Building and linking mbedTLS

Hi all,

I’m trying to build and link to mbedTLS library. Here’s what I’ve tried to do so far..

Found the source within the “DiscDev” sources, and thus tried to build using Builder. Selected environment ROOL.BCM2835. Selected options: Clean, Export headers, Export libraries, Export resources. These options are mostly guesswork rather than an informed opinion on my part.

This finishes up with:

Error running make clean on module ‘Messages’
Error creating directory ‘Install.ROOL.BCM2835’

I’m not really sure what to expect here; I guess I was sort of hoping that somehow it would generate me an `o` and `h` for mbedTLS.

The second thing I tried was just dragging the Makefile inside RiscOS.Sources.Lib.mbedTLS directly onto Amu. This seems to do a fair amount of stuff; generating many `o` files :) But then ends up failing with:

cc -Wp -c -depend !Depend -DMBEDLS_CONFIG_FILE=“\”h.ro_config\"" -DRISCOS -ITCPIPLibs: -ff -fah -zM -o oz.entropy_poll c.entropy_poll

Wondering if anyone else has managed to link against mbedTLS and can offer me some guidance to save me stumbling around in the dark!

Thanks

Dave

Just out of interest, why bother linking another copy of the library, rather than use the AcornSSL module which already includes it?

That thought crossed my mind, but then perhaps he needs access to the lower level stuff that AcornSSL doesn’t export?

In an ideal world, the mbedTLS library will be its own module and other things (including AcornSSL) could make use of it, precisely to stop the need for multiple copies of the same thing (especially if things get out of step).

But, this world is far from ideal…

Selected environment ROOL.BCM2835.

Possibly a typo? Environment should be DiscDev.

Export resources

This is not required for a DiscDev build, see the end of this page

A bit later. mbedTLS.!MkExport then works, header and libraries appear in h and o directories.

Here’s how I did it:

1. Downloaded the latest source either from the gitlab page or with git clone https://gitlab.riscosopen.org/RiscOS/Sources/Lib/mbedTLS.git
2. Open Builder, chose Build Directory (this controls where the completed library is copied to), and environment ROOL.BCM2835 (I don’t understand this option, but this worked). I didn’t tick any Build Options, I only use those if I’m doing a build of an entire ROM or similar.
3. Set the next wimp-slot to ‘quite big’ (otherwise I get ‘No writable memory at this address’).
4. Double-click !MkExport in the mbedTLS source.
5. Some time later, the finished library appeared.

Thanks for all the replies. I think that all I needed to do was change `ROOL.BCM2835` to `DiscDev`. I also got rid of Export resources. Then the disc built completely. My key error here being failing to read to the end of the documentation before diving in. :(

Then changing the wimp-slot allowed me to run !MkExport successfully!

The reason for wanting this is indeed to get access to bits of the low-level library.

Follow up question (I think I’m nearly there) …

As mentioned, I did manage to !MkExport, and now I’ve written a bunch of code that uses mbedTLS; I’ve even made it compile successfully! The final hurdle is a linker error. My assumption is there is some shared library I need to add to my LIBS. Right now I have this in my Makefile:

LIBS = SFLib:o.SFLib OSLib:o.OSLib32 MbedTLS:o.mbedTLS

But when I run Mk (this is all with Norcroft/DDE by the way) I get:

ARM Linker: (Error) Undefined symbol(s).
ARM Linker: gettimeofday, referred to from MbedTLS:o.mbedTLS(timing).
ARM Linker: Errors in link, no output generated
ARM Linker: finished, 2 informational, 0 warnings and 1 error messages.

Does anyone know what library I need to be linking against for the `gettimeofday` function?

Thanks in advance! All help most appreciated!

That’s in TCPIPLibs:o.unixlib

Amazing! Thanks Julie my app now builds!

Really appreciate all the help. I think I now have most of the basic pieces I need integrated and building (mbedTLS, SQLite) so it’s now just a question of building the thing!