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===============================================
Release notes for the Genode OS Framework 11.02
===============================================
Genode Labs
One year ago, the release 10.02 was our break-through with regard to the support
of multiple kernels as base platform for Genode. With the added support for
the NOVA hypervisor and the Codezero kernel, Genode applications could be executed
on 6 different kernels. With the current release, we take our commitment to
kernel platform support even further. With the added support for the Fiasco.OC
kernel, we make Genode available on one of the most feature-rich modern microkernels.
Additionally, we entered the realms of kernel design with our new platform support
for the Xilinx MicroBlaze architecture. This platform support comes in the shape
of a custom kernel specifically targeted to the MicroBlaze CPU architecture.
Furthermore, we updated our support for the NOVA Hypervisor to the bleeding-edge
version 0.3, which has been released earlier this month.
With the current support for 8 different kernel platforms (L4/Fiasco, Linux,
L4ka::Pistachio, OKL4, NOVA, Codezero, Fiasco.OC, and native MicroBlaze), testing
and integrating application scenarios across all platforms becomes increasingly
challenging. Therefore, we introduce a new framework for automating such tasks.
Thanks to the tight integration of the automation tool with Genode's build system,
going back and forth between different kernels becomes an almost seamless
experience.
Functionality-wise, the release carries on our vision to create a highly secure
yet easy to use general-purpose operating system. Because the Genode framework
is developed on Linux using the wonderful GNU tools, we consider the
availability of the GNU user land on Genode as crucial for using the system by
ourself. This motivation drives the creation of a custom execution environment
for GNU software on top of Genode. With the current release, we are proud to
present the first pieces of this execution environment. Even though not fully
functional yet, it clearly shows the direction of where we are heading.
Support for Fiasco.OC
#####################
The OC in the name of the Fiasco.OC kernel stands for "object capability", hinting
at the most significant feature that sets current-generation microkernels such as
NOVA, seL4, and Fiasco.OC apart from their predecessors. Whereas previous L4 kernels
succeeded in protecting subsystems from each other, the new generation of kernels
is geared towards strict security policies. Traditionally, two protection domains
were able to communicate with each other if they both agreed. Communication partners
were typically globally known via their respective thread/task IDs. Obviously, this
policy is not able to guarantee the separation of subsystems. If two subsystems
conspire, they could always share information. Object-capability-based kernels
are taking the separation much further by prohibiting any communication between
protection domains by default. Two protection domains can communicate only if
a common acquaintance of both agrees. This default-deny policy facilitates the
creation of least-privilege security policies. From the ground up, Genode has
been designed as a capability-based system which is naturally capable of leveraging
kernel-based object-capability support if present. After NOVA, Fiasc.OC is the
second of Genode's base platforms that provides this feature.
Apart from being a capability-based kernel, Fiasco.OC has a number of compelling
features such as thorough support for ARM platforms and the x86 32/64 bit
architectures. It supports SMP, hardware virtualization, and provides special
optimizations for running paravirtualized operating systems.
Technically, Fiasco.OC is the successor of the L4/Fiasco kernel developed by
the OS group of the TU-Dresden. However, the kernel interface of Fiasco.OC has
not much in common with L4/Fiasco. Some heritages are still there (e.g., IPC
timeouts) but the kernel API has evolved to a fully object-oriented model.
:Thanks:
We are indebted to the main developer of Fiasco.OC Alexander Warg for being
very reponsive to our inquiries while doing the porting work. Thanks to his
support, the adaptation of Genode to this kernel has been an almost smooth
ride.
Prerequisites
=============
You need GNU C & C++ Compilers, GNU Binutils, GNU Make, and Perl to use the
Fiasco.OC build system. On Debian/Ubuntu systems, you have to install the
following packages:
! apt-get install make gawk g++ binutils pkg-config subversion
Moreover, you need to download and install the tool-chain used by Genode. Have
a look at this page:
:[http://genode.org/download/tool-chain]:
Genode tool-chain
Downloading and building Fiasco.OC
==================================
Checkout the Fiasco.OC sources and tool-chain to an appropriated directory:
! export REPOMGR_SVN_REV=27
! svn cat http://svn.tudos.org/repos/oc/tudos/trunk/repomgr |\
! perl - init http://svn.tudos.org/repos/oc/tudos fiasco l4re
Building the kernel
~~~~~~~~~~~~~~~~~~~
Create the build directory for the kernel:
! cd <path_to_fiasco_src_dir>/src/kernel/fiasco
! make BUILDDIR=<path_to_kernel_build_dir>
Go to the build directory, configure the kernel:
! cd mybuild
! make config
This will launch the configuration menu. Here you can configure your kernel.
