols, parsing binaries
|
|
for file paths injected by the compiler, and collecting a sum of the number of
|
|
lines found in each file, we get an estimate of the total line count for each
|
|
component. Building a set of every source file used in the minimal system,
|
|
excluding the unikernel itself, the sum of lines of code does not exceed
|
|
50,000. We assert that this is a fraction of the size of any Unix-derived
|
|
hosting environment.
|
|
|
|
[image solo5_tcb_sloc]
|
|
|
|
|
|
Base framework and OS-level infrastructure
|
|
##########################################
|
|
|
|
Component health monitoring
|
|
===========================
|
|
|
|
Scenarios where components are known to sometimes fail call for a mechanism
|
|
that continuously checks the health of components and reports anomalies. To
|
|
accommodate such use cases, we introduced a low-level health-monitoring
|
|
mechanism into the foundation of the framework and made this mechanism
|
|
available via init's configuration concept.
|
|
|
|
At the lowest level, the parent interface received two new RPC functions. The
|
|
'heartbeat_sigh' function allows a child to register a signal handler for
|
|
heartbeat signals. The 'heartbeat_response' function allows a child to confirm
|
|
its health to the parent. With this basic interface, a parent becomes able to
|
|
periodically ask for a life sign from each of its children.
|
|
|
|
[image heartbeat]
|
|
|
|
Each component installs a heartbeat signal handler during its initialization.
|
|
This happens under the hood and is thereby transparent to application code.
|
|
The default heartbeat handler invokes the 'heartbeat_response' function at
|
|
the parent interface and thereby confirms that the component is still able to
|
|
respond to external events.
|
|
|
|
With this low-level mechanism in place, we enhanced the init component with the
|
|
ability to monitor components hosted on top of init. A global (for this init
|
|
instance) heartbeat rate can be configured via a '<heartbeat rate_ms="1000"/>'
|
|
node at the top level of init's configuration. The heartbeat rate can be
|
|
specified in milliseconds. If configured, init uses a dedicated timer session
|
|
for performing health checks periodically. Each component that hosts a
|
|
'<heartbeat>' node inside its '<start>' node is monitored. In each period,
|
|
init requests heartbeat responses from all monitored children and maintains a
|
|
count of outstanding heartbeats for each component. The counter is incremented
|
|
in each period and reset whenever the child responds to init's heartbeat
|
|
request. Whenever the number of outstanding heartbeats of a child becomes
|
|
higher than 1, the child may be in trouble. Init reports this information in
|
|
its state report via the new attribute 'skipped_heartbeats="N"' where N
|
|
denotes the number of periods since the child became unresponsive.
|
|
|
|
Of course, the mechanism won't deliver 100% accuracy. There may be situations
|
|
like long-running calculations where long times of unresponsiveness are
|
|
expected from a healthy component. Vice versa, in a multi-threaded
|
|
application, the crash of a secondary thread may go undetected if the primary
|
|
(checked) thread stays responsive. However, in the majority of cases where a
|
|
component crashes (page fault, stack overflow), gets stuck in a busy loop,
|
|
produces a deadlock, or throws an unhandled exception (abort), the mechanism
|
|
nicely reflects the troublesome situation to the outside.
|
|
|
|
|
|
Enhanced window-management flexibility
|
|
======================================
|
|
|
|
Genode's
|
|
[https://genode.org/documentation/release-notes/14.08#New_GUI_architecture - custom GUI architecture]
|
|
consists of multiple components with strictly distinguished roles. The central
|
|
broker between those components is a low-complexity window-manager (wm)
|
|
component, which is complemented by a so-called decorator that defines how
|
|
windows look, and a layouter that defines how they behave. Since the layouter
|
|
and decorator are sandboxed components without access to the application
|
|
window's content nor the user input into the applications, those components
|
|
are largely uncritical for the information security of GUI applications.
|
|
|
|
|
|
New window layouter
|
|
~~~~~~~~~~~~~~~~~~~
|
|
|
|
The window layouter complements the window manager with the policy of how
|
|
windows are positioned on screen and how they behave when the user interacts
|
|
with window elements like the maximize button or the window title. The current
|
|
release replaces the former "floating_window_layouter" with a new
|
|
"window_layouter" component that supports the subdivision of screen space into
|
|
columns and rows, the concept of layers, and the principle ability to store
|
|
window layout information across reboots.
