[RFC PATCH v2 00/21] Modernize U-Boot shell

[Francis Laniel]

Hi.

First I hope you are fine and the same for your relatives.

During 2021 summer, Sean Anderson wrote a contribution to add a new shell, based
on LIL, to U-Boot [1][2].
While one of the goals of this contribution was to address the fact actual
U-Boot shell, which is based on Busybox hush, is old there was a discussion
about adding a new shell versus updating the actual one [3][4].

So, in this series, with Harald Seiler, we updated the actual U-Boot shell to
reflect what is currently in Busybox source code.
Basically, this contribution is about taking a snapshot of Busybox shell/hush.c
file (as it exists in commit 37460f5da) and adapt it to suit U-Boot needs.

This contribution was written to be as backward-compatible as possible to avoid
breaking the existing.
So, the 2021 hush flavor offers the same as the actual, that is to say:
1. Variable expansion.
2. Instruction lists (;, && and ||).
3. If, then and else.
4. Loops (for, while and until).
No new features offered by Busybox hush were implemented (e.g. functions).

In terms of testing, new unit tests were added to ut to ensure the new behavior
is the same as the old one and it does not add regression.
Nonetheless, if old behavior was buggy and fixed upstream, the fix is then added
to U-Boot [5].
In sandbox, all of these tests pass smoothly:
2021> printenv board
board=sandbox
2021> ut hush
Running 20 hush tests
...
Failures: 0
Thanks to the effort of Harald Seiler, I was successful booting a board:
2021> printenv board_rev
board_rev=iMX8MP
2021> boot
...
root at iMX8MPboard:~# fw_printenv board_rev
board_rev=iMX8MP

I marked this contribution as RFC to indeed collect your opinion.
My goal is not to change suddenly actual shell to this one, we clearly need a
transition period to think about it.
I think it is better to see this contribution as a proof of concept which shows
it is possible to update the actual shell.

If you want to review it - your review will really be appreciated - here are
some information regarding the commits:
* commits marked as "test:" deal with unit tests.
* commit "cli: Add Busybox upstream hush.c file." copies Busybox shell/hush.c
into U-Boot tree, this explain why this commit contains around 12000 additions.
* commit "cli: Port Busybox 2021 hush to U-Boot." modifies previously added file
to permit us to use this as new shell.
The really good idea of #include'ing Busybox code into a wrapper file to define
some particular functions while minimizing modifications to upstream code comes
from Harald Seiler.
* Other commits focus on enabling features we need (e.g. if).

Changes since v1:
* Renamed cli_hush_2021_upstream.c to cli_hush_upstream.c.
* Addressed reviews regarding variable expansion unit test.

Francis Laniel (21):
  test: Add framework to test hush behavior
  test: hush: Test hush if/else
  test/py: hush_if_test: Remove the test file
  test: hush: Test hush variable expansion
  test: hush: Test hush commands list
  test: hush: Test hush loops.
  cli: Add Busybox upstream hush.c file
  cli: Port Busybox 2021 hush to U-Boot
  cli: Add choice for hush parser
  cli: Add HUSH_2021_PARSER to hush parser choice
  cli: Enables using hush 2021 parser as command line parser
  cli: hush_2021: Enable variables expansion for hush 2021
  cli: hush_2021: Add functions to be called from run_command()
  cli: Modify run_command() to add hush 2021 as parser
  test: hush: Fix instructions list tests for hush 2021
  test: hush: Fix variable expansion tests for hush 2021
  cli: hush_2021: Enable using \< and \> as string compare operators
  cli: hush_2021: Enable if keyword
  test: hush: Fix if tests for hush 2021
  cli: hush_2021: Enable loops
  test: hush: Fix loop tests for hush 2021

 cmd/Kconfig                        |    22 +
 common/Makefile                    |     3 +-
 common/cli.c                       |    27 +-
 common/cli_hush_2021.c             |   309 +
 common/cli_hush_upstream.c         | 12791 +++++++++++++++++++++++++++
 include/cli_hush.h                 |     8 +
 include/test/hush.h                |    15 +
 include/test/suites.h              |     1 +
 test/Makefile                      |     3 +
 test/cmd_ut.c                      |     6 +
 test/hush/Makefile                 |    10 +
 test/hush/cmd_ut_hush.c            |    20 +
 test/hush/dollar.c                 |   226 +
 test/hush/if.c                     |   351 +
 test/hush/list.c                   |   127 +
 test/hush/loop.c                   |    84 +
 test/py/tests/test_hush_if_test.py |   184 -
 17 files changed, 13999 insertions(+), 188 deletions(-)
 create mode 100644 common/cli_hush_2021.c
 create mode 100644 common/cli_hush_upstream.c
 create mode 100644 include/test/hush.h
 create mode 100644 test/hush/Makefile
 create mode 100644 test/hush/cmd_ut_hush.c
 create mode 100644 test/hush/dollar.c
 create mode 100644 test/hush/if.c
 create mode 100644 test/hush/list.c
 create mode 100644 test/hush/loop.c
 delete mode 100644 test/py/tests/test_hush_if_test.py


Best regards and thank you in advance for your reviews.
---
[1] https://lists.denx.de/pipermail/u-boot/2021-July/453347.html
[2] https://runtimeterror.com/tech/lil/
[3] https://lists.denx.de/pipermail/u-boot/2021-July/453790.html
[4] https://lists.denx.de/pipermail/u-boot/2021-July/453848.html
[5] https://lists.denx.de/pipermail/u-boot/2021-August/458569.html
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