The default config is just fine to test the Genode port. It will build a
uniprocessor IA32 kernel with debugging features enabled. You can exit the menu and
save the configuration by simply typing 'x'.
Now, build Fiasco.OC by invoking:
! make
Building necessary tools
~~~~~~~~~~~~~~~~~~~~~~~~
To practically use Fiasco.OC, you need in addition to the kernel a tool to
bootstrap it, and the initial pager of the system, namely 'sigma0'. Both tools
can be found in the L4 runtime environment's base directory. Outgoing from
the directory where you checked out the sources, you have to change to the
following directory:
! cd <path_to_fiasco_src_dir>/src/l4
Create another build directory:
! make B=<path_to_l4re_build_dir>
Again, you might want to tweak the configuration:
! make O=<path_to_l4re_build_dir> config
Finally, build the tools:
! make O=<path_to_l4re_build_dir>
Building the Fiasco.OC version of Genode
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The Fiasco.OC version of Genode is available at the Genode public subversion repository:
:http://genode.org/download/subversion-repository:
Information about accessing the Genode public subversion repository
Go to a directory where you want the Genode/Fiasco.OC build directory to remain. Use
the helper script in the 'tool/builddir' directory of the Genode source tree to
create the initial build environment. You need to state the absolute path to the
build directory of the L4 runtime environment as 'L4_DIR', as it contains the kernel
bindings needed by the Genode port.
! <path_to_genode_src_dir>/tool/builddir/create_builddir foc_x86_32 \
! L4_DIR=<path_to_l4re_build_dir> \
! GENODE_DIR=<path_to_genode_src_dir> \
! BUILD_DIR=<path_to_genode_build_dir>
Now, go to the newly created build directory and type make.
! cd <path_to_genode_build_dir>
! make
Booting Genode on top of Fiasco.OC
==================================
Example GRUB configuration entry:
! timeout 0
! default 0
!
! title Genode on Fiasco.OC
! kernel /bootstrap -modaddr=0x01100000
! module /fiasco -serial_esc
! module /sigma0
! module /core
! module /init
! module /config
! module /pci_drv
! module /vesa_drv
! module /ps2_drv
! module /timer
! module /nitpicker
! module /launchpad
! module /liquid_fb
! module /scout
! module /testnit
! module /nitlog
For an example of a matching Genode 'config' file, please take a look
at 'os/config/demo'.
The Genode binaries are located in '<path_to_genode_build_dir>/bin',
the 'fiasco' kernel in '<path_to_kernel_build_dir>'. Assuming you compiled
for x86/586 (the default), you can find the 'bootstrap' binary in
'bin/x86_586' and 'sigma0' in 'bin/x86_586/l4f' within the
'<path_to_l4re_build_dir>' directory.
Current state
=============
The adaptation of Genode to Fiasco.OC covers most parts of the Genode API
including advanced semantics such as cancelable locks and support for
real-time priorities. So far, it has been tested on the x86 architecture.
Because 'base-foc' does not contain x86-specific code, we expect no major
roadblocks for running Genode on Fiasco.OC on ARM. However, we have not
exercised tests in this regard.
As of today, there exist the following limitations of the Fiasco.OC support:
* The dynamic linker is not yet adapted to Fiasco.OC. Special care must
be taken for handling the parent capability for dynamically loaded
programs. We have already covered this issue for the NOVA version but
the adaptation to Fiasco.OC remains yet to be done.
* The destruction of sub systems is not yet fully stable. Because Genode
forms a more dynamic workload than the original userland accompanied with
the kernel, the usage pattern of the kernel API triggers different
effects. We are working with the Fiasco.OC developers to remedy this
issue.
* The signalling framework is not yet supported. A design exist but it is
not implemented yet.
We believe however that none of these limitations are a significant hurdle for
starting to use Genode with this kernel. Please expect this issues to be
resolved with the upcoming Genode release.
Technical details about 'base-foc'
==================================
The following technical bits are worth noting when exploring the use of
Genode with the 'base-foc' platform.
* The timer implementation uses a one thread-per-client mode of operation.
We use IPC timeouts as time source. Hence, the timer driver is hardware
independent and should work out of the box on all hardware platforms
supported by Fiasco.OC.
