MODPOST __copy_from_user module compilation issue

[Altera_Forum]

Hello! 

 I'm encountering a problem while compiling USB modules under Nios2Linux-MMU.  In Kernel config I select USB Host driver support and execute 'make modules'. At the end of the process I get the following errors:   Building modules, stage 2. MODPOST 21 modules ERROR: "__copy_from_user" undefined! ERROR: "__copy_to_user" undefined! Does anyone know good documentation about this modpost stuff? Actually I have no clue and can't find anything on this topic...  Btw, also when I use the __copy_*_user and copy_*_user in my own modules it results in the same error. As a workaround 've been using the put_user and get_user functions. But this couldn't be a solution.  regards  steron

[Altera_Forum]

It seems nobody can help me. I'm still trying to fix that and found out some things: 

 Now I'm trying to compile my own module where I use the function mentioned above.   The module is a char device driver and the important parts are the following:  # include <linux/init.h># include <linux/module.h># include <linux/ioport.h># include <linux/fs.h># include <asm/io.h># include <asm/uaccess.h> __copy_from_user(cmd,buffer,2); Now i don't get the errors anymore, but warnings instead:   Building modules, stage 2. MODPOST 1 modules WARNING: "__copy_from_user" undefined! The Makefile: (for building outside the kernel tree)   obj-m := mymod.o all: $(MAKE) -C ../../../uClinux-dist SUBDIRS=$(PWD) modules Eventually the module is built, but when I try to plug it into the running kernel, I get this error:  root:~> insmod mymod.ko mymod: Unknown symbol __copy_from_user insmod: can't insert 'mymod.ko': unknown symbol in module, or unknown parameter Am I missing something here? Cause the symbol _is_ actually defined, as I can see from /proc/kallsyms:   root:~> cat /proc/kallsyms | grep copy_from_user c8006854 T __copy_from_user c8008210 T copy_from_user_page c805075c t __iovec_copy_from_user_inatomic c805081c T iov_iter_copy_from_user c80508ac T iov_iter_copy_from_user_atomic c8086654 t pipe_iov_copy_from_user c8123d58 T csum_partial_copy_from_user One other thing I've found is this post on the forum: http://www.alteraforum.com/forum/showthread.php?t=14426 (http://www.alteraforum.com/forum/showthread.php?t=14426&highlight=copy_from_user)  wentao suggests to include another EXPORT_SYMBOL in the according file. I did the same in arch/nios/mm/uaccess.c but it didn't help.  Thanks for your support  steron

[Altera_Forum]

Hi, 

   --- Quote Start ---   It seems nobody can help me. I'm still trying to fix that and found out some things:   --- Quote End ---     Before complaining to forum members, please 'grep' the kernel source directories and find the definition of '__copy_from_user'. Maybe it exists in the file  /nios2-linux/linux-2.6/arch/nios2/mm/uaccess.c  and its header file is  /nios2-linux/linux-2.6/arch/nios2/include/uaccess.h  And please check again whether your 'include path' is right or not.  Kazu

[Altera_Forum]

Hi! 

   --- Quote Start ---  Before complaining to forum members  --- Quote End ---    Complaining was not my intention. I'm sorry if it sounded like that. I just wanted to give you more information because the error messages from my first were probably not enough.  I checked the definition of the function and the include path. Eventually I put the EXPORT_SYMBOL(__copy_from_user); line into the arch/nios2/mm/uaccess.c file.  Don't know if it's only a workaround, because it seems strange that other users haven't encountered such errors.  By the way, in my last post when I wrote   --- Quote Start ---   I did the same in arch/nios/mm/uaccess.c but it didn't help.   --- Quote End ---  I just got confused with the directories in my kernel tree. Surprisingly I got another 'nios2' directory below 'arch/nios2' but this seems to be a result of any messy copying action.

[Altera_Forum]

Hi, 

   --- Quote Start ---   I checked the definition of the function and the include path. Eventually I put the EXPORT_SYMBOL(__copy_from_user); line into the arch/nios2/mm/uaccess.c file.  Don't know if it's only a workaround, because it seems strange that other users haven't encountered such errors.   --- Quote End ---     You mean that you don't have the description EXPORT_SYMBOL(__copy_from_user); in your 'uaccess.c' file ?  Modules are loaded dynamically and the linker must resolve the locations. To do this, the kernel must expose the symbol's location, and you need the macro 'EXPORT_SYMBOL(symbol)' if you want to use the 'symbol' in your module. In fact, the symbols   EXPORT_SYMBOL(__copy_from_user); EXPORT_SYMBOL(copy_from_user); EXPORT_SYMBOL(__copy_to_user); EXPORT_SYMBOL(copy_to_user); EXPORT_SYMBOL(get_ds); EXPORT_SYMBOL(get_fs); EXPORT_SYMBOL(set_fs); are exported in my 'arch/nios2/mm/uaccess.c'.  The macro 'EXPORT_SYMBOL' exports symbols as follows  /* For every exported symbol, place a struct in the __ksymtab section */# define __EXPORT_SYMBOL(sym, sec) extern typeof(sym) sym; __CRC_SYMBOL(sym, sec) static const char __kstrtab_##sym __attribute__((section("__ksymtab_strings"), aligned(1))) = MODULE_SYMBOL_PREFIX# sym; static const struct kernel_symbol __ksymtab_##sym __used __attribute__((section("__ksymtab" sec), unused)) = { (unsigned long)&sym, __kstrtab_##sym } # define EXPORT_SYMBOL(sym) __EXPORT_SYMBOL(sym, "") And it seems that Wind River guys did not test the module loadings at all. Please see this  http://www.alteraforum.com/forum/showpost.php?p=78791&postcount=48 .  Kazu

[Altera_Forum]

Shame on me, I actually got confused with file versioning. In the recent versions there are the correct macro calls in 'arch/nios2/mm/uaccess.c' and others. 

Thanks for the hint!  steron

[Altera_Forum]

Steron, 

I actually have the same problem. Can you tell me how you fixed it? Thanks

[Altera_Forum]

I got all the necessary definitions simply by updating to the most recent git tree. :-) 

Where exactly are you encountering this problem?

[Altera_Forum]

I inserted my module and I got a unknown symbol error.

[Altera_Forum]

Hey, 

 I think we need more information on your module. Can you show us some code?

[Altera_Forum]

I did a upgrade and the problem has gone. thanks