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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 03 Jun '13

03 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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Kernel debugger in MP mode causes double fault
by Markus Partheymueller 31 May '13

31 May '13

Hi folks, has anyone tried to invoke the kernel debugger in a multiprocessor setup? When I boot the demo scenario in qemu with qemu -smp 2 -cpu core2duo and then hit Escape, the system crashes with a double fault. Without smp or with -cpu qemu32 the problem doesn't occur. Can someone confirm this issue or give a hint what could be wrong? Cheers Markus

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L4Re: FATAL: Exception Operation not permitted: ''"
by Maximin Coste 31 May '13

31 May '13

Hi, I'm running an edited and "old" (September 2012) version of L4Linux & uC-OS/II in top of Fiasco+L4RE (updated here). When launching the image I have generated, I have the following error: MOE: cmdline: moe rom/l4lx_ucos.cfg MOE: Starting: rom/ned rom/l4lx_ucos.cfg MOE: loading 'rom/ned' Ned says: Hi World! Ned: loading file: 'rom/l4lx_ucos.cfg' Ucos | L4Re: FATAL: Exception Operation not permitted: '' Ucos | Exception: Operation not permitted: : backtrace ... l4linux | L4Re: FATAL: Exception Operation not permitted: '' l4linux | Exception: Operation not permitted: : backtrace ... io | Dev_factory: register factory for N2Hw6DeviceE io | GTF: register factory for 7Pci_dev io | GTF: register factory for N2Hw12Msi_resourceE io | Dev_factory: register factory for N2Hw11Gpio_deviceE io | Io service io | Ready. Waiting for request. Can I see more about what's going wrong ? Can I see the backtrace those logs talks about ? :) -- Maximin COSTE-LEENHARDT

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How to boot Fiasco microkernel on raspberry pi
by Rahul Singhal 31 May '13

31 May '13

I want to port Fiasco microkernel to RPi. I found that Fiasco now supports RPi. I am a newbie in this kernel field. I have compiled the L4 microkernel and the L4 runtime environment for RPi succesfully but I don't know how to use the generated binaries to run RPi. I am running on ubuntu 12.04. Could you please tell me the procedure and files to be put on the sd card of RPi so that it boots into the L4 runtime environment.

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sigma0 memory space
by joel＠nider.org 30 May '13

30 May '13

I have been reading about the structure of L4Ka::Pistachio, and discovered that they use idempotent (1:1) page table mapping in their sigma0 process. I am wondering if Fiasco also takes this approach? If so, does the kernel also use idempotent mapping? I would imagine that this would have some implications on demand paging in the kernel. Does the kernel even use demand paging? (I mean at some point during boot the kernel will start to use memory to store kernel objects - either the kernel 'guesses' how much it will ever need and statically allocates that memory, or it's going to have to ask for pages later on, which will be owned by some other process). I tried to read the code, but found it very hard to traverse - the C++ classes don't make it easy to follow a flow. Can you please point out the file(s) where the kernel sets up the memory space for sigma0, and where it passes the initial ownership (from kernel space to sigma0 space)? Thanks, Joel

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