* Each 'Server_object' of Genode corresponds to a so-called IPC gate,
which is the Fiasco.OC kernel object used for capability invocation.
Therefore, protection and object integrity is provided at the fine
granularity of single 'Server_objects'. This is in line with our
support for NOVA's implementation of capability-based security.
* In contrast to the lock implementation that we used with the original
L4/Fiasco kernel, the 'base-foc' lock is a fully-featured Genode lock
with support for lock cancellation and blocking. For blocking and
waking up lock applicants, we use Fiasco.OC's IRQ objects.
* The allocator used for managing process-local capability selectors
does not yet support the reuse of capability selectors.
Further Information
===================
:genode/tool/builddir/README:
Reference manual for the 'create_builddir' script
:[http://os.inf.tu-dresden.de/fiasco]:
Official website for the Fiasco.OC microkernel.
Noux - an execution environment for the GNU userland
####################################################
Even though Genode is currently mainly geared to the classical special-purpose
application domains for microkernel-based systems, the main property that sets
Genode apart from traditional systems is the thorough support for dynamic
workloads and the powerful mechanisms for handling hardware resources and
security policies in highly dynamic setting. We are convinced that Genode's
architecture scales far beyond static special-purpose domains and believe in
the feasibility of Genode as a solid foundation for a fully-fledged general
purpose operating system. Internally at Genode Labs, we set up the ultimate
goal to switch from Linux to Genode for our day-to-day work. We identified
several functionalities that we could not live without and systematically try
to bring those features to Genode. Of course, the most fundamental programs
are the tools needed to develop and build Genode. Currently we are developing
on Linux and enjoy using the GNU userland.
Consequently, we require a solution for using this rich tool set on Genode.
The straight-forward way for making these tools available on Genode would be
running them within a virtualized Linux instance (e.g., using OKLinux on OKL4).
However, this approach would defeat our actual goal to create a highly secure
yet easy to use working environment because adding Linux to the picture would
involve administering the virtualized Linux system. We would prefer a native
solution that makes the overall system less, not more, complicated. This way
the idea for a native execution environment for the GNU userland on Genode
was born. The implementation is called Noux and the first bits of code are
featured in the 'ports' repository. Noux consists of two parts, a build
environment for compiling GNU programs such that they can be run as Genode
processes and an execution environment that provides the classical UNIX
functionality to these programs.
Noux build environment
======================
From our experience, porting existing UNIX applications to a non-UNIX system
tends to be a task of manual and time-consuming labour. One has to loosely
understand the build system and the relationship of the involved source codes,
implement dummy functions for unresolved references, and develop custom glue
code that interfaces the ported application to the actual system. Taking the
shortcut of changing the original code has to be avoided at any cost because
this produces recurring costs in the future when updating the application. In
short, this long-winding process does not scale. For porting a tool set such as
the GNU userland consisting of far more than a three-digit number of individual
programs, this manual approach becomes unfeasible. Therefore, we have created
a build environment that facilitates the use of the original procedure of
invoking './configure && make'. The challenge is to supply configure with
the right arguments and environment variables ('CFLAGS' and the like) such that
the package is configured against the Genode environment. The following
considerations must be taken:
* Configure must not detect any global headers (e.g., '/usr/include/')
or libraries (e.g., '/usr/lib/'). This can be achieved by the '-nostdinc' and
'-nostdlib' options
* Configure has to use the same include-search paths as used for compiling
normal libc-using Genode programs
* Configure must use the Genode tool chain
* The final linking stage must use the Genode linker script, the Genode
base libraries, and other Genode-specific linker arguments.
Thanks to the power of the GNU build system, all this can be achieved by
supplying arguments to './configure' and indirectly to the 'make' process via
environment variables. The new Noux build environment takes care of these
precautions. It comes in the form of the 'ports/mk/noux.mk' file which enables
the seamless integration of GNU packages with the Genode build system. To
compile a GNU package, the manual steps needed are reduced to the creation of a
'target.mk' file representing the package. This 'target.mk' defines the name
of the package (by default, the basename of the 'target.mk' enclosing directory
is assumed) and the location of the source package. With this approach, we
managed to build 'coreutils' (over 100 small UNIX utilities such as 'ls', 'cp',
'sort'), 'binutils' (GNU linker, assembler, object-file tools), 'findutils'
('find', 'xargs'), 'bash', 'dash', GNU make, and finally the GNU compiler
collection including 'g++'. The resulting binaries are ready to be executed as
native Genode processes. However, without the right environment that presents
the program the needed UNIX functionality, those programs won't do much.
