584 lines
14 KiB
Groff
584 lines
14 KiB
Groff
.\" Copyright (c) 1999 Daniel C. Sobral
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.Dd September 29, 2021
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.Dt LOADER_4TH 8
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.Os
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.Sh NAME
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.Nm loader_4th
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.Nd kernel bootstrapping final stage
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.Sh DESCRIPTION
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The program called
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.Nm
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is the final stage of
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.Fx Ns 's
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kernel bootstrapping process.
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On IA32 (i386) architectures, it is a
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.Pa BTX
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client.
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It is linked statically to
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.Xr libsa 3
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and usually located in the directory
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.Pa /boot .
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.Pp
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It provides a scripting language that can be used to
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automate tasks, do pre-configuration or assist in recovery
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procedures.
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This scripting language is roughly divided in
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two main components.
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The smaller one is a set of commands
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designed for direct use by the casual user, called "builtin
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commands" for historical reasons.
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The main drive behind these commands is user-friendliness.
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The bigger component is an
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.Tn ANS
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Forth compatible Forth interpreter based on FICL, by
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.An John Sadler .
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.Pp
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During initialization,
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.Nm
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will probe for a console and set the
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.Va console
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variable, or set it to serial console
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.Pq Dq Li comconsole
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if the previous boot stage used that.
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If multiple consoles are selected, they will be listed separated by spaces.
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Then, devices are probed,
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.Va currdev
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and
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.Va loaddev
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are set, and
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.Va LINES
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is set to 24.
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Next,
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.Tn FICL
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is initialized, the builtin words are added to its vocabulary, and
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.Pa /boot/boot.4th
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is processed if it exists.
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No disk switching is possible while that file is being read.
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The inner interpreter
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.Nm
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will use with
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.Tn FICL
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is then set to
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.Ic interpret ,
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which is
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.Tn FICL Ns 's
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default.
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After that,
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.Pa /boot/loader.rc
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is processed if available.
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These files are processed through the
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.Ic include
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command, which reads all of them into memory before processing them,
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making disk changes possible.
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.Pp
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At this point, if an
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.Ic autoboot
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has not been tried, and if
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.Va autoboot_delay
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is not set to
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.Dq Li NO
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(not case sensitive), then an
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.Ic autoboot
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will be tried.
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If the system gets past this point,
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.Va prompt
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will be set and
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.Nm
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will engage interactive mode.
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Please note that historically even when
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.Va autoboot_delay
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is set to
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.Dq Li 0
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user will be able to interrupt autoboot process by pressing some key
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on the console while kernel and modules are being loaded.
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In some
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cases such behaviour may be undesirable, to prevent it set
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.Va autoboot_delay
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to
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.Dq Li -1 ,
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in this case
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.Nm
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will engage interactive mode only if
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.Ic autoboot
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has failed.
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.Sh BUILTIN COMMANDS
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In
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.Nm ,
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builtin commands take parameters from the command line.
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Presently,
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the only way to call them from a script is by using
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.Pa evaluate
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on a string.
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If an error condition occurs, an exception will be generated,
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which can be intercepted using
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.Tn ANS
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Forth exception handling
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words.
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If not intercepted, an error message will be displayed and
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the interpreter's state will be reset, emptying the stack and restoring
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interpreting mode.
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The commands are described in the
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.Xr loader_simp 8
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.Dq BUILTIN COMMANDS
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section.
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.Ss BUILTIN ENVIRONMENT VARIABLES
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The environment variables common to all interpreters are described in the
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.Xr loader_simp 8
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.Dq BUILTIN ENVIRONMENT VARIABLES
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section.
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.Ss BUILTIN PARSER
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When a builtin command is executed, the rest of the line is taken
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by it as arguments, and it is processed by a special parser which
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is not used for regular Forth commands.
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.Pp
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This special parser applies the following rules to the parsed text:
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.Bl -enum
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.It
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All backslash characters are preprocessed.
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.Bl -bullet
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.It
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\eb , \ef , \er , \en and \et are processed as in C.
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.It
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\es is converted to a space.
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.It
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\ev is converted to
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.Tn ASCII
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11.
