openssl/Configurations

Intro
=====

This directory contains a few sets of files that are used for
configuration in diverse ways:

*.conf Target platform configurations, please read
'Configurations of OpenSSL target platforms' for more
information.
*.tmpl Build file templates, please read 'Build-file
programming with the "unified" build system' as well
as 'Build info files' for more information.
*.pm Helper scripts / modules for the main `Configure`
script. See 'Configure helper scripts for more
information.


Configurations of OpenSSL target platforms
==========================================

Configuration targets are a collection of facts that we know about
different platforms and their capabilities. We organise them in a
hash table, where each entry represent a specific target.

Note that configuration target names must be unique across all config
files. The Configure script does check that a config file doesn't
have config targets that shadow config targets from other files.

In each table entry, the following keys are significant:

inherit_from => Other targets to inherit values from.
Explained further below. [1]
template => Set to 1 if this isn't really a platform
target. Instead, this target is a template
upon which other targets can be built.
Explained further below. [1]

sys_id => System identity for systems where that
is difficult to determine automatically.

enable => Enable specific configuration features.
This MUST be an array of words.
disable => Disable specific configuration features.
This MUST be an array of words.
Note: if the same feature is both enabled
and disabled, disable wins.

as => The assembler command. This is not always
used (for example on Unix, where the C
compiler is used instead).
asflags => Default assembler command flags [4].
cpp => The C preprocessor command, normally not
given, as the build file defaults are
usually good enough.
cppflags => Default C preprocessor flags [4].
defines => As an alternative, macro definitions may be
given here instead of in `cppflags' [4].
If given here, they MUST be as an array of
the string such as "MACRO=value", or just
"MACRO" for definitions without value.
includes => As an alternative, inclusion directories
may be given here instead of in `cppflags'
[4]. If given here, the MUST be an array
of strings, one directory specification
each.
cc => The C compiler command, usually one of "cc",
"gcc" or "clang". This command is normally
also used to link object files and
libraries into the final program.
cxx => The C++ compiler command, usually one of
"c++", "g++" or "clang++". This command is
also used when linking a program where at
least one of the object file is made from
C++ source.
cflags => Defaults C compiler flags [4].
cxxflags => Default C++ compiler flags [4]. If unset,
it gets the same value as cflags.

(linking is a complex thing, see [3] below)
ld => Linker command, usually not defined
(meaning the compiler command is used
instead).
(NOTE: this is here for future use, it's
not implemented yet)
lflags => Default flags used when linking apps,
shared libraries or DSOs [4].
ex_libs => Extra libraries that are needed when
linking shared libraries, DSOs or programs.
The value is also assigned to Libs.private
in $(libdir)/pkgconfig/libcrypto.pc.

shared_cppflags => Extra C preprocessor flags used when
processing C files for shared libraries.
shared_cflag => Extra C compiler flags used when compiling
for shared libraries, typically something
like "-fPIC".
shared_ldflag => Extra linking flags used when linking
shared libraries.
module_cppflags
module_cflags
module_ldflags => Has the same function as the corresponding
`shared_' attributes, but for building DSOs.
When unset, they get the same values as the
corresponding `shared_' attributes.

ar => The library archive command, the default is
"ar".
(NOTE: this is here for future use, it's
not implemented yet)
arflags => Flags to be used with the library archive
command. On Unix, this includes the
command letter, 'r' by default.

ranlib => The library archive indexing command, the
default is 'ranlib' it it exists.

unistd => An alternative header to the typical
''. This is very rarely needed.

shared_extension => File name extension used for shared
libraries.
obj_extension => File name extension used for object files.
On unix, this defaults to ".o" (NOTE: this
is here for future use, it's not
implemented yet)
exe_extension => File name extension used for executable
files. On unix, this defaults to "" (NOTE:
this is here for future use, it's not
implemented yet)
shlib_variant => A "variant" identifier inserted between the base
shared library name and the extension. On "unixy"
platforms (BSD, Linux, Solaris, MacOS/X, ...) this
supports installation of custom OpenSSL libraries
that don't conflict with other builds of OpenSSL
installed on the system. The variant identifier
becomes part of the SONAME of the library and also
any symbol versions (symbol versions are not used or
needed with MacOS/X). For example, on a system
where a default build would normally create the SSL
shared library as 'libssl.so -> libssl.so.1.1' with
the value of the symlink as the SONAME, a target
definition that sets 'shlib_variant => "-abc"' will
create 'libssl.so -> libssl-abc.so.1.1', again with
an SONAME equal to the value of the symlink. The
symbol versions associated with the variant library
would then be 'OPENSSL_ABC_' rather than
the default 'OPENSSL_'. The string inserted
into symbol versions is obtained by mapping all
letters in the "variant" identifier to upper case
and all non-alphanumeric characters to '_'.