This leads us to the Noux execution environment.
Noux execution environment
==========================
The Noux execution environment plays the role of a UNIX kernel for programs
built via the Noux build environment. In contrast to a real kernel, the Noux
environment is a plain Genode user-level process that plays the role of being
the parent of one or multiple Noux processes. In addition of providing the
'Genode::Parent' interface, Noux also provides a locally implemented service called
'Noux::Session' that offers UNIX-like system-calls via an RPC interface. Each
hosted program is linked against a special Noux libc plugin that catches all
libc calls that would normally result in a system call. It then transparently
forwards this function call to the 'Noux::Session' interface.
Currently the Noux execution environment implements the following
system calls: 'getcwd', 'write', 'stat', 'fstat', 'fcntl', 'open',
'close', 'dirent', 'fchdir', 'read', and 'execve'.
The execution environment submits arguments (argc, argv, environment) to the
hosted program, manages its current working directory and receives its exit
code. File operations are targeted to a custom VFS infrastructure, which
principally allows a flexible configuration of the virtual file system visible
to the hosted programs. At the current stage, Noux supports mounting plain tar
archives obtained from core's ROM service as read-only file system. On startup,
the Noux environment starts one process (the init process) and connects the
file descriptor 1 (stdout) to Genode's LOG service.
State of the implementation
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The infrastructure implemented so far already allows the execution of many simple
UNIX tools such as 'ls -lRa', 'echo', 'seq', 'find'. The 'execve' system call
is implemented such that a new process is started that inherits the file
descriptors and the PID of the calling process. This allows using the exec
functionality of the 'bash' shell. However, because 'fork' is not implemented
yet, there is currently no way to start multiple programs hosted in a single
Noux execution environment.
As of today, the Noux environment is not considered to be usable for practical
purposes. However, it clearly shows the feasibility of the path we are walking.
With the foundation laid, we are looking forward to expanding Noux to a capable
solution for running our beloved GNU userland tools on Genode.
Vision
~~~~~~
The most significant intermediate result of pursuing the development of Noux is
the realization that such an environment is not exceedingly complex. Because of
the combination with Genode, we only need to provide a comfortable runtime as
expected by user processes but we can leave much of intricate parts of UNIX out
of the picture. For example, because we handle device drivers on Genode, we do
not need to consider device-user interaction in Noux. As another example,
because the problem of bootstrapping the OS is already solved by Genode, there
is no need to run an 'init' process within Noux. Our vision foresees that Noux
runtimes are to be created on demand for individual tasks such as editing a
file (starting a custom Noux instance containing only the file to edit and the
text editor), compiling source code (starting a custom Noux instance with only
the source code and the build tools). Because Noux is so simple, we expect the
runtime overhead of starting a Noux instance to be not more than the time
needed to spawn a shell in a normal UNIX-like system.
Test drive
~~~~~~~~~~
To give Noux a spin, we recommend using Linux as base platform as this is
the platform we use for developing it. First, you will need to download the
source code of the GNU packages. From within the 'ports' repository,
use the following command:
! make prepare PKG=coreutils
This command will download the source code of the GNU coreutils. You may
also like to give the other packages a try. To see what is available,
just call 'make' without any argument.
Create a build directory (e.g., using tool/builddir/create_builddir).
Change to the build directory and issue the command
! make run/noux
This command will execute the run script provided at 'ports/run/noux.run'.
First it builds core, init, and coreutils. Then it creates a tar archive
containing the installed coreutils. Finally, it starts the Noux environment on
Genode. Noux then mounts the TAR archive as file system and executes 'ls -laR',
showing the directory tree.
