June 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

what should NIC do in order to support TSO?
by Gang Lei (雷刚) June 10, 2011

June 10, 2011

HI All: As the title. I saw someone mentioned that NIC should support S/G DMA, TCP checksum offload and auto insert IP header,TCP header. The S/G DMA is easy to understand since large mount of data can’t be allocated into one single page, but why it need hardware to auto insert TCP header? As I know, the TCP header should only exist in the first fragments, and it ‘s already in skb->data, for other fragments, it’s in skb->frags, hardware only need to insert IP header for them, so I don’t see such need to auto insert TCP header by Hardware. And another question about checksum offload is that, how can hardware support rx checksum verification if received packets are fragmented? Thanks for your answer in advance. Rick

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Check out my photos on Facebook
by Ashutosh Kumar Mishra June 10, 2011

June 10, 2011

Hi Linux, I set up a Facebook profile where I can post my pictures, videos and events and I want to add you as a friend so you can see it. First, you need to join Facebook! Once you join, you can also create your own profile. Thanks, Ashutosh To sign up for Facebook, follow the link below: http://www.facebook.com/p.php?i=100001153629448&k=Z6E3Y6V5VX3N2FLJPB63QVTVS… Already have an account? Add this email address to your account: http://www.facebook.com/n/?merge_accounts.php&e=kernelnewbies%40kernelnewbi… ======================================= kernelnewbies(a)kernelnewbies.org was invited to join Facebook by Ashutosh Kumar Mishra. If you don't want to receive these emails from Facebook in the future, please follow the link below to unsubscribe. http://www.facebook.com/o.php?k=e17023&u=100002550610804&mid=45ba24fG5af3a8… Learn more about this email: http://www.facebook.com/help/?faq=17151\nFacebook, Inc. P.O. Box 10005, Palo Alto, CA 94303

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Not able to see all the symbols in the output of "nm" command
by Madhavi Manchala June 10, 2011

June 10, 2011

Dear All, I build the OpenWRT image for my target device. I am able to see the "vmlinux" image in trunk/build_dir/linux-s3c2510/linux-2.6.36 directory where linux-s3c2510 indicates my target device. I am NOT able to see some of the function names (symbols), which I developed, in the output of the "nm" command for vmlinux image. Am I missing any thing while building the image for getting all the symbols into the image? I am NOT able to see all the function names which are defined in arch/arm/plat-samsung/include/uncompress.h file. Please let me know if I am missing any thing. Thanks for your suggestions / hints. Thanks and Regards, Madhavi M.

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Calling function from address
by Micha M. June 9, 2011

June 9, 2011

Hi! Is it possible to call a function that is somewere in the physical-address space? So I'd like to jump to a certain physical address, execute the code there and then return to my kernel module. I already tried to ioremap that address and cast the new address to a funtion pointer and then call the function, but there where some page faults. Regards #micha -- /* To err is human; to really fuck things up requires the root password */

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Problems with hypercalls
by emilie lefebvre June 9, 2011

June 9, 2011

Hi all, I try to do hypercalls but I always have a kernel panic that I don't understand. I have Scentific Linux 6 installed on kvm and my computer has ubuntu. I try to modify the SL6 kernel to do hypercalls. I have a function in that kernel which check all syscalls in the VM. When I put the hypercall at the beginning of this function, it perfectly works, but when I try to put it in the middle of the function I have a kernel panic with this error: "divide error: 0000 [#1] SMP ... [<ffffffff813f8cdd>] panic+0x78/0x137 [<ffffffff813fcb94>] oops_end+0xe4/0x100 [<ffffffff8101021b>] die+0x5b/0x90 [<ffffffff813fc444>] do_trap+0xc4/0x160 [<ffffffff8100df2f>] do_divide_error+0x8f/0xb0 [<ffffffff811f974c>] ? my_function+0xdc/0xe70 " Could you have any suggestions ? With regards, Emilie

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Re: OS Books suggestion
by Ezequiel García June 9, 2011

June 9, 2011

I appreciate all the answers. But actually I was just looking for a review on the three books I asked for. Thanks anyway. Ezequiel.

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mmap on a block device
by Kaustubh Ashtekar June 7, 2011

June 7, 2011

Hello All, Is it possible to mmap on a block device? I am writing my own kernel space filesystem on Linux (academic project). I am writing a user space tool to format the block device (again my own ramdisk driver). It would be much simpler if I could just mmap the block device into my address space. -Kaustubh

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OS Books suggestion
by Ezequiel García June 7, 2011

June 7, 2011

I am looking for some biblographic material for OS learning (mostly for linux). I've read Linux Device Drivers, and I am interested in these: * The design of unix operating system (Bach) * Modern operative systems (Tanenbaum) * Operating Systems design and implementation(Tanenbaum) I haven't done formal Computer Science studies, and I don't the time to read the three of them, but as I am working very close to the linux kernel, I am trying to sharp my skills a little. All books seem very well rated, and the first one is a real classic. I would like to have further suggestions so I can decide myself better. Thanks. Ezequiel.

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Weird problem while compiling kernel
by Manish Katiyar June 6, 2011

June 6, 2011

/home/kernel> make net CHK include/linux/version.h CHK include/generated/utsrelease.h CALL scripts/checksyscalls.sh CC net/netlink/genetlink.o mv: cannot move `net/netlink/.genetlink.o.tmp' to `net/netlink/.genetlink.o.cmd': No such file or directory make[2]: *** [net/netlink/genetlink.o] Error 1 make[1]: *** [net/netlink] Error 2 make: *** [net] Error 2 Hi, This is perhaps OOT, but I have been struggling to figure out the problem. While compiling kernel I'm getting the below error. Everything seems fine and I can see the file, however for some reason 'mv' can see the source file. strace revealed that its failing with ENOENT. I don't think there is anything special with this directory (given that other things compile just fine), except that this directory is on a ntfs mounted partition. /home/kernel> make net CHK include/linux/version.h CHK include/generated/utsrelease.h CALL scripts/checksyscalls.sh CC net/netlink/genetlink.o mv: cannot move `net/netlink/.genetlink.o.tmp' to `net/netlink/.genetlink.o.cmd': No such file or directory make[2]: *** [net/netlink/genetlink.o] Error 1 make[1]: *** [net/netlink] Error 2 make: *** [net] Error 2 /home/kernel> ls -lrt net/netlink/.genetlink.o.tmp -rwxrwxrwx 1 root root 39301 2011-06-06 00:08 net/netlink/.genetlink.o.tmp /home/kernel> mv net/netlink/.genetlink.o.tmp net/netlink/.genetlink.o.cmd mv: cannot move `net/netlink/.genetlink.o.tmp' to `net/netlink/.genetlink.o.cmd': No such file or directory /home/kernel> mount|grep kernel /dev/sda1 on /home/kernel type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /home/kernel> ls net/netlink/.genetlink.o.cmd net/netlink/.genetlink.o.cmd /home/kernel> rm net/netlink/.genetlink.o.cmd rm: cannot remove `net/netlink/.genetlink.o.cmd': No such file or directory /home/kernel> stat net/netlink/.genetlink.o.cmd File: `net/netlink/.genetlink.o.cmd' Size: 32093 Blocks: 64 IO Block: 4096 regular file Device: 801h/2049d Inode: 223366 Links: 1 Access: (0777/-rwxrwxrwx) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2011-06-06 00:08:26.394585000 -0700 Modify: 2011-06-06 00:08:18.121035000 -0700 Change: 2011-06-06 00:08:44.087640000 -0700 Any suggestions, what I might be missing ? -- Thanks - Manish

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how setbuf is working in c program
by Prabhu June 6, 2011

June 6, 2011

Hi all, I am writing user- space driver. My intention is to print whatever string i am enter into terminal. Here i am using setbuf function to sent the data to the print after some fixed string length. I wrote below program for understand setbuf functionality. But i am getting unpredictable result for some output . can any one explain the why i am getting these result. root@desktop:/home/prabhu# cat a.c #include <stdio.h> main() { char buff2[]= "hello world"; char buf1[6]=""; setbuf(stdin, buf1); getchar(); printf ("%s",buf1); } root@desktop:/home/prabhu# cc a.c root@desktop:/home/prabhu# ./a.out a a root@desktop:/home/prabhu# ./a.out aa aa root@desktop:/home/prabhu# ./a.out aaa aaa root@desktop:/home/prabhu# ./a.out aaaa aaaa root@desktop:/home/prabhu# ./a.out aaaaa aaaaa hello worldroot@desktop:/home/prabhu# ./a.out aaaaaa aaaaaa ello worldroot@desktop:/home/prabhu# ./a.out aaaaaaa aaaaaaa llo worldroot@desktop:/home/prabhu# ./a.out aaaaaaaa aaaaaaaa lo worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaa aaaaaaaaa o worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaaa aaaaaaaaaa worldroot@desktop:/home/prabhu# ./a.out aaaaaaaaaaa aaaaaaaaaaa Thanks, Prabhu

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