freebsd-src/sys/boot/common/loader.8

.\" Copyright (c) 1999 Daniel C. Sobral
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" $FreeBSD$
.\"
.\" Note: The date here should be updated whenever a non-trivial
.\" change is made to the manual page.
.Dd March 14, 1999
.Dt LOADER 8
.Os
.Sh NAME
.Nm loader
.Nd kernel bootstrapping final stage
.Sh DESCRIPTION
The program called
.Nm
is the final stage of FreeBSD's kernel bootstrapping process.
On IA32 (i386) architectures, it is a
.Pa BTX
client.
It is linked statically to
.Xr libstand 3
and usually located in the directory
.Pa /boot .
.Pp
It provides a scripting language that can be used to
automate tasks, do pre-configuration or assist in recovery
procedures.
This scripting language is roughly divided in
two main components.
The smaller one is a set of commands
designed for direct use by the casual user, called "builtin
commands" for historical reasons.
The main drive behind these commands is user-friendlyness.
The bigger component is an
.Tn ANS
Forth compatible Forth interpreter based on ficl, by
.An John Sadler .
.Pp
During initialization,
.Nm
will probe for a console and set the
.Va console
variable, or set it to serial console
.Pq Dq comconsole
if the previous boot stage used that.
Then, devices are probed,
.Va currdev
and
.Va loaddev
are set, and
.Va LINES
is set to 24.
Next, 
.Tn FICL
is initialized, the builtin words are added to its vocabulary, and
.Pa /boot/boot.4th
will be processed if it exists.
No disk switching is possible while that file is being read.
The inner interpreter
.Nm
will use with
.Tn FICL
is then set to
.Ic interpret ,
which is
.Tn FICL Ns 's
default.
After that,
.Pa /boot/loader.rc
is processed if available, and, failing that,
.Pa /boot/boot.conf
will be read for historical reasons.
These files are processed through the
.Ic include
command, which read all of them into memory before processing them,
making disk changes possible.
.Pp
At this point, if an
.Ic autoboot
has not been tried, and if
.Va autoboot_delay
is not set to
.Dq NO
(not case sensitive), then an
.Ic autoboot
will be tried.
If the system gets past this point,
.Va prompt
will be set and
.Nm
will engage interactive mode.
.Sh BUILTIN COMMANDS
.Nm Loader Ns No 's
builtin commands take its parameters from the command line.
Presently,
the only way to call them from a script is by using
.Pa evaluate
on a string.
If an error condition occurs, an exception will be generated,
which can be intercepted using
.Tn 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.
.Pp
The builtin commands available are:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ic autoboot Op Ar seconds
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.
.Pp
.It Ic bcachestat
Displays statistics about disk cache usage.
For depuration only.
.Pp
.It Ic boot
.It Ic boot Ar kernelname Op Cm ...
.It Ic boot Fl flag Cm ...
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.
.Pp
.Em WARNING:
The behavior of this builtin is changed if
.Xr loader.4th 8
is loaded.
.Pp
.It Ic echo Xo
.Op Fl n
.Op Aq message
.Xc
Displays a text on the screen.
A new line will be printed unless
.Fl n
is specified.
.Pp
.It Ic heap
Displays memory usage statistics.
For debugging purposes only.
.Pp
.It Ic help Op topic Op subtopic
Shows help messages read from
.Pa /boot/loader.help .
The special topic
.Em index
will list the topics available.
.Pp
.It Ic include Ar file Op Ar
Process script files.
Each file is, at a turn, completely read into memory,
and then have each of its lines passed to the command line interpreter.
If any error is returned by the interpreter, the include
commands aborts immediately, without reading any other files, and
returns an error itself (see
.Sx ERRORS ) .
.Pp
.It Ic load Xo
.Op Fl t Ar type
.Ar file Cm ...
.Xc
Loads a kernel, kernel loadable module (kld), or a file of opaque
contents tagged as being of the type
.Ar 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.
Notice, though, that, at the present, this does not work for the kernel.
.Pp
.It Ic ls Xo
.Op Fl l
.Op Ar path
.Xc
Displays a listing of files in the directory
.Ar path ,
or the root directory if 
.Ar path
is not specified.
If
.Fl l
is specified, file sizes will be shown too.
.Pp
.It Ic lsdev Op Fl v
Lists all of the devices from which it may be possible to load modules.
If
.Fl v
is specified, more details are printed.
.Pp
.It Ic lsmod Op Fl v
Displays loaded modules.
If
.Fl v
is specified, more details are shown.
