Re: Where does the linux kernel put local variables
Hi, Dave If you look at the linker script file for the kernel http://lxr.free-electrons.com/source/arch/arm/kernel/vmlinux.lds.S#L244 , you'll see that INIT_TASK_DATA (which includes the kernel stack) is between _data and _edata. This is the stack used for kernel booting and then taken over by the init task. Thanks for your advice ,after read http://lxr.free-electrons.com/source/arch/arm/kernel/head-common.S#L122, I'v got my answer. -- Rock Lee ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Newbie help
Rishabh Chakrabarti bassdevelo...@gmail.com writes: Hello all, Where can I search the archives and other resources for answering the following questions: 1. How to dive into the code? i.e. entry points Wherever your interest is. There are no strict rules. If you don't know ahere your interest is, then you should ask yourself why you are interested in the Linux kernel in the first place. Out of your areas of interest, try to find a part of the kernel which is well maintained and have (semi-)sufficient reviewer resources, because you will need that as a newbie. You may use the Status field in MAINTAINERS as an initial guide, but only recent mailing list archives will tell for sure. Look for comments and feedback on patches. 2. What are the pre-requisites for understanding the whole code? I don't think that is possible... You should understand the part you want to modify. You'll need some knowledge of C, and an ability to learn. The latter is most important. 3. Best books and resource material I see that Documentation/ and LDD3 is already mentioned. Other than that: The source code is there, and is much more readable and commented than most other C projects. Use it. Reading code, and trying to figure out how it works and why it was written like that, is a great way to learn. Use the git commit messsages to help understanding if there is something which isn't obvious (there will be, of course). Every single commit is justified and explained and in detail in git. And you will have to do the same, so you should familiarize yourself with those messages in any case. Bjørn ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Where does the linux kernel put local variables
Hi Rock, On Mon, Aug 3, 2015 at 7:28 PM, Rock Lee rocklee_...@outlook.com wrote: Hi, all: I print a local variable address in start_kernel(), and I realize this address is between __data_start and _edata. In my opinion, local variables should be located in stack, why is this local variable located in data section? BTW, I use a arm11 board with linux-2.6.28. If you look at the linker script file for the kernel http://lxr.free-electrons.com/source/arch/arm/kernel/vmlinux.lds.S#L244 , you'll see that INIT_TASK_DATA (which includes the kernel stack) is between _data and _edata. This is the stack used for kernel booting and then taken over by the init task. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Newbie help
If your goals tend towards * creating something new or * having a clearer look onto the interfaces between modules/layers get a copy of Linux Device Drivers (abbreviated LDD3 here), which is available online. The example code from that book is definitey outdated and will not compile as is since it is based on 2.6.10(?), but finding the errors is a good exercise too. Since the book is widely known, you will also find several repos, which brought the code up to some more recent kernel version. I guess we are all more or less eagerly waiting for LDD4, which should be released in end of November. Regards, Moritz -Ursprüngliche Nachricht- Von: kernelnewbies-boun...@kernelnewbies.org [mailto:kernelnewbies- boun...@kernelnewbies.org] Im Auftrag von Rishabh Chakrabarti Gesendet: Montag, 3. August 2015 16:38 An: kernelnewbies@kernelnewbies.org Betreff: Newbie help Hello all, Where can I search the archives and other resources for answering the following questions: 1. How to dive into the code? i.e. entry points 2. What are the pre- requisites for understanding the whole code? 3. Best books and resource material Kindly keep a lay person in mind while answering. Please direct me to the right place and the rest i'll DIY. Thank you. Regards, Rishabh ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Newbie help
On Tue, 4 Aug 2015 at 13:51 Bjørn Mork bj...@mork.no wrote:
Rishabh Chakrabarti bassdevelo...@gmail.com writes:
Hello all,
Where can I search the archives and other resources for answering the
following questions:
1. How to dive into the code? i.e. entry points
2. What are the pre-requisites for understanding the whole code?
3. Best books and resource material
You can refer this answer from Stackoverflow:
http://unix.stackexchange.com/questions/1003/linux-kernel-good-beginners-tutorial/177539#177539
It basically provides a bird's eye view of the Linux kernel along with it's
broader subsystems with links to related books/resources. I am reproducing
parts of the answer below:
**TODO** +editPic: Linux Kernel Developer - (Ring Layer 0) +addSection:
Kernel Virtualization Engine KERN_WARN_CODING_STYLE: Do not Loop unless you
absolutely have to.
Recommended Books for the Uninitialized void *i: Men do not understand
books until they have a certain amount of life, or at any rate no man
understands a deep book, until he has seen and lived at least part of its
contents. –Ezra Pound. A journey of a thousand code-miles must begin with
a single step. If you are in confusion about which of the following books
to start with, don't worry, pick any one of your choice. Not all those who
wander are lost. As all roads ultimately connect to highway, you will
explore new things in your kernel journey as the pages progress without
meeting any dead ends, and ultimately connect to the code-set. Read with
alert mind and remember: Code is not Literature.
