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Simple custom pager
by Daniel Waddington 21 Jul '11

21 Jul '11

Hi, As a toy exercise I'm trying to write a very simple custom pager which simply allocates memory from RAM to handle page faults. When I try to handle the fault I get a region conflict exception. Can someone tell me why?? I think I am missing something fundamental here. Thanks Daniel ---- #include <base/printf.h> #include <base/sleep.h> #include <base/rpc_server.h> #include <cap_session/connection.h> #include <dataspace/client.h> #include <rom_session/connection.h> #include <rm_session/connection.h> #include <ram_session/connection.h> #include <root/component.h> #include <util/avl_string.h> #include <util/misc_math.h> #include <assert.h> #define PAGE_SIZE 4096 using namespace Genode; namespace Test { /** * Example pager class * * @return */ class Pager : public Thread<8192> { private: Signal_receiver _receiver; public: Signal_receiver *signal_receiver() { return &_receiver; } void entry(); }; /** * Example backing store class - this one uses physical memory * */ class Physical_backing_store : public Signal_context { private: Rm_connection _rm; size_t _size; public: // ctor Physical_backing_store(size_t size): _rm(0,_size) { _size = size; assert(_size > 0); } virtual ~Physical_backing_store() { } /** * Page fault handler. * */ void handle_fault() { Rm_session::State state = _rm.state(); printf("Test::Physical_backing_store:: rm session state is %s, pf_addr=0x%lx\n", state.type == Rm_session::READ_FAULT ? "READ_FAULT" : state.type == Rm_session::WRITE_FAULT ? "WRITE_FAULT" : state.type == Rm_session::EXEC_FAULT ? "EXEC_FAULT" : "READY", state.addr); if (state.type == Rm_session::READY) return; try { Dataspace_capability _ds; try { _ds = env()->ram_session()->alloc(PAGE_SIZE); } catch(...) { PERR("Actual page allocation failed.\n"); } _rm.attach_at(_ds, state.addr & ~(PAGE_SIZE - 1)); PDBG("attached data space OK!\n"); } catch (Genode::Rm_session::Region_conflict) { PERR("Region conflict - this should not happen\n"); } catch (Genode::Rm_session::Out_of_metadata) { PERR("Out of meta data!\n"); } catch(...) { PERR("Something else caused attach to fail in fault handler.\n"); } return; } Rm_connection *rm() { return &_rm; } Dataspace_capability ds() { return _rm.dataspace(); } void connect_pager(Pager& _pager) { /* connect pager signal receiver to the fault handler */ _rm.fault_handler(_pager.signal_receiver()->manage(this)); } }; /** * Entry point for pager thread. * */ void Pager::entry() { printf("Pager thread started OK.\n"); while (true) { try { Signal signal = _receiver.wait_for_signal(); for (int i = 0; i < signal.num(); i++) { static_cast<Physical_backing_store *>(signal.context())->handle_fault(); } } catch (...) { PDBG("unexpected error while waiting for signal"); } } } } int main() { Genode::printf("Test-pager example. ;-))\n"); Test::Pager _pager; /* start pager thread */ _pager.start(); /* create dataspace etc. */ try { enum { MANAGED_DS_SIZE = 64*1024*1024 }; Test::Physical_backing_store bs(MANAGED_DS_SIZE); /* connect pager to fault handler */ bs.connect_pager(_pager); /* attach to dataspace */ char * addr = (char*) env()->rm_session()->attach(bs.ds()); assert(addr); /* trigger read fault */ printf("!!!Triggering fault...\n"); printf("%c%c%c\n",addr[0],addr[1],addr[2]); printf("Fault handled OK.\n"); } catch(...) { PERR("Something failed ????.\n"); } printf("test-pager completed.\n"); Genode::sleep_forever(); return 0; }

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Genode r161 + Fiasco.OC r36
by Daniel Waddington 21 Jul '11

21 Jul '11

Hi, Can someone test the test-lwip_httpsrv on this distribution? It used to work but I think there may now be an issue. Message "received IPC instead of IRQ" does not seem to healthy. Thanks Daniel int main(): --- create local services --- int main(): --- start init --- int main(): transferred 2943 MB to init int main(): --- init created, waiting for exit condition --- [init -> test-lwip_httpsrv] Starting ldso ... [init -> pci_drv] PCI driver started [init -> test-lwip_httpsrv] Starting application ... environ: 4058 [init -> gpxe_nic_drv] virtual Nic::Session_component* Nic::Root::_create_session(const char*): --- init DDE NIC [init -> gpxe_nic_drv] scan_pci(): Found: 00:03.0 1022:2000 (rev 40) IRQ 0a [init -> gpxe_nic_drv] probe_pci_device(): using driver pcnet32 [init -> gpxe_nic_drv] snprintf not implemented [init -> gpxe_nic_drv] virtual Nic::Session_component* Nic::Root::_create_session(const char*): number of devices: 1 received IPC instead of IRQ [init -> gpxe_nic_drv] void Nic::dde_tx_handler(): --- init rx_callbacks [init -> test-lwip_httpsrv] int main(): Create new socket ... [init -> test-lwip_httpsrv] int main(): Now, I will bind ... [init -> test-lwip_httpsrv] int main(): Now, I will listen... received IPC instead of IRQ [init -> test

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set pager in foc
by Chen Tian - SISA 01 Jul '11