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.It
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\ez is just skipped.
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Useful for things like
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.Dq \e0xf\ez\e0xf .
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.It
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\e0xN and \e0xNN are replaced by the hex N or NN.
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.It
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\eNNN is replaced by the octal NNN
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.Tn ASCII
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character.
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.It
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\e" , \e' and \e$ will escape these characters, preventing them from
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receiving special treatment in Step 2, described below.
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.It
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\e\e will be replaced with a single \e .
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.It
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In any other occurrence, backslash will just be removed.
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.El
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.It
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Every string between non-escaped quotes or double-quotes will be treated
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as a single word for the purposes of the remaining steps.
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.It
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Replace any
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.Li $VARIABLE
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or
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.Li ${VARIABLE}
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with the value of the environment variable
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.Va VARIABLE .
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.It
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Space-delimited arguments are passed to the called builtin command.
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Spaces can also be escaped through the use of \e\e .
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.El
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.Pp
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An exception to this parsing rule exists, and is described in
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.Sx BUILTINS AND FORTH .
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.Ss BUILTINS AND FORTH
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All builtin words are state-smart, immediate words.
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If interpreted, they behave exactly as described previously.
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If they are compiled, though,
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they extract their arguments from the stack instead of the command line.
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.Pp
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If compiled, the builtin words expect to find, at execution time, the
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following parameters on the stack:
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.D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
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where
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.Ar addrX lenX
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are strings which will compose the command line that will be parsed
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into the builtin's arguments.
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Internally, these strings are concatenated in from 1 to N,
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with a space put between each one.
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.Pp
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If no arguments are passed, a 0
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.Em must
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be passed, even if the builtin accepts no arguments.
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.Pp
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While this behavior has benefits, it has its trade-offs.
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If the execution token of a builtin is acquired (through
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.Ic '
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or
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.Ic ['] ) ,
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|
and then passed to
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.Ic catch
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or
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.Ic execute ,
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the builtin behavior will depend on the system state
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.Bf Em
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at the time
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.Ic catch
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or
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.Ic execute
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is processed!
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.Ef
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This is particularly annoying for programs that want or need to
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handle exceptions.
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In this case, the use of a proxy is recommended.
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For example:
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.Dl : (boot) boot ;
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.Sh FICL
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.Tn FICL
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is a Forth interpreter written in C, in the form of a forth
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virtual machine library that can be called by C functions and vice
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|
versa.
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.Pp
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|
In
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.Nm ,
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|
each line read interactively is then fed to
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.Tn FICL ,
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|
which may call
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.Nm
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|
back to execute the builtin words.
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|
The builtin
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.Ic include
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will also feed
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.Tn FICL ,
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one line at a time.
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.Pp
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The words available to
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.Tn FICL
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can be classified into four groups.
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The
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.Tn ANS
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Forth standard words, extra
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.Tn FICL
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words, extra
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.Fx
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words, and the builtin commands;
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the latter were already described.
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The
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.Tn ANS
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Forth standard words are listed in the
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.Sx STANDARDS
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section.
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The words falling in the two other groups are described in the
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following subsections.
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.Ss FICL EXTRA WORDS
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.Bl -tag -width wid-set-super
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.It Ic .env
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.It Ic .ver
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.It Ic -roll
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.It Ic 2constant
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.It Ic >name
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.It Ic body>
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.It Ic compare
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|
This is the STRING word set's
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.Ic compare .
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.It Ic compile-only
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.It Ic endif
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.It Ic forget-wid
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.It Ic parse-word
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.It Ic sliteral
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This is the STRING word set's
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.Ic sliteral .
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.It Ic wid-set-super
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.It Ic w@
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.It Ic w!
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.It Ic x.
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.It Ic empty
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.It Ic cell-
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.It Ic -rot
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.El
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.Ss FREEBSD EXTRA WORDS
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.Bl -tag -width XXXXXXXX
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.It Ic \&$ Pq --
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Evaluates the remainder of the input buffer, after having printed it first.
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.It Ic \&% Pq --
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Evaluates the remainder of the input buffer under a
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.Ic catch
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exception guard.
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.It Ic .#
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Works like
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.Ic "."
