l4-hackers June 2013

l4-hackers@os.inf.tu-dresden.de

14 participants
19 discussions

Re: <http://l4ka.org/> down?
by Thomas Schwinge 08 Jun '13

08 Jun '13

Hi! As the l4ka mailing list also seems to be defunct (though, my email didn't bounce), forwarding the question to the Dresden L4 folks as well as the registrant of the l4ka.org domain: On Thu, 06 Jun 2013 10:06:02 +0200, Thomas Schwinge <thomas(a)codesourcery.com> wrote: > On Wed, 05 Jun 2013 17:10:11 +0200, I wrote: > > On Wed, 5 Jun 2013 17:02:03 +0300, Fotis Koutoulakis <fotis.koutoulakis(a)gmail.com> wrote: > > > On http://www.gnu.org/software/hurd/microkernel.html the link for the > > > paper "On Microkernel Construction" appears to be dead. This patch > > > replaces the dead link with a working one. > > > > > [ mkernelconstructionurl.patch: application/octet-stream (as text/x-diff) ] > > > 14c14 > > > < [[Liedtke]] explains in [On Microkernel Construction](http://l4ka.org/publications/paper.php?docid=642) > > > [...] > > > As it appears that <http://l4ka.org/> generally is down (»Unconfigured > > server«) Now the server completely disappeared. > > at the moment. I suggest we wait a few days and see whether it > > comes back. If not (huh...), I'd like to use a more canonical [...] > > Any comments from the l4ka list? Is this a permanent outage, or just > temporary? Grüße, Thomas

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arm-linux-ld not found while compiling l4-fiasco microkernel
by Rahul Singhal 06 Jun '13

06 Jun '13

I am trying to port L4-fiasco + L4Re to raspberry pi. But when I compile fiasco, it throws an error saying arm-linux-ld not found. I found that I will need cross compiler binaries to compile the fiasco microkernel. But where to find them. Please help! Thanks in advance.

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Hello scenario gets stuck
by Markus Partheymueller 06 Jun '13

06 Jun '13

Hey, I'm having trouble booting the hello example on real hardware. The following config is booted via PXE: addr 0x2000000 exec mparthey/foc/bootstrap -serial load mparthey/foc/fiasco -serial -serial_esc -esc load mparthey/foc/sigma0 load mparthey/foc/moe load mparthey/foc/l4re load mparthey/foc/hello But it hangs after "MOE: Hello world". I can still enter the Kernel debugger, listing these task and thread objects: [Objects] 1 f007e020 [Task ] {KERNEL} R=2 6 ffdc6134 [Thread ] {KERNEL} C=0 R=1 current 7 fffe8f70 [Task ] {sigma0 } R=3 8 ffd80134 [Thread ] {sigma0 } C=0 S=D:7 R=3 9 fffe8f18 [Task ] R=3 a ffd83134 [Thread ] C=0 S=D:9 R=4 Backtrace on thread a yields an address 0x143d7d in moe (?), belonging to void List_alloc::merge() { List_alloc_sanity_guard __attribute__((unused)) guard(this, __func__); Mem_block *c = _first; while (c && c->next) 143d7d: 8b 00 mov (%eax),%eax 143d7f: 85 c0 test %eax,%eax 143d81: 75 ee jne 143d71 <_ZN22Single_page_alloc_base5_freeEPvmb+0x51> _ZN22Single_page_alloc_base5_freeEPvmb(): [...]/src/l4/pkg/moe/server/src/page_alloc.cc:109 } On a different machine the exact same setup works fine. Has anyone got a clue what goes wrong here? If I should get more information out of the kernel debugger, just let me know. Cheers Markus

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Re: How to catch unhandled exceptions ?
by Björn Döbel 04 Jun '13

04 Jun '13

Hi, [..] > So far so good! This is exactly what I want to do, to have a way to be notified > by the kernel about any exception of a thread. Now my problem is that I > get no notification when something bad happens (e.g. division by 0 or a > page fault), is there any example where I can look to see how to use > thread control + exc_handler and co ? I don't think I really know what to > pass to exc_handler method, I tried to pass a L4::Server_Object::obj_cap() > object but nothing happened ... The page fault handler and the exception handler are Fiasco.OC threads. Hence, you pass thread capabilities to those calls. Page faults go to the PF handler , all other exceptions end up in the exception handler thread. In the thread you would then do something like while (1) { msg = l4_ipc_receive(); inject_exception(); } In inject_exception() you can use the Thread::ex_regs system call, which allows you to modify the IP/SP of a thread. [..] >> Also, C++ exceptions need to be caught in the thread that raised the >> exception, otherwise the exceptions causes a call to std::terminate, >> wich will abort your application. Hence, you'd need try/catch statements >> for all potential hardware exceptions around all your threads' code. >> > > Of course you need to add try/catch statements :) The beauty is that if > you'll do it, you'll have a chance to survive to save your data, if not, > then, as you said, std::terminate will be called and you get the same > effect. There may be libraries (e.g., libc_be_signal) that spawn their own threads and where you do not have control over potential try/catch statements in their code. But that might not be an issue for you. >> I'm not saying it can't be done (I vaguely remember Choices OS [1] doing >> this), it's just not what we are doing on Fiasco right now. >> > > AH, sorry , I think is a misunderstanding here, I don't want you to do it in > Fiasco (even I think it will be very nice feature), I want to be able to do it > in my apps (at user-level not kernel level)! Sure, that's what I meant as well. Cheers, Bjoern

