[RFC PATCH v1 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).

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_2021_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                 |   242 +
 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, 14015 insertions(+), 188 deletions(-)
 create mode 100644 common/cli_hush_2021.c
 create mode 100644 common/cli_hush_2021_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, thank you in advance for your reviews and happy new year!
---
[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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