May 2014 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Capturing all writes as fault on a memory mapped page.
by Pranay Srivastava May 28, 2014

May 28, 2014

Hi I need to capture all writes on page which is memory mapped by the user program. I've tried setting the vm_page_prot by disabling the VM_WRITE flag but even then the page fault occurs only once during the first write. VM_SHARED is set to stop COW in the __do_fault. I was also trying to set_memory_ro(this may not be available for all archs?) however I can't do that while handling the fault since the page table entries are created later after the vm_operations_struct->fault has installed the page for the fault. I'm not having any clues on how to do this. Any help would be really helpful on this. Thanks -- ---P.K.S

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Can i change address of Master Boot Record
by Saurabh Jain May 28, 2014

May 28, 2014

Hello every one ! I was reading the booting process of Linux kernel. I got to know that generally the location of MBR is first sector of the bootable device. I want to know that whether we can change the location (Starting address ) of Master Boot Record or not . Can we do this for Linux and Windows both.

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Download Linus's latest git tree
by Anurudh Tiwari May 28, 2014

May 28, 2014

Hi, I want to download the latest kernel version using git. Trying following command git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git it takes very long time and tries to download whole repository. But i need only latest stable version. Any way to get it?? Thanks Regards Anurudh

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Simple Misc Driver - Problem with string copy to user
by Lucas Tanure May 28, 2014

May 28, 2014

Hi! Goal, when the user do : # head -1 /dev/miscdrv The driver prints: Hello World! Steps: # Make # insmod misc.ko # head -1 /dev/miscdrv Why my driver doesn't work ? What is worg with my read operation? static ssize_t misc_drv_read(struct file *filp, char __user * buf, size_t count, loff_t * offp){ int nbytes; char * string = "hello World"; nbytes = copy_to_user(buf, string, 12); return nbytes; } -- Lucas Tanure Brazil

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Re: Open and copy a file from the kernel
by Pranay Srivastava May 27, 2014

May 27, 2014

On Tue, May 27, 2014 at 3:05 PM, Nada Saif <nada.saif7(a)gmail.com> wrote: > Hi Srivastava, > Thanks for your answer. > > I want to make a backup of any opened file.. whenever the file is opened or > updated , it's reflected on its backup.. Hmm, not really done this but i guess you need inotify hooks and some sort of user space daemon that hooks those inotify events. I've not done this but i know it shouldn't be too hard. Just search for inotify. What you are trying isn't kernel thing to do, however i guess you are trying to do something sort of snapshot per change of a file. But again since you are not doing this at file system level I won't recommend doing this inside kernel (opening and copying). Just hook the inotify events in the userspace daemon and let it worry about maintaining a separate version for all files changed. But if you do this won't you run out of space so soon, plus the files you'll create will eat up the inodes which really are earlier versions you are maintaining. Probably you should come up with a consolidated layout of versions you are going to save. Maybe what you can do is have diffs of file in a particular custom format which can then all be zipped into a version database you can maintain. Now just think of doing all this inside kernel. See it's a bad idea and you know it!. You can use scripts to simplify everything. The search operations within your database to lookup a particular version, like going from version 3 to version 8 would require applying diffs which you can easily do in script. If you are not doing the above things I said, then my bad. You need to tell some more about project then maybe I can help. > > Regards > > On May 27, 2014 11:29 AM, "Pranay Srivastava" <pranjas(a)gmail.com> wrote: >> >> On Tue, May 27, 2014 at 12:49 PM, Nada Saif <nada.saif7(a)gmail.com> wrote: >> > Hi, >> > >> > I want to process a copy operation from file sent from user space - this >> > copying should be inside the kernel.. >> > >> > I read about using filp_open , will this help me ? >> >> I guess you want to open the files inside kernel and then copy from >> one to another. >> >> That's just not good. If you are trying to learn something like >> passing data from user space to >> kernel, you should probably look at sysfs. >> >> Very simple wrappers exist that allow you to create a dummy sysfs >> file(s) where you can have your store and show callbacks do the magic >> you want to learn. >> >> >> > >> > Thanks, >> > Nada >> > >> > _______________________________________________ >> > Kernelnewbies mailing list >> > Kernelnewbies(a)kernelnewbies.org >> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >> > >> >> >> >> -- >> ---P.K.S -- ---P.K.S

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Open and copy a file from the kernel
by Nada Saif May 27, 2014

May 27, 2014

Hi, I want to process a copy operation from file sent from user space - this copying should be inside the kernel.. I read about using filp_open , will this help me ? Thanks, Nada

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Kernel backup
by Nada Saif May 27, 2014

May 27, 2014

Hi, I'm working on a project and might do multiple making - I'm afraid if things go wrong. How to keep a backup of the current kernel? Thanks

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error in oldconfig
by Nada Saif May 27, 2014

May 27, 2014

Hi, Why this appear to me when I use make oldconfig : *** Error during writing of the configuration. make[2]: *** [silentoldconfig] Error 1 make[1]: *** [silentoldconfig] Error 2 mkdir: cannot create directory `arch/x86/syscalls/../include/generated': Permission denied mkdir: cannot create directory `arch/x86/syscalls/../include/generated': Permission denied SYSHDR arch/x86/syscalls/../include/generated/uapi/asm/unistd_32.h /usr/src/linux-3.13.11/arch/x86/syscalls/syscallhdr.sh: line 27: arch/x86/syscalls/../include/generated/uapi/asm/unistd_32.h: No such file or directory make[1]: *** [arch/x86/syscalls/../include/generated/uapi/asm/unistd_32.h] Error 1 make: *** [archheaders] Error 2 Thanks

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Writing kernel in C
by Saurabh Jain May 26, 2014

May 26, 2014

Hello every one ! I want to make a new kernel in C for educational purpose . Any one can help me , from where i should start , any step by step guide to tell what i should do next ?

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Regarding parsing of cifs header
by Ramana Reddy May 26, 2014

May 26, 2014

Hi All, I would like to know how to extract the cifs protocol header from skb buffer in the linux kernel. I want to parse the cifs header and do some stuff based on the content of the header. Help in this regards is highly appreciated. Best Regards, Ramana.

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