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About Genode::Signal reception
by Frank Kaiser 06 Jul '10

06 Jul '10

Hello I want to use the Genode signalling scheme to control asynchrones data exchange between a client and a server. To get familiar with it I started with a test implementation on the server side. The server's main function fills some data into a buffer and instantiates a Signal receiver thread which shall dump the buffer content on signal reception. Then it instantiates a Signal transmitter to fire a signal at the receiver for one time. The unexpected outcome is that it looks as if the receiver gets the signal twice. This is the implementation in main(): Signal_receiver s_rcvr; Signal_context ct; Receiver *ser_rx = new (env()->heap()) Receiver(s_rcvr, srv.transmit); Signal_context_capability send_cap = s_rcvr.manage(&ct); Signal_transmitter tx(send_cap); tx.submit(); The receiver thread's entry() function (class Receiver derived from class Thread<>; the constructor's 2nd parameter is a handle to the buffer already filled with data, which is accessed thru _transmit inside the function): void entry() { uint8_t ch[32]; int cnt = 0; while (1) { Signal signal = _receiver.wait_for_signal(); #if 1 for (unsigned out = 0; out < sizeof(ch); ++out) { int rd = _transmit.read_byte(); if (rd >= 0) ch[out] = uint8_t(rd); else break; } ++cnt; ch[31] = '\0'; printf("Found characters: %s\n", &ch[0]); ch[0] = '\0'; printf("Caught signals: %d\n", cnt); #endif } } The debug output shows that the 2 printf()s inside the while() loop are called 2 times, which clearly indicates that _receiver.wait_for_signal() returned 2 times. I wonder what goes wrong, and what I should do to get rid of this odd behaviour. Regards Frank

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Constructing objects from dataspaces
by Frank Kaiser 05 Jul '10

05 Jul '10

Hello I recently stumbled over a missing placement new operator in the Genode framework. I needed an object to be shared between a client and a server. The server should construct the object. The client should connect to the server, and in response receive a capability allowing the client to access the data held by the object. The class defining the object provides a constructor to do some necessary initialisation of the object. It looks like this: class Object { ... Object(...) : ... { ... } }; The chosen approach is to create a dataspace capability with the size of the object. On the server side the object is instantiated: Dataspace_capability cap = env()->ram_session()->alloc(sizeof(Object)); Object *obj = static_cast<Object *>(env()->rm_session()->attach(cap)); However, this does not work as expected, since this way Object's constructor is never called. To achieve this applying the new operator is required: Dataspace_capability cap = env()->ram_session()->alloc(sizeof(Object)); Object *obj = new(env()->rm_session()->attach(cap)) Object(); However, this does not work either, because it leads to a type error with the placement parameter. The reason is that the only publicly available placement new operator is: void *operator new(Genode::size_t size, Genode::Allocator *allocator) And worse, its implementation tries to effectively allocate the object's space, something which is not wanted in the given context. What is needed here is a new operator which just returns the placement parameter as the address of the object so that its constructor is invoked when applying the operator. Something like this: void *operator new(Genode::size_t size, void *addr) { return addr; } I found such an operator locally defined in some Genode source files (allocator_avl.cc for instance). I wonder why such an operator is not publicly available although its usefulness is obvious. For the time being I created a local inplementation for my purpose by cloning it from an exisiting one. It would be helpful to have it generally thru a system include file. Regards Frank

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Question regarding parent capabilities
by Steffen Liebergeld 09 Jun '10

09 Jun '10

Hi, for my porting efforts, I need to map the physical parent Capability into the protection domain of a newly created Child. To do so, I extended the Cpu_session with a method "native_thread", which --given a Genode::Capability-- will tell me the "physical" Capability of a thread. I map the parent capability into a known place of the child address space using the assign_parent method of Platform_pd. Unfortunately at this point I am stuck. Can you give me some advice on where assign_parent is called and how I can provide it with the correct capability (as my tries of implementing that in Process::Process have failed)? Many thanks in advance, Steffen -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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Using the HTTP server via TAP
by Peter Nguyen 03 Jun '10

03 Jun '10

Hi, I was just wondering in using TAP with the HTTP server (and following the instructions in the genode 10.02 documentation), i've noticed that when i have multiple connections to the server, whereby i have a windows xp virtual machine making requests to the server in addition to the host operating system (the XP vm is running in qemu as well as the web server), the IP addresses that the web server obtains are always the same regardless of the machine making the requests. Does anyone know how to provide unique IP addresses for each VM ie. is there an option i can/need to specify when i run qemu? or is there something i have to do with dhcpd3 or the conf,pid or lease files to ensure this functionality. Thanks Peter

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Strange behaviour of member addresses
by Steffen Liebergeld 01 Jun '10

01 Jun '10

Hi, I am experiencing some strange behaviour in genode. In base/include/base/heap.h I placed debug output in the Heap::Heap constructor: Heap(Ram_session *ram_session, Rm_session *rm_session, size_t quota_limit = UNLIMITED, void *static_addr = 0, size_t static_size = 0) : _ds_pool(ram_session, rm_session), _quota_limit(quota_limit), _quota_used(0), _chunk_size(MIN_CHUNK_SIZE) { PDBG("quota_limit=%d this=0x%p &_quota_limit=0x%p", _quota_limit, (void*)this, &_quota_limit); enter_kdebug("quota_limit"); if (static_addr) _alloc.add_range((addr_t)static_addr, static_size); } This prints the following: quota_limit=-1 this=0x1851d8 &_quota_limit=0x185630 Then I placed some debug output in base/src/base/heap/heap.cc:alloc bool Heap::alloc(size_t size, void **out_addr) { /* serialize access of heap functions */ Lock::Guard lock_guard(_lock); PDBG("size=%d _quota_used=%d _quota_limit=%d *this=0x%p &_quota_limit=0x%p", size, _quota_used, _quota_limit, (void*)this, &_quota_limit); And this prints the following: _quota_limit=0 *this=0x1851d8 &_quota_limit=0x18563c Seems to me like the compiler did not correctly calculate the member addresses (this problem appears to be the same that caused the previous error I posted). Do you have an idea why that happened and how to fix it? Mand thanks in advance, Steffen Liebergeld -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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Rm_session_cap invalid
by Steffen Liebergeld 28 May '10

28 May '10

Hi again, during startup of the init task, the init thread tries to get an "Env::rm_session" from core. Core responds by giving it a capability with local_name() == 0, which is invalid in my context. The cap is returned from _process.rm_session_cap(), which is implemented in process.h: Rm_session_capability rm_session_cap() const {return _rm.cap(); } _rm is defined as Rm_connection in class Process. I am unsure however, which Constructor belongs to to Rm_connection, and why it sets the capability to zero. Can you help me by pointing me to the right spots? Many thanks in advance. Greetings, Steffen -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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Announcement: Genode OS Framework version 10.05 released
by Norman Feske 27 May '10

27 May '10

We are happy to announce the new version 10.05 of the Genode OS Framework. This version brings many functional improvements, most notably a new configuration concept that allows for the definition of arbitrary client-server relationships and least-privilege policies. We also want to highlight the new audio infrastructure, which enables the playback and mixing of multiple audio streams on popular PC sound hardware. To increase the productivity for developers, there is a new build system, improving the performance on multi-processor systems. Release-notes summary for version 10.05 --------------------------------------- * Mandatory access control and session routing * Added audio-out support * OKLinux stub drivers for sound and GUI * New build system optimized for parallel builds * Arora web browser * Port of libSDL You can find the complete release notes for the version 10.05 here: http://genode.org/documentation/release-notes/10.05/ The new release is available to the project's subversion repository and at the Genode download page: http://genode.org/download/latest-release Regards -- Norman Feske Genode Labs http://www.genode-labs.com · http://genode.org Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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Init startup sequence
by Steffen Liebergeld 22 May '10

