Builtin Commands

In loader, builtin commands take parameters from the command line. If an error condition occurs, an exception will be generated, which can be intercepted using ANS Forth exception handling words. If not intercepted, an error message will be displayed and the interpreter's state will be reset, emptying the stack and restoring interpreting mode.

The builtin commands available are:

autoboot [seconds [prompt]]

Proceeds to bootstrap the system after a number of seconds, if not interrupted by the user. Displays a countdown prompt warning the user the system is about to be booted, unless interrupted by a key press. The kernel will be loaded first if necessary. Defaults to 10 seconds.

bcachestat

Displays statistics about disk cache usage. For debugging only.

boot

 

boot kernelname [...]

 

boot -flag ...

Immediately proceeds to bootstrap the system, loading the kernel if necessary. Any flags or arguments are passed to the kernel, but they must precede the kernel name, if a kernel name is provided.

WARNING: The behavior of this builtin is changed if loader.4th(7) is loaded.

chain device

Chain load another boot loader from the specified device. Device can be either disk name, partition or file name. In case of x86 BIOS boot, the file must be copy of MBR or PBR. For UEFI boot, the file is efi application.

echo [-n] [⟨message⟩]

Displays text on the screen. A new line will be printed unless -n is specified.

heap

Displays memory usage statistics. For debugging purposes only.

help [topic [subtopic]]

Shows help messages read from /boot/loader.help. The special topic index will list the topics available.

include file [file ...]

Process script files. Each file, in turn, is completely read into memory, and then each of its lines is passed to the command line interpreter. If any error is returned by the interpreter, the include command aborts immediately, without reading any other files, and returns an error itself (see ERRORS).

load [-t type] file ...

Loads a kernel or file of opaque contents tagged as being of the type type. Kernel and modules can be either in a.out or ELF format. Any arguments passed after the name of the file to be loaded will be passed as arguments to that file.

ls [-l] [path]

Displays a listing of files in the directory path, or the root directory if path is not specified. If -l is specified, file sizes will be shown too.

lsdev [-v]

Lists all of the devices from which it may be possible to load modules. In addition to disks and partitions, ZFS pools are also listed. If -v is specified, more details are printed. For ZFS pools the output resembles zpool status output.

lsmod [-v]

Displays loaded modules. If -v is specified, more details are shown.

lszfs filesystem

A ZFS extended command that can be used to explore the ZFS filesystem hierarchy in a pool. Lists the immediate children of the filesystem. The filesystem hierarchy is rooted at a filesystem with the same name as the pool.

more file [file ...]

Display the files specified, with a pause at each screen-#rows displayed.

read [-t seconds] [-p prompt] [variable]

Reads a line of input from the terminal, storing it in variable if specified. A timeout can be specified with -t, though it will be canceled at the first key pressed. A prompt may also be displayed through the -p flag.

reboot [-f]

Immediately reboots the system. On a UEFI system, if the -f flag is set, or the BOOT_TO_FW_UI environment variable exists, and the firmware supports this feature, the system will automatically enter the firmware setup after reboot.

set variable

 

set variable=value

Set loader's environment variables.

show [variable]

Displays the specified variable's value, or all variables and their values if variable is not specified.

unload

Remove all modules from memory.

unset variable

Removes variable from the environment.

?

Lists available commands.

ZFS Features

loader supports the following format for specifying ZFS filesystems which can be used wherever loader refers to a device specification:

zfs:pool/filesystem:

where pool/filesystem is a ZFS filesystem name as described in zfs(8).

Builtin Environment Variables

The loader has actually two different kinds of ‘environment’ variables. There are ANS Forth's environmental queries, and a separate space of environment variables used by builtins, which are not directly available to Forth words. It is the latter type that this section covers.

Environment variables can be set and unset through the set and unset builtins, and can have their values interactively examined through the use of the show builtin. Their values can also be accessed as described in BUILTIN PARSER.

Notice that these environment variables are not inherited by any shell after the system has been booted.