Approaching platform support for Xilinx MicroBlaze
##################################################
With the release 11.02, we are excited to include the first version of our
custom platform support for the Xilinx MicroBlaze CPU architecture. MicroBlaze
is a so-called softcore CPU, which is commonly used as part of FPGA-based
System-on-Chip designs. At Genode Labs, we are regularly using this IP core,
in particular for our Genode FPGA Graphics Project, which is a GUI software stack
and a set of IP cores for implementing fully-fledged windowed GUIs on FPGAs:
:Website of the Genode FPGA Graphics Project:
[http://genode-labs.com/products/fpga-graphics]
Ever since we first released the Genode FPGA project, we envisioned to combine
it with the Genode OS Framework. In Spring 2010, Martin Stein joined our team
at Genode Labs and accepted the challenge to bring the Genode OS Framework to
the realms of FPGA-based SoCs. Technically, this implies porting the framework
to the MicroBlaze CPU architecture. In contrast to most softcore CPUs such as
the popular Lattice Mico32, the MicroBlaze features a MMU, which is a fundamental
requirement for implementing a microkernel-based system. Architecturally-wise
MicroBlaze is a RISC CPU similar to MIPS. Many system parameters of the CPU
(caches, certain arithmetic and shift instructions) can be parametrized at
synthesizing time of the SoC. We found that the relatively simple architecture
of this CPU provides a perfect playground for pursuing some of our ideas about
kernel design that go beyond the scope of current microkernels. So instead of
adding MicroBlaze support into one of the existing microkernels already
supported by Genode, we went for a new kernel design. Deviating from the typical
microkernel, which is a self-sufficient program running in kernel mode that
executes user-level processes on top, our design regards the kernel as a part of
Genode's core. It is not a separate program but a library that implements the
glue between user-level core and the raw CPU. Specifically, it provides the
entrypoint for hardware exceptions, a thread scheduler, an IPC mechanism, and
functions to manipulate virtual address spaces (loading and flushing entries
from the CPU's software-loaded TLB). It does not manage any physical memory
resources or the relationship between processes. This is the job of core.
From the kernel-developer's point of view, the kernel part can be summarized as
follows:
* The kernel provides user-level threads that are scheduled in a round-robin
fashion.
* Threads can communicate via synchronous IPC.
* There is a mechanism for blocking and waking up threads. This mechanism
can be used by Genode to implement locking as well as asynchronous
inter-process communication.
* There is a single kernel thread, which never blocks in the kernel code paths.
So the kernel acts as a state machine. Naturally, there is no concurrency in the
execution paths traversed in kernel mode, vastly simplifying these code parts.
However, all code paths are extremely short and bounded with regard to
execution time. Hence, we expect the interference with interrupt latencies
to be low.
* The IPC operation transfers payload between UTCBs only. Each thread has a
so-called user-level thread control block which is mapped transparently by
the kernel. Because of this mapping, user-level page faults cannot occur
during IPC transfers.
* There is no mapping database. Virtual address spaces are manipulated by
loading and flushing physical TLB entries. There is no caching of mappings
done in the kernel. All higher-level information about the interrelationship
of memory and processes is managed by the user-level core.
* Core runs in user mode, mapped 1-to-1 from the physical address space
except for its virtual thread-context area.
* The kernel paths are executed in physical address space (MicroBlaze).
Because both kernel code and user-level core code are observing the same
address-space layout, both worlds appear to run within a single address
space.
* User processes can use the entire virtual address space (4G) except for a
helper page for invoking syscalls and a page containing atomic operations.
There is no reservation used for the kernel.
* The MicroBlaze architecture lacks an atomic compare-and-swap instruction. On
user-level, this functionality is emulated via delayed preemption. A kernel-
provided page holds the sequence of operations to be executed atomically and
prevents (actually delays) the preemption of a thread that is currently
executing instructions at that page.
* The MicroBlaze MMU supports several different page sizes (1K up to 16MB).
Genode fully supports this feature for page sizes >= 4K. This way, the TLB
footprint can be minimized by choosing sensible alignments of memory
objects.
Current state
=============
The MicroBlaze platform support resides in the 'base-mb' repository. At the
current stage, core is able to successfully start multiple nested instances of
the init process. Most of the critical kernel functionality is working. This
includes inter-process communication, address-space creation, multi-threading,
thread synchronization, page-fault handling, and TLB eviction.
This simple scenario already illustrates the vast advantage of
using different page sizes supported by the MicroBlaze CPU. If using
4KB pages only, a scenario with three nested init processes produces more than
300.000 page faults. There is an extremely high pressure on the TLB, which
only contains 64 entries. Those entries are constantly evicted so that
threshing effects are likely to occur. By making use of flexible page
sizes (4K, 16K, 64K, 256K, 1M, 4M, 16M), the number of page faults gets
slashed to only 1.800, speeding up the boot time by factor 10.
Currently, there is no restriction of IPC communication rights. Threads are
addressed using their global thread IDs (in fact, using their respective
indices in the KTCB array). For the future, we are planning to add
capabilty-based delegation of communication rights.
Building and using Genode on MicroBlaze
=======================================
For building Genode for the MicroBlaze platform, you need the MicroBlaze
tool chain as it comes with the Xilinx EDK. The tool chain is typically
prefixed with 'mb-'. Please make sure that the tool chain's 'bin/' directory
is included in your 'PATH' environment variable.
For building and starting Genode on MicroBlaze, you first need to create
a build directory using the build-directory creation tool:
! tool/builddir/create_builddir microblaze \
! BUILD_DIR=</path/to/build/dir> \
! GENODE_DIR=</path/to/genode/dir>
The 'base-mb' repository comes with support for Genode's run tool. In order to
use it, you will first need to declare the location of your qemu binary using
the 'QEMU=/path/to/qemu' variable in the '<build-dir>/etc/microblaze.conf'
file. Then you will be able to start an example scenario by issuing the
following command from within your build directory:
! make run/nested_init
Thereby, the 'run' tool will attempt to start core using the microblaze version
of qemu.
You can also find a simple hello-world example at 'base-mb/src/test/hello'.
The corresponding run script is located at 'base-mb/run/hello.run'. You can
execute it via 'make run/hello' from the build directory.
Note that currently, all boot modules are linked against the core binary.
To change the boot modules, the file 'base-mb/src/core/boot_modules.s' must
be modified.
For reference, we are using the following tools:
* mb-g++ (GCC) 4.1.1 20060524 (Xilinx 11.2 Build EDK_LS2.2
20 Apr 2009 Xilinx 11.2 Build EDK_LS2.2 23 Apr 2009)
* GNU ld version 2.16 Xilinx 11.2 Build EDK_LS2.2 23 Apr 2009
* GNU assembler 2.16 Xilinx 11.2 Build EDK_LS2.2 23 Apr 2009
* QEMU emulator version 0.14.50, Copyright (c) 2003-2008 Fabrice Bellard
Petalogix linux reference design targeting Xilinx Spartan 3ADSP-1800 boards.
Supporting the NOVA hypervisor version 0.3
##########################################
NOVA is a so called microhypervisor - a modern capability-based microkernel
with special support for hardware-based virtualization and IOMMUs. Since we
incorporated the initial support for the NOVA hypervisor in Genode one year
ago, this kernel underwent multiple revisions. The latest version was released
earlier this month. To our delight, much of the features that we missed from
the initial release had been implemented during the course of the last year. We
are especially happy about the fully functional 'revoke' system call and the
support for remote kernel-object creation.
With the Genode release 11.02, we officially support the latest NOVA version.
The update of Genode to the new version required two steps. First, because many
details of the kernel interface were changed between version 0.1 and version
0.3, we had to revisit our syscall bindings and adapting our code to changed
kernel semantics. Second, we filled our 'base-nova' code related to object
destruction and unmapping with life to benefit from NOVA's 'revoke' system
call. Consequently, we are now able to run the complete Genode software stack
including the dynamic linker on NOVA.
Note that for using Genode on NOVA, you will need to apply a small patch to the
NOVA source code. This patch enables the re-use of user-level thread control
blocks in the kernel. The patch can be found at 'base-nova/patches/utcb.patch'.
When executing NOVA on qemu, please specify the '-cpu coreduo' argument to the
qemu command line. When using Genode 'run' tool, you may assign this argument
to the 'QEMU_OPT' variable in '<build-dir>/etc/build.conf'.
:Thanks:
We are grateful for the ongoing very pleasant collaboration with Udo Steinberg
who is the driving force behind NOVA. Thanks for the ultra-fast responses to our
questions and for considering our suggestions regarding the feature set of
NOVA's kernel interface!
Base framework
##############
Upgrading existing sessions
===========================
Genode enables a client of a service to lend parts of its own resources to
the service when opening a session. This way, servers do not need to allocate
own resources on behalf of their clients and become inherently robust against
resource-exhaustion-based denial-of-service attacks.
However, there are cases when the client can not decide about the amount of
resources to lend at session-creation time. In such cases, we used to devise an
overly generous client policy. Now, we have added a new 'upgrade' function to
the 'Parent' and 'Root' interfaces that enables a client to upgrade the
resources of an existing session.
For the 'env()->rm_session()' and 'env()->ram_session()' of processes using
the Genode 'env' library, we implemented a transparent quota upgrade that kicks in
in the event of an exceeded metadata backing store.
