September 2014 - l4-hackers - example.com Site

Re: std::cin in Fiasco/L4Re (with 'make qemu')
by Stark, Josef 23 Sep '14

23 Sep '14

Hi, >I'm not sure where you enter this. >For me, the following works quite fine: > >#include <stdio.h> > >int main(void) >{ > printf("Press some key: "); > char c = getchar(); > printf("\nYour input: %c (%d)\n", c, c); > > printf("Enter a number: "); > int number; > scanf("%x", &number); > printf("Your number: %d\n", number); > > return 0; >} If I copy this code into the hello example, and change the Makefile accordingly: PKGDIR ?= ../.. L4DIR ?= $(PKGDIR)/../.. TARGET = hello SRC_C = main.c REQUIRES_LIBS = libc_be_file_stdin include $(L4DIR)/mk/prog.mk I can successfully run it IF moe runs hello directly (without Ned and a config, as a "make qemu E=hello" does). If, however, hello is run through a config file and therefore Ned, as in hello-cfg, it doesn't work. Execution does not halt and outputs invalid values: MOE: Starting: rom/ned rom/hello.cfg MOE: loading 'rom/ned' Ned says: Hi World! Ned: loading file: 'rom/hello.cfg' hello | Press some key: hello | Your input: � (-1) hello | Enter a number: Your number: -2147450972 How to make it work? Pass a certain capability to hello? Josef

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l4/sys/syscalls.h: No such file or directory
by Valentin Hauner 18 Sep '14

18 Sep '14

Hi, I'm using the following example provided by Michael Hohmuth in 2000 to create new tasks and threads: http://os.inf.tu-dresden.de/pipermail/l4-hackers/2000/000384.html I've placed the code in a copy of the hello example, but added > REQUIRES_LIBS = l4sys to the Makefile. The directory structure is located at './l4/pkg/taskcreat'. Nevertheless, compilation is terminated due to a fatal error: > ./l4/pkg/taskcreat/server/src/main.c:5:29: fatal error: l4/sys/syscalls.h: No such file or directory Why is syscalls.h missing here? Best regards, Valentin

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How to debug Fiasco Kernel
by cem akpolat 18 Sep '14

18 Sep '14

Dear all, I was searching how to debug the fiasco kernel through JDB. The following link gives a good approach how to it through minicom. http://os.inf.tu-dresden.de/l4env/doc/html/dev-overview/ However, even if I see the messages on the screen, is it possible to interact with JDB without having an exception? I looked at also the "Fiasco Kernel Debugger Manual", however, I couldn't figure out how to exactly interact with JDB. Until now I could only interact with JDB in case of any exception occurrence. Thanks in advance. Sincerely, Cem Akpolat

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Trimming uclibc in l4
by Masti Ramya Jayaram 18 Sep '14

18 Sep '14

Dear all, I would like to extract the minimal subset of uclibc required by bootstrap, sigma and their dependencies only. My idea is to have these modules use the smaller libc while retain the usual uclibc build for the other packages. I intend to go about this by copying uclibc (say into uclibc_min) and then modifying the contrib_files_all.lst and contrib_files_x86.lst. Is this the correct way to do this? Also, I extracted all the package dependencies of bootstrap and sigma from the control files (below) bootstrap: drivers_uart drivers_of libc l4util cxx_io drivers-frst:libc l4util: crtn libc crtn: l4sys l4sys: ldscripts l4util: crtn libc cxx: l4sys l4util ulibc: l4sys sigma0: crtn l4sys l4util libsigma0 cxx_io libsigma0: l4sys Is this the correct way to do this as well? Thanks, Ramya

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Physical memory allocation to L4linux
by Masti Ramya Jayaram 16 Sep '14

16 Sep '14

Hi all, I start l4linux by specifying 64M on memory in its configuration file. I would like this memory to be a fixed range of physical memory and I was wondering if there is a way to do it. I understand from my earlier posts that the image of l4linux is in the same location everytime because the boot loader puts it there. I am not referring to this memory. I am concerned with the 64M that will potentially get allocated to l4linux. Thanks in advance, ramya

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Question about dec_lock_cnt method in Context class
by Yuxin Ren 16 Sep '14

16 Sep '14

Hi All, I have a question about the dec_lock_cnt method in Context class under multiple processor. In its implementation, it checks if thread's home cpu is equal to current cpu. If not, it does not unset "_running_under_lock" variable, even if the _lock_cnt is 0. Why does it check if home cpu is equal to current cpu? Consider the following case: Thread A is running on core 1 holding a helping lock, but is preempted by another high priority thread. Thread B is running on core 2, and tries to take the same helping lock. It finds the lock is held by A, so it helps A to run by migrating A to core 2. When A releases its lock, finding the current cpu is not its home cpu, so it does not set "_running_under_lock" to false. Then A continues to run on core 1 and tries to take that lock again. But now it can never take the lock, as the implementation of helping lock. PRIVATE inline bool NO_INSTRUMENT Switch_lock::set_lock_owner(Context *o) { bool have_no_locks = o->_lock_cnt < 1; if (have_no_locks) { assert_kdb (current_cpu() == o->home_cpu()); for (;;) { if (EXPECT_FALSE(access_once(&o->_running_under_lock))) continue; if (EXPECT_TRUE(mp_cas(&o->_running_under_lock, Mword(false), Mword(true)))) break; } } ... } Do I misunderstand anything here? Thank you very much. Best, Yuxin

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Re: Using IO-Server
by Martin Schröder 12 Sep '14

12 Sep '14

Hi Korbinian, Am 12.09.2014 um 13:44 schrieb Korbinian Ederer: > Hi, > Thanks for the resources. > The given Documents are describing the use of th *.io and *.cfg files, this is also documented in L4 Doc. > My question now is how to access the configured Device in Server Code. then continue with this example: /src/l4linux/arch/l4/kernel/arch-arm/mach_setup.c In copy_platform_device you can see how the IO resources (IRQ, MEM, IO) are enumerated. Also search for the functions l4io_lookup_resource and l4io_request_iomem to see how this is mapped in your address. The rest is up to your driver. Best regards, Martin. > Am 10.09.2014 um 15:33 schrieb Martin Schröder: >> Hi Korbinian, >> >> Am 10.09.2014 um 14:24 schrieb Korbinian Ederer: >>> Hello Community, >>> I'm relative new to l4RE. My Goal is to get access to an Hardware Device which is Build in the Processor. >>> After some research i came to the conclusion that the IO-Server is the thing I need, but i have no clue how to invoke it. >>> It would be great if someone could supply a short example >> >> Try this: >> https://os.inf.tu-dresden.de/L4Re/doc/io.html >> /src/l4/conf/examples/*.io, *.cfg >> https://fooprotected.wordpress.com/2012/04/12/l4linux-patch-for-mv643xx-eth… >> >> >> Best regards, >> Martin.

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Does Fiasco have yield system call or something similar
by Yuxin Ren 10 Sep '14

10 Sep '14

Hi All, Does Fiasco support yield system call? Or other mechanism one thread can switch to another one without IPC? Thank you very much. Yuxin

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Using IO-Server
by Korbinian Ederer 10 Sep '14

10 Sep '14

Hello Community, I'm relative new to l4RE. My Goal is to get access to an Hardware Device which is Build in the Processor. After some research i came to the conclusion that the IO-Server is the thing I need, but i have no clue how to invoke it. It would be great if someone could supply a short example Thanks Korbinian

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Aborted L4linux due to CLI/STI
by Masti Ramya Jayaram 10 Sep '14

10 Sep '14

Dear all, I get an error during L4linux boot when I enter the debugger (using ESC) and resume: Aborted L4linux due to CLI/STI at 0x534911. When I disassemble this using gdb: (gdb) disassemble 0x534911 Dump of assembler code for function cmpxchg8b_emu: 0x00534910 <+0>: pushf 0x00534911 <+1>: cli 0x00534912 <+2>: cmp (%esi),%eax 0x00534914 <+4>: jne 0x534922 <cmpxchg8b_emu+18> 0x00534916 <+6>: cmp 0x4(%esi),%edx 0x00534919 <+9>: jne 0x534924 <half_same> 0x0053491b <+11>: mov %ebx,(%esi) 0x0053491d <+13>: mov %ecx,0x4(%esi) 0x00534920 <+16>: popf 0x00534921 <+17>: ret 0x00534922 <+18>: mov (%esi),%eax 0x00534924 <+0>: mov 0x4(%esi),%edx 0x00534927 <+3>: popf 0x00534928 <+4>: ret When I built l4linux, I had to disable CONFIG_X86_CMPXCHG, CONFIG_CMPXCHG_LOCAL and CONFIG_X86_CMPXCHG64 despite building for the Pentium because my processor does not support PAE (which is the option that enables this). I am guessing This is the reason it tries to emulate the CMPXCHG instructions. What is the correct l4linux configuration to use for a machine that does not support any of the atomic instructions like CMPXCHG8, ATOMIC, etc.? Thanks, ramya

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