regen

unix v7是最后一个广泛发布的研究型UNIX版本

.TL
Regenerating System Software
.AU
Charles B. Haley
.AU
Dennis. M. Ritchie
.MH
.SH
Introduction
.PP
This document discusses how to
assemble or compile various parts of the
.UX
system software.
This may be necessary because
a command or library is accidentally
deleted or otherwise
destroyed;
also, it may be desirable to install a modified
version of some command or library routine.
A few commands depend
to some degree on the current configuration
of the system;
thus in any new system modifications to some commands
are advisable.
Most of the likely modifications
relate to the standard disk devices contained
in the system.
For example, the df(1) (`disk free')
command has built into it the names of
the standardly present disk storage drives
(e.g. `/dev/rf0', `/dev/rp0').
Df(1) takes an argument to indicate which
disk to examine, but it is convenient
if its default argument is adjusted to
reflect the ordinarily present devices.
The companion document `Setting up UNIX'
discusses which commands are likely to require
changes.
.SH
Where Commands and Subroutines Live
.PP
The
source files for commands and subroutines reside
in several subdirectories
of the directory /usr/src.
These subdirectories, and a general
description of their contents, are
.IP cmd 12
Source files for commands.
.IP libc/stdio 12
Source files making up the `standard i/o package'.
.IP libc/sys 12
Source files for the C system call interfaces.
.IP libc/gen 12
Source files for most of the remaining routines described
in section 3 of the manual.
.IP libc/crt 12
Source files making up the C runtime support package, as
in call save-return and long arithmetic.
.IP libc/csu 12
Source for the C startup routines.
.IP games 12
Source for (some of) the games.
No great care has been taken to try to make it obvious how
to compile these; treat it as a game.
.IP libF77 12
Source for the Fortran 77 runtime library, exclusive of IO.
.IP libI77 12
Source for the Fortran 77 IO runtime routines.
.IP libdbm 12
Source for the `data-base manager' package
.I dbm
(3).
.IP libfpsim 12
Source for the floating-point simulator routine.
.IP libm 12
Source for the mathematical library.
.IP libplot 12
Source for plotting routines.
.SH
Commands
.PP
The regeneration of most commands
is straightforward.
The `cmd' directory will contain either a source file
for the command or a subdirectory containing the set
of files that make up the command.
If it is a single file the command
.DS
cd /usr/src/cmd
cmake cmd_name
.DE
suffices. (Cmd_name is the name of the command you
are playing with.)
The result of the cmake command will be an executable version.
If you type
.DS
cmake \-cp cmd_name
.DE
the result
will be copied to /bin
(or perhaps /etc or other places if appropriate).
.PP
If the source files are in a subdirectory there will be a `makefile'
(see make(1)) to control the regeneration.
After changing to the proper directory (cd(1)) you type one of the following:
.IP "make all" 12
The program is compiled and loaded; the executable is
left in the current directory.
.IP "make cp" 12
The program is compiled and loaded, and the executable is
installed.
Everything is cleaned up afterwards;
for example .o files are deleted.
.IP "make cmp" 12
The program is compiled and loaded, and the executable is compared
against the one in /bin.
.PP
Some of the makefiles have other options. Print (cat(1)) the ones you
are interested in to find out.
.SH
The Assembler
.PP
The assembler consists of two executable files:
/bin/as and /lib/as2.
The first is the 0-th pass:
it reads the source program, converts it to
an intermediate form in a temporary file `/tmp/atm0?',
and estimates the final locations
of symbols.
It also makes two or three other temporary
files which contain the ordinary symbol table,
a table of temporary symbols (like 1:)
and possibly an overflow intermediate file.
The program /lib/as2
acts as an ordinary multiple pass assembler
with input taken from the files produced by /bin/as.
.PP
The source files for /bin/as
are named `/usr/src/cmd/as/as1?.s'
(there are 9 of them);
/lib/as2 is produced
from the source files
`/usr/src/cmd/as/as2?.s';
they likewise are 9 in number.
Considerable care should be exercised
in replacing either component of the
assembler.
Remember that if the assembler is lost,
the only recourse is to replace it from some backup storage;
a broken assembler cannot assemble itself.
.SH
The C Compiler
.PP
The C compiler consists of
seven routines:
`/bin/cc',
which calls the phases of the compiler proper,
the compiler control line expander `/lib/cpp',
the assembler (`as'), and the loader (`ld').
The phases of the C compiler are
`/lib/c0', which is the first phase of the compiler;
`/lib/c1', which is the second phase of the compiler;
and `/lib/c2', which is the optional
third phase optimizer.
The loss of the C compiler is as serious
as that of the assembler.
.PP
The source for /bin/cc
resides in `/usr/src/cmd/cc.c'.
Its loss alone (or that of c2) is not fatal.
If needed,
prog.c can be compiled by
.DS
/lib/cpp prog.c >temp0
/lib/c0 temp0 temp1 temp2
/lib/c1 temp1 temp2 temp3
as \- temp3
ld \-n /lib/crt0.o a.out \-lc
.DE
.PP
The source for the compiler proper is in the
directory /usr/src/cmd/c.
The first phase (/lib/c0)
is generated from the files c00.c, ..., c05.c,
which must be compiled by the C compiler.
There is also c0.h, a header file
.I included
by the C programs of the first phase.
To make a new /lib/c0 use
.DS
make c0
.DE
Before installing the new c0, it is prudent to save the old one someplace.
.PP
The second phase of C (/lib/c1)
is generated from the source files c10.c, ..., c13.c,
the include-file c1.h, and a set
of object-code tables combined into table.o.
To generate a new second phase use
.DS
make c1
.DE
It is likewise prudent to save c1 before
installing a new version.
In fact in general it is wise to save the
object files for the C compiler so that
if disaster strikes C can be reconstituted
without a working version of the compiler.
.PP
In a similar manner,
the third phase of the C compiler
(/lib/c2)
is made up from the files
c20.c and c21.c together with c2.h.
Its loss is not critical since it is completely optional.
.PP
The set of tables mentioned above
is generated from the file
table.s.
This `.s' file is not in fact assembler source;
it must be converted by use of the 
.I cvopt
program, whose source and object are
located in the C directory.
Normally this is taken care of by make(1). You
might want to look at the makefile to see what it does.
.SH
UNIX
.PP
The source and object programs for UNIX are kept in
four subdirectories of
.I /usr/sys.
In the subdirectory 
.I h
there are several files ending in `.h';
these are header files which are
picked up (via `#include ...')
as required by each system module.
The subdirectory
.I dev
consists mostly of the device drivers
together with a few other things.
The subdirectory
.I sys
is the rest of the system.
There are files of the form LIBx in the directories
sys and dev. These are archives (ar(1)) which contain the
object versions of the routines in the directory.
.PP
Subdirectory
.I conf
contains the files which control
device configuration of the system.
.I L.s
specifies the
contents of the interrupt vectors;
.I c.c
contains the tables which relate device numbers
to handler routines.
A third file,
.I mch.s ,
contains all the
machine-language code in the system.
A fourth file,
.I mch0.s ,
is generated by mkconf(1) and contains
flags indicating what sort of tape drive is available
for taking crash dumps.
.PP
There are two ways to recreate the system. Use
.DS
cd /usr/sys/conf