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but without outputting a trailing space.
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.It Ic fclose Pq Ar fd --
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Closes a file.
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.It Ic fkey Pq Ar fd -- char
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Reads a single character from a file.
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.It Ic fload Pq Ar fd --
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Processes a file
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.Em fd .
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.It Ic fopen Pq Ar addr len mode Li -- Ar fd
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Opens a file.
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Returns a file descriptor, or \-1 in case of failure.
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The
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.Ar mode
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parameter selects whether the file is to be opened for read access, write
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access, or both.
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The constants
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.Dv O_RDONLY , O_WRONLY ,
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|
and
|
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.Dv O_RDWR
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are defined in
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.Pa /boot/support.4th ,
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indicating read only, write only, and read-write access, respectively.
|
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.It Xo
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.Ic fread
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.Pq Ar fd addr len -- len'
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.Xc
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Tries to read
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.Em len
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bytes from file
|
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.Em fd
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into buffer
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.Em addr .
|
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Returns the actual number of bytes read, or -1 in case of error or end of
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file.
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.It Ic heap? Pq -- Ar cells
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Return the space remaining in the dictionary heap, in cells.
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This is not related to the heap used by dynamic memory allocation words.
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.It Ic inb Pq Ar port -- char
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Reads a byte from a port.
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.It Ic key Pq -- Ar char
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Reads a single character from the console.
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.It Ic key? Pq -- Ar flag
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Returns
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.Ic true
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if there is a character available to be read from the console.
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.It Ic ms Pq Ar u --
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Waits
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.Em u
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microseconds.
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.It Ic outb Pq Ar port char --
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Writes a byte to a port.
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.It Ic seconds Pq -- Ar u
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Returns the number of seconds since midnight.
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.It Ic tib> Pq -- Ar addr len
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Returns the remainder of the input buffer as a string on the stack.
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.It Ic trace! Pq Ar flag --
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Activates or deactivates tracing.
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Does not work with
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.Ic catch .
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.El
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.Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
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.Bl -tag -width Ds
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.It arch-i386
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.Ic TRUE
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if the architecture is IA32.
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.It FreeBSD_version
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.Fx
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version at compile time.
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.It loader_version
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.Nm
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version.
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.El
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.Sh SECURITY
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Access to the
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.Nm
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command line provides several ways of compromising system security,
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including, but not limited to:
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.Pp
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.Bl -bullet
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.It
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Booting from removable storage, by setting the
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.Va currdev
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or
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.Va loaddev
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variables
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.It
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Executing binary of choice, by setting the
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.Va init_path
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or
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.Va init_script
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variables
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.It
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Overriding ACPI DSDT to inject arbitrary code into the ACPI subsystem
|
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.El
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.Pp
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One can prevent unauthorized access
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to the
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.Nm
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command line by setting the
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.Va password ,
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or setting
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.Va autoboot_delay
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to -1.
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|
See
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.Xr loader.conf 5
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for details.
|
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In order for this to be effective, one should also configure the firmware
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(BIOS or UEFI) to prevent booting from unauthorized devices.
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.Sh MD
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Memory disk (MD) can be used when the
|
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.Nm
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was compiled with
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.Va MD_IMAGE_SIZE .
|
|
The size of the memory disk is determined by
|
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.Va MD_IMAGE_SIZE .
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|
If MD available, a file system can be embedded into the
|
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.Nm
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with
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.Pa /sys/tools/embed_mfs.sh .
|
|
Then, MD will be probed and be set to
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.Va currdev
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during initialization.
|
|
.Pp
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|
Currently, MD is only supported in
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.Xr loader.efi 8 .
