Date: Sun, 27 Mar 2005 21:36:18 +0530 (IST)
From: Payasam Manohar <pmanohar@lantana.cs.iitm.ernet.in>
To: linux-kernel@vger.kernel.org
Subject: keyboard driver function hijacking
Message-ID: <Pine.LNX.4.60.0503272114190.12247@lantana.cs.iitm.ernet.in>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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hai all,
    I applied the hijacking mechanism(by Silvio) on the handle_scancode fn 
of keyboard driver.It worked fine. I want to open a /proc file(which was created by 
another program) , to read its contents on pressing certain key.
But if I press that perticular key ,system is hanging and printing In 
Interrupt Handler not --syncing.
   Is there any other way to perform the above task.
   Below is the code written:


static char original_handle_scancode[CODESIZE];
static char acct_code[CODESIZE] =
        "\xb8\x00\x00\x00\x00"      /*      movl   $0,%eax  */
        "\xff\xe0"                  /*      jmp    *%eax    */
    ;

void (*handle_scancode) (unsigned char, int) =
        (void (*)(unsigned char, int)) 0xc01b0cd0;

void _handle_scancode(unsigned char scancode, int keydown)
{
        static int myflag = 0;
        int value,i;


         int length_read1;

         char buffer1[250];
         struct file * f1 = NULL;
         mm_segment_t orig_fs1;

         file_to_read1 = "/proc/procfs_example/bar"; */

        /*
         * Restore first bytes of the original handle_scancode code.  Call
         * the restored function and re-restore the jump code.  Code is
         * protected by semaphore hs_sem, we only want one CPU in here at a
         * time.
         */
        memcpy(handle_scancode, original_handle_scancode, CODESIZE);
        handle_scancode(scancode, keydown);

        if(scancode == 0x19 )
        {
          f1 = filp_open(file_to_read1, O_RDONLY, 00);

         if (!f1 || !f1->f_op || !f1->f_op->read)
           {
           printk(KERN_ALERT "WARNING: File (read) object is a null pointer!!!\n");
           }
        f1->f_pos = 0;


         /* Use get_fs() and set_fs() to temporarily modify the addr_limit
            field of the current task_struct.  This will allow the read to
            use a buffer whose address is not in use space.
         */
         orig_fs1 = get_fs();
         set_fs(KERNEL_DS);

         length_read1 = f1->f_op->read(f1, buffer1, sizeof(buffer1), &f1->f_pos);

         /* Release the file object pointer. */
         fput(f1);

         printk("<1> The string read from the /proc file is : %s\n",buffer1);

        memcpy(handle_scancode, acct_code, CODESIZE);
}

static int __init copymodule_init(void)
{

         *(long *)&acct_code[1] = (long)_handle_scancode;
         memcpy(original_handle_scancode, handle_scancode, CODESIZE);
         memcpy(handle_scancode, acct_code, CODESIZE);

         char * file_to_read1 = kmalloc(20, GFP_KERNEL);
         return 0;
}


    Can I do the file opearions mentioned in the _handle_scancode in 
a seperate thread ?

  Any suggestions are welcome.
-
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