A few variables are set automatically by loader. Others can affect the behavior of either loader or the kernel at boot. Some options may require a value, while others define behavior just by being set. Both types of builtin variables are described below.

autoboot_delay

Number of seconds autoboot will wait before booting. If this variable is not defined, autoboot will default to 10 seconds.

If set to “NO”, no autoboot will be automatically attempted after processing /boot/loader.rc, though explicit autoboot's will be processed normally, defaulting to 10 seconds delay.

If set to “0”, no delay will be inserted, but user still will be able to interrupt autoboot process and escape into the interactive mode by pressing some key on the console while kernel and modules are being loaded.

If set to “-1”, no delay will be inserted and loader will engage interactive mode only if autoboot has failed for some reason.

boot_ask

Will set kernel(8) -a option.

boot_debug

Will set kernel(8) -d option.

boot_kmdb

Will set kernel(8) -k option.

boot_reconfigure

Will set kernel(8) -r option.

boot_single

Will set kernel(8) -s option.

boot_verbose

Will set kernel(8) -v option.

boot-args

Will set custom arguments for the kernel. If set in loader configuration, the loader startup will parse the boot-args value to set boot prefixed variables listed above, any unrecognized options are added to kernel command line verbatim.

bootfile

The name of the kernel.

chain_disk

If set, contains the device or file name used with chain command and will cause chain command menu entry to appear on loader main menu. The alternate method to use chain loader is to add menu entries into menu.lst(5) file.

console

Defines the current console or consoles. Multiple consoles may be specified. In that case, the first listed console will become the default console for the kernel(8).

currdev

Selects the default device. Syntax for devices is odd.

interpret

Has the value “ok” if the Forth's current state is interpreting.

screen-#rows

Define the number of lines on the screen, to be used by the pager.

module_path

Sets the list of directories which will be searched for modules named in a load command or implicitly required by a dependency. The default value for this variable is “/platform/i86pc/${ISADIR}”

prompt

Value of loader's prompt. Defaults to “${interpret}”. If variable prompt is unset, the default prompt is ‘>’.

os_console

If set, the value is used to set kernel(8) console property.

twiddle_divisor

Throttles the output of the ‘twiddle’ I/O progress indicator displayed while loading the kernel and modules. This is useful on slow serial consoles where the time spent waiting for these characters to be written can add up to many seconds. The spinner is updated only once every twiddle_divisor operations. The default value for twiddle_divisor is 16.

Other variables are used for loader or to set kernel properties or for informational purposes.

Builtin Parser

When a builtin command is executed, the rest of the line is taken by it as arguments, and it is processed by a special parser which is not used for regular Forth commands.

This special parser applies the following rules to the parsed text:

1. All backslash characters are preprocessed.
   • \b , \f , \r , \n and \t are processed as in C.
   • \s is converted to a space.
   • \v is converted to ASCII 11.
   • \z is just skipped. Useful for things like “\0xf\z\0xf”.
   • \0xN and \0xNN are replaced by the hex N or NN.
   • \NNN is replaced by the octal NNN ASCII character.
   • \" , \' and \$ will escape these characters, preventing them from receiving special treatment in Step 2, described below.
   • \\ will be replaced with a single \ .
   • In any other occurrence, backslash will just be removed.
2. Every string between non-escaped quotes or double-quotes will be treated as a single word for the purposes of the remaining steps.
3. Replace any $VARIABLE or ${VARIABLE} with the value of the environment variable VARIABLE.
4. Space-delimited arguments are passed to the called builtin command. Spaces can also be escaped through the use of \\ .

An exception to this parsing rule exists, and is described in Builtins And FORTH.

Builtins And FORTH

All builtin words are state-smart, immediate words. If interpreted, they behave exactly as described previously. If they are compiled, though, they extract their arguments from the stack instead of the command line.

If compiled, the builtin words expect to find, at execution time, the following parameters on the stack:

If no arguments are passed, a 0 must be passed, even if the builtin accepts no arguments.

While this behavior has benefits, it has its trade-offs. If the execution token of a builtin is acquired (through ' or [']), and then passed to catch or execute, the builtin behavior will depend on the system state

FICL

FICL is a Forth interpreter written in C, in the form of a forth virtual machine library that can be called by C functions and vice versa.

In loader, each line read interactively is then fed to FICL, which may call loader back to execute the builtin words. The builtin include will also feed FICL, one line at a time.

The words available to FICL can be classified into four groups. The ANS Forth standard words, extra FICL words, extra FreeBSD words, and the builtin commands; the latter were already described. The ANS Forth standard words are listed in the STANDARDS section. The words falling in the two other groups are described in the following subsections.

FICL Extra Words

.env

 

.ver

 

-roll

 

2constant

 

>name

 

body>

 

compare

This is the STRING word set's compare.

compile-only

 

endif

 

forget-wid

 

parse-word

 

sliteral

This is the STRING word set's sliteral.

wid-set-super

 

w@

 

w!

 

x.

 

empty

 

cell-

 

-rot

 

Loader Extra Words

$ (--)

Evaluates the remainder of the input buffer, after having printed it first.

% (--)

Evaluates the remainder of the input buffer under a catch exception guard.

.#

Works like . but without outputting a trailing space.

fclose (fd --)

Closes a file.

fkey (fd -- char)

Reads a single character from a file.

fload (fd --)

Processes a file fd.

fopen (addr len mode -- fd)

Opens a file. Returns a file descriptor, or -1 in case of failure. The mode parameter selects whether the file is to be opened for read access, write access, or both. The constants O_RDONLY, O_WRONLY, and O_RDWR are defined in /boot/forth/support.4th, indicating read only, write only, and read-write access, respectively.

fread (fd addr len -- len')

Tries to read len bytes from file fd into buffer addr. Returns the actual number of bytes read, or -1 in case of error or end of file.

heap? (-- cells)

Return the space remaining in the dictionary heap, in cells. This is not related to the heap used by dynamic memory allocation words.

inb (port -- char)

Reads a byte from a port.

isvirtualized? (-- addr len flag | flag)

Returns true and string with virtualization engine name or false.

key (-- char)

Reads a single character from the console.

key? (-- flag)

Returns true if there is a character available to be read from the console.

ms (u --)

Waits u microseconds.

outb (port char --)

Writes a byte to a port.

seconds (-- u)

Returns the number of seconds since midnight.

tib> (-- addr len)

Returns the remainder of the input buffer as a string on the stack.

Loader Extra Framebuffer Words

fb-bezier (x1 y1 x2 y2 x3 y3 width --)

Draws a quadratic Bezier curve in the current foreground color using the three provided points and specified line with.

fb-drawrect (x1 y1 x2 y2 fill --)

Draws a rectangle to the screen with the top left at (x1,y1) and the bottom right at (x2,y2) , using the current foreground color. If fill is true then the rectangle will be filled in.

fb-line (x1 y1 x2 y2 width --)

Draws a line from (x1,y1) to (x2,y2) in the current foreground color and with the specified width.

fb-putimage (flags x1 y1 x2 y2 addr len -- flag)

Outputs an image to the screen. Returns true if the image was able to be written and false otherwise. Only truecolor PNG images are supported and the path to the file must be provided through the addr and len arguments on the stack. The image will be displayed in the rectangular screen region with the top left at (x1,y1) and the bottom right at (x2,y2)

Either x2 or y2 can be set to "0" which causes it to be calculated to maintain the aspect ratio of the image. If both are "0" then the native resolution of the image will be used.

If x1 is "0", then the image will be placed as far over to the right of the screen as possible. Similarly, if y1 is "0", then the image will be placed as far down the screen as possible.

Flags is a bitfield; the following bits are defined:

1

Draw a single pixel border around the image in the current foreground color.

2

Do not scroll the image with the rest of the screen.

128

Output diagnostic information (for debugging).

fb-setpixel (x y --)

Colors the pixel at (x,y) with the current foreground color.

term-drawrect (x1 y1 x2 y2 --)

Draws a rectangle with rounded corners using terminal coordinates and the current foreground color.

Loader Defined Environmental Queries

arch-i386

TRUE if the architecture is IA32.

loader_version

loader version.

Errors

The following values are thrown by loader: