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Compare two diiferent kernel version
by vish chopra April 22, 2016

April 22, 2016

Hi, i'm new to driver development. how can i compare two different kernel version to see changes and also help me with how i can make changes to kernel and notice its effect. please help with this. thank you Regards, Vishal Chopra +91-7837583269

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single, comprehensive kernel data types document?
by Robert P. J. Day April 22, 2016

April 22, 2016

is there a single, decent online doc that explains the proper data types (int16_t, int32_t and so on) to use in kernel code? including the relationship with types to be used in code to be exported to user space (include/uapi/linux/types.h)? rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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Microsoft wireless usb mouse frequently fails to detect in ubuntu 15.10/16.04
by rootsr April 21, 2016

April 21, 2016

Hello all, I am using ubuntu 16.04 (upgraded yesterday from 15.10) on Dell inspiron 15 3000 series (core i7). While using Microsoft wireless mouse, it fails to detect most of the time. The issue is not there when I use the same mouse in Windows / other linux distro / TV / PS4 etc. Here is the Kernel log for the failure. ---------------------------------------------------- [ 74.186391] usb 1-1.3: new full-speed USB device number 7 using ehci-pci [ 74.258396] usb 1-1.3: device descriptor read/64, error -32 [ 74.434356] usb 1-1.3: device descriptor read/64, error -32 [ 74.610315] usb 1-1.3: new full-speed USB device number 8 using ehci-pci [ 74.682322] usb 1-1.3: device descriptor read/64, error -32 [ 74.858322] usb 1-1.3: device descriptor read/64, error -32 [ 75.034320] usb 1-1.3: new full-speed USB device number 9 using ehci-pci [ 75.446330] usb 1-1.3: device not accepting address 9, error -32 [ 75.518334] usb 1-1.3: new full-speed USB device number 10 using ehci-pci [ 75.926331] usb 1-1.3: device not accepting address 10, error -32 [ 75.926400] usb 1-1-port3: unable to enumerate USB device [ 93.835769] usb 1-1.3: new full-speed USB device number 11 using ehci-pci [ 93.908028] usb 1-1.3: device descriptor read/64, error -32 [ 94.084569] usb 1-1.3: device descriptor read/64, error -32 [ 94.261110] usb 1-1.3: new full-speed USB device number 12 using ehci-pci [ 94.333337] usb 1-1.3: device descriptor read/64, error -32 [ 94.509893] usb 1-1.3: device descriptor read/64, error -32 [ 94.686342] usb 1-1.3: new full-speed USB device number 13 using ehci-pci [ 95.095548] usb 1-1.3: device not accepting address 13, error -32 [ 95.167686] usb 1-1.3: new full-speed USB device number 14 using ehci-pci [ 95.576740] usb 1-1.3: device not accepting address 14, error -32 [ 95.576848] usb 1-1-port3: unable to enumerate USB device ----------------------------------------------------------------- After multiple connect/disconnect of the wireless dongle, it finally detects. Here is the detection log. ------------------------------------------------------ [ 110.221269] usb 1-1.3: new full-speed USB device number 15 using ehci-pci [ 110.319427] usb 1-1.3: New USB device found, idVendor=045e, idProduct=0745 [ 110.319431] usb 1-1.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0 [ 110.319433] usb 1-1.3: Product: Microsoft® 2.4GHz Transceiver v8.0 [ 110.319435] usb 1-1.3: Manufacturer: Microsoft [ 110.361146] usbcore: registered new interface driver usbhid [ 110.361151] usbhid: USB HID core driver [ 110.380274] input: Microsoft Microsoft® 2.4GHz Transceiver v8.0 as /devices/pci0000:00/0000:00:1d.0/usb1/1-1/1-1.3/1-1.3:1.0/0003:045E:0745.0002/input/input14 [ 110.433886] hid-generic 0003:045E:0745.0002: input,hidraw1: USB HID v1.11 Keyboard [Microsoft Microsoft® 2.4GHz Transceiver v8.0] on usb-0000:00:1d.0-1.3/input0 [ 110.434274] input: Microsoft Microsoft® 2.4GHz Transceiver v8.0 as /devices/pci0000:00/0000:00:1d.0/usb1/1-1/1-1.3/1-1.3:1.1/0003:045E:0745.0003/input/input15 [ 110.489634] hid-generic 0003:045E:0745.0003: input,hidraw2: USB HID v1.11 Mouse [Microsoft Microsoft® 2.4GHz Transceiver v8.0] on usb-0000:00:1d.0-1.3/input1 [ 110.500335] input: Microsoft Microsoft® 2.4GHz Transceiver v8.0 as /devices/pci0000:00/0000:00:1d.0/usb1/1-1/1-1.3/1-1.3:1.2/0003:045E:0745.0004/input/input16 [ 110.553640] hid-generic 0003:045E:0745.0004: input,hiddev0,hidraw3: USB HID v1.11 Device [Microsoft Microsoft® 2.4GHz Transceiver v8.0] on usb-0000:00:1d.0-1.3/input2 ------------------------------------------------------------- I am not sure of this weird behaviour. Is there some issue with ubuntu kernel for input device? or is there a problem with microsoft mouse driver? regards -Shekhar

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filesystem: Details of mount_ref_count in struct mount
by manty kuma April 21, 2016

April 21, 2016

Hi, I am looking into an issue where unmounting /data is failing. I receive -EBUSY as the sum off all mnt_count(mnt->mnt_pcp->mnt_count) of all cpu's > 2 (the value in my case is 3). I am debugging from linux crash dump. Is there any way that I can know the owners/responsible drivers that have incereased this refcount and left it like that without decrementing? Kindly share any helpful information. Thank you. Best Regards, Manty

