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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hello all,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am very new to kernel programming. In fact, I have been working on it for a week now.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am taking a computer science class, and one of our assignments is to hook some of the system calls in a 2.6.28 kernel.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have the basic module created, and I am hooking into the sys_read function. The assignment is to print to the log what is being read using sys_read.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have some checks in my function to limit my printing to only a certain file, so I don’t get the contents of every file being read on the system.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>OnceI know I have the right file, I decided to print the size of the buffer.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The function signature is:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Asmlinkage long sys_read(unsigned int fd, char __user *buf, size_t count);<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>So I do:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Printk(KERN_INFO “Read buffer is [%d] bytes.\n”,count);<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The particular file I am reading has 2 lines the first is 14 bytes long and the second is 30 bytes long.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The output from my printk statements are 8192 and 4096 respectively.<o:p></o:p></p><p class=MsoNormal>Why is the count so large?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Also I do a strlen(buf) and print the value as well, and it is 29 and 16 respectively.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Next I did copy_from_user(tbuf,buf,strlen(buf))<o:p></o:p></p><p class=MsoNormal>And tried to print the contents of the buffer but it came out garbage.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Does anyone have any ideas how I can get this to work?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>BTW: the assignment is due on Sunday so any help would be aappreciated.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'>-- <br>Best Regards, Donald<o:p></o:p></span></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><a href="http://www.oracle.com/" target="_blank"><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:black;text-decoration:none'><img border=0 width=114 height=26 id="_x0000_i1026" src="cid:image001.gif@01CE84E8.A7FC6C20" alt=Oracle></span></a><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><br></span><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:#666666'>Donald raikes | Accessibility Specialist/ QA Engineer<br>Phone: <a href="tel:+15202717608"><span style='color:black'>+15202717608</span></a> | Mobile: <a href="tel:+15202717608"><span style='color:black'>+15202717608</span></a> <br></span><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:red'>Oracle</span><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:#666666'> Quality Assurance<br>| Tucson, Arizona </span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p><table class=MsoNormalTable border=0 cellpadding=0><tr><td style='padding:.75pt .75pt .75pt .75pt'><p class=MsoNormal><a href="http://www.oracle.com/commitment" target="_blank"><span style='font-size:12.0pt;font-family:"Times New Roman","serif";color:black;text-decoration:none'><img border=0 width=44 height=28 id="_x0000_i1025" src="cid:image002.gif@01CE84E8.A7FC6C20" alt="Green Oracle"></span></a><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p></td><td style='padding:.75pt .75pt .75pt .75pt'><p class=MsoNormal><span style='font-size:7.5pt;font-family:"Verdana","sans-serif";color:#4B7D42'>Oracle is committed to developing practices and products that help protect the environment</span><span style='font-size:12.0pt;font-family:"Times New Roman","serif"'><o:p></o:p></span></p></td></tr></table><p class=MsoNormal><o:p> </o:p></p></div></body></html>