On Wed, 18 Jul 2018 02:35:09 +0200 Richard Siegfried <richard_siegfried@systemli.org> wrote:

On 14/07/18 18:04, Athul Joy wrote:

...

Dear friends, I am new to the Linux kernel development. Can anyone help me how to start my journey in order to build my own kernel? For me the debian kernel handbook was a great help especially chapter 4 and section 4.6. (https://kernel-team.pages.debian.net/kernel-handbook/ch-common-tasks.html#s-...)

There also is a book from greg kroah hartmann about building your own kernel that has a good reputation.

And I would recommend to start conservative, which means don't try out too many new/changed kernel options at once. Start with "make oldconfig" or even "make oldconfig". (If you don't know these two start with "make help").

$ make help make: *** No rule to make target 'help'. Stop. d You can always read about new kernel options

and features inside the "make menuconfig" application with pressing "?"

Thanks, -- Richard

-- In modern fantasy (literary or governmental), killing people is the usual solution to the so-called war between good and evil. My books are not conceived in terms of such a war, and offer no simple answers to simplistic questions. ----- Ursula Le Guin

On Wed, 18 Jul 2018 00:41:56 -0400 valdis.kletnieks@vt.edu wrote:

Were you cd'ed into the directory that had the base of the kernel source tree?

I wasn't. I also suggest make help | less Thanks, Dave

2018-07-18 1:39 GMT-03:00 inventsekar <inventsekar@gmail.com>:

Hi Athul... This is my collegemate's writing, ... This will solve all your confusions....

---

The most important quality that you need to inculcate if you want to do any kernel space programming is "Patience" (or persistence if you will). Though it is a good quality for any large scale project, it is a fundamental requirement for kernel programming. It is very easy to see progress and make an impact on userspace projects, but even simple changes in the kernel core will take a lot of time to get accepted, and will often require multiple rewrites. But fear not, as there are plenty of people who have conquered this mountain and it is not something to be worried about.

The starting steps will be:

1) Try to understand how to use git <http://git-scm.com/>. We were (are ?) not taught to use a version control system in our college and it is such a fundamental thing. So start using git for college assignments and get the hang of it.

2) Start writing a lot of C programs and get experienced with pointers, memory allocation, threading. You can start implementing things like Stack, Queue, Trees etc. (whatever you study in datastructures) in a simple, thread-safe way. Do not focus on how you can visualize these datastructures but how you can effectively implement their functionality and thread safety. Use pthreads for threading. Do not use any library (like Glib) for giving you convenient datastructures (like Strings). Implement each of the things on your own. (But when you are writing code for a product, use a standard library always instead of re-inventing the wheel)

Write these C programs on Linux and compile using gcc. In our college days we were using turboc on windows and I hope things have changed. Use a linux distro (fedora <http://fedoraproject.org/>, debian <https://www.debian.org/>, openSUSE <http://en.opensuse.org/>, Gentoo <https://www.gentoo.org/> etc.) exclusively; Do not use Windows (at least for a while) to make yourself aware of the sysadmin, shell-scripting parts of linux, which will come in handy.

3) Grab a (any) book on Operating Systems theory and read it. The dinosaur book <http://en.wikipedia.org/wiki/Operating_System_Concepts> by Silberschatz et. al. is a good start.

4) Without hesitation buy, Robert Love's Linux Kernel Programming <http://www.amazon.com/gp/product/0672329468/> book. It is one of the best beginner material and start reading it parallel to the OS book. This is easier to read than the previous one and more practical. But the previous one adds more value and is more theoretical. Handle (3) and (4) in parallel without blocking on any of the other activities.

I can confirm, this book is GOOOOOOD! Also check LDD3, it's open and online available, you may find some of it's authors in this mailist! :-). http://www.makelinux.net/ldd3/ it's a outdated but it was a very valuable source to me. You can find the examples updated on the internet.

5) After you are done with (1) and (2), and feel sufficiently confident with C and pointers, grab the linux kernel sources from http://git.kernel.org/ and try to build the sources yourself. http:// kernelnewbies.org/KernelBuild should help. Learn how to install and boot with the kernel that you have built.

6.1) Subscribe to Kernel Newbies mailing list http://kernelnewbies.org/ MailingList and read every mail, *even* if you do not understand most of it.

6.2) Watch: https://www.youtube.com/watch?v=LLBrBBImJt4

6.3) Subscribe to http://lwn.net RSS feeds.

After this, you should be able to fix and send any trivial, documentation, staging fixes. Once you have done this and get the hang of the process, you will know how to send patches for any parts of the kernel.

By this time, you would have found your areas of interest in kernel (filesystems, memory management, io scheduler, CPU scheduling etc.). You will then have to dig deeper in those particular areas, by: a) subscribing to the individual mailing lists (such as fs-devel <http://marc.info/?l=linux-fsdevel>, etc.) b) reading about the bug reports for the individual component c) finding the literature that is relevant for your subsystem (The linux memory management book <https://www.kernel.org/doc/gorman/pdf/understand.pdf>Mel Gorman, etc).

Three other non-technical things that I would recommend are:

1) Create a new email address and use that for all your open source activities. That way you do not miss any important updates from your friends.