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target CPU does not support ARM mode
by Maximin Coste 04 Jun '13

04 Jun '13

I have a new error, appears from nowhere... I dowloaded the last L4RE version from the website, edited the mk/Makeconf file to put my "arm-none-aebi-" compilator and when i type: $ make O=build config/ I select ARM 7A / BeagleBoard, as usual, as it always worked... Here is my output: [...] <stdin>:1:0: error: target CPU does not support ARM mode [...] tmp.312625562.c:1:0: error: target CPU does not support ARM mode int main(void){} ^ He always create tmp file at the folder root whith nothing else than int main(void) {} inside. I did NOT change anything and everything was working fine yesterday.. Thanks, -- Maximin COSTE-LEENHARDT

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Region overflow in bootstrap
by Markus Partheymueller 04 Jun '13

04 Jun '13

When booting Fiasco/L4Re on my test machine (16G RAM, quad-core i7), I get the following error message, unless I have all CPUs and HyperThreading active: L4 Bootstrapper Build: #2 Mon Jun 3 14:15:47 CEST 2013, x86-32, 4.8.0 Limiting 'RAM' region [100000000, 43e5fffff] {33e600000} to [100000000, 10ea803ff] { ea80400} due to 3024 MB limit Bootstrap: add_nolimitcheck: Region overflow As soon as I deactivate CPUs in the BIOS or deactivate HT, it fails. Increasing the buffer __ram[8] to, e.g., __ram[16] in bootstrap/server/src/startup.cc:L67 does the trick. Maybe that buffer is too small for some machines?

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All *.cpp files are ignored by Makefile
by BogDan 02 Jun '13

02 Jun '13

Hi, I tried to add a few .cpp files to Makefile but it seems that L4Re build systems ignores this extension. This is the content of the Makefile: #################################### PKGDIR ?= ../.. L4DIR ?= $(PKGDIR)/../.. TARGET = test_cpp SRC_CC = main.cpp class1.cpp class2.cpp REQUIRES_LIBS = libstdc++ include $(L4DIR)/mk/prog.mk #################################### I tried to replace SRC_CC with SRC_CXX or SRC_CPP but with no luck ... This bug prevents the port of most of C++ libs out there to L4Re. BTW, is there any chance to use other build-systems (cmake, qbs, premake, SCons, etc.) to build L4Re libs/apps ? Cheers, BogDan.

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How to catch unhandled exceptions ?
by BogDan 02 Jun '13

02 Jun '13

Hi, Is there any way to catch all system unhandled exceptions (seg fault, fpu fault, etc.) and "transform" them into C++ exceptions ? I tried to use a combination of "L4::Thread::control" with "L4::Thread::Attr::exc_handler" to catch the system exception but it didn't worked for me, most probably I didn't understood the meaning of "l4_thread_control_exc_handler" or how to use it. Any example/help will be very appreciated. Of course, after I'll catch the exception, I need a way to "resume" the thread execution to another ip (address) which actually is a simple function that throws the C++ exception, any example/help on the matter will also be highly appreciated. Cheers, BogDan.

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Can't use cxx::Thread
by BogDan 02 Jun '13

02 Jun '13

Hello, I tried to create a very simple application that uses cxx::Thread, but I have some link problems: ... Compiling main.o ==> Linking test_cxx_thread main.o:(.rodata._ZTI10TestThread[_ZTI10TestThread]+0x8): undefined reference to `typeinfo for cxx::Thread' Also I think it will be cleaner/better for developers if run, execute and shutdown methods will be moved to a protected section. This is the main.cc content: /////////////////////////////////////////////// #include <iostream> #include <l4/cxx/thread> #include <thread> class TestThread : public cxx::Thread { public: TestThread():cxx::Thread(true){} private: virtual void run() { std::cout << "TestThread" << std::endl; } }; static void TestStdThread(int param) { std::cout << "TestStdThread param:" << param << std::endl; } int main(int argc, char ** argv) { (void)argc; (void)argv; TestThread cxxTh; cxxTh.start(); std::thread stdTh(TestStdThread, 1); for (;;) { std::cout << "Hello World!" << std::endl; sleep( 1 ); } stdTh.join(); } /////////////////////////////////////////////// This is the Makefile content: #################################### PKGDIR ?= ../.. L4DIR ?= $(PKGDIR)/../.. TARGET = test_cxx_thread SRC_CC = main.cc CXXFLAGS += -std=c++11 REQUIRES_LIBS = cxx_thread cxx_libc_io cxx_io libstdc++ libpthread include $(L4DIR)/mk/prog.mk #################################### Yours, BogDan.

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l4-hackers June 2013