.Pp
.It Ic more Ar file Op Ar
Display the files specified, with a pause at each
.Va LINES
displayed.
.Pp
.It Ic pnpscan Op Fl v
Scans for Plug-and-Play devices.
This is not functional at the present.
.Pp
.It Ic read Xo
.Op Fl t Ar seconds
.Op Fl p Ar prompt
.Op Va variable
.Xc
Reads a line of input from the terminal, storing it in
.Va variable
if specified.
A timeout can be specified with
.Fl t ,
though it will be canceled at the first key pressed.
A prompt may also be displayed through the
.Fl p
flag.
.Pp
.It Ic reboot
Immediately reboots the system.
.Pp
.It Ic set Ar variable
.It Ic set Ar variable Ns = Ns Ar value
Set loader's environment variables.
.Pp
.It Ic show Op Va variable
Displays the specified variable's value, or all variables and their
values if
.Va variable
is not specified.
.Pp
.It Ic unload
Remove all modules from memory.
.Pp
.It Ic unset Va variable
Removes
.Va variable
from the environment.
.Pp
.It Ic \&?
Same as
.Dq help index .
.Pp
.El
.Ss BUILTIN ENVIRONMENT VARIABLES
The
.Nm
has actually two different kinds of
.Sq environment
variables.
There are ANS Forth's
.Em environmental queries ,
and a separate space of environment variables used by builtins, which
are not directly available to Forth words.
It is the later ones that this session covers.
.Pp
Environment variables can be set and unset through the use of the
.Ic set
and
.Ic unset
builtins, and have their value interactively examined through the
use of the
.Ic show
builtin.
Their values can also be accessed as described in
.Sx BUILTIN PARSER .
.Pp
Notice that this environment variables are not inherited by any shell
after the system has been booted.
.Pp
A few variables are set automatically by
.Nm loader .
Others can affect either
.Nm
or kernel's behavior at boot.
While some of these may require a value,
others define behavior just by being set.
These are described below.
.Bl -tag -width bootfile -offset indent
.It Va autoboot_delay
Number of seconds
.Ic autoboot
will wait before booting.
If this variable is not defined,
.Ic autoboot
will default to 10 seconds.
.Pp
If set to
.Dq NO ,
no
.Ic autoboot
will be automatically attempted after processing
.Pa /boot/loader.rc ,
though explict
.Ic autoboot Ns 's
will be processed normally, defaulting to 10 seconds delay.
.It Va boot_askname
Instructs the kernel to prompt the user for the name of the root device
when the kernel is booted.
.It Va boot_ddb
Instructs the kernel to start in the DDB debugger, rather than
proceeding to initialise when booted.
.It Va boot_gdb
Selects gdb-remote mode for the kernel debugger by default.
.It Va boot_single
Prevents the kernel from initiating a multi-user startup, single-user
mode will be entered when the kernel has finished device probes.
.It Va boot_userconfig
Requests that the kernel's interactive device configuration program
be run when the kernel is booted.
.It Va boot_verbose
Setting this variable causes extra debugging information to be printed
by the kernel during the boot phase.
.It Va bootfile
List of semicolon-separated search path for bootable kernels.
The default is
.Li Dq kernel;kernel.old .
.It Va console
Defines the current console.
.It Va currdev
Selects the default device.
Syntax for devices is odd.
.It Va init_path
Sets the list of binaries which the kernel will try to run as initial
process.
The default is
.Li Dq /sbin/init:/sbin/oinit:/sbin/init.bak:/stand/sysinstall .
.It Va interpret
Has the value 
.Li Dq ok
if the Forth's current state is interpreting.
.It Va LINES
Define the number of lines on the screen, to be used by the pager.
.It Va module_path
Sets the list of directories which will be searched in for modules
named in a load command or implicitly required by a dependancy.
The default value for this variable is
.Li Dq /;/boot;/modules .
.It Va num_ide_disks
Sets the number of IDE disks as a work around for some problems in
finding the root disk at boot.
This has been deprecated in favour of
.Va root_disk_unit .
.It Va prompt
Value of
.Nm Ns No 's
prompt.
Defaults to
.Li Dq "${currdev}>" .
.It Va root_disk_unit
If the code which detects the disk unit number for the root disk is
confused, eg. by a mix of SCSI and IDE disks, or IDE disks with
gaps in the sequence (eg. no primary slave), the unit number can
be forced by setting this variable.
.It Va rootdev
By default the value of
.Va currdev
is used to set the root filesystem
when the kernel is booted.