Comprehensive accounting of core resources
==========================================
We changed all services of core to limit their respective resource usage
specifically for each individual session. For example, the number of dataspaces
that can be handled by a particular region-manager (RM) session depends on the
resource donation attached to the session. To implement this accounting scheme
throughout core, we added a generic 'Allocator_guard' utility to
'base/include/'. We recommend using this utility when implementing resource
multiplexers, in particular multi-level services. Thanks to this change in
core, the need for a slack memory reservation in core has vanished.
Various changes
===============
The remaining parts of the base API underwent no fundamental revision. The
changes are summarized as follows.
:C++ Support:
We removed 'libgcc' from our C++ support library ('cxx') and link
it to each individual final target and shared library instead. This change alleviates
the need to abuse the 'KEEP_SYMBOLS' mechanism that we used in 'cxx' to
keep libc-dependencies of GCC's support libraries local to the 'cxx'
library. Besides the benefit of reducing heuristics, this change improves
the compatibility with recent cross-compiling tool chains.
Furthermore, we added 'realloc' to the local libc support of the 'cxx'
library because recent ARM tool chains tend to use this function.
:Argument handling for 'main()':
We added a hook to the startup code to enable the implementation of
custom facilities for passing arguments to the main function. The
hook uses the global variables 'genode_argc' and 'genode_argv'.
:Child-exit policy hook:
We enhanced the 'Child_policy' with a new policy interface that allows
a simplified implementation of policies related to program termination.
:Changed API of 'Range_allocator':
We changed the return value of 'alloc_addr' to distinguish different error
conditions. Note that the boolean meaning of the return value is inverted.
Please check your uses of 'alloc_addr'!
Operating-system services and libraries
#######################################
C Runtime
=========
In conjunction with our work on Noux, we improved Genode's C runtime at many
places. First, we added libstdtime and some previously missing bits of libgdtoa
to the libc. These additions largely alleviate the need for dummy stubs, in
particular time-related functions. Second, we added the following functions to
our libc plugin interface: 'dup2', 'fchdir', 'fcntl', 'fstat', 'stat', and
'write'. This enables the creation of advanced libc plugins simulating a whole
file system as done with Noux. Still, there are a number of dummy stubs found
at 'libc/src/lib/libc/dummy.cc'. However, those stubs are now all defined as
weak symbols such that they can be overridden by libc plugins. Finally, we have
replaced the original 'exit' implementation that comes with the libc with a
Genode-specific version. The new version reports the exit code of the
application to the parent process via an 'Parent::exit()' RPC call.
Until now, Genode's libc magically handled output to stdout and stderr by
printing messages via Genode's LOG interface. We have now replaced this
hard-wired interface by an optional libc plugin called 'libc_log'. If present, write
operations to stdout are caught at the libc plugin interface and delegated to
the plugin, which implements the output to the LOG interface. If you have an
application using Genode's libc, you might consider adding the 'libc_log'
library to your 'target.mk' file.
Support for big numbers by the means of libgmp and libmpfr
==========================================================
We have now include both the GNU Multiple Precision Arithmetic Library and
(GMP) and MPFR to the 'ports' repository. This work was specifically motivated
by our port of GCC to Genode as GCC version 4.4.5 requires both libraries.
Because we intend to use those libraries primarily on x86_32, the current port
covers only this architecture. However, expanding the port to
further CPU architectures should be straight-forward if needed.
Furthermore, you can now also find GCC's 'longlong.h' header at
'libports/include/gcc'.
Qt4 updated to version 4.7.1
############################
The current release bumps the supported Qt4 version from 4.6.2 to 4.7.1 and the
Arora web browser (located at the ports repository) from version 0.10.2 to
version 0.11. Of course, we updated our custom additions such as our custom
Nitpicker plugin widget that enables the seamless integration of native
Nitpicker GUI clients into Qt4 applications to work with the new Qt4 version.
Tools
#####
Tool chain update to GCC 4.4.5 and Binutils 2.21
================================================
We upgraded the official Genode tool chain from gcc 4.2.4 to gcc 4.4.5. Please
update your tool chain by downloading the new binary archive (available for x86_32)
or building the tool chain from source using our 'tool/tool_chain' utility.
