MFC r340040, r340152: lualoader boot-conf and chainload

r340040:
lualoader: Implement boot-conf

r340152:
lualoader: Add chainload menu entry

Approved by: re (rgrimes)

Remove "All Rights Reserved" on files that I hold sole copyright on

See r333391 for more detail; in summary: it holds no weight and may be
removed.

lualoader: Return status in cli_execute_unparsed properly

cli_execute was changed to return the status, cascade that to
cli_execute_unparsed.

This fixes a lot of false "Failed to execute" errors fo

lualoader: Return status in cli_execute_unparsed properly

cli_execute was changed to return the status, cascade that to
cli_execute_unparsed.

This fixes a lot of false "Failed to execute" errors following r330620; no
failures actually occurred, but [module]_error would've then promptly
executed (and also "failed")

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lualoader: Fix name, cli.execute_unparsed -> cli_execute_unparsed

lualoader: Expose loader.parse and add cli_execute_unparsed

This will be used for scenarios where the command to execute is coming in
via the environment (from, for example, loader.conf(5)) and is t

lualoader: Expose loader.parse and add cli_execute_unparsed

This will be used for scenarios where the command to execute is coming in
via the environment (from, for example, loader.conf(5)) and is thus not
necessarily trusted.

cli_execute_unparsed will immediately be used for handling
module_{before,after,error} as well as menu_timeout_command. We still want
to offer these variables the ability to execute Lua-intercepted loader
commands, but we don't want them to be able to execute arbitrary Lua.

Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D14580

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lualoader: Return meaningful value in cli_execute

loader.command(...) will return whatever the executed function returns, so
follow suit and return whatever loader.command() returned or whatever the

lualoader: Return meaningful value in cli_execute

loader.command(...) will return whatever the executed function returns, so
follow suit and return whatever loader.command() returned or whatever the
Lua function returns.

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lualoader: Explain deviation from naming guidelines

cli_execute is likely the only exception that we should make, due to it
being a global. We don't really need other globals, so this won't really e

lualoader: Explain deviation from naming guidelines

cli_execute is likely the only exception that we should make, due to it
being a global. We don't really need other globals, so this won't really end
up an epidemic.

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lualoader: Clean up naming conventions a little bit

We mostly use camel case for function names, but some local functions got
mixed in using internal underscores. Doubles down on camel case.

lualoader: Use "local function x()" instead of "local x = function()"

The latter is good, but the former is more elegant and clear about what 'x'
is. Adopt it, preferably only using the latter kind

lualoader: Use "local function x()" instead of "local x = function()"

The latter is good, but the former is more elegant and clear about what 'x'
is. Adopt it, preferably only using the latter kind of notation where needed
as values for tables.

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Add SPDX tags to lua files

lualoader: Address some 'luacheck' concerns

luacheck pointed out an assortment of issues, ranging from non-standard
globals being created as well as unused parameters, variables, and redundant
assig

lualoader: Address some 'luacheck' concerns

luacheck pointed out an assortment of issues, ranging from non-standard
globals being created as well as unused parameters, variables, and redundant
assignments.

Using '_' as a placeholder for values unused (whether it be parameters
unused or return values unused, assuming multiple return values) feels clean
and gets the point across, so I've adopted it. It also helps flag candidates
for cleanup later in some of the lambdas I've created, giving me an easy way
to re-evaluate later if we're still not using some of these features.

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lualoader: Attach cli command functions to cli module

Instead of the global namespace, let's attach these to the cli module. Other
users, including the "local" module, can attach functions to the cl

lualoader: Attach cli command functions to cli module

Instead of the global namespace, let's attach these to the cli module. Other
users, including the "local" module, can attach functions to the cli module
at will to add other cli commands and things will still Just Work.

This distills down the candidates for functions that may be invoked via the
cli to a minimal set (boot, autoboot, arguments), rather than any function
that happens to live in the global lua namespace.

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lualoader: Pull argument extraction for cli functions into cli.arguments

This will be the translation layer for varargs -> cmd_name, argv for cli
commands. We reserve the right to break exactly what

lualoader: Pull argument extraction for cli functions into cli.arguments

This will be the translation layer for varargs -> cmd_name, argv for cli
commands. We reserve the right to break exactly what the varargs inclulde,
but this gives us a stable way to pull the arguments out of varargs.

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lualoader: Unbreak 'boot [kernel]' by including config

lualoader: Split cli bits out into a cli module

This module will, in the not-so-distant future, grow functionality for
reducing boilerplate in functions that implement cli commands. It will
likely a

lualoader: Split cli bits out into a cli module

This module will, in the not-so-distant future, grow functionality for
reducing boilerplate in functions that implement cli commands. It will
likely also house most in-tree cli commands.

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