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Serial driver in-band control message
by Ramon Fried April 20, 2016

April 20, 2016

Hi. I'm developing a driver for a rather weird serial controller hardware. The HW allows the host to put it in low power state. The command for entering low power is an ASCII message sent in-band. Till now, I used a user-space application to open the TTY port and send the command through it. This is not acceptable solution as the device needs to be put in low power mode by its driver in the kernel. I didn't find any example or reference on how to write characters to the serial device, or how to open and write to the TTY device from the kernel space. I guess this is discouraged. Do I have any other options to do so from the kernel space ? Warm regards, Ramon

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Kernel symbol naming rules
by Wenda Ni April 20, 2016

April 20, 2016

Hi all, When doing insmod, we find our function named "rxe_mem_alloc" is renamed as "rxe_mem_alloc.isra.2" in kernel symbol table @ /proc/kallsyms I am curious why the kernel appends ".isra.2" to the original function. Why this happens? What is this for? Thank you for sharing your thoughts. Cheers, Wenda Ni, Ph.D.

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SimpleFlow: simple information-flow-based security module for Linux
by W. Michael Petullo April 20, 2016

April 20, 2016

Some colleagues and I have been working on SimpleFlow, a simple information-flow-based security module for Linux. Our goal is to investigate the feasibility of implementing such a security model on top of LSM and to produce a prototype which is useful for education and certain computer-security competitions. We have adopted a very simple view of information flow (we do not claim to approach HiStar, etc.). The system administrator designates some filesystem objects as "confidential" and some programs as "trusted" (both stored using extended attributes). Any process not loaded from a trusted program will become "tainted" upon reading a confidential object. The kernel transfers this taint status from process to process as a result of inter-process communication (i.e., an untainted process reads from a tainted process over an IPC channel). If a tainted process writes to the network, the packet gets its RFC 3514 evil bit set. All of this seems to sort of work. We do our best to handle the forms of IPC including shared memory. The grand multi-source transformer X11 poses a problem; we presently set X11 as trusted, but we have plans to deal with X11 in X11 as SELinux has attempted. We tried to avoid making changes to the core kernel. One such change is an additional LSM call in fs/pipe.c. The other is a #define for the RFC 3514 evil bit. For practical reasons, we have so far targeted 3.10.0. We intend to eventually port to a kernel that supports LSM stacking. We are presently preparing a paper that describes some of the things we have done with SimpleFlow, and we are interested in hearing any feedback on our approach or code. We attached a patch which represents our work so far. We realize this is niche work, and perhaps SimpleFlow itself does not belong in the mainline kernel. However, we would be keen to discuss the concept even with people who are mildly interested. Thank you, -- Mike :wq

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of device trees and powerpcs and low memory
by Robert P. J. Day April 18, 2016

April 18, 2016

a question about device trees for those (probably numerous) members of this list that know more about them than i do. recently, was given the following patch to be applied to a device tree source file for a fairly elderly (MPC83xx-based) powerpc platform that has 1G of RAM: memory { device_type = "memory"; linux,phandle = <300>; - reg = <0x00000000 0x40000000>; + reg = <0x00000000 0x20000000>; }; i was puzzled by the change that now seemed to define 512M of RAM instead of the full 1G. the explanation i was given is that that is how one defines where kernel low memory ends, thereby leaving the remaining 512M for high memory in kernel space. that's the first i ever heard of that. is it true? and if it is, where in the kernel source code can i see that information being processed and low memory being established based on reading that node from the DTB? in any event, i'd never heard this before -- if i was going to define low memory on a powerpc, i would think the proper way is to use this snippet from arch/powerpc/Kconfig: menu "Advanced setup" depends on PPC32 config ADVANCED_OPTIONS bool "Prompt for advanced kernel configuration options" help This option will enable prompting for a variety of advanced kernel configuration options. These options can cause the kernel to not work if they are set incorrectly, but can be used to optimize certain aspects of kernel memory management. Unless you know what you are doing, say N here. comment "Default settings for advanced configuration options are used" depends on !ADVANCED_OPTIONS config LOWMEM_SIZE_BOOL bool "Set maximum low memory" depends on ADVANCED_OPTIONS help This option allows you to set the maximum amount of memory which will be used as "low memory", that is, memory which the kernel can access directly, without having to set up a kernel virtual mapping. This can be useful in optimizing the layout of kernel virtual memory. Say N here unless you know what you are doing. config LOWMEM_SIZE hex "Maximum low memory size (in bytes)" if LOWMEM_SIZE_BOOL default "0x30000000" thoughts? i thought i understood device trees reasonably well, but i had never heard of this alleged configuration. rday -- ======================================================================== Robert P. J. Day Ottawa, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ========================================================================

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rmap-test
by Jan-Simon Möller April 18, 2016

April 18, 2016

does anyone know under what license https://www.kernel.org/pub/linux/kernel/people/mbligh/tools/rmap-test.c is released? As it's on kernel.org one may assume its GPLv2, but it is written nowhere ... -- -- Jan-Simon

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fork
by Nitin Varyani April 18, 2016

April 18, 2016

Linux kernel development by Robert Love describes the fork process as fork() -> clone() -> do_fork() -> copy_process() I am unable to find the clone() system call in linux 3.13. Can someone explain the proper flow of fork() system call initiated by the user? Where can I find the libc implementation for fork()? I want the code of all the functions involved in fork.

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