New support for automated integration and testing
=================================================
With the growing number of supported base platforms, the integration and testing
of Genode application scenarios across all kernels becomes
increasingly challenging. Each kernel has a different boot mechanism and
specific requirements such as the module order of multiboot modules (Fiasco's
bootstrap, Pistachio's sigma0 and kickstart), kernel parameters, or the
invocation of a single-image creation tool (OKL4's elfweaver). To make our
life supporting all those platforms easier, we have created a tool called
'run', which is tightly integrated within Genode's build system. In short 'run'
gathers the intrinsics in the form of a 'run/env' file specific for the
platform used by the current build directory from the respective
'base-<platform>' repository. It then executes a so-called run script, which
contains all steps needed to configure, build, and integrate an application
scenario. For example, a typical run script for building and running a test
case resides in a file called '<any-repository>/run/<run-script-name>.run' and
looks as follows:
! build "core init test/exception"
! create_boot_directory
! install_config {
! <config>
! <parent-provides>
! <!--<service name="ROM"/>-->
! <service name="LOG"/>
! </parent-provides>
! <default-route>
! <any-service> <parent/> </any-service>
! </default-route>
! <start name="test-exception">
! <resource name="RAM" quantum="1M"/>
! </start>
! </config>
! }
! build_boot_image "core init test-exception"
! append qemu_args "-nographic -m 64"
! run_genode_until {.*Exception \(label 0xffb0\) occured.*} 10
First, the build system is instructed to create the targets specified as argument
for the 'build' function. Next, for the integration part, a new boot directory is
created. On most kernel platform, the respective location of the boot directory
is '<build-dir>/var/run/<run-script-name>'. Initially, this directory is empty.
It gets populated with a 'config' file specified as argument of the 'install_config'
command, and by the boot modules specified at the 'build_boot_image' command.
Now that the integration is complete, the scenario is executed via the
'run_genode_until' command. This command takes a regular expression as
argument, which determines the successful termination of the test case. The
second argument is a timeout (is seconds). In the example, the test case will
fail if its output does not match the regular expression within the execution
time of 10 seconds.
The command 'append qemu_args' specifies run-script-specific qemu arguments in
the case that qemu is used to execute the scenario. This is the case for most
kernel platforms (except for Linux where core gets executed directly on the host).
Additional build-directory-specific qemu arguments can be specified in the
'etc/build.conf' file by defining the 'QEMU_OPT' variable. For example, to
prevent KVM being used on Ubuntu Linux, specify:
! QEMU_OPT = -no-kvm
To execute the run script from with build directory, you need to have Expect
installed. Typically, the Linux package is called 'expect'. Simply issue
the following command from within your build directory:
! make run/<run-script>
Note that you will need to have a GRUB 'stage2_eltorito' binary available
at '<genode-dir>/tool/grub' on base platforms that use an ISO image as boot
stategy.
Because the whole chain of actions, building, integrating, executing, and
validating an application scenario is now at the fingertips of issuing a
single command with no kernel-specific considerations needed, it has never
been easier to run the same scenario on a wide range of different kernels.
Please find further instructive examples at 'os/run/'. The 'ldso' run
script executes the test of the dynamic linker. It is completely generic.
The 'demo' run script starts Genode's default demo scenario and shows how
platform-specific considerations (e.g., which device drivers to use) can be
taken into account.
We found that the 'run' tool significantly boosted our productivity not
only for testing purposes but also for accelerating the development-test
cycle during our day-to-day work.
:Technical notes:
The 'run' tool uses Expect as automation tool. Expect is a Tcl interpreter,
which is accompanied by special functionality for automating interactive
command-line applications. Technically, a run script is an Expect script
which gets included by the 'tool/run' script. For the reference of
run-specific functions, please revise the documentation in the 'tool/run'
script. Because each run script is actual Expect source code, it is possible
to use all Tcl and Expect scripting features in a run script.
In particular, a run script may issue shell commands using Tcl's 'exec'
function. This way, even complex integration tasks can be accomplished.
For example, the integration of the Genode Live CD was done via a single
run script.
Build system
============
To facilitate the integration of 3rd-party build systems into the Genode build
process, we added support for pseudo targets that do not require any 'SRC'
declaration. Such 'target.mk' may contain custom rules that will be executed
when the target is revisited by the build system. The bindings are as follows:
! build_3rd_party:
! ...custom commands...
!
! $(TARGET): build_3rd_party
!
! clean_3rd_party:
! ...custom commands...
!
! clean_prg_objects: clean_3rd_party: