Where to get Zero Footprint Profile?

Where to get Zero Footprint Profile?

[droiddermo]

It is said that Zero Footprint Profile allows some restricted Ada subset to be compiled and run on bare metal (without relying on any code from standard Ada's runtime library). So for example ZFP should allow us to create operating system using Ada. Basically ZFP is a tiny runtime library, that implements only compiler's intrinsics and doesn't rely on any services that are provided by operating system. But where to get ZFP?  GNAT GPL provides only default runtime library (profile). I've googled out that some people reinvent a tiny subset of ZFP in order to make their OS experiments, like it is done here: https://github.com/Lucretia/tamp... So is there any ZFP available and where to get it, or I have to reimplement it myself?

Re: Where to get Zero Footprint Profile?

[ake.ragnar.dahlgren]

Have you read the information at the Ada Bare Bones site?

http://wiki.osdev.org/Ada_Bare_bones

Best regards,
Åke Ragnar Dahlgren

Re: Where to get Zero Footprint Profile?

[droiddermo]

> Have you read the information at the Ada Bare Bones site?
Yes, I have. This is exactly what is done in Tamp project (I've put the link in the first post). The article suggest to reimplement ZFP yourself by copying and editing some files from original runtime library. I'd like to have a look at the full ZFP. It seems that Adacore provide it only for their customers.

Re: Where to get Zero Footprint Profile?

[Luke A. Guest]

<droiddermo@gmail.com> wrote:
>> Have you read the information at the Ada Bare Bones site?
> Yes, I have. This is exactly what is done in Tamp project (I've put the
> link in the first post). The article suggest to reimplement ZFP yourself
> by copying and editing some files from original runtime library. I'd like
> to have a look at the full ZFP. It seems that Adacore provide it only for their customers.

They are both my projects.

You create the zfp by copying the relevant source files from the version of
gnat source you have, they are all intrinsics so don't need any rt.
Interfaces.c needs to have the subprigrams removing as they return I
constrained types, unless you enable a simple secondary stack.

Like

Re: Where to get Zero Footprint Profile?

[droiddermo]

> You create the zfp by copying the relevant source files from the version of
> gnat source you have, they are all intrinsics so don't need any rt.
> Interfaces.c needs to have the subprigrams removing as they return I
> constrained types, unless you enable a simple secondary stack.
Thanks! So as far as I understood there is no ready to use ZFP available for free? Is there any good read about Ada's runtime, compiler's intrinsics and using Ada for bare bones development in general? For example I don't quite understand what is secondary stack and what it is used for. Also from reading Ada bare bones page on osdev I didn't understand why you had to disable recursive calls, is it somehow dependent on some runtime's code?

Re: Where to get Zero Footprint Profile?

[Luke A. Guest]

<droiddermo@gmail.com> wrote:
>> You create the zfp by copying the relevant source files from the version of
>> gnat source you have, they are all intrinsics so don't need any rt.
>> Interfaces.c needs to have the subprigrams removing as they return I
>> constrained types, unless you enable a simple secondary stack.
> Thanks! So as far as I understood there is no ready to use ZFP available
> for free? Is there any good read about Ada's runtime, compiler's
> intrinsics and using Ada for bare bones development in general? For
> example I don't quite understand what is secondary stack and what it is
> used for. Also from reading Ada bare bones page on osdev I didn't
> understand why you had to disable recursive calls, is it somehow
> dependent on some runtime's code?

If you grab tamp, look at the rts dir that has a zfp ready runtime using
the 4.6.x source, do a diff on the latest version in case of changes but I
doubt there will be any. It also buds using gpr files.

I probably disabled reversion as you have limited stack. There's a ton of
things you can restrict or turn off.

Re: Where to get Zero Footprint Profile?

[Robert A Duff]

droiddermo@gmail.com writes:

> ...For example I don't quite understand what is secondary stack
> and what it is used for.

The secondary stack is used for caller-unknown-sized function results.
That is, function results that are of indefinite subtype.
For example, if you have:

    function F(...) return String is
        Length: Natural := ...; -- who knows what?
        Result: String(1..Length) := (others => 'A');
    begin
        return Result;
    end F;

Then somewhere else:

    X: constant String := F(...);

then F will return its result on the secondary stack.
The caller (declaration of X) doesn't know the size of the
result of F.  So F allocates its result on the secondary stack,
and then returns the address of that result to the caller.

You can look at s-secsta.ad[sb] to see how it works by default.

If the result subtype of F were "subtype S is String(1..80);",
then it would not use the secondary stack.

- Bob

Re: Where to get Zero Footprint Profile?

[Brian Drummond]

On Sun, 25 May 2014 11:42:27 -0700, droiddermo wrote:

>> You create the zfp by copying the relevant source files from the
>> version of gnat source you have, they are all intrinsics so don't need
>> any rt. Interfaces.c needs to have the subprigrams removing as they
>> return I constrained types, unless you enable a simple secondary stack.

> Thanks! So as far as I understood there is no ready to use ZFP available
> for free? Is there any good read about Ada's runtime, compiler's
> intrinsics and using Ada for bare bones development in general? For
> example I don't quite understand what is secondary stack and what it is
> used for. Also from reading Ada bare bones page on osdev I didn't
> understand why you had to disable recursive calls, is it somehow
> dependent on some runtime's code?

There is a slightly more developed version for the AVR microprocessors, 
which appears to support a secondary stack, at 
http://sourceforge.net/projects/avr-ada/

I found it relatively easy to adapt for the TI MSP430 processors, at 
http://sourceforge.net/projects/msp430ada/

You may get some idea of what's involved by comparing these two, and 
adapting as required for your target processor. If so, please put your 
work out there so that some day, we may draw together all these disparate 
efforts into something more coherent...

Another unrelated effort targetting ARM processors, with the intent 
eventually to support the Ravenscar profile:

http://sourceforge.net/projects/arm-ada/

- Brian