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.Sh FILES
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|
.Bl -tag -width /usr/share/examples/bootforth/ -compact
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|
.It Pa /boot/loader
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|
.Nm
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|
itself.
|
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.It Pa /boot/boot.4th
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|
Additional
|
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.Tn FICL
|
|
initialization.
|
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.It Pa /boot/defaults/loader.conf
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|
.It Pa /boot/loader.4th
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|
Extra builtin-like words.
|
|
.It Pa /boot/loader.conf
|
|
.It Pa /boot/loader.conf.local
|
|
.Nm
|
|
configuration files, as described in
|
|
.Xr loader.conf 5 .
|
|
.It Pa /boot/loader.rc
|
|
.Nm
|
|
bootstrapping script.
|
|
.It Pa /boot/loader.help
|
|
Loaded by
|
|
.Ic help .
|
|
Contains the help messages.
|
|
.It Pa /boot/support.4th
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|
.Pa loader.conf
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|
processing words.
|
|
.It Pa /usr/share/examples/bootforth/
|
|
Assorted examples.
|
|
.El
|
|
.Sh EXAMPLES
|
|
Boot in single user mode:
|
|
.Pp
|
|
.Dl boot -s
|
|
.Pp
|
|
Load the kernel, a splash screen, and then autoboot in five seconds.
|
|
Notice that a kernel must be loaded before any other
|
|
.Ic load
|
|
command is attempted.
|
|
.Bd -literal -offset indent
|
|
load kernel
|
|
load splash_bmp
|
|
load -t splash_image_data /boot/chuckrulez.bmp
|
|
autoboot 5
|
|
.Ed
|
|
.Pp
|
|
Set the disk unit of the root device to 2, and then boot.
|
|
This would be needed in a system with two IDE disks,
|
|
with the second IDE disk hardwired to ada2 instead of ada1.
|
|
.Bd -literal -offset indent
|
|
set root_disk_unit=2
|
|
boot /boot/kernel/kernel
|
|
.Ed
|
|
.Pp
|
|
Set the default device used for loading a kernel from a ZFS filesystem:
|
|
.Bd -literal -offset indent
|
|
set currdev=zfs:tank/ROOT/knowngood:
|
|
.Ed
|
|
.Pp
|
|
.Sh ERRORS
|
|
The following values are thrown by
|
|
.Nm :
|
|
.Bl -tag -width XXXXX -offset indent
|
|
.It 100
|
|
Any type of error in the processing of a builtin.
|
|
.It -1
|
|
.Ic Abort
|
|
executed.
|
|
.It -2
|
|
.Ic Abort"
|
|
executed.
|
|
.It -56
|
|
.Ic Quit
|
|
executed.
|
|
.It -256
|
|
Out of interpreting text.
|
|
.It -257
|
|
Need more text to succeed -- will finish on next run.
|
|
.It -258
|
|
.Ic Bye
|
|
executed.
|
|
.It -259
|
|
Unspecified error.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr libsa 3 ,
|
|
.Xr loader.conf 5 ,
|
|
.Xr tuning 7 ,
|
|
.Xr boot 8 ,
|
|
.Xr btxld 8
|
|
.Sh STANDARDS
|
|
For the purposes of ANS Forth compliance, loader is an
|
|
.Bf Em
|
|
ANS Forth System with Environmental Restrictions, Providing
|
|
.Ef
|
|
.Bf Li
|
|
.No .( ,
|
|
.No :noname ,
|
|
.No ?do ,
|
|
parse, pick, roll, refill, to, value, \e, false, true,
|
|
.No <> ,
|
|
.No 0<> ,
|
|
compile\&, , erase, nip, tuck
|
|
.Ef
|
|
.Em and
|
|
.Li marker
|
|
.Bf Em
|
|
from the Core Extensions word set, Providing the Exception Extensions
|
|
word set, Providing the Locals Extensions word set, Providing the
|
|
Memory-Allocation Extensions word set, Providing
|
|
.Ef
|
|
.Bf Li
|
|
\&.s,
|
|
bye, forget, see, words,
|
|
\&[if],
|
|
\&[else]
|
|
.Ef
|
|
.Em and
|
|
.Li [then]
|
|
.Bf Em
|
|
from the Programming-Tools extension word set, Providing the
|
|
Search-Order extensions word set.
|
|
.Ef
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
first appeared in
|
|
.Fx 3.1 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm
|
|
was written by
|
|
.An Michael Smith Aq msmith@FreeBSD.org .
|
|
.Pp
|
|
.Tn FICL
|
|
was written by
|
|
.An John Sadler Aq john_sadler@alum.mit.edu .
|