|
|
|
|
|
|
Layout rules
|
|
------------
|
|
|
|
The window layouter positions windows according to rules defined by the
|
|
component's configuration. The rules consist of two parts, the definition of
|
|
the screen's layout and the assignment of client windows to the defined parts
|
|
of the screen's layout.
|
|
|
|
! <config>
|
|
! <rules>
|
|
! <screen>
|
|
! ...definition of screen layout...
|
|
! </screen>
|
|
! <assign label_prefix="..." target="..."/>
|
|
! ,,,
|
|
! </rules>
|
|
! ...
|
|
! </config>
|
|
|
|
The '<screen>' node can host any number of '<column>' nodes, which partition
|
|
the screen horizontally into columns. By default, each column has the same
|
|
size. By specifying an optional 'weight' attribute, column sizes can be
|
|
weighted relative to one another. The default weight is '1'. Alternatively,
|
|
the 'width' of a column can be explicitly specified in pixels.
|
|
Each column can host any number of '<row>' nodes, which subdivide the column
|
|
vertically. Analogously to columns, rows can be dimensioned via an optional
|
|
'weight' attribute or an explicit 'height' in pixels. A '<row>' can, in turn,
|
|
contain '<column>' nodes, thereby further subdividing the screen.
|
|
Each '<column>' or '<row>' can be used as window-placement target when
|
|
equipped with a 'name' attribute. Each name must occur only once within the
|
|
'<screen>' node. In the following, a named column or row is referred to as
|
|
_target_. Each target can host an optional 'layer' attribute. If not
|
|
specified, the layer 9999 is assumed. A target with a lower layer overlaps
|
|
targets with higher layers.
|
|
|
|
The assignment of windows to targets is defined via '<assign>' nodes. Each
|
|
'<assign>' node must be equipped with a 'label', 'label_prefix', or
|
|
'label_suffix' attribute, which is used to match window labels. For a given
|
|
window, the first matching '<assign>' node takes effect.
|
|
|
|
Each '<assign>' node must have a 'target' attribute that refers to the name
|
|
of a column or row. By default, the window is sized to fit the target area.
|
|
However, it is possible to position the window relative to the target area by
|
|
specifying the 'xpos', 'ypos', 'width', and 'height' attributes together with
|
|
the 'maximized="no"' attribute.
|
|
|
|
If multiple windows are assigned to the same target area, the order of their
|
|
'<assign>' rules defines their stacking order. The window with the earliest
|
|
'<assign>' rule is displayed in front.
|
|
|
|
|
|
Dynamic layouts
|
|
---------------
|
|
|
|
The window layouter is able to respond to rule changes at runtime.
|
|
|
|
By specifying the '<config>' attribute 'rules="rom"', the window layouter
|
|
tries to obtain the layout rules from a distinct ROM module. Should the ROM
|
|
module not contain valid rules, the '<rules>' sub node of the '<config>' comes
|
|
into effect.
|
|
|
|
Any window-layout change such as the movement of a floating window is realized
|
|
as a change of the window-layout rules. To support interactive adjustments of
|
|
the window layout, the layouter responds to certain user interactions by
|
|
generating new rules by itself in the form of a "rules" report. The generation
|
|
of such rules can be enabled via the '<report>' sub node of the configuration:
|
|
|
|
! <config>
|
|
! <report rules="yes"/>
|
|
! ...
|
|
! </config>
|
|
|
|
By feeding back the rules generated by the window layouter into the window
|
|
layouter itself via a 'report_rom' service, the window layout becomes
|
|
adjustable interactively. As the rules entail the complete state of the
|
|
present window layout, it is possible to save/restore the layout state.
|
|
|
|
|
|
Dynamic rule-generation mechanism
|
|
---------------------------------
|
|
|
|
Whenever a new window appears that solely matches a wildcard '<assign>' rule
|
|
(one that uses a 'label_prefix' or 'label_suffix'), the layouter generates a
|
|
new '<assign>' rule with the window's label as 'label' attribute. The
|
|
explicitly labeled '<assign>' rules appear before any wildcard '<assign>'
|
|
rules.
|
|
|
|
If the user brings a window to front, the window layouter will change the
|
|
order of the explicit '<assign>' rules such that the window's '<assign>' rule
|
|
comes first. When moving or resizing a window, the 'xpos', 'ypos', 'width',
|
|
and 'height' attribute of the window's assign rule are updated. When
|
|
maximizing or unmaximizing a window, the 'maximized' attribute of its
|
|
'<assign>' rule is toggled.
|
|
|
|
|
|
Modularized window system in Sculpt OS
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Sculpt OS used to come with a package called "wm", which comprised a
|
|
ready-to-use composition of window-system components, including the layouter,
|
|
a decorator, and the configuration of these components. Even though this
|
|
package was convenient for a start, we desire more flexibility. For example, a
|
|
user may wish to replace the decorator at runtime or tweak the configuration
|
|
of the individual components at runtime. For this reason, we split up the wm
|
|
package. For the convenient use in run scripts, we preserved the former wm
|
|
package as "motif_wm".
|
|
|
|
With the move of the window layouter and window decorators into dedicated
|
|
packages, those components can now be combined with the "wm" server at runtime
|
|
and restarted/reconfigured/swapped-out independently. To use the window
|
|
manager in Sculpt, one must launch the "wm", "window_layouter", and one of the
|
|
"motif_decorator" or "themed_decorator" packages. It is possible to replace
|
|
one decorator by the other at runtime.
|
|
|
|
The window layouter package depends on a so-called "recall_fs" component,
|
|
which is a file system used for *remembering the window layouter's state*.
|
|
Sculpt comes with a ready-to-use "recall_fs" launcher, which hands out the
|
|
directory _/recall_ of the used file system. When the window layouter is
|
|
started, a file _/recall/window_layouter/rules_ reflects the current state of
|
|
the layouter. It serves two purposes. First, it preserves the window layout
|
|
across reboots. Second, it can be edited by the user or (potentially) by other
|
|
components. Thereby, the layout policy can be tweaked without limits, and the
|
|
rules can simply be swapped out by mere file operations.
|
|
|
|
|
|
Network-stack improvements
|
|
==========================
|
|
|
|
The transition from lwIP as a plugin to the libc library to a plugin to the
|
|
VFS library is complete. As a result, POSIX applications can no longer be
|
|
linked to lwIP through the 'libc_lwip' library. Instead they need only to link
|
|
with the 'libc' library and be configured at runtime to open network
|
|
connections through the local VFS. The 'libc' library now features networking
|
|
support by default with the actual TCP/IP stack implemented in dynamically
|
|
loaded VFS plugins. An example configuration for using lwIP with DHCP follows:
|
|
|
|
! <start name="...">
|
|
! <config>
|
|
! <libc socket="/sockets"/>
|
|
! <!-- configure the libc to use a sockets directory -->
|
|
! <vfs>
|
|
! <dir name="sockets">
|
|
! <!-- create a "socket" directory with virtual control files -->
|
|
! <lwip dhcp="yes"/>
|
|
! </dir>
|
|
! </vfs>
|
|
! </config>
|
|
! </start>
|
|
|
|
The lwIP library has also been updated to the latest 2.1.2 release.
|
|
|
|
|
|
Java language runtime
|
|
=====================
|
|
|
|
OpenJDK support has been added to Genode with release 18.05. At that time, we
|
|
were only able to offer support for Java's interpreter mode, because of issues
|
|
that arose on ARM platforms (please refer to the release notes of
|
|
[https://genode.org/documentation/release-notes/18.05#Java_language_support - Genode 18.05]).
|
|
In this mode, byte code is not compiled but interpreted which, of course,
|
|
introduces a serious performance penalty. Since 18.05, we worked on enabling
|
|
Java's just-in-time compiler (JIT), which translates byte code to actual
|
|
machine code. We were able to add support for both ARM and x86 platforms, but
|
|
for this release, we stopped short of enabling the compiler by default because
|
|
some stability issues remain.
|
|
|
|
Please note: OpenJDK has been moved from Genode's base system to the
|
|
[https://github.com/genodelabs/genode-world Genode-world] repository and is
|
|
now also available as a Genode package.
|
|
|
|
|
|
Ada language runtime
|
|
====================
|
|
|
|
Genode's support for the Ada programming language is maintained by
|
|
[https://componolit.com - Componolit]. With the current release, the
|
|
runtime-specific code moved to a
|
|
[https://github.com/Componolit/ada-runtime - distinct repository], which is
|
|
integrated with Genode as a port. It can be installed by executing the
|
|
following command from the base of Genode's source tree:
|
|
|
|
! ./tool/ports/prepare_port ada-runtime
|
|
|
|
|
|
C language runtime
|
|
==================
|
|
|
|
The pthread library has been integrated into the libc library with this
|
|
release. This has no effect on the semantics of pthreads. Applications simply
|
|
do not need to link to this library anymore. This is in contrast to normal
|
|
Unix systems that provide a _libpthread_ library. Our POSIX implementation
|
|
exists in userspace while supporting the blocking I/O patterns commonly used
|
|
in Unix. To do this, we run a "kernel" task within the libc library that
|
|
dispatches I/O as application threads are blocked. This task operates on a
|
|
secondary stack of the primary thread but is also re-entrant from secondary
|
|
threads. Maintaining a common implementation for multi-threaded and
|
|
single-threaded applications has been the most practical approach, and merging
|
|
pthreads completely into the libc clears the path to improving multithreaded
|
|
I/O during the next releases.
|
|
|
|
|
|
Improved performance of Zynq network driver
|
|
===========================================
|
|
|
|
Since the network driver for the Xilinx Zynq-7000 platform was burdened with
|
|
performance issues, it underwent a review to identify and mitigate conceptual
|
|
bottlenecks. Although the Gigabit Ethernet MAC (GEM) controller allows
|
|
DMA-accelerated transmission and reception of network packets, the driver still
|
|
needed to copy each packet from the packet-stream interface to the DMA memory
|
|
region. As the latter was additionally attached as uncached memory, the driver
|
|
showed a very poor performance (i.e. throughput).
|
|
|
|
Fortunately, the design of the packet-stream interface enabled a zero-copy
|
|
implementation of the Zynq network driver. Instead of copying each packet from
|
|
the bulk buffer of the packet-stream interface to a dedicated DMA memory
|
|
region, the allocated packet buffers are now directly handed over to the GEM
|
|
for DMA-accelerated packet transmission and reception. In particular, the
|
|
driver will allocate up to 1024 packet buffers, depending on the bulk buffer
|
|
size provided by its Nic client.
|
|
|
|
In addition to the zero-copy implementation, checksum offloading has been
|
|
enabled. For outbound packets, the GEM automatically fills in the IP, UDP and
|
|
TCP checksum header fields. Inbound packets will be dropped if their checksum
|
|
fields are incorrect. Note, that IP checksum offloading is not implemented by
|
|
qemu.
|
|
|
|
Furthermore, MAC 802.3 pause frames have been enabled.
|
|
|
|
|
|
Base API changes
|
|
================
|
|
|
|
The framework's base API received two minor improvements.
|
|
|
|
First, the _util/reconstructible.h_ utility has a new method called
|
|
'conditional', which simplifies the typical use case for 'Constructible'
|
|
objects where the constructed/destructed state depends on a configuration
|
|
parameter. The method alleviates the need to re-implement the logic manually.
|
|
|
|
Second, when creating a secondary entrypoint, the CPU affinity of the
|
|
entrypoint is now specified as an argument.
|
|
|
|
|
|
Libraries and applications
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##########################
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Initial version of the Genode SDK
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=================================
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To allow Genode components to be built independently from our build system, we
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have added a script to generate a Software Development Kit (SDK) that contains
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headers, pre-built libraries, linker scripts, and
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[https://www.freedesktop.org/wiki/Software/pkg-config/ - pkg-config]
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metadata. The SDK is still experimental and lacks documentation, but has been
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shown to be useful when combined with some external Make-based build systems
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as well as the Nimble package manager provided with the Nim programming
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language.
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The SDK includes support for native Genode services as well a C runtime and
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the C++ standard library.
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A simple [https://github.com/libretro/nxengine-libretro/commit/f6ea7cd2e260731a00e20ebe239ccdc6bbf31e50 - example]
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of using the SDK within a makefile to build a library:
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! ...
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! ifeq ($(platform), genode)
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! CC := $(shell pkg-config genode-base --variable=cc)
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! CXX := $(shell pkg-config genode-base --variable=cxx)
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! LD := $(shell pkg-config genode-base --variable=ld)
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! AR := $(shell pkg-config genode-base --variable=ar) -rcs
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! CFLAGS += $(shell pkg-config --cflags genode-libc)
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! CXXFLAGS += $(shell pkg-config --cflags genode-stdcxx)
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! LDFLAGS += $(shell pkg-config --libs genode-lib genode-libc genode-stdcxx)
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! endif
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!
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! %.o: %.c
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! $(CC) $(CFLAGS) -c $< -o $@
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!
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! %.o: %.cpp
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! $(CXX) $(CXXFLAGS) -c $< -o $@
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!
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! $(TARGET): $(OBJECTS)
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! $(LD) $(OBJECTS) $(LDFLAGS) -o $@
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! ...
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To link a program, the link flags may be obtained with 'pkg-config --libs genode-prg',
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for libraries with 'pkg-config --libs genode-lib'.
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In any case, the tools that invoke pkg-config, Make or otherwise, need a
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'PKG_CONFIG_PATH' environmental variable set to the location of the
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'pkgconfig' directory in the SDK, such as with the following shell command:
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! PKG_CONFIG_PATH=/opt/genode-sdk-x86_64-18.08/pkgconfig make
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It is important to stress that shared libraries must be sourced exclusively
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from the SDK or otherwise built by the SDK. It is not possible to mix host
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libraries with cross-compiled Genode libraries. In practice it has not been a
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problem to build libraries commonly available in the form of shared libraries
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as static bundled dependencies, such as libogg, libpng, SQLite, etc.
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In the future we will investigate expanding the scope of the SDK or
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complimenting it with add-on SDKs, such as for Qt or SDL.
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SSH terminal server
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===================
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Up to now, we mostly focused on covering the direct interaction of a user with
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the system. Besides a minimal TCP terminal, there was no component to
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accommodate remote access. Instead of extending this component to add vital
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features like TLS or user authentication, we turned to using an existing
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protocol. For this use case the SSH protocol is the most popular choice as
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clients and server programs are available for virtually all OSes.
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So with this release, we introduce a component that makes Genode's terminal
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session accessible via SSH. It is based on the server implementation of
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libssh, which was updated to version 0.8.4. On the Genode side of things, the
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component acts as a terminal-session server, to which Terminal clients can
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connect. From the outside, users may access a specific terminal session by
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logging in via SSH given they provide the proper login credentials. For now,
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only the SSH channel 'shell' and 'term' requests have been implemented, i.e.,
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the server can be used for interactive sessions but not for scp/rsync or other
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operations that rely on the 'exec' request. Since the component merely makes
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terminal sessions available, the SSH connection needs to be forcefully closed
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by issuing the well-known '~.' sequence rather than using '^D' (EOF) which the
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underlying terminal session may not handle as expected.
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The following exemplary snippet shows how the component can by configured:
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!<config port="2022" ed25519_key="/etc/ed25519_host_key
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! allow_password="yes" allow_publickey="yes"/>
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!
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! <policy label="noux-system" user="root" password="toor"/>
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! <policy label="noux-user" user="user" pub_key="/etc/user.pub"/>
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!
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! <vfs>
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! <dir name="dev">
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! <log/> <rtc/> <jitterentropy name="random"/>
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! </dir>
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! <dir name="socket"> <lxip dhcp="yes"/> </dir>
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! <dir name="etc"> <fs/> </dir>
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! </vfs>
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! <libc stdout="/dev/log" stderr="/dev/log" rtc="/dev/rtc" socket="/socket"/>
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!</config>
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The component is configured to listen on port '2022' for incoming SSH
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connections and allows for logging in by using either a password or public
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key. The '<policy>' configuration is used to link the terminal session to the
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SSH login. In this case, the terminal session of the client with the label
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'noux-system' may be accessed via the 'root' login. The '<vfs>' configures the
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file system of the component. Besides access to the needed services, like the
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real-time clock, a random device, and the TCP/IP stack a file system session
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mounted at '/etc' for housing the files required by the component. In
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particular, these files are the SSH server's host key and the public key for
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'user' login.
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For more information, please read _repos/gems/src/server/ssh_terminal/README_
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and take _repos/gems/run/ssh_terminal.run_ for a ride.
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Removed networking support from Noux
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====================================
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Support for networking has been removed from the Noux runtime as a side effect
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of moving IP stacks from libc plugins into VFS plugins. In practice, Noux has
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seldom been used for networking and our recommendation remains that networked
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applications should link with the libc library and not use the Noux runtime.
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New depot packages
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==================
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Our work on the Genode-based test-automation framework prompted us to a
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package for each individual test. As a nice byproduct, we introduced depot
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recipes of all components the tests depend on, and a few more. Thereby, the
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following new depot content has become available:
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Source archives for the base-hw microkernel for various platforms:
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* src/base-hw-arndale
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* src/base-hw-imx53_qsb
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* src/base-hw-imx53_qsb_tz
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* src/base-hw-odroid_xu
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* src/base-hw-panda
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* src/base-hw-rpi
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* src/base-hw-wand_quad
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Source archives for the Fiasco.OC microkernel for a few platforms:
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* src/base-foc-pc
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* src/base-foc-arndale
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* src/base-foc-pbxa9
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Source archives of components used by the test scenarios:
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* src/nic_bridge
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* src/python
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Source archives and package runtimes needed for hosting the gcov tool and
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the GCC tool chain:
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* src/gmp, src/mpc, src/mpfr
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* src/binutils_x86, src/gcc_x86
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* src/gnumake, src/sed, src/tar, src/which
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* pkg/gcov
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* pkg/noux-build-x86
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Platforms
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#########
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NOVA microhypervisor
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====================
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Up to now, the NOVA kernel reserved a statically configured part of the system
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memory as kernel memory. The configured memory had to be chosen at link time.
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However, in the case of Sculpt, the actual target machine and its available
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system memory is unknown beforehand, which makes it hard to choose a
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kernel-memory amount well suited to a such broad use case.
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We can't lift this structural issue, but we were able to mitigate it to some
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degree. The kernel now looks up the overall available system memory at boot
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time and allocates the kernel memory depending on three build-time
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configuration options. So, the overall kernel memory is still static, but
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dimensioned depending on the target machine.
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The three configuration options can be adjusted in the Makefile of the kernel.
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CONFIG_MEMORY_BOOT is the amount of kernel memory allocated in the BSS
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statically, effectively a link time decision.
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CONFIG_MEMORY_DYN_MIN and CONFIG_MEMORY_DYN_PER_MILL configures the dynamic
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part of the kernel-memory allocation applied during early kernel boot time.
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CONFIG_MEMORY_DYN_MIN is the amount of memory which should be allocated at
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least. The default is 28 MiB. CONFIG_MEMORY_DYN_PER_MILL defines the amount of
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the system memory in per mill, which should be allocated at most, and has a
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default value of 10‰. The overall maximum kernel memory is restricted to ~1G
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for 64bit, due to the chosen internal virtual memory layout.
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Execution on bare hardware (base-hw)
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====================================
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Regarding our own kernel development, the current release increases the
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performance on supported ARM platforms. Most significantly, the FPU is enabled
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by default on all boards. All components built for ARMv6 and ARMv7a are now
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compiled to take advantage of this feature. Therefore, the runtime behaviour
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of certain scenarios can change significantly on ARM when using the 18.11
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release.
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Moreover, after recognizing poor memory-access latency on several Cortex-A9
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platforms, a regression in the enabling of the L2 cache got discovered and
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fixed. Especially, the i.MX6 based Wandboard Quad cache, clocking and power
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settings got tweaked well to achieve reasonable CPU and memory performance.
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This performance-wise line of work will be continued with regard to the next
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release.
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