22 May '10

Hi again, I am unsure about the startup sequence of the init task (or any other task other than core, for that matter). The setup looks like this: Task Thread Core main (initializes core, sleeps) activation (used as service provider by core's threads) pager (pager for all(?) threads started by core) init(0) (service thread for init) Init init(1) Now init(1) calls init(0), does some initialization in finally gets stuck in __cxa_guard_acquire. The stack trace looks like this: ========================= 1 0x182818 .... 0x159110 __cxa_guard_acquire(T) + 0x20 = 0x1590f0 2 0x182838 32 0x15d31c Genode::env()(T) + 0x2c = 0x15d2f0 3 0x182868 48 0x1591b5 malloc(t) + 0x25 = 0x159190 4 0x182898 48 0x1596c8 __cxa_allocate_exception(T) + 0x28 = 0x1596a0 5 0x1828d8 64 0x15f00f Genode::Ipc_client::_call()(T) + 0x11f = 0x15eef0 6 0x182918 64 0x15dcb3 Genode::Parent_client::session(char const*, char const*)(W) + 0x183 = 0x15db30 7 0x1829b8 160 0x15cdf5 Genode::Platform_env::Platform_env()(W) + 0xb5 = 0x15cd40 8 0x1829d8 32 0x15d32c Genode::env()(T) + 0x3c = 0x15d2f0 9 0x182a08 48 0x1591b5 malloc(t) + 0x25 = 0x159190 10 0x182a28 32 0x157a2c __register_frame(T) + 0x2c = 0x157a00 11 0x182a38 16 0x1590e0 init_exception_handling()(T) + 0x20 = 0x1590c0 12 0x182a58 32 0x163168 _main(T) + 0x28 = 0x163140 13 0x0 .... 0x1631c0 _start(T) + 0xc = 0x1631b4 =========================== It is unclear to me, why init has to grab a lock. Is it using data structures that reside in shared memory with core? What should happen next? Many thanks in advance, Steffen -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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Problems with c++ exceptions
by Steffen Liebergeld 21 May '10

21 May '10

Hello Genoders, I'm having troubles with the C++ exception mechanism: In base/src/platform/_main.cc:_main(), the exception frames are set up in function init_exeption_handling(). Unfortunately, during startup of the init task, this runs into a null pointer. I could trace this back to base/src/base/cxx/exception.cc:__register_frame(__eh_frame_start), which obviously calls some gcc-provided function. I am using the toolchain you provide on your website. Did you have similar experiences during your development? Do you have an idea what is going wrong in my setup? Where should I start my investigations? Many thanks in advance, Steffen -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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Server badges in Core
by Steffen Liebergeld 17 May '10

17 May '10

Hello friendly Genode-people, I am having difficulties unterstanding the handling of the server badge (currently in core only) As far as I understand, the badge identifies the receipient-object. Therefore the sender encodes the address of the receiving object's capability in the first slot of the send buffer. On the receiver side, in Server_activation_base::entry(), the badge is used to identify the correct object, whose dispatch() Method is then called. The server however has to insert the capability into the Object_pool first, which is done at Server_entrypoint::manage(). Now I am currently having problems in core's main function. During Ram_session_client(init_ram_session_cap).ref_account(env()->ram_session-cap()), an IPC call is sent to the "activation"-Thread, during which an invalid badge is used. Consequently the activation thread does not find the corresponding object and returns ERR_INVALID_OBJECT. This raises the following questions: a) Which object is the correct handler for this call, and b) where is the capability of the receiver allocated and registered at the Object_pool? I am looking forward to hearing from you. Many thanks in advance. Greetings, Steffen -- Dipl.-Inf. Steffen Liebergeld <steffen@...37...> Security in Telecommunications TU Berlin/ Deutsche Telekom Laboratories Ernst-Reuter-Platz 7, 10587 Berlin Phone: +30 8353 58 263 Web: http://www.t-labs.tu-berlin.de/sect

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