RE: FC3 module sys_print how...

["Mukund JB." <mukundjb@esntechnologies.co.in>]

Dear Richard,

I have tried your module to print message to the file in the kernel
level.
I am able to get it work till the initialization level. Later when I
insert the card the system hangs.

Please suggest me what could be the problem. Or is there a way to get
all my LOG messages perfectly even when the system hangs after the
reboot.

Waiting for ur suggestions.

Regards,
Mukund Jampala

>-----Original Message-----
>From: Richard B. Johnson [mailto:linux-os@localhost.localdomain]
>Sent: Friday, July 15, 2005 11:18 PM
>To: Mukund JB.
>Cc: Linux kernel
>Subject: Re: FC3 module sys_print how...
>
>
>Third try.......
>
>On Fri, 15 Jul 2005, Richard B. Johnson wrote:
>
>>
>> Second try.........
>>
>> On Fri, 15 Jul 2005, Richard B. Johnson wrote:
>>
>>>
>>> It's no longer exported. You can either modify your kernel to
>>> export it or you can use that attached work-around to extract
>>> the symbol offset from /boot/System.map.
>>>
>>> Please note that manipulating files from within a module has
>>> never been supported. It just "sort of" works sometimes. In
>>> your demo code, it will work because the process-context that
>>> obtains the file-handle is the process that is running 'insmod'.
>>> If somebody else tried to write to that file after the module
>>> was installed, all bets are off. I strongly suggest that
>>> you provide hooks in your module (ioctl() or mmap(), etc) that
>>> a user-mode helper program can use to send or receive file-data
>>> from your module.
>>>
>>>
>>> On Fri, 15 Jul 2005, Mukund JB. wrote:
>>>>
>>>>
>>>> Dear Linux-lovers.
>>>>
>>>>
>>>>
>>>> I am trying to build a 2.6.10 linux kernel module to print messages
to
>a
>>>> file. I have done this 2.4 and I was successful but I am failing
here.
>>>>
>>>>
>>>>
>>>> I am using the sys_open, sys_write calls to do so.
>>>>
>>>> I am getting a compilation warning and I find no .ko file created
>>>> finally instead I find an .o.ko file.
>>>>
>>>>
>>>>
>>>> *** WARNIG: "sys_write" [/home/cf.o.ko] undefined!
>>>>
>>>> Below is the module code. Please suggest me what could be the
problem:-
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> #include <linux/kernel.h>
>>>>
>>>> #include <linux/module.h>
>>>>
>>>> #include <linux/moduleparam.h>
>>>>
>>>> #include <asm/fcntl.h>        /* for O_WRONLY */
>>>>
>>>> #include <linux/syscalls.h>   /* for sys_ functions */
>>>>
>>>> #include <asm/uaccess.h>      /* for set_fs(), get_fs() etc. */
>>>>
>>>> #include <linux/string.h>     /* for string length */
>>>>
>>>> #include <linux/slab.h>       /* for kmalloc */
>>>>
>>>>
>>>>
>>>> MODULE_LICENSE("GPL");
>>>>
>>>> /*
>>>>
>>>> #define DBG
>>>>
>>>> #define PRINTK(fmt,arg...) printk("DBG INFO <%s> | "
>>>> fmt,__FUNCTION__,##arg)
>>>>
>>>> #else
>>>>
>>>> #define PRINTK(fmt,arg...) while(0)
>>>>
>>>> #endif
>>>>
>>>> */
>>>>
>>>>
>>>>
>>>> typedef struct tagWRITE_TEST
>>>>
>>>> {
>>>>
>>>>      unsigned long fd;
>>>>
>>>>      unsigned long x;
>>>>
>>>>
>>>>
>>>> }WRITE_TEST, *PWRITE_TEST;
>>>>
>>>>
>>>>
>>>> PWRITE_TEST ptest;
>>>>
>>>>
>>>>
>>>> void SysPrint(char * pString, ...)
>>>>
>>>> {
>>>>
>>>>      static char buff[1024];
>>>>
>>>>      va_list ap;
>>>>
>>>>
>>>>
>>>>      va_start(ap,pString);
>>>>
>>>>      vsprintf((char *)buff, pString, ap);
>>>>
>>>>      va_end(ap);
>>>>
>>>>
>>>>
>>>>      sys_write(ptest->fd,(char *)buff,(size_t)strlen(buff));
>>>>
>>>> }
>>>>
>>>>
>>>>
>>>> int init_module(void)
>>>>
>>>> {
>>>>
>>>>
>>>>
>>>>      printk("<%s> invoked!\n",__FUNCTION__);
>>>>
>>>>      printk("File Creation Testing in Kernel Module!\n");
>>>>
>>>>
>>>>
>>>>      set_fs(get_ds());
>>>>
>>>>
>>>>
>>>>      /* allocate the memory for structre */
>>>>
>>>>      ptest = (PWRITE_TEST)kmalloc(sizeof(WRITE_TEST),GFP_KERNEL);
>>>>
>>>>      if(ptest == NULL)
>>>>
>>>>      {
>>>>
>>>>            printk("Structure Memory Allocation Fails!\n");
>>>>
>>>>            return -ENOMEM;
>>>>
>>>>      }
>>>>
>>>>
>>>>
>>>>      ptest->fd = sys_open("srcdebug.txt", O_CREAT | O_WRONLY, 644);
>>>>
>>>>      if (ptest->fd == 0)
>>>>
>>>>      {
>>>>
>>>>            SysPrint("File Creation Error!!!\n");
>>>>
>>>>            return 1;
>>>>
>>>>      }
>>>>
>>>>
>>>>
>>>>      SysPrint("File Creation Testing in Kernel Module!\n");
>>>>
>>>>      SysPrint("Srinivas Testing the File Creation\n");
>>>>
>>>>      sys_close(ptest->fd);
>>>>
>>>>
>>>>
>>>>      return 0;
>>>>
>>>> }
>>>>
>>>>
>>>>
>>>> void cleanup_module(void)
>>>>
>>>> {
>>>>
>>>>      printk("Good bye!\n");
>>>>
>>>>
>>>>
>>>>      /* free the allocated memory */
>>>>
>>>>      kfree(ptest);
>>>>
>>>> }
>>>>
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Mukund jampala
>>>>
>>>>
>>>>
>>>>
>>>> -
>>>> To unsubscribe from this list: send the line "unsubscribe
linux-kernel"
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>>>>
>>>
>>> Cheers,
>>> Dick Johnson
>>> Penguin : Linux version 2.6.12 on an i686 machine (5537.79
BogoMips).
>>> Notice : All mail here is now cached for review by Dictator Bush.
>>>                 98.36% of all statistics are fiction.
>>
>> Cheers,
>> Dick Johnson
>> Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
>> Notice : All mail here is now cached for review by Dictator Bush.
>>                 98.36% of all statistics are fiction.
>
>Cheers,
>Dick Johnson
>Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips).
>  Notice : All mail here is now cached for review by Dictator Bush.
>                  98.36% of all statistics are fiction.
-
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