Re: Excited for Xen Project in Outreachy

Re: Excited for Xen Project in Outreachy

[Lars Kurth]

Hi Kanika,

I CC'ed two lists and the mentors of projects. Thank you for your interest in the project.

> I seek guidance in choosing the suitable sub-project in Xen according to my skill set.
We have two sets of projects on https://www.outreachy.org/communities/cfp/xen-project/
* 3 around Unikraft (mentor: Simon the technical side, I on the process/people side). We are both based in UTC+1 - IRC is #unikraft
* 1 for Xen on ARM (mentors: Stefano & Edgar). Stefano is in UTC-8, Edgar is UTC-7 or 6 (can't quite recall) - IRC is #xendevel

> I wish to begin my contribution as soon as possible. I request you to connect me to the mentors in case IRC is not the best way to get in touch with them.
Simon is unfortunately not around this week but will be next week.
Stefano and Edgar, are around I believe

For practical reasons:
* Please sign up to the minios-devel@lists.xenproject.org or xen-devel@lists.xenproject.org (as appropriate)
   (see http://lists.xenproject.org for instructions: if you use the "subscribe subject pattern" make sure you send the mail to minios-devel-request@lists.xenproject.org, ...) 
* Please double check time requirements: This is because in the past there frequently were issues with Outreachy and University course time requirements in particular with Universities from India. I believe that there will be extra checks later in the application process, which may require letters from your University. We had one case, where an applicant did a small project, but we were not allowed to accept her due to time requirements.
* Let us know timezone you are in and when you can hang out on IRC 
* Your registered IRC nickname (please register your nick - see https://www.xenproject.org/help/irc.html under Netiquette)

Note that my IRC nick is lars_kurth, Simon's is skuezer, Stefano's is sstabellini, and I am afraid I can't remember Edgar's

If you are interested in Unikraft
* Build the hello world unikraft app: see https://wiki.xenproject.org/wiki/Category:Unikraft & http://unikraft.neclab.eu/ and report back
* Familiarize yourself with the workflow at https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches#How_to_Generate.2C_and_Submit_a_Xen_Project_Patch_to_MiniOS_and_Unikraft (please read the entire document) 

For the ARM project, I will let Stefano and Edgar decide.

Regards
Lars


From: KANIKA SAINI <kanika16047@iiitd.ac.in>
Date: Wednesday, 14 February 2018 at 17:25
To: Lars Kurth <lars.kurth@citrix.com>
Subject: Excited for Xen Project in Outreachy

Greetings, Lars.

I'm Kanika Saini and I'm super excited to begin contributing to Xen!

I seek guidance in choosing the suitable sub-project in Xen according to my skill set. I'm currently pursuing a course in Operating Systems and hence, have been gaining knowledge in kernel programming by short assignments like the implementation of a system call. I'm familiar with assembly programming in MIPS, ARM and x86 as well. 
About high-level programming - I have experience with Java and have used it for desktop applications and parallel programming.

There are certain projects listed on the project page and I'm looking for mentors' suggestion on what could be the best for both me and Xen. I have introduced myself on the #unikraft channel and I'm expecting a reply from the community.

I wish to begin my contribution as soon as possible. I request you to connect me to the mentors in case IRC is not the best way to get in touch with them.

Thank you!


-- 
Yours sincerely,
Kanika Saini
CSE, IIITD Class of 2020



‌

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Re: Excited for Xen Project in Outreachy

[Stefano Stabellini]

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Hello Kanika,

Thanks for your interest in Xen Project!
One reply inline below.

On Wed, 14 Feb 2018, Lars Kurth wrote:
> Hi Kanika,
> 
> I CC'ed two lists and the mentors of projects. Thank you for your interest in the project.
> 
> > I seek guidance in choosing the suitable sub-project in Xen according to my skill set.
> We have two sets of projects on https://www.outreachy.org/communities/cfp/xen-project/
> * 3 around Unikraft (mentor: Simon the technical side, I on the process/people side). We are both based in UTC+1 - IRC is #unikraft
> * 1 for Xen on ARM (mentors: Stefano & Edgar). Stefano is in UTC-8, Edgar is UTC-7 or 6 (can't quite recall) - IRC is #xendevel
> 
> > I wish to begin my contribution as soon as possible. I request you to connect me to the mentors in case IRC is not the best way to get in touch with them.
> Simon is unfortunately not around this week but will be next week.
> Stefano and Edgar, are around I believe
> 
> For practical reasons:
> * Please sign up to the minios-devel@lists.xenproject.org or xen-devel@lists.xenproject.org (as appropriate)
>    (see http://lists.xenproject.org for instructions: if you use the "subscribe subject pattern" make sure you send the mail to minios-devel-request@lists.xenproject.org, ...) 
> * Please double check time requirements: This is because in the past there frequently were issues with Outreachy and University course time requirements in particular with Universities from India. I believe that there will be extra checks later in the application process, which may require letters from your University. We had one case, where an applicant did a small project, but we were not allowed to accept her due to time requirements.
> * Let us know timezone you are in and when you can hang out on IRC 
> * Your registered IRC nickname (please register your nick - see https://www.xenproject.org/help/irc.html under Netiquette)
> 
> Note that my IRC nick is lars_kurth, Simon's is skuezer, Stefano's is sstabellini, and I am afraid I can't remember Edgar's
> 
> If you are interested in Unikraft
> * Build the hello world unikraft app: see https://wiki.xenproject.org/wiki/Category:Unikraft & http://unikraft.neclab.eu/ and report back
> * Familiarize yourself with the workflow at https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches#How_to_Generate.2C_and_Submit_a_Xen_Project_Patch_to_MiniOS_and_Unikraft (please read the entire document) 
> 
> For the ARM project, I will let Stefano and Edgar decide.

For the ARM project, it would be good to get familiar with Xen on ARM,
to learn how to build it:

https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions#Building_Xen_on_ARM

and use QEMU to emulate an ARM board to run Xen on it, for testing and
development:

https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions/qemu-system-aarch64

Feel free to ask any questions!


> Regards
> Lars
> 
> 
> From: KANIKA SAINI <kanika16047@iiitd.ac.in>
> Date: Wednesday, 14 February 2018 at 17:25
> To: Lars Kurth <lars.kurth@citrix.com>
> Subject: Excited for Xen Project in Outreachy
> 
> Greetings, Lars.
> 
> I'm Kanika Saini and I'm super excited to begin contributing to Xen!
> 
> I seek guidance in choosing the suitable sub-project in Xen according to my skill set. I'm currently pursuing a course in Operating Systems and hence, have been gaining knowledge in kernel programming by short assignments like the implementation of a system call. I'm familiar with assembly programming in MIPS, ARM and x86 as well. 
> About high-level programming - I have experience with Java and have used it for desktop applications and parallel programming.
> 
> There are certain projects listed on the project page and I'm looking for mentors' suggestion on what could be the best for both me and Xen. I have introduced myself on the #unikraft channel and I'm expecting a reply from the community.
> 
> I wish to begin my contribution as soon as possible. I request you to connect me to the mentors in case IRC is not the best way to get in touch with them.
> 
> Thank you!
> 
> 
> -- 
> Yours sincerely,
> Kanika Saini
> CSE, IIITD Class of 2020
> 
> 
> 
> ‌
> 
> 

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Re: Excited for Xen Project in Outreachy

[KANIKA SAINI]

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Hi Lars,

I'm already on #unikraft with the registered username - kanik.
My timezone is UTC+5:30h and I can be available for a chat at any time of
the day post noon usually.

I have subscribed to the mailing lists and gone through the documentation
at
https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches#How_to_Generate.2C_and_Submit_a_Xen_Project_Patch_to_MiniOS_and_Unikraft
thoroughly.

Also, I have completed the first task you suggested, that is, to build the
hello world app. Below is the screenshot of it running on my system.
[image: Inline image 1]

Keeping my skill set and experience in mind, I'm mostly interested in and
suitable for projects -  Enhanced Profiling and Tracing Support for
Unikraft and High-level Language Support with Unikraft.

I was having my exams this week and hence, couldn't start with much force
but now, I'm all pumped up to make significant contributions. :D
If there are not many people already working on it, please, let me know the
next steps to begin contributing.

Thank you!




‌

On Thu, Feb 15, 2018 at 4:15 AM, Stefano Stabellini <sstabellini@kernel.org>
wrote:

> Hello Kanika,
>
> Thanks for your interest in Xen Project!
> One reply inline below.
>
> On Wed, 14 Feb 2018, Lars Kurth wrote:
> > Hi Kanika,
> >
> > I CC'ed two lists and the mentors of projects. Thank you for your
> interest in the project.
> >
> > > I seek guidance in choosing the suitable sub-project in Xen according
> to my skill set.
> > We have two sets of projects on https://www.outreachy.org/
> communities/cfp/xen-project/
> > * 3 around Unikraft (mentor: Simon the technical side, I on the
> process/people side). We are both based in UTC+1 - IRC is #unikraft
> > * 1 for Xen on ARM (mentors: Stefano & Edgar). Stefano is in UTC-8,
> Edgar is UTC-7 or 6 (can't quite recall) - IRC is #xendevel
> >
> > > I wish to begin my contribution as soon as possible. I request you to
> connect me to the mentors in case IRC is not the best way to get in touch
> with them.
> > Simon is unfortunately not around this week but will be next week.
> > Stefano and Edgar, are around I believe
> >
> > For practical reasons:
> > * Please sign up to the minios-devel@lists.xenproject.org or
> xen-devel@lists.xenproject.org (as appropriate)
> >    (see http://lists.xenproject.org for instructions: if you use the
> "subscribe subject pattern" make sure you send the mail to
> minios-devel-request@lists.xenproject.org, ...)
> > * Please double check time requirements: This is because in the past
> there frequently were issues with Outreachy and University course time
> requirements in particular with Universities from India. I believe that
> there will be extra checks later in the application process, which may
> require letters from your University. We had one case, where an applicant
> did a small project, but we were not allowed to accept her due to time
> requirements.
> > * Let us know timezone you are in and when you can hang out on IRC
> > * Your registered IRC nickname (please register your nick - see
> https://www.xenproject.org/help/irc.html under Netiquette)
> >
> > Note that my IRC nick is lars_kurth, Simon's is skuezer, Stefano's is
> sstabellini, and I am afraid I can't remember Edgar's
> >
> > If you are interested in Unikraft
> > * Build the hello world unikraft app: see https://wiki.xenproject.
> org/wiki/Category:Unikraft & http://unikraft.neclab.eu/ and report back
> > * Familiarize yourself with the workflow at https://wiki.xenproject.
> org/wiki/Submitting_Xen_Project_Patches#How_to_
> Generate.2C_and_Submit_a_Xen_Project_Patch_to_MiniOS_and_Unikraft (please
> read the entire document)
> >
> > For the ARM project, I will let Stefano and Edgar decide.
>
> For the ARM project, it would be good to get familiar with Xen on ARM,
> to learn how to build it:
>
> https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions#
> Building_Xen_on_ARM
>
> and use QEMU to emulate an ARM board to run Xen on it, for testing and
> development:
>
> https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions/
> qemu-system-aarch64
>
> Feel free to ask any questions!
>
>
> > Regards
> > Lars
> >
> >
> > From: KANIKA SAINI <kanika16047@iiitd.ac.in>
> > Date: Wednesday, 14 February 2018 at 17:25
> > To: Lars Kurth <lars.kurth@citrix.com>
> > Subject: Excited for Xen Project in Outreachy
> >
> > Greetings, Lars.
> >
> > I'm Kanika Saini and I'm super excited to begin contributing to Xen!
> >
> > I seek guidance in choosing the suitable sub-project in Xen according to
> my skill set. I'm currently pursuing a course in Operating Systems and
> hence, have been gaining knowledge in kernel programming by short
> assignments like the implementation of a system call. I'm familiar with
> assembly programming in MIPS, ARM and x86 as well.
> > About high-level programming - I have experience with Java and have used
> it for desktop applications and parallel programming.
> >
> > There are certain projects listed on the project page and I'm looking
> for mentors' suggestion on what could be the best for both me and Xen. I
> have introduced myself on the #unikraft channel and I'm expecting a reply
> from the community.
> >
> > I wish to begin my contribution as soon as possible. I request you to
> connect me to the mentors in case IRC is not the best way to get in touch
> with them.
> >
> > Thank you!
> >
> >
> > --
> > Yours sincerely,
> > Kanika Saini
> > CSE, IIITD Class of 2020
> >
> >
> >
> > ‌
> >
> >
>



-- 
Yours sincerely,
Kanika Saini
CSE, IIITD Class of 2020

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Re: Excited for Xen Project in Outreachy

[KANIKA SAINI]

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*Issue suggested by Simon*
In Unikraft - whenever compiler flags are changed due to an addition of a
library or something else according to the build rules, the make command
doesn't force recompilation of those files affected by the flag change
unless the files are altered too. The only way out is to "make clean" and
"make" again all the files which can be redundantly time-consuming.


*Solution*One way is to create flag files for objects and add those as
their dependency in the Makefile.


Apart from this, I'm wondering if rules are passed on to the Makefile and
changes are depicted in the Makefile itself, can we add Makefile as the
dependency of objects to solve this issue?


Thank you.



‌

On Wed, Feb 21, 2018 at 9:16 PM, KANIKA SAINI <kanika16047@iiitd.ac.in>
wrote:

>
> Hi Lars,
>
> I'm already on #unikraft with the registered username - kanik.
> My timezone is UTC+5:30h and I can be available for a chat at any time of
> the day post noon usually.
>
> I have subscribed to the mailing lists and gone through the documentation
> at https://wiki.xenproject.org/wiki/Submitting_Xen_Project_P
> atches#How_to_Generate.2C_and_Submit_a_Xen_Project_Patch_to_
> MiniOS_and_Unikraft thoroughly.
>
> Also, I have completed the first task you suggested, that is, to build the
> hello world app. Below is the screenshot of it running on my system.
> [image: Inline image 1]
>
> Keeping my skill set and experience in mind, I'm mostly interested in and
> suitable for projects -  Enhanced Profiling and Tracing Support for
> Unikraft and High-level Language Support with Unikraft.
>
> I was having my exams this week and hence, couldn't start with much force
> but now, I'm all pumped up to make significant contributions. :D
> If there are not many people already working on it, please, let me know
> the next steps to begin contributing.
>
> Thank you!
>
>
>
>
> ‌
>
> On Thu, Feb 15, 2018 at 4:15 AM, Stefano Stabellini <
> sstabellini@kernel.org> wrote:
>
>> Hello Kanika,
>>
>> Thanks for your interest in Xen Project!
>> One reply inline below.
>>
>> On Wed, 14 Feb 2018, Lars Kurth wrote:
>> > Hi Kanika,
>> >
>> > I CC'ed two lists and the mentors of projects. Thank you for your
>> interest in the project.
>> >
>> > > I seek guidance in choosing the suitable sub-project in Xen according
>> to my skill set.
>> > We have two sets of projects on https://www.outreachy.org/comm
>> unities/cfp/xen-project/
>> > * 3 around Unikraft (mentor: Simon the technical side, I on the
>> process/people side). We are both based in UTC+1 - IRC is #unikraft
>> > * 1 for Xen on ARM (mentors: Stefano & Edgar). Stefano is in UTC-8,
>> Edgar is UTC-7 or 6 (can't quite recall) - IRC is #xendevel
>> >
>> > > I wish to begin my contribution as soon as possible. I request you to
>> connect me to the mentors in case IRC is not the best way to get in touch
>> with them.
>> > Simon is unfortunately not around this week but will be next week.
>> > Stefano and Edgar, are around I believe
>> >
>> > For practical reasons:
>> > * Please sign up to the minios-devel@lists.xenproject.org or
>> xen-devel@lists.xenproject.org (as appropriate)
>> >    (see http://lists.xenproject.org for instructions: if you use the
>> "subscribe subject pattern" make sure you send the mail to
>> minios-devel-request@lists.xenproject.org, ...)
>> > * Please double check time requirements: This is because in the past
>> there frequently were issues with Outreachy and University course time
>> requirements in particular with Universities from India. I believe that
>> there will be extra checks later in the application process, which may
>> require letters from your University. We had one case, where an applicant
>> did a small project, but we were not allowed to accept her due to time
>> requirements.
>> > * Let us know timezone you are in and when you can hang out on IRC
>> > * Your registered IRC nickname (please register your nick - see
>> https://www.xenproject.org/help/irc.html under Netiquette)
>> >
>> > Note that my IRC nick is lars_kurth, Simon's is skuezer, Stefano's is
>> sstabellini, and I am afraid I can't remember Edgar's
>> >
>> > If you are interested in Unikraft
>> > * Build the hello world unikraft app: see https://wiki.xenproject.or
>> g/wiki/Category:Unikraft & http://unikraft.neclab.eu/ and report back
>> > * Familiarize yourself with the workflow at https://wiki.xenproject.org
>> /wiki/Submitting_Xen_Project_Patches#How_to_Generate.2C_and_
>> Submit_a_Xen_Project_Patch_to_MiniOS_and_Unikraft (please read the
>> entire document)
>> >
>> > For the ARM project, I will let Stefano and Edgar decide.
>>
>> For the ARM project, it would be good to get familiar with Xen on ARM,
>> to learn how to build it:
>>
>> https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization
>> _Extensions#Building_Xen_on_ARM
>>
>> and use QEMU to emulate an ARM board to run Xen on it, for testing and
>> development:
>>
>> https://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization
>> _Extensions/qemu-system-aarch64
>>
>> Feel free to ask any questions!
>>
>>
>> > Regards
>> > Lars
>> >
>> >
>> > From: KANIKA SAINI <kanika16047@iiitd.ac.in>
>> > Date: Wednesday, 14 February 2018 at 17:25
>> > To: Lars Kurth <lars.kurth@citrix.com>
>> > Subject: Excited for Xen Project in Outreachy
>> >
>> > Greetings, Lars.
>> >
>> > I'm Kanika Saini and I'm super excited to begin contributing to Xen!
>> >
>> > I seek guidance in choosing the suitable sub-project in Xen according
>> to my skill set. I'm currently pursuing a course in Operating Systems and
>> hence, have been gaining knowledge in kernel programming by short
>> assignments like the implementation of a system call. I'm familiar with
>> assembly programming in MIPS, ARM and x86 as well.
>> > About high-level programming - I have experience with Java and have
>> used it for desktop applications and parallel programming.
>> >
>> > There are certain projects listed on the project page and I'm looking
>> for mentors' suggestion on what could be the best for both me and Xen. I
>> have introduced myself on the #unikraft channel and I'm expecting a reply
>> from the community.
>> >
>> > I wish to begin my contribution as soon as possible. I request you to
>> connect me to the mentors in case IRC is not the best way to get in touch
>> with them.
>> >
>> > Thank you!
>> >
>> >
>> > --
>> > Yours sincerely,
>> > Kanika Saini
>> > CSE, IIITD Class of 2020
>> >
>> >
>> >
>> > ‌
>> >
>> >
>>
>
>
>
> --
> Yours sincerely,
> Kanika Saini
> CSE, IIITD Class of 2020
>



-- 
Yours sincerely,
Kanika Saini
CSE, IIITD Class of 2020

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Re: [Minios-devel] Excited for Xen Project in Outreachy

[Lars Kurth]

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Hi Kanika,

> On 22 Feb 2018, at 20:34, KANIKA SAINI <kanika16047@iiitd.ac.in> wrote:
> 
> 
> Issue suggested by Simon
> In Unikraft - whenever compiler flags are changed due to an addition of a library or something else according to the build rules, the make command doesn't force recompilation of those files affected by the flag change unless the files are altered too. The only way out is to "make clean" and "make" again all the files which can be redundantly time-consuming.
> 
> Solution
> One way is to create flag files for objects and add those as their dependency in the Makefile.


> Apart from this, I'm wondering if rules are passed on to the Makefile and changes are depicted in the Makefile itself, can we add Makefile as the dependency of objects to solve this issue?

I think the answer is in the documentation, which explains the UI (if you to call it that way) for the build system (see http://unikraft.neclab.eu/developers-app.html <http://unikraft.neclab.eu/developers-app.html>)

You can also usually figure out which parameters are passed to make via the command line by searching for the origin function, in particular for "command line" return values (https://www.gnu.org/software/make/manual/html_node/Origin-Function.html <https://www.gnu.org/software/make/manual/html_node/Origin-Function.html>). This will give you a sense of the values that can be passed to the build system from outside of a makefile.

Now, you do need to make sure that you don't change the UI interface, as this would break everyone who uses Unikraft.

Assuming that all the flags we care about are already encoded in a Makefile (and don't come through the command line or through any other means), then adding a dependency may be sufficient. There is the question how granular you want this to be: 
a) Is it OK for everything to be rebuilt when say you change a -Dfoo 
b) Do you want this to be more fine grained

Have a google for something like "rebuilding when makefile flags change" and you will find a few example patterns with different trade-offs to solve this problem in general

The second challenge is that most substantial build rules get created dynamically via [unikraft/unikraft.git] <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;hb=HEAD> / support <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;f=support;hb=HEAD> / build <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;f=support/build;hb=HEAD> / * 
Thus, adding a dependency on a makefile may not be as simple as it sounds

Lars 

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Re: [Minios-devel] Excited for Xen Project in Outreachy

[KANIKA SAINI]

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Thank you, Lars.
The links you have provided have managed to make things clearer to me now.

I understand how a flag in the makefile can be changed by passing a
parameter to the make command in the command line and how
"origin" checks where the variable comes from.
I did realize creating the dependency of the Makefile itself would indeed
not be a good idea at the finer level of granularity.
I went through the documentation at
http://unikraft.neclab.eu/developers-app.html and can now understand the
structure of makefiles of libraries better.

I spent some time studying the problem and came across this solution at
https://www.cmcrossroads.com/article/rebuilding-when-cppflags-changes which
uses the concept of signatures.
I also understood how rules are dynamically being set by the Makefiles in
support/build/ directory.

To be able to draft a solution there's one more thing lacking my
understanding, which is the order of the execution of the makefiles.
What calls the dynamic makefiles and when is the main makefile called and
how do the dynamic makefiles pass those parameters to the main one?

According to what I understood, the flags for the addition of new libraries
or new configurations through the menu config are already being taken care
of by the dynamic checking if that's right. We only have to handle the
additional flags passed through the command line.

I appreciate your time and guidance.

Thank you.




‌

On Fri, Feb 23, 2018 at 2:31 PM, Lars Kurth <lars.kurth.xen@gmail.com>
wrote:

> Hi Kanika,
>
> On 22 Feb 2018, at 20:34, KANIKA SAINI <kanika16047@iiitd.ac.in> wrote:
>
> *Issue suggested by Simon*
> In Unikraft - whenever compiler flags are changed due to an addition of a
> library or something else according to the build rules, the make command
> doesn't force recompilation of those files affected by the flag change
> unless the files are altered too. The only way out is to "make clean" and
> "make" again all the files which can be redundantly time-consuming.
>
>
> *Solution*One way is to create flag files for objects and add those as
> their dependency in the Makefile.
>
>
>
> Apart from this, I'm wondering if rules are passed on to the Makefile and
> changes are depicted in the Makefile itself, can we add Makefile as the
> dependency of objects to solve this issue?
>
>
> I think the answer is in the documentation, which explains the UI (if you
> to call it that way) for the build system (see http://unikraft.neclab.
> eu/developers-app.html)
>
> You can also usually figure out which parameters are passed to make via
> the command line by searching for the origin function, in particular for
> "command line" return values (https://www.gnu.org/software/
> make/manual/html_node/Origin-Function.html). This will give you a sense
> of the values that can be passed to the build system from outside of a
> makefile.
>
> Now, you do need to make sure that you don't change the UI interface, as
> this would break everyone who uses Unikraft.
>
> Assuming that all the flags we care about are already encoded in a
> Makefile (and don't come through the command line or through any other
> means), then adding a dependency may be sufficient. There is the question
> how granular you want this to be:
> a) Is it OK for everything to be rebuilt when say you change a -Dfoo
> b) Do you want this to be more fine grained
>
> Have a google for something like "rebuilding when makefile flags change"
> and you will find a few example patterns with different trade-offs to solve
> this problem in general
>
> The second challenge is that most substantial build rules get created
> dynamically via* [unikraft/unikraft.git]
> <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;hb=HEAD> / support
> <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;f=support;hb=HEAD> / build
> <http://xenbits.xen.org/gitweb/?p=unikraft/unikraft.git;a=tree;f=support/build;hb=HEAD> /
> * *
> Thus, adding a dependency on a makefile may not be as simple as it sounds
>
> Lars
>



-- 
Yours sincerely,
Kanika Saini
CSE, IIITD Class of 2020

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Re: [Minios-devel] Excited for Xen Project in Outreachy

[Lars Kurth]

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Hi Kanika,

> On 24 Feb 2018, at 20:40, KANIKA SAINI <kanika16047@iiitd.ac.in> wrote:
> 
> Thank you, Lars. 
> The links you have provided have managed to make things clearer to me now.
> 
> I understand how a flag in the makefile can be changed by passing a parameter to the make command in the command line and how 
> "origin" checks where the variable comes from.
> I did realize creating the dependency of the Makefile itself would indeed not be a good idea at the finer level of granularity. 
> I went through the documentation at http://unikraft.neclab.eu/developers-app.html <http://unikraft.neclab.eu/developers-app.html> and can now understand the structure of makefiles of libraries better. 
> 
> I spent some time studying the problem and came across this solution at https://www.cmcrossroads.com/article/rebuilding-when-cppflags-changes <https://www.cmcrossroads.com/article/rebuilding-when-cppflags-changes> which uses the concept of signatures. 
> I also understood how rules are dynamically being set by the Makefiles in support/build/ directory. 
> 
> To be able to draft a solution there's one more thing lacking my understanding, which is the order of the execution of the makefiles. 
> What calls the dynamic makefiles and when is the main makefile called and how do the dynamic makefiles pass those parameters to the main one?

I am not sure I understand your question.

Generally, you can debug makefiles which can help you understand what is going on: e.g. see http://www.oreilly.com/openbook/make3/book/ch12.pdf <http://www.oreilly.com/openbook/make3/book/ch12.pdf>

But in a nutshell: you call make ... in your directory and the Makefile is invoked
* Other rules, e.g. in support / build are included via include statements
* All the other *.uk makefiles are also included 
=> The makefile in unikraft / unikraft.git drives everything related to building and configuration (including menuconfig)

In some cases you have nested makefile execution, where another makefile is invoked via "@make" as in the Hello World app

Lars


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