01 Jul '11

Hello, After the set_pager function of a thread is called through a cpu_session, the _pager of that thread is set and used when the actual platform thread starts. But there is only one thread (pager) to resolve all page faults for all threads. I think the pager mapping happened in platform_thread::start (platform_thread.cc:40-47). Can somebody please explain to me the meaning of this l4_task_map call? I suspect that "_remote_pager_cap" is corresponding to the global pager, but cannot find any evidence. Thanks a lot. Best, Chen

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Rm_session::Out_of_memory.
by Chen Tian - SISA 30 Jun '11

30 Jun '11

Hello, I want to measure the thread creation time in Genode via Cpu_session create_thread, start and kill_thread interface. However, after sometime (around 139th thread creation), I always get a "Quota exceed! Amount=61440, size=4096, consumed=61440" error. And a message "C++ runtime: Genode::Rm_session::Out_of_memory" follows that. I expected all resources used by a thread should be released when "kill_thread" is called. This is apparently not the case. Can someone explain to me why this error happened and how I can adjust the Rm_sesion quota? Thanks, Best, Chen

2 1

Create servers on different core.
by Chen Tian - SISA 27 Jun '11

27 Jun '11

Hello, Without changing Genode, can I create a server on a different core than core 0? Also, is that possible to announce multiple services in a server and create multiple threads to provide different services? Thanks. Best, Chen

3 4

Create multiple processes.
by Chen Tian - SISA 17 Jun '11

17 Jun '11

Hi, I want to launch multiple Genode processes. One obvious way is to take advantage of init process. But it seems like all these init-created processes will share the same RM session (provided by Core) and hence the same pager. To allow each process to have its own region map, shall I write my own launching process or modify init ? Thanks. Best, Chen

3 5

Two ways on running Android on top of Genode
by Magnus G. Andersson 15 Jun '11

15 Jun '11

Hi everybody As I can see it there are two ways you can run Android on top of Genode. 1. Port it, like L4Android, make it a para-virtualized system, or 2. Run Android natively on Genode Well, option number two is more of running Android apps not the whole Android OS if I have understood it correct? But my question about this is, which one do you think is best, with regards to security, updates and performance? By running Android as para-virtualized, shouldn't an attack be constrained inside the Android OS, because the underlying software (Genode) isn't visible and can't be reached? Updates on the system might be hard in both cases, or what do you think? The reason for this question is that I'm currently doing my master thesis with the aim of implementing Android on a system allowing other programs or OSes to be run in parallel with Android and I found that Genode looks like a great candidate for doing this Regards Magnus

2 1

Data space creation and physical memory allocation strategy.
by Chen Tian - SISA 13 Jun '11

13 Jun '11

Hi, When a data space is created, physical memory is reserved and cannot be used by other processes until the data space is destructed. I wonder if it would be a possible situation where physical memory may get wasted. For example, an application may first allocate a huge chunk of memory (through malloc, which will eventually lead to the creation of one or more data spaces), but only touch a small portion of it throughout the entire execution. Another example would be to have a large binary where a significant portion of the binary are not actually executed. Thus, reserving physical memory for these instruction when a program is loaded may not be good, especially in a resource-constrained environment. Does anybody know whether Linux has a similar mechanism (i.e. reserve a chunk of physical memory for a virtual memory region before the first access to this region)? If not, what are the pros and cons of these two strategies? Thank you. Best, Chen

4 6

L4Android on Genode
by Magnus Andersson 10 Jun '11

10 Jun '11

Hi just read through the release note for Genode 11.05 and noticed the support for L4Linux by emulating L4re. By emulating the L4re shouldn't the L4Android (http://l4android.org/) port of Android work as well? Also, does the emulation on L4re only work when running Genode on top if Fiasco.OC? Regards Magnus

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Re: Prerequisite mechanism that Genode expects from a new kernel
by Althaf 09 Jun '11

09 Jun '11

> the Base API can be regarded as a "bottom layer specification" (its > implementation is typically less than 10KLOC) of the whole system but > there is no fixed base-internal interface. This gives each platform > maximum flexibility about how the API is implemented. Given the vast > differences of the mechanisms used, this flexibility is needed. E.g., by > comparing the ways processes are created and address spaces are managed > on Linux and L4, you will see that the respective base code has almost > nothing in common. On Linux, 'rm_session()->attach()' is implemented > locally by the calling process using mmap. In contrast, on L4, the same > API function is an RPC to core, which, in turn, manipulates the address > space on demand (using L4's map/unmap) when a page fault occurs. > Yes, i get the notion, actully at the moment i'm trying to understand base-linux. I must admit the source became much more clear after your explained the actual idea of why 'no solid bottom specification'. Another fact, i read a lot of code from various projects, genode code the most readable with well structured cpp and build setup. > topic "Microkernelizing Linux" described on our "Challenges" Wiki page? > http://genode.org/community/wiki/Challenges Yes infact. > Let me suggest two pointers that we stumbled upon when we brain-stormed > this idea. First, we were pointed to Linux' "resource containers", which > promise to allow the assignment of fine-grained resource constraints to > individual processes. This looks like an interesting mechanism to > support Genode's resource-trading concept. Secondly, we were made aware > of the Capsicum project, which brings capability-based security to Linux. > > http://www.cl.cam.ac.uk/research/security/capsicum/ > Linux containers should be LXC project from IBM.?

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