.\"
.\" Copyright (c) 2024 Netflix, Inc.
.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.Dd February 6, 2024
.Dt LOADER.LUA 8
.Os
.Sh NAME
.Nm loader.lua
.Nd Fx Lua loader module
.Sh DESCRIPTION
The built-in Lua bindings for the
.Fx
boot loaders using the Lua interpreter
are available via the
.Ic loader
table.
.Pp
The
.Ic loader
table is always available in Lua scripts.
There is no need to require it like other loader-specific modules.
.Ss Exported Variables
The following variables are provided by the Lua interpreter in the
.Nm loader
table:
.Bl -tag -width machine_arch
.It Ic machine
The target's
.Va hw.machine
.Xr sysctl 8
value.
.It Ic machine_arch
The target's
.Va hw.machine_arch
.Xr sysctl 8
value.
Some boot loaders are 32-bit applications that then load a 64-bit
kernel.
In these cases,
.Ic machine_arch
represents the 32-bit architecture, not the 64-bit architecture.
.It Ic lua_path
The current lua loading path.
.It Ic version
The version of the boot program.
.El
.Ss Exported Functions
The following functions are exported in the
.Nm loader
table.
.Bl -tag -width term_putimage
.It Fn delay usec
Delay for
.Va usec
microseconds.
.It Fn command_error
Returns the error string from the last command to fail.
.It Fn command argc argv
Like
.Fn perform
but the arguments are already parsed onto the stack.
.It Fn exit status
Exit the boot loader back to the firmware with a status of
.Va status .
The interpretation of this value is firmware specific.
.It Fn interpret str
Execute the loader builtin command
.Va str
as if it were typed by the user.
This will first try to execute
.Va str
as Lua.
If that fails, it will attempt to execute it as a cli command,
including those defined by the
.Xr cli.lua 8
mechanism.
If that fails, it will attempt to execute it as a builtin command
and return the same values as
.Fn perform .
.It Fn parse str
Parses the command
.Va str
into its words and return those words on the stack.
.It Fn getenv name
Obtains the value of the environment variable
.Va name .
.It Fn has_command cmd
returns
.Va true
if
.Va commmand
is present in the interpreter as a builtin.
Otherwise it returns
.Va nil
and an error string.
It does not check the
.Dq cli
table to see if a user defined command has been created.
.It Fn has_feature feature
returns
.Va true
if the
.Va feature
is enabled.
Otherwise it returns
.Va nil
and an error string.
.It Fn perform str
Execute the loader builtin command
.Va str .
Returns the result of the command, one of the following values:
.Bl -tag -width loader -offset indent
.It loader.CMD_OK
The command completed successfully.
.It loader.CMD_WARN
The command was successful, but the user stopped its output
prematurely.
.It loader.CMD_ERROR
The command did not complete successfully.
Use
.Va command_error
to retrieve the error.
.It loader.CMD_CRIT
The command returned a critical error that was already printed.
.It loader.CMD_FATAL
The command determined continuation was not possible
and the loader panicked.
In practice, though,
.Fn panic
does not return.
.El
.It Fn printc str
Outputs the string using the loader's
.Fn putchar
function.
This function is also available globally as
.Fn printc .
.It Fn setenv name value
Insert or reset the environment variable
.Va name
into the loader's environment list.
If no environment variable with this name exists, one is created.
If one exists, its value is replaced.
.It Fn time
Returns the loader's notion of time, in seconds since 1970.
The value of loader's notion varies somewhat between different loading
environments.
.It Fn unsetenv name
Removes the environment variable
.Va name
from the loader's environment list.
.El
.Ss Compatibility
The functions
.Fn fb_bezier ,
.Fn fb_drawrect ,
.Fn fb_line ,
.Fn fb_putimage ,
.Fn fb_set_pixel ,
.Fn term_drawrect ,
and
.Fn term_putimage
have moved to the
.Ic gfx
table.
They remain in the
.Ic loader
table for a transition period and are documented in
.Xr gfx.lua 8 .
.Ss Default File
In addition, the Lua interpreters start with the file
.Pa /boot/lua/loader.lua
when they start to boot the system.
The default one will fixup the screen, load the configuration files, check for a
password, and then load the menu or load the kernel file and then return.
If autoboot is enabled, the loaded files will boot.
.Sh SEE ALSO
.Xr loader.conf 5 ,
.Xr core.lua 8 ,
.Xr gfx.lua 8 ,
.Xr loader 8 ,
.Xr sysctl 8
.Sh AUTHORS
The
.Nm
man page was written by
.An Warner Losh Aq Mt imp@FreeBSD.org .
.Sh BUGS
.Fn command
and
.Fn perform
should return a tuple when there's
.Va CMD_ERROR
or worse.