This can be overridden by setting
.Va rootdev
explicitly.
.El
.Pp
Other variables are used to override kernel tunable parameters.
The following tunables are available:
.Bl -tag -width Va -offset indent
.It Va kern.ipc.nmbclusters
Set the number of mbuf clusters to be allocated.
The value cannot be set below the default
determined when the kernel was compiled.
Modifies
.Va NMBCLUSTERS .
.It Va kern.vm.kmem.size
Sets the size of kernel memory (bytes).
This overrides completely the value
determined when the kernel was compiled.
Modifies
.Va VM_KMEM_SIZE .
.It Va machdep.pccard.pcic_irq
Overrides the IRQ normally assigned to a PCCARD controller.
Typically the first available interrupt will be allocated,
which may conflict with other hardware.
If this value is set to 0,
an interrupt will not be assigned
and the controller will operate in polled mode only.
.It Va net.inet.tcp.tcbhashsize
Overrides the compile-time set value of
.Va TCBHASHSIZE
or the preset default of 512.
Must be a power of 2.
.El
.Ss 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.
.Pp
This special parser applies the following rules to the parsed text:
.Pp
.Bl -enum
.It
All backslash characters are preprocessed.
.Bl -bullet
.It
\eb , \ef , \er , \en and \et are processed as in C.
.It
\es is converted to a space.
.It
\ev is converted to
.Tn ASCII
11.
.It
\ez is just skipped.
Useful for things like
.Dq \e0xf\ez\e0xf .
.It
\e0xN and \e0xNN are replaced by the hex N or NN.
.It
\eNNN is replaced by the octal NNN
.Tn ASCII
character.
.It
\e" , \e' and \e$ will escape these characters, preventing them from
receiving special semantics on the step 2 described below.
.It
\e\e will be replaced with a single \e .
.It
In any other occurance, backslash will just be removed.
.El
.It
Every string between non-escaped quotes or double-quotes will be treated
as a single word for the purposes of the remaining steps.
.It
Replace any
.Li $VARIABLE
or
.Li ${VARIABLE}
with the value of the environemnt variable
.Va VARIABLE .
.It
Passes multiple space-delimited arguments to the builtin command called.
Spaces can also be escaped through the use of \e\e .
.El
.Pp
An exception to this parsing rule exists, and is described in
.Sx BUILTINS AND FORTH .
.Ss 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.
.Pp
If compiled, the builtin words expect to find, at execution time, the
following parameters on the stack:
.D1 Ar addrN lenN ... addr2 len2 addr1 len1 N
where
.Ar addrX lenX
are strings which will compose the command line that will be parsed
into the builtin's arguments.
Internally, these strings are concatenated in from 1 to N,
with a space put between each one.
.Pp
If no arguments are passed, a 0
.Em must
be passed, even if the builtin accepts no arguments.
.Pp
While this behavior has benefits, it has its trade-offs.
If the execution token of a builtin is acquired (through
.Ic No '
or
.Ic No ['] ) ,
and then passed to
.Ic catch
or
.Ic execute ,
the builtin behavior will depend on the system state
.Bf Em
at the time
.Ic catch
or
.Ic execute
is processed
.Ef
\&! This is particular annoying for programs that want or need to
treat exceptions.
In this case, it is recommended the use of a proxy.
For example:
.Dl : (boot) boot ;
.Sh FICL
.Tn 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.
.Pp
In
.Nm No ,
each line read interactively is then fed to
.Tn FICL ,
which may call
.Nm
back to execute the builtin words.
The builtin
.Ic include
will also feed
.Tn FICL ,
one line at a time.
.Pp
The words available to
.Tn FICL
can be classified in four groups.
The
.Tn ANS
Forth standard words, extra
.Tn FICL
words, extra
.Os
words, and the builtin commands.
The later were already described.
The
.Tn ANS
Forth standard words are listed in the
.Sx STANDARDS
section.
The words falling in the two other groups are described in the
following subsections.
.Ss FICL EXTRA WORDS
.Bl -tag -width wid-set-super -offset indent
.It Ic .env
.It Ic .ver
.It Ic -roll
.It Ic 2constant
.It Ic >name
.It Ic body>
.It Ic compare
This is the STRING word set's
.Ic compare .
.It Ic compile-only
.It Ic endif
.It Ic forget-wid
.It Ic parse-word
.It Ic sliteral
This is the STRING word set's
.Ic sliteral .
.It Ic wid-set-super
.It Ic w@
.It Ic w!
.It Ic x.
