April 2012 - l4-hackers - example.com Site

libgendep on Ubuntu 11.10
by Christian Helmuth 03 Apr '12

03 Apr '12

Hi, with current SVN (r38) I get the following error: gcc -fPIC -Wall -pedantic -g -m64 -c /plain/krishna/src/genode/genode.git/base-foc/contrib/l4/tool/gendep/deptrack.c -o /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/deptrack.64.o gcc -fPIC -Wall -pedantic -g -m64 -c /plain/krishna/src/genode/genode.git/base-foc/contrib/l4/tool/gendep/syscall.c -o /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/syscall.64.o mkdir -p /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/64 gcc -m64 -shared -Wl,-soname,/plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/64/libgendep.so -ldl -o /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/64/libgendep.so /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/deptrack.64.o /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/syscall.64.o /usr/local/genode-gcc/bin/genode-x86-gcc: symbol lookup error: /plain/krishna/build/genode.foc_x86_32/l4/tool/gendep/64/libgendep.so: undefined symbol: dlsym The attached patch fixed the issue for me and I'd like to share it here ;-) Greets -- Christian Helmuth Genode Labs http://www.genode-labs.com/ · http://genode.org/ · /ˈdʒiː.nəʊd/ Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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L4Android kernel didn't intialize L4 stack for the server thread.
by Mai, Haohui 03 Apr '12

03 Apr '12

Hi, It seems that I found a bug in the latest version of L4Android kernel. I'm familiar enough with the code base so your comments are highly appreciated. The main thread for L4Linux (i.e., the thread running l4x_server_loop()) didn't initialize l4x_stack before execution. Therefore, this thread crashes whenever it calls cli() / sti(). Calling vmalloc() and kmalloc() can reproduce this bug reliably. Here is a patch to fix this problem. ~Haohui --- a/arch/l4/kernel/main.c +++ b/arch/l4/kernel/main.c @@ -2501,6 +2501,8 @@ int __init_refok L4_CV main(int argc, char **argv) * for these areas so far */ //l4x_register_pointer_section(&_edata, 0, "data"); + l4x_stack_setup(current_thread_info(), l4_utcb(), 0); + /* Send start message to main thread. */ l4_ipc_send(l4lx_thread_get_cap(main_id), l4_utcb(), l4_msgtag(0, 0, 0, 0), L4_IPC_NEVER);

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Question on sending capability through IPC
by Mai, Haohui 02 Apr '12

02 Apr '12

Hi, I'm a little bit confused by how Fiasco.OC sending capabilities through IPC. Particularly, it seems that one has to pack the capability in message register, rather than buffer register. Here is a code sending some capability to the client, which works with Fiasco.OC: l4_utcb_t * u = l4_utcb(); l4_utcb_mr_u(u)->mr[0] = ipc_id; l4_utcb_mr_u(u)->mr[1] = L4_ITEM_MAP; l4_utcb_mr_u(u)->mr[2] = l4_obj_fpage(cap, 0, L4_FPAGE_RWX).raw; l4_utcb_br_u(u)->bdr = 0; tag = l4_msgtag(label, 1, 1, 0); ipc_call(...); Notice that the capability is assigned into mr[1] and mr[2], but not br[1] and br[2]. It seems that this behavior is controlled by the constructor of L4_snd_item_iter, at kern/l4_buf_iter.cpp:52 explicit L4_snd_item_iter(Utcb const *utcb, unsigned offset) : _buf(&utcb->values[offset]), _max(&utcb->values[Utcb::Max_words]) {} My question is that whether this is the desired behavior? I didn't find any specification on this. ~Haohui

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ARM and PCI?
by Stefan Fritsch 02 Apr '12

02 Apr '12

Hi, do you know what remains to be done to use PCI on ARM (e.g. Realview in qemu) with L4Re and IO? I guess that io needs some changes to support PCI-IO-Ports mapped into memory. Or should that already work? Cheers, Stefan

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