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opensecura / 3p / tock / libtock-rs / cf2a543085aaa479197f354a25e36a0e03dbd654
commitcf2a543085aaa479197f354a25e36a0e03dbd654[log] [tgz]
authorbors[bot] <26634292+bors[bot]@users.noreply.github.com>Fri Jun 26 09:57:22 2020 +0000
committerGitHub <noreply@github.com>Fri Jun 26 09:57:22 2020 +0000
tree67a1381f67990a49a16334fe2a87eb8c140268ac
parenta76b21316d9d22b641129795e081d41293be6f69 [diff]
parentb65c3c8e9ebb74053e9c17e0a1bda734cf61d643 [diff]
Merge #191

191: Undefined instruction fix for start_item_arm r=valexandru a=valexandru

I ported libtock-rs for the i.MX RT 1052 EVKB and while trying to run a simple hello_world application, when switching to the userspace, after running the first instruction, it failed with a hard fault. The cause of the hard fault was the instruction "sub r4, pc, #4" from the function _start in the core/src/entry_point/start_item_arm.rs file. The same instruction, simply run separately as 
`subw r4, pc, #4`
seems to work. 

Apparently, the reason for this was that my compiler on Mac OS compiled with T3 ARM Encoding which translated the instruction to 
`sub.w   r4, pc, #4`

which caused hard fault with Undefined Instruction.

The reason for this is that for T3 encoding, if Rn == PC, the behaviour is **upredictable**. More information about this can be found in the [ARMv7 Architecture Manual](https://static.docs.arm.com/ddi0403/eb/DDI0403E_B_armv7m_arm.pdf), section A7.7.171
SUB (immediate), pages 448-449

The solution I propose: 
`mov r4, pc
sub r4, r4, #4`
as both work no matter what ARM encoding is used.

Co-authored-by: Vochescu Alexandru <alexvochescu@gmail.com>
tree: 67a1381f67990a49a16334fe2a87eb8c140268ac
  1. .cargo/
  2. .github/
  3. .vscode/
  4. boards/
  5. codegen/
  6. core/
  7. doc/
  8. examples/
  9. examples-features/
  10. src/
  11. test_runner/
  12. tools/
  13. tock
  14. .gitignore
  15. .gitmodules
  16. .travis.yml
  17. bors.toml
  18. build.rs
  19. Cargo.toml
  20. CHANGELOG.md
  21. CONTRIBUTING.md
  22. layout_generic.ld
  23. LICENSE-APACHE
  24. LICENSE-MIT
  25. Makefile
  26. README.md
  27. rust-toolchain
  28. rustfmt.toml
README.md

Build Status

libtock-rs

Rust userland library for Tock (WIP)

Generally this library was tested with tock Release 1.5. Since then changes have been made that might not work with the Tock release 1.5, but instead target Tock master. For example this library might support newer boards (Apollo3), changed boards (HiFive1 revB) or new drivers (HMAC).

The library works in principle on most boards, but there is currently the showstopper bug #28 that prevents the generation of relocatable code. This means that all applications must be installed at the flash address they are compiled with, which usually means that they must be compiled especially for your board and that there can only be one application written in rust at a time and it must be installed as the first application on the board, unless you want to play games with linker scripts. There are some boards/layout_*.ld files provided that allow to run the examples on common boards. Due to MPU region alignment issues they may not work for applications that use a lot of RAM, in that case you may have to change the SRAM start address to fit your application.

Getting Started

This project is nascent and still under heavy development, but first steps:

  1. Ensure you have rustup installed.

  2. Clone the repository:

    git clone --recursive https://github.com/tock/libtock-rs
cd libtock-rs

  3. Install the dependencies:

    make setup

  4. Use make to build examples

    make nrf52 # Builds all examples for the nrf52 platform

    make opentitan # Builds all examples for the OpenTitan platform

    make opentitan FEATURES=alloc # Builds all examples for the OpenTitan platform, with alloc feature enabled

    make flash-hail EXAMPLE=blink # Flash the example 'blink' program to the hail platform

    For an unknown platform, you may have to create your own memory layout definition. Place the layout definition file at boards/layout_<platform>.ld and do not forget to enhance the tockloader_flags dispatching section in tools/flash.sh. You are welcome to create a PR, s.t. the number of supported platforms grows.

Using libtock-rs

The easiest way to start using libtock-rs is adding an example to the examples folder. The boiler plate code you would write is

#![no_std]

use libtock::result::TockResult;

#[libtock::main]
async fn main() -> TockResult<()> {
  // Your code
}

If you want to use heap based allocation you will have to add

extern crate alloc;

to the preamble and store your example in the examples-alloc folder.

To build the examples for your board you can use

make <platform> [FEATURES=alloc]

An example can be flashed to your board after the build process by running:

make flash-<platform> EXAMPLE=<example>

This script does the following steps for you:

  • cross-compile your program
  • create a TAB (tock application bundle)
  • if you have a J-Link compatible board connected: flash this TAB to your board (using tockloader)

License

libtock-rs is licensed under either of

at your option.

Submodules have their own licenses.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

The contribution guidelines can be found here: contribution guidelines