2) Kernel programming will not give you big money in the short and medium term (at least in India). If your motivation is not excellence in engineering, but becoming popular or rich (it is not wrong btw) then you should focus on some other areas of programming (developing apps, websites, solving user problems, making meaning etc.).

It will often take months (or even years) before you make a significant contribution that is not merely a memory leak or bug fix. Be prepared for that. But since you have age, energy, time (once you get married and/or have kids you will understand) on your side, it is not that difficult.

Many people try kernel programming and then quit because they do not have the patience and perseverance. It may also happen that they have found a more interesting technology at its nascent stage (like Distributed Computing, Artificial Intelligence, Containers, NLP etc.) It is not wrong to quit midway :) Any little time spent on kernel programming will immensely benefit you as a programmer even when you are doing user space programming. This holds good for not just kernel programming but any large-code-base/system programming (like Compilers, glibc, webkit, chrome, firefox etc.)

3) Be more aware of the GSoC community in colleges around you.

All the best.

On Sat 14 Jul, 2018, 9:36 PM Athul Joy, <aathuljjoy333@gmail.com> wrote:

...

Dear friends, I am new to the Linux kernel development. Can anyone help me how to start my journey in order to build my own kernel? _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

-- “If you're going to try, go all the way. Otherwise, don't even start. ..." Charles Bukowski

On Wed, 18 Jul 2018 14:29:41 -0700, Dave Stevens said:

On Wed, 18 Jul 2018 18:19:05 -0300 "Daniel." <danielhilst@gmail.com> wrote:

...

...

Hi Athul... This is my collegemate's writing, ... This will solve all your confusions....

is it the policy on this list to trim?

Only the irrelevant parts, leave the parts that are the context for the reply. So that *should* have been trimmed down to: ---

4) Without hesitation buy, Robert Love's Linux Kernel Programming book. It is one of the best beginner material and start reading it parallel to the OS book. This is easier to read than the previous one and more practical. But the previous one adds more value and is more theoretical. Handle (3) and (4) in parallel without blocking on any of the other activities.

I can confirm, this book is GOOOOOOD! Also check LDD3,  it's open and online available, you may find some of it's authors in this mailist! :-). http:// www.makelinux.net/ldd3/ it's a outdated but it was a very valuable source to me. You can find the examples updated on the internet. --- Also, MUAs the encourage top-posting and allowing quoting without a '> ' or other indicator of quoting depth are a pox on email.

On Wed, 18 Jul 2018 22:16:07 -0300, "Daniel." said:

Sorry. Do I did something bad? I wasn't intended to.. I didn't think that trimming was a bad idea, I just want to reinforce the book suggestion ... Sorry

It's OK.. just remember to trim out the non-important stuff next time. :)

On Wed, Jul 18, 2018 at 10:09:28AM +0530, inventsekar wrote:

Hi Athul... This is my collegemate's writing, ... This will solve all your confusions....

---

The most important quality that you need to inculcate if you want to do any kernel space programming is "Patience" (or persistence if you will).

Very true!! Patience.. :)

Though it is a good quality for any large scale project, it is a fundamental requirement for kernel programming. It is very easy to see progress and make an impact on userspace projects, but even simple changes in the kernel core will take a lot of time to get accepted, and will often require multiple rewrites. But fear not, as there are plenty of people who have conquered this mountain and it is not something to be worried about.

The starting steps will be:

1) Try to understand how to use git <http://git-scm.com/>. We were (are ?) not taught to use a version control system in our college and it is such a fundamental thing. So start using git for college assignments and get the hang of it.

You'll learn eventually... For instance, when you base your work on old an tree and send cleanup to Greg. And Greg patiently explains "the patch doesn't apply, please rebase :( " Then you get know how to do an interactive rebase and more preferably base your work on -next(https://www.kernel.org/doc/man-pages/linux-next.html)

2) Start writing a lot of C programs and get experienced with pointers, memory allocation, threading. You can start implementing things like Stack, Queue, Trees etc. (whatever you study in datastructures) in a simple, thread-safe way. Do not focus on how you can visualize these datastructures but how you can effectively implement their functionality and thread safety. Use pthreads for threading. Do not use any library (like Glib) for giving you convenient datastructures (like Strings). Implement each of the things on your own. (But when you are writing code for a product, use a standard library always instead of re-inventing the wheel)

Write these C programs on Linux and compile using gcc. In our college days we were using turboc on windows and I hope things have changed. Use a linux distro (fedora <http://fedoraproject.org/>, debian <https://www.debian.org/> , openSUSE <http://en.opensuse.org/>, Gentoo <https://www.gentoo.org/> etc.) exclusively; Do not use Windows (at least for a while) to make yourself aware of the sysadmin, shell-scripting parts of linux, which will come in handy.

Now, this part of section is really important and somehow if you think you really learnt C well in the course offered at University. Then please take a look at implicit conversions: https://en.cppreference.com/w/c/language/conversion assert(sizeof(int) > -1); That should be enough to shatter your confidence. I learnt various concepts by reading ISO-C11 draft: https://port70.net/~nsz/c/c11/n1570.html You can also grab a pdf copy and refer when in doubt.

3) Grab a (any) book on Operating Systems theory and read it. The dinosaur book <http://en.wikipedia.org/wiki/Operating_System_Concepts> by Silberschatz et. al. is a good start.

If you're a computer undergrad, then you can certainly skip and move to Love. Otherwise if you're an electronics student like me then you should read this atleast few chapters.

4) Without hesitation buy, Robert Love's Linux Kernel Programming <http://www.amazon.com/gp/product/0672329468/> book. It is one of the best beginner material and start reading it parallel to the OS book. This is easier to read than the previous one and more practical. But the previous one adds more value and is more theoretical. Handle (3) and (4) in parallel without blocking on any of the other activities.

Highly recommended!

5) After you are done with (1) and (2), and feel sufficiently confident with C and pointers, grab the linux kernel sources from http://git.kernel.org/ and try to build the sources yourself. http://kernelnewbies.org/KernelBuild should help. Learn how to install and boot with the kernel that you have built.

6.1) Subscribe to Kernel Newbies mailing list http://kernelnewbies.org/MailingList and read every mail, *even* if you do not understand most of it.

Indeed.

6.2) Watch: https://www.youtube.com/watch?v=LLBrBBImJt4

That's how I started :) Thanks Greg!

6.3) Subscribe to http://lwn.net RSS feeds.

Another great resource. Thanks Jonathan!

After this, you should be able to fix and send any trivial, documentation, staging fixes. Once you have done this and get the hang of the process, you will know how to send patches for any parts of the kernel.

By this time, you would have found your areas of interest in kernel (filesystems, memory management, io scheduler, CPU scheduling etc.). You will then have to dig deeper in those particular areas, by: a) subscribing to the individual mailing lists (such as fs-devel <http://marc.info/?l=linux-fsdevel>, etc.) b) reading about the bug reports for the individual component c) finding the literature that is relevant for your subsystem (The linux memory management book <https://www.kernel.org/doc/gorman/pdf/understand.pdf>Mel Gorman, etc).

Three other non-technical things that I would recommend are:

1) Create a new email address and use that for all your open source activities. That way you do not miss any important updates from your friends.

2) Kernel programming will not give you big money in the short and medium term (at least in India). If your motivation is not excellence in engineering, but becoming popular or rich (it is not wrong btw) then you should focus on some other areas of programming (developing apps, websites, solving user problems, making meaning etc.).

It will often take months (or even years) before you make a significant contribution that is not merely a memory leak or bug fix. Be prepared for that. But since you have age, energy, time (once you get married and/or have kids you will understand) on your side, it is not that difficult.

Many people try kernel programming and then quit because they do not have the patience and perseverance.

I know few students especially Indians. Sad :(

It may also happen that they have found a more interesting technology at its nascent stage (like Distributed Computing, Artificial Intelligence, Containers, NLP etc.) It is not wrong to quit midway :) Any little time spent on kernel programming will immensely benefit you as a programmer even when you are doing user space programming. This holds good for not just kernel programming but any large-code-base/system programming (like Compilers, glibc, webkit, chrome, firefox etc.)

3) Be more aware of the GSoC community in colleges around you.

I can certainly help you on this _any_ time. Background: I am an undergraduate student(3rd year), started nearly one year ago and have contributed significantly in kernel. Currently working on Google Summer of Code project: https://summerofcode.withgoogle.com/projects/#6691473790074880 And probably I will be pushing nearly 1.3k lines of code next week for the mainline, and more if we need advanced features for the sensor. https://lore.kernel.org/lkml/20170726143215.GB28875@nazgul.tnic/ You see how things have changed in *exactly* 1 year ;) Another great source is Linux Foundation's Youtube channel: If you want know what I'm working on, I mean what IIO actually is then take a look https://www.youtube.com/watch?v=lBU77crSvcI But Documentation is more important! Lastly, thanks inventsekar for such a lucid explaination :) Goodluck & Best wishes! -- Himanshu Jha Undergraduate Student Department of Electronics & Communication Guru Tegh Bahadur Institute of Technology

And the K&R book on C does successive trimming of an strcpy(), and finishes with

void strcpy(char *a, *b) { while (*a++ = *b++); }

The thing that's actually used a lot in the Linux kernel that gives a lot of C newcomers heartburn is the widespread use of structures of function pointers.. For example, this from include/linux/fs.h:

struct lock_manager_operations { int (*lm_compare_owner)(struct file_lock *, struct file_lock *); unsigned long (*lm_owner_key)(struct file_lock *); fl_owner_t (*lm_get_owner)(fl_owner_t); void (*lm_put_owner)(fl_owner_t); void (*lm_notify)(struct file_lock *); /* unblock callback */ int (*lm_grant)(struct file_lock *, int); bool (*lm_break)(struct file_lock *); int (*lm_change)(struct file_lock *, int, struct list_head *); void (*lm_setup)(struct file_lock *, void **); };

That's the structure definition. Novice challenge: Find one or more places where this structure is initialized, and understand how and why that works.

That kind of stuff is not taught in C programming. An answer can be very educating.

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