What is left is not a thing or an emotion or an image or a mental picture
or a memory or even an idea. It is a function. A process of some sort. An
aspect of Life that could be described as a function of something larger.
And therefore, it appears that it is not really separate from that
something else. Like the function of a knife - cutting something - is not,
in fact, separate from the knife itself. The function may or may not be in
use at the moment, but it is potentially NEVER separate.
Solovay Strassen Derandomized Algorithm for Primality Test: Read not to
contradict and confute; nor to believe and take for granted; nor to find
talk and discourse; but to weigh and consider. Some books are to be tasted,
others to be swallowed, and some few to be chewed and digested: that is,
some books are to be read only in parts, others to be read, but not
curiously, and some few to be read wholly, and with diligence and
attention.
---
Core Linux ( 5 - 1 - 3 - 2 - 7 - 4 - 6 ) “Nature has neither kernel
nor shell; she is everything at once” -- Johann Wolfgang von Goethe Reader
should be well versed with operating system concepts; a fair understanding
of long running processes and its differences with processes with short
bursts of execution; fault tolerance while meeting soft and hard real time
constraints. While reading, it's important to understand and n/ack the
design choices made by the linux kernel source in the core subsystems.
Threads [and] signals [are] a platform-dependent trail of misery, despair,
horror and madness (~Anthony Baxte). That being said you should be a
self-evaluating C expert, before diving into the kernel. You should also
have good experience with Linked Lists, Stacks, Queues, Red Blacks Trees,
Hash Functions, et al. volatile int i; int main(void) { int c; for (i=0;
i3; i++) { c = ii; printf(%d\n, c); /* find c */ } return 0; } The
beauty and art of the Linux Kernel source lies in the deliberate code
obfuscation used along. This is often necessitated as to convey the
computational meaning involving two or more operations in a clean and
elegant way. This is especially true when writing code for multi-core
architecture.
-
Device Drivers ( 1 - 2 - 4 - 3 - 8 - ... ) Music does not carry you
along. You have to carry it along strictly by your ability to really just
focus on that little small kernel of emotion or story. -- Debbie Harry
Your task is basically to establish a high speed communication interface
between the hardware device and the software kernel. You should read the
hardware reference datasheet/manual to understand the behavior of the
device and it's control and data states and provided physical channels.
Knowledge of Assembly for your particular architecture and a fair knowledge
of VLSI Hardware Description Languages like VHDL or Verilog will help you
in the long run. Intel® 64 and IA-32 Architectures Software Developer’s
Manual ARM Architecture Reference Manual ARM System Developer's Guide Q:
But, why do I have to read the hardware specs? A: Because, There is a
chasm of carbon and silicon the software can't bridge - Rahul Sonnad
However, the above doesn't poses a problem for Computational Algorithms
(Driver code - bottom-half processing), as it can
Requirement to customize Linux Network Interface naming Convention
Hi, We have a requirement to tweak the Linux Network Interface Naming conventions so that, it can support names of interfaces with / character. For example, ip tuntap add dev fe/1/1 mode tap With iproute2 it simply shows error as INVALID Argument. What are the changes we supposed to do inside Kernel and iproute2 package? Thanks Akash Bhatnagar ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: debugging kernel module __init function?
On Tue, 04 Aug 2015 12:23:18 -0700, Nicholas Murphy said: How do I debug the __init function (that is called on module load)? Is your .init function actually doing so much odd stuff that a few carefully placed printk() calls aren't sufficient? pgpAYpKItGKDg.pgp Description: PGP signature ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
debugging kernel module __init function?
I can’t for the life of me figure out how to set a breakpoint on a kernel module’s __init function. Everything I’ve read talks about using add-symbol-file with the values for .text, .bss, and .data after the module is loaded, a la: https://www.linux.com/learn/linux-training/33991-the-kernel-newbie-corner-kernel-and-module-debugging-with-gdb How do I debug the __init function (that is called on module load)? Thanks, Nick ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: debugging kernel module __init function?
In this case, no. But I’m curious if there’s a way to pull this off, or if it’s fundamentally impossible? Thanks, Nick On Aug 4, 2015, at 1:07 PM, valdis.kletni...@vt.edu wrote: On Tue, 04 Aug 2015 12:23:18 -0700, Nicholas Murphy said: How do I debug the __init function (that is called on module load)? Is your .init function actually doing so much odd stuff that a few carefully placed printk() calls aren't sufficient? ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: debugging kernel module __init function?
In this case, no. But I’m curious if there’s a way to pull this off, or if it’s fundamentally impossible? What happens 'after' __init gets called ? After boot, the kernel frees up a special section. All functions marked with __init and data structures marked with __initdata are dropped after boot is complete. Similarly 'modules' DISCARD this memory after initialization. So what is the workaround ? Write the module_init function without the __init attribute. ( They never read the documentation : /Documentation/DocBook/kernel-hacking.tmpl , I never used to read the documentation either :) ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
