September 2011 - kernelnewbies@kernelnewbies.org

Query about custom fedora build process
by Vaibhav Jain Sept. 8, 2011

Sept. 8, 2011

Hi, I am trying to build a custom fedora kernel on a fedora (FC15) machine by reading the article: http://fedoraproject.org/wiki/Building_a_custom_kernel but i am unable to make any progress as my changes are not getting reflected. So I have query about the procedure given in the article. The article asks to first create hardliks between files in .new and .orig directories and then to make changes and to .new directory and to generate a patch by a diff between the .orig and .new directories. But I am just wondering if the files in both the directories are hardlinks then how can diff work because after changing a file in .new directory the file in .orig directory should also change. cp -r ~/rpmbuild/BUILD/kernel-2.6.$ver.$fedver/linux-2.6.$ver.$arch ~/rpmbuild/BUILD/kernel-2.6.$ver$fedver.orig cp -al ~/rpmbuild/BUILD/kernel-2.6.$ver.$fedver.orig ~/rpmbuild/BUILD/kernel-2.6.$ver.$fedver.new cd ~/rpmbuild/BUILD diff -uNrp kernel-2.6.$ver.$fedver.orig kernel-2.6.$ver.$fedver.new > ../SOURCES/linux-2.6-my-new-patch.patch Thanks Vaibhav Jain

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Doubt regarding asmlinkage
by rohan puri Sept. 8, 2011

Sept. 8, 2011

Hi All, asmlinkage is used in front of the each system call prototype. For x86 arch it indicates that the the parameters are on stack instead of the registers and for x86_64 arch the parameters are in registers only. Doubt i have is whats the need for 32-bit intel arch to put parameters on stack and not registers in a way similar to x86_64? Regards, Rohan.

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Why the PF_SUPERPRIV flag is cleared?
by Parmenides Sept. 8, 2011

Sept. 8, 2011

Hi, When forking a child process, the copy_process() function will by default clear the PF_SUPERPRIV flag, which indicates whether a process use superuser privileges. That means a superuser process will create a child process does not has superuser privileges. I think the child process of a superuser process should also be a superuser one, while the child process of a normal process by default should also be a normal one (except that the setuid bit of the child executable is turn on). In both cases it is not necessary that the PF_SUPERPRIV flag to be cleared. So, I wonder why the PF_SUPERPRIV flag is cleared by defult.

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Paging of Kernel Memory
by Vijay Chauhan Sept. 8, 2011

Sept. 8, 2011

Hi, i was going through the Linux Kernel Development book. It mention the following: "Additionally, kernel memory is not pageable.Therefore, every byte of memory you consume is one less byte of available physical memory." What is the meaning of 'Kernel memory is not pageable'? Anyone can give details would help me in understanding. Thanks, Vijay

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Doubt fork system call
by rohan puri Sept. 8, 2011

Sept. 8, 2011

Every time a fork() is callled in any user-space code, it internally invokes the clone() sys call, But if we linux kernel source code there is a system call by name fork(). So, what i really want to know is that, is there any case in which this syscall is getting called, or this code is deprecated. Regards, Rohan

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Invitation to connect on LinkedIn
by Anil Unnikrishnan via LinkedIn Sept. 8, 2011

Sept. 8, 2011

LinkedIn ------------ Anil Unnikrishnan requested to add you as a connection on LinkedIn: ------------------------------------------ Deepak, I'd like to add you to my professional network on LinkedIn. - Anil Accept invitation from Anil Unnikrishnan http://www.linkedin.com/e/8z2206-gsb6oul9-1a/L90NvsYL3GREvJdnM0f-HnfkWNbSD_… View invitation from Anil Unnikrishnan http://www.linkedin.com/e/8z2206-gsb6oul9-1a/L90NvsYL3GREvJdnM0f-HnfkWNbSD_… -- (c) 2011, LinkedIn Corporation

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How to identify the SD card in Linux.
by varun Yadav Sept. 7, 2011

Sept. 7, 2011

Hi, I want to identify SD card in Linux, like if we connect a usb mass storage device and SD card then how we can identify the SD card. Is usb driver sending some information regarding device type, class or sub class to user spaceby which i can identify that connected device is sd card? Regards, Varun

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Re: project on linux kernel
by Mulyadi Santosa Sept. 6, 2011

Sept. 6, 2011

On Tue, Sep 6, 2011 at 17:08, sugnan prabhu <sugnan.prabhu(a)gmail.com> wrote: >i am very much interested work on networking sub system, can you >please give me a project... I am not really into networking stuffs these days, so maybe folks here could help....folks? -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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freeze_bdev
by Mike Gibson Sept. 6, 2011

Sept. 6, 2011

Which filesystems are supported by freeze_bdev? The man page for fsfreeze shows Ext3/4, ReiserFS, JFS, and XFS. Is this correct? Mike Gibson

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analysis of kernel panic logs.
by sandeep kumar Sept. 6, 2011

Sept. 6, 2011

Hi, im working on android, kernel version 2.6.35.11 I got these logs showing kernel panic and the target is rebooting. >From the logs i understood in init process something is causing kernel panic. <3>[ 85.235589] init: [boot time] processing action 0x4c5e8 (property:init.svc.samsungani=stopped) <3>[ 85.236565] init: [boot time] processing action 0x4ef20 (property:init.svc.samsungani=stopped) <0>[ 85.236840] Kernel panic - not syncing: Attempted to kill init! <4>[ 85.236932] [<c01076b8>] (unwind_backtrace+0x0/0x164) from [<c072436c>] (panic+0x6c/0xec) <4>[ 85.237023] [<c072436c>] (panic+0x6c/0xec) from [<c01a931c>] (do_exit+0x70/0x6a0) <4>[ 85.237115] [<c01a931c>] (do_exit+0x70/0x6a0) from [<c01a99dc>] (do_group_exit+0x90/0xc0) <4>[ 85.237176] [<c01a99dc>] (do_group_exit+0x90/0xc0) from [<c01b8fc4>] (get_signal_to_deliver+0x3e0/0x424) <4>[ 85.237267] [<c01b8fc4>] (get_signal_to_deliver+0x3e0/0x424) from [<c01039d8>] (do_signal+0x68/0x640) <4>[ 85.237359] [<c01039d8>] (do_signal+0x68/0x640) from [<c0103fc8>] (do_notify_resume+0x18/0x38) <4>[ 85.237450] [<c0103fc8>] (do_notify_resume+0x18/0x38) from [<c0100bd0>] (work_pending+0x1c/0x20) <0>[ 85.237542] Rebooting in 5 seconds.. <2>[ 85.237572] CPU0: stopping <4>[ 85.237603] [<c01076b8>] (unwind_backtrace+0x0/0x164) from [<c0100338>] (do_IPI+0xd8/0x154) <4>[ 85.237695] [<c0100338>] (do_IPI+0xd8/0x154) from [<c0728188>] (__irq_usr+0x48/0xe0) <4>[ 85.237756] Exception stack(0xdc18dfb0 to 0xdc18dff8) <4>[ 85.237817] dfa0: 00000000 0000007c 00000000 4097b240 <4>[ 85.237878] dfc0: 45957cfe 4ba95bd8 4fc24a48 000000f4 80118200 ffffe9f4 00000000 801a6374 <4>[ 85.237939] dfe0: 000000f4 4fc249f8 8011d0a8 8011bf18 20000010 ffffffff But how to interpret the Exception stack, dfa0 etc., to narrow down what exactly caused the panic. And in similer cases when oops happens also we will get the register dump, i know how to interpret PC, but what about the rest of the registers. how they are useful in analysing the situation. -- With regards, Sandeep Kumar Anantapalli,

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