l4-hackers June 2010

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

4 participants
6 discussions

l4vfs and stdin/stdout handles
by Valery V. Sedletski 02 Jul '10

02 Jul '10

Hi all. I am trying to make a test using l4vfs libc backends so the three predefined file descriptors 0, 1, 2 work for stdin, stdout and stderr correspondingly. It appears that these file descriptors are already predefined for some purpose: when I am trying to open files like this: // open initial file descriptors // stdin fd = open("/vc/vc0", O_RDONLY); LOG("stdin: fd=%d, errno=%d", fd, errno); // strout fd = open("/vc/vc0", O_WRONLY); LOG("stdout: fd=%d, errno=%d", fd, errno)… [View More]; // stderr fd = open("/vc/vc0", O_WRONLY); LOG("stderr: fd=%d, errno=%d", fd, errno); -- like in term_con_test example for term_con server, the 3, 4, 5 descriptors are returned from open(). If I not use term_con at all, and not open vc0 three times as above, read(0, ....); and write(1,....); works but strangely. For example, read() returns immediately with no error and returns a single symbol (EOF, I think). But as I tested in Linux and OS/2 operating systems, when stdin is a console, read(0,...); must block until '\n' is returned (user pressed an Enter key). So, it seems that the file descriptors 0, 1, 2 are reserved, but they are not working as expected. Maybe, my setup is incorrect or something is not yet implemented? I have a menu.lst entry like this: title The "Hello, world!" program kernel $(A)/bootstrap -serial modaddr 0x02000000 module $(B)/fiasco $(FIASCOARGS) module $(B)/sigma0 module $(B)/roottask \ task modname 'simple_file_server' attached 6 modules module $(B)/log module $(B)/names module $(B)/dm_phys module $(B)/l4io module $(B)/rtc module $(B)/l4con module $(B)/simple_ts -t 300 module $(B)/name_server module $(B)/term_con module $(B)/simple_file_server -v 14 module $(B)/os2/config.sys module $(B)/os2/mini33.exe module $(B)/os2/minicmd.exe module $(B)/os2/msg.dll module $(B)/os2/doscalls.dll module $(B)/os2/sub32.dll module $(B)/fstab \ -c /file \ -c /file/system -v 14 -b / -m /file/system \ -c /vc -v 132 -b / -m /vc module $(B)/os2/os2server -d c: -m /file/system vbeset $(VBE_MODE) I needed to relink a term_con server to an address 0x01450000 instead of the default one of 0x01400000 because the latter was the same as with simple_ts server (0x01400000 too). I was not able to use loader server to load at other address because I needed to launch two l4vfs servers, term_con and simple_file_server where simple_file_server serves all files through fprov_proxy file provider (I don't want to use an extra bmodfs server to serve files for loader -- it would be an ugly decision, I think). The 'os2server' server uses the files that were served by simple_file_server and it tries to use l4vfs servers for reading from stdin. My makefile looks like this: PKGDIR ?= ../.. L4DIR ?= $(PKGDIR)/../.. TARGET = os2server # the default relocation address. This may be superseded by a STATIC file. DEFAULT_RELOC = 0x01800000 # list your .c files here # os2server.c SRC_C = main.c utility.c io.c MountReg.c globals.c native_dynlink.c l4_alloc_mem.c \ Shared/token.c \ Shared/modmgr.c \ Shared/ixfmgr.c \ Shared/ixfmgr_lx.c \ Shared/ixfmgr_lx_load.c \ Shared/ixfmgr_ne.c \ Shared/ixfmgr_lx_fixuplx.c \ Shared/ixfmgr_lx_loadobjlx.c \ Shared/ixfmgr_lx_modlx.c \ Shared/ixfmgr_lx_execlx.c \ Shared/ixfmgr_lx_debuglx.c \ Shared/memmgr.c \ Shared/api/apistub.c \ Shared/cfgparser.c \ Shared/processmgr.c #Shared/ow_dlfcn.c \ # if your server implements the server side of an idl defined in an idl-file # of your package, list the idl file name(s) here (no path needed) SERVERIDL = os2server.idl # list additional library paths and libraries here LIBS = -los2server -lparsecmdline -lthread -lcon -lcontxt -lconstream-server CFLAGS = -I$(PKGDIR)/include MODE=l4env_base include $(L4DIR)/mk/prog.mk Maybe some libs are interfere with l4vfs ones or something like this? I suspect the l4con server libs interfere with l4vfs libs. For example, l4con has its own getchar() implementation but in uCLibc this function is implemented through l4vfs backends. When I am trying to use getchar() or scanf() functions, I see that read() function is called behind the scenes, and it don't get blocked until Enter is pressed. So, any help is appreciated. WBR, valery [View Less]

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l4vfs and opendir()/readdir()
by Valery V. Sedletski 20 Jun '10

20 Jun '10

Hi all. I am trying to mount a flat file system by simple_file_server in l4vfs tree and then navigating over the file systen, i.e. opening/reading the root directory by opendir()/readdir(), searching the files in the directory and then opening them by open(). Doing this, I found that opendir() sometimes fails, trying to allocate a big (almost 2 gigabytes) dataspace at dm_phys. When I tried to compile my program and l4vfs servers with debug output, I had seen that this is done by calloc() … [View More]

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L4Re and Fiasco.OC
by Adam Lackorzynski 18 Jun '10

18 Jun '10

Hi, I'm happy to announce the availability of a major revamp of the Fiasco microkernel and the corresponding user-level infrastructure. Highlights include a completely new interface based on capabilities, support for multi-processor systems and virtualization. The runtime environment provides core servers and services, including a C++ and C programming environment, standard libraries (such as libc, stdc++, pthreads), programmable program launching and much more. http://os.inf.tu-dresden.… [View More]

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IPC error: resolved
by Valery V. Sedletski 08 Jun '10

08 Jun '10

I Finally understood the cause of an error. It appears that the stack of trampoline() task was the same as the one of LX executable being started. So, the LX executable had trampoline() local variables overwritten, and CORBA_Environment was corrupted ;) This is because IPC operation returned an error. Sorry for inconvenience, WBR, valery

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IPC error
by Valery V. Sedletski 08 Jun '10

08 Jun '10

Hi all I am writing a program (API server which implements API and support for LX format executables found in OS/2 operating system). So, it parses an executable, applies fixups and starts it. At the moment it loads a simple executable which calls a single API printing a string on a screen. It generally works, but I got strange IPC problems. There is a function in a server, trampoline() which starts a previously prepared executable in a separate task (it is a kind of wrapper around that … [View More]executable). After executable termination, trampoline() must synchronize with the server, passing it a message about termination. Then the API server can terminate itself. For synchronization, I tried two ways: 1) sending a message to main server thread through DICE interfaces. As I understand, a problem can be with that client and server stubs are linked to a single program. A code of trampoline() looks like that: static void trampoline(unsigned long esp_data, unsigned long eip_data) { CORBA_Environment env = dice_default_environment; l4_threadid_t dest; l4_msgdope_t result; l4_umword_t w0, w1; int err; asm( "pop %%eax\n" "pop %%eax\n" "movl %[esp_data], %%eax \n" /* Put old esp in eax */ "movl %[eip_data], %%ecx \n" "movl %%ebp, %%edx \n" /* Copy ebp to edx. Base pointer for this functions local variables.*/ "movl %%eax, %%esp \n" /* Copy eax to esp. Stack pointer*/ /* We have changed the stack so it now points to out LX image.*/ "call *%%ecx \n" /* Call our main() */ : :[esp_data] "m" (esp_data), /* esp+ data_mmap+8+*/ [ebp_data] "m" (ebp_data), /* esp+ data_mmap+8+*/ [eip_data] "m" (eip_data)); LOG("task end"); // query OS/2 server task id names_query_name("os2server", &dest) ; LOG("os2server uid=%x.%x", dest.id.task, dest.id.lthread); // send a signal about termination to OS/2 server env.utcb = l4_utcb_get(); os2server_wakeup_call (&dest, &env); if (DICE_HAS_EXCEPTION(&env)) printf("Error: %d.%d", DICE_EXCEPTION_MAJOR(&env), DICE_EXCEPTION_MINOR(&env)); } Without setting env.utcb to UTCB pointer, it traps because of null pointer dereferencing. (In os2server_wakeup_call() function code generated by DICE. This is the disassembly code: _os2server_wakeup_wakeup_wakeup_msg_buffer_t *_dice_msg_buffer = (_os2server_wakeup_wakeup_wakeup_msg_buffer_t*)_dice_corba_env->utcb->values; 1806a19: 8b 45 0c mov 0xc(%ebp),%eax 1806a1c: 8b 40 10 mov 0x10(%eax),%eax 1806a1f: 89 45 dc mov %eax,0xffffffdc(%ebp) l4_umword_t _exception __attribute__ ((unused)); l4_umword_t _dummy __attribute__ ((unused)); l4_msgtag_t tag_dummy __attribute__ ((unused)) = l4_msgtag(0,0,0,0); l4_msgdope_t _dice_result = { raw: 0 }; _dice_msg_buffer->wakeup_wakeup_in._dice_opcode = _OS2SERVER_WAKEUP_WAKEUP_OPCODE; 1806a22: c7 00 01 00 10 00 movl $0x100001,(%eax) -- it traps when assigning an opcode at the last instruction. I thought this is because of UTCB pointer in env points to OS/2 server's main thread UTCB but trampoline() executes in different task, so UTCB is other. When I added UTCB pointer, it stopped trapping but I got DICEexception with MAJOR code 2 and MINOR 2 (IPC error). On server side, a function os2server_wakeup_component() must be called which intended to reset a semaphore, on which a main thread waits for trampoline() termination: void DICE_CV os2server_wakeup_component (CORBA_Object _dice_corba_obj, CORBA_Server_Environment *_dice_corba_env) { LOG("wakeup called"); l4semaphore_up(&sem); } -- It never gets called because of IPC error in os2server_wakeup_call (). 2) Also, I tried another way -- there is a thread on the server side waiting for a message (I decided to create another thread besides the main one to not interfere with DICE): static void os2server_wakeup_thread (void) { l4_msgdope_t result; l4_threadid_t src, id; l4_umword_t w0, w1; /* because of l4thread_create(..., L4THREAD_CREATE_SYNC) */ l4thread_started(0); names_register("os2server.wakeup"); while (1) { LOG("waiting for message"); l4_ipc_wait (&src, L4_IPC_SHORT_MSG, &w0, &w1, L4_IPC_NEVER, &result); LOG("message received"); if (w0 == 0 && w1 == 0) { l4semaphore_up(&sem); LOG("semaphore reset"); } } } trampoline() code is modified this way: static void trampoline(unsigned long esp_data, unsigned long eip_data) { l4_threadid_t dest; l4_msgdope_t result; l4_umword_t w0, w1; int err; asm( "pop %%eax\n" "pop %%eax\n" "movl %[esp_data], %%eax \n" /* Put old esp in eax */ "movl %[eip_data], %%ecx \n" "movl %%ebp, %%edx \n" /* Copy ebp to edx. Base pointer for this functions local variables.*/ "movl %%eax, %%esp \n" /* Copy eax to esp. Stack pointer*/ /* We have changed the stack so it now points to out LX image.*/ "call *%%ecx \n" /* Call our main() */ : :[esp_data] "m" (esp_data), /* esp+ data_mmap+8+*/ [ebp_data] "m" (ebp_data), /* esp+ data_mmap+8+*/ [eip_data] "m" (eip_data)); LOG("task end"); if (!names_waitfor_name("os2server.wakeup", &dest, 10000)) LOG("wakeup thread not found"); else LOG("wakeup thread found, uid=%x.%x", dest.id.task, dest.id.lthread); w0 = 0; w1 = 0; err = l4_ipc_send(dest, L4_IPC_SHORT_MSG, w0, w1, L4_IPC_NEVER, &result); if (err) LOG("error: %ld", err); else LOG("message transmitted"); LOG("msgdope = %lu", result); LOG("mini33 exit"); } This way I get an IPC error too. The return code from l4_ipc_send() is equal to 16 but msgdope is clear (zeroes). I found a description of errors returned in message dopes but what means a return code of 16, I don't know. (For message dope, a error code of 0x10 means that source or destination does not exist, but I am sure it exists) So, l4_ipc_send() exits and l4_ipc_wait() on other side never exits. Maybe, someone can help understanding why it won't work? Thanks in advance. [View Less]

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a minor bug in claim_irq
by Da Zheng 06 Jun '10

06 Jun '10

Hello, Here is a minor bug in claim_irq when ddekit_interrupt_attach fails. We should be set used_irqs properly in case ddekit_interrupt_attach fails. The fix is in the attachment. Best regards, Zheng Da

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l4-hackers June 2010