.It Ic empty
.It Ic cell-
.It Ic -rot
.El
.Ss FREEBSD EXTRA WORDS
.Bl -tag -width XXXXXXXX -offset indent
.It Ic \&$ Pq --
Evaluates the remainder of the input buffer, after having printed it first.
.It Ic \&% Pq --
Evaluates the remainder of the input buffer under a
.Ic catch
exception guard.
.It Ic .#
Works like
.Ic .
but without outputting a trailing space.
.It Ic fclose Pq Ar fd --
Closes a file.
.It Ic fkey Pq Ar fd -- char
Reads a single character from a file.
.It Ic fload Pq Ar fd --
Process file
.Em fd .
.It Ic fopen Pq Ar addr len -- fd
Open a file.
Returns a file descriptor, or -1 in case of failure.
.It Xo
.Ic fread
.Pq Ar fd addr len -- len'
.Xc
Tries to read
.Em len
bytes from file
.Em fd
into buffer
.Em addr .
Returns the actual number of bytes read, or -1 in case of error or end of
file.
.It Ic heap? Pq -- Ar cells
Return the space remaining in the dictionary heap, in cells.
This is not related to the heap used by dynamic memory allocation words.
.It Ic inb Pq Ar port -- char
Reads a byte from a port.
.It Ic key Pq -- Ar char
Reads a single character from the console.
.It Ic key? Pq -- Ar flag
Returns
.Ic true
if there is a character available to be read from the console.
.It Ic ms Pq Ar u --
Waits
.Em u
microseconds.
.It Ic outb Pq Ar port char --
Writes a byte to a port.
.It Ic seconds Pq -- Ar u
Returns the number of seconds since midnight.
.It Ic tib> Pq -- Ar addr len
Returns the remainder of the input buffer as a string on the stack.
.It Ic trace! Pq Ar flag --
Activates or deactivates tracing.
Does not work with
.Ic catch .
.El
.Ss FREEBSD DEFINED ENVIRONMENTAL QUERIES
.Bl -tag -width Ds -offset indent
.It arch-i386
.Ic TRUE
if the architecture is IA32.
.It arch-alpha
.Ic TRUE
if the architecture is AXP.
.It FreeBSD_version
.Fx
version at compile time.
.It loader_version
.Nm
version.
.El
.Ss SYSTEM DOCUMENTATION
.Sh FILES
.Bl -tag -width /dev/loader.helpX -compact
.It Pa /boot/loader
.Nm
itself.
.It Pa /boot/boot.4th
Additional
.Tn FICL
initialization.
.It Pa /boot/boot.conf
.Nm
bootstrapping script.
Deprecated.
.It Pa /boot/defaults/loader.conf
.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.
.El
.Sh EXAMPLES
Boot in single user mode:
.Pp
.Dl boot -s
.Pp
Loads kernel's user configuration file.
Notice that a kernel must be loaded before any other
.Ic load
command is attempted.
.Pp
.Bd -literal -offset indent -compact
load kernel
load -t userconfig_script /boot/kernel.conf
.Ed
.Pp
Loads the kernel, a splash screen, and then autoboots in five seconds.
.Pp
.Bd -literal -offset indent -compact
load kernel
load splash_bmp
load -t splash_image_data /boot/chuckrulez.bmp
autoboot 5
.Ed
.Pp
Sets the disk unit of the root device to 2, and then boots.
This would be needed in the case of a two IDE disks system,
with the second IDE hardwired to wd2 instead of wd1.
.Pp
.Bd -literal -offset indent -compact
set root_disk_unit=2
boot /kernel
.Ed
.Pp
See also:
.Bl -tag -width /usr/share/examples/bootforth/X
.It Pa /boot/loader.4th
Extra builtin-like words.
.It Pa /boot/support.4th
.Pa loader.conf
processing words.
.It Pa /usr/share/examples/bootforth/
Assorted examples.
.El
.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 libstand 3 ,
.Xr loader.conf 5 ,
.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 No [then]
.Bf Em
from the Programming-Tools extension word set, Providing the
Search-Order extensions word set.
.Ef
.Sh HISTORY
.Nm
first appeared in
.Fx 3.1 .
.Sh AUTHORS
.Bl -item
.It
.Nm
was written by
.An Michael Smith Aq msmith@freebsd.org .
.It
.Tn FICL
was written by
.An John Sadler Aq john_sadler@alum.mit.edu .
.El
.Sh BUGS
The
.Ic expect
and
.Ic accept
words will read from the input buffer instead of the console.
The latter will be fixed, but the former will not.