thread_scheme => The type of threads is used on the
configured platform. Currently known
values are "(unknown)", "pthreads",
"uithreads" (a.k.a solaris threads) and
"winthreads". Except for "(unknown)", the
actual value is currently ignored but may
be used in the future. See further notes
below [2].
dso_scheme => The type of dynamic shared objects to build
for. This mostly comes into play with
modules, but can be used for other purposes
as well. Valid values are "DLFCN"
(dlopen() et al), "DLFCN_NO_H" (for systems
that use dlopen() et al but do not have
fcntl.h), "DL" (shl_load() et al), "WIN32"
and "VMS".
asm_arch => The architecture to be used for compiling assembly
source. This acts as a selector in build.info files.
uplink_arch => The architecture to be used for compiling uplink
source. This acts as a selector in build.info files.
This is separate from asm_arch because it's compiled
even when 'no-asm' is given, even though it contains
assembler source.
perlasm_scheme => The perlasm method used to create the
assembler files used when compiling with
assembler implementations.
shared_target => The shared library building method used.
This serves multiple purposes:
- as index for targets found in shared_info.pl.
- as linker script generation selector.
To serve both purposes, the index for shared_info.pl
should end with '-shared', and this suffix will be
removed for use as a linker script generation
selector. Note that the latter is only used if
'shared_defflag' is defined.
build_scheme => The scheme used to build up a Makefile.
In its simplest form, the value is a string
with the name of the build scheme.
The value may also take the form of a list
of strings, if the build_scheme is to have
some options. In this case, the first
string in the list is the name of the build
scheme.
Currently recognised build scheme is "unified".
For the "unified" build scheme, this item
*must* be an array with the first being the
word "unified" and the second being a word
to identify the platform family.

multilib => On systems that support having multiple
implementations of a library (typically a
32-bit and a 64-bit variant), this is used
to have the different variants in different
directories.

bn_ops => Building options (was just bignum options in
the earlier history of this option, hence the
name). This is a string of words that describe
algorithms' implementation parameters that
are optimal for the designated target platform,
such as the type of integers used to build up
the bignum, different ways to implement certain
ciphers and so on. To fully comprehend the
meaning, the best is to read the affected
source.
The valid words are:

THIRTY_TWO_BIT bignum limbs are 32 bits,
this is default if no
option is specified, it
works on any supported
system [unless "wider"
limb size is implied in
assembly code];
BN_LLONG bignum limbs are 32 bits,
but 64-bit 'unsigned long
long' is used internally
in calculations;
SIXTY_FOUR_BIT_LONG bignum limbs are 64 bits
and sizeof(long) is 8;
SIXTY_FOUR_BIT bignums limbs are 64 bits,
but execution environment
is ILP32;
RC4_CHAR RC4 key schedule is made
up of 'unsigned char's;
RC4_INT RC4 key schedule is made
up of 'unsigned int's;


[1] as part of the target configuration, one can have a key called
'inherit_from' that indicate what other configurations to inherit
data from. These are resolved recursively.

Inheritance works as a set of default values that can be overridden
by corresponding key values in the inheriting configuration.

Note 1: any configuration table can be used as a template.
Note 2: pure templates have the attribute 'template => 1' and
cannot be used as build targets.

If several configurations are given in the 'inherit_from' array,
the values of same attribute are concatenated with space
separation. With this, it's possible to have several smaller
templates for different configuration aspects that can be combined
into a complete configuration.

instead of a scalar value or an array, a value can be a code block
of the form 'sub { /* your code here */ }'. This code block will
be called with the list of inherited values for that key as
arguments. In fact, the concatenation of strings is really done
by using 'sub { join(" ",@_) }' on the list of inherited values.

An example:

"foo" => {
template => 1,
haha => "ha ha",
hoho => "ho",
ignored => "This should not appear in the end result",
},
"bar" => {
template => 1,
haha => "ah",
hoho => "haho",
hehe => "hehe"
},
"laughter" => {
inherit_from => [ "foo", "bar" ],
hehe => sub { join(" ",(@_,"!!!")) },
ignored => "",
}

The entry for "laughter" will become as follows after processing:

"laughter" => {
haha => "ha ha ah",
hoho => "ho haho",
hehe => "hehe !!!",
ignored => ""
}

[2] OpenSSL is built with threading capabilities unless the user
specifies 'no-threads'. The value of the key 'thread_scheme' may
be "(unknown)", in which case the user MUST give some compilation
flags to Configure.

[3] OpenSSL has three types of things to link from object files or
static libraries:

- shared libraries; that would be libcrypto and libssl.
- shared objects (sometimes called dynamic libraries); that would
be the modules.
- applications; those are apps/openssl and all the test apps.

Very roughly speaking, linking is done like this (words in braces
represent the configuration settings documented at the beginning
of this file):

shared libraries:
{ld} $(CFLAGS) {lflags} {shared_ldflag} -o libfoo.so \
foo/something.o foo/somethingelse.o {ex_libs}

shared objects:
{ld} $(CFLAGS) {lflags} {module_ldflags} -o libeng.so \
blah1.o blah2.o -lcrypto {ex_libs}

applications:
{ld} $(CFLAGS) {lflags} -o app \
app1.o utils.o -lssl -lcrypto {ex_libs}

[4] There are variants of these attribute, prefixed with `lib_',
`dso_' or `bin_'. Those variants replace the unprefixed attribute
when building library, DSO or program modules specifically.

Historically, the target configurations came in form of a string with
values separated by colons. This use is deprecated. The string form
looked like this:

"target" => "{cc}:{cflags}:{unistd}:{thread_cflag}:{sys_id}:{lflags}:{bn_ops}:{cpuid_obj}:{bn_obj}:{ec_obj}:{des_obj}:{aes_obj}:{bf_obj}:{md5_obj}:{sha1_obj}:{cast_obj}:{rc4_obj}:{rmd160_obj}:{rc5_obj}:{wp_obj}:{cmll_obj}:{modes_obj}:{padlock_obj}:{perlasm_scheme}:{dso_scheme}:{shared_target}:{shared_cflag}:{shared_ldflag}:{shared_extension}:{ranlib}:{arflags}:{multilib}"


Build info files
================

The build.info files that are spread over the source tree contain the
minimum information needed to build and distribute OpenSSL. It uses a
simple and yet fairly powerful language to determine what needs to be
built, from what sources, and other relationships between files.

For every build.info file, all file references are relative to the
directory of the build.info file for source files, and the
corresponding build directory for built files if the build tree
differs from the source tree.

When processed, every line is processed with the perl module
Text::Template, using the delimiters "{-" and "-}". The hashes
%config and %target are passed to the perl fragments, along with
$sourcedir and $builddir, which are the locations of the source
directory for the current build.info file and the corresponding build
directory, all relative to the top of the build tree.

'Configure' only knows inherently about the top build.info file. For
any other directory that has one, further directories to look into
must be indicated like this:

SUBDIRS=something someelse

On to things to be built; they are declared by setting specific
variables:

PROGRAMS=foo bar
LIBS=libsomething
MODULES=libeng
SCRIPTS=myhack

Note that the files mentioned for PROGRAMS, LIBS and MODULES *must* be
without extensions. The build file templates will figure them out.

For each thing to be built, it is then possible to say what sources
they are built from:

PROGRAMS=foo bar
SOURCE[foo]=foo.c common.c
SOURCE[bar]=bar.c extra.c common.c

It's also possible to tell some other dependencies:

DEPEND[foo]=libsomething
DEPEND[libbar]=libsomethingelse

(it could be argued that 'libsomething' and 'libsomethingelse' are
source as well. However, the files given through SOURCE are expected
to be located in the source tree while files given through DEPEND are
expected to be located in the build tree)

It's also possible to depend on static libraries explicitly:

DEPEND[foo]=libsomething.a
DEPEND[libbar]=libsomethingelse.a

This should be rarely used, and care should be taken to make sure it's
only used when supported. For example, native Windows build doesn't
support building static libraries and DLLs at the same time, so using
static libraries on Windows can only be done when configured
'no-shared'.

In some cases, it's desirable to include some source files in the
shared form of a library only:

SHARED_SOURCE[libfoo]=dllmain.c

For any file to be built, it's also possible to tell what extra
include paths the build of their source files should use:

INCLUDE[foo]=include

It's also possible to specify C macros that should be defined:

DEFINE[foo]=FOO BAR=1

In some cases, one might want to generate some source files from
others, that's done as follows:

GENERATE[foo.s]=asm/something.pl $(CFLAGS)
GENERATE[bar.s]=asm/bar.S

The value of each GENERATE line is a command line or part of it.
Configure places no rules on the command line, except that the first
item must be the generator file. It is, however, entirely up to the
build file template to define exactly how those command lines should
be handled, how the output is captured and so on.

Sometimes, the generator file itself depends on other files, for
example if it is a perl script that depends on other perl modules.
This can be expressed using DEPEND like this:

DEPEND[asm/something.pl]=../perlasm/Foo.pm

There may also be cases where the exact file isn't easily specified,
but an inclusion directory still needs to be specified. INCLUDE can
be used in that case:

INCLUDE[asm/something.pl]=../perlasm

NOTE: GENERATE lines are limited to one command only per GENERATE.

Finally, you can have some simple conditional use of the build.info
information, looking like this:

IF[1]
something
ELSIF[2]
something other
ELSE
something else
ENDIF

The expression in square brackets is interpreted as a string in perl,
and will be seen as true if perl thinks it is, otherwise false. For
example, the above would have "something" used, since 1 is true.

Together with the use of Text::Template, this can be used as
conditions based on something in the passed variables, for example:

IF[{- $disabled{shared} -}]
LIBS=libcrypto
SOURCE[libcrypto]=...
ELSE
LIBS=libfoo
SOURCE[libfoo]=...
ENDIF


Build-file programming with the "unified" build system
======================================================

"Build files" are called "Makefile" on Unix-like operating systems,
"descrip.mms" for MMS on VMS, "makefile" for nmake on Windows, etc.

To use the "unified" build system, the target configuration needs to
set the three items 'build_scheme', 'build_file' and 'build_command'.
In the rest of this section, we will assume that 'build_scheme' is set
to "unified" (see the configurations documentation above for the
details).

For any name given by 'build_file', the "unified" system expects a
template file in Configurations/ named like the build file, with
".tmpl" appended, or in case of possible ambiguity, a combination of
the second 'build_scheme' list item and the 'build_file' name. For
example, if 'build_file' is set to "Makefile", the template could be
Configurations/Makefile.tmpl or Configurations/unix-Makefile.tmpl.
In case both Configurations/unix-Makefile.tmpl and
Configurations/Makefile.tmpl are present, the former takes
precedence.

The build-file template is processed with the perl module
Text::Template, using "{-" and "-}" as delimiters that enclose the
perl code fragments that generate configuration-dependent content.
Those perl fragments have access to all the hash variables from
configdata.pem.

The build-file template is expected to define at least the following
perl functions in a perl code fragment enclosed with "{-" and "-}".
They are all expected to return a string with the lines they produce.

generatesrc - function that produces build file lines to generate
a source file from some input.

It's called like this:

generatesrc(src => "PATH/TO/tobegenerated",
generator => [ "generatingfile", ... ]
generator_incs => [ "INCL/PATH", ... ]
generator_deps => [ "dep1", ... ]
generator => [ "generatingfile", ... ]
incs => [ "INCL/PATH", ... ],
deps => [ "dep1", ... ],
intent => one of "libs", "dso", "bin" );

'src' has the name of the file to be generated.
'generator' is the command or part of command to
generate the file, of which the first item is
expected to be the file to generate from.
generatesrc() is expected to analyse and figure out
exactly how to apply that file and how to capture
the result. 'generator_incs' and 'generator_deps'
are include directories and files that the generator
file itself depends on. 'incs' and 'deps' are
include directories and files that are used if $(CC)
is used as an intermediary step when generating the
end product (the file indicated by 'src'). 'intent'
indicates what the generated file is going to be
used for.

src2obj - function that produces build file lines to build an
object file from source files and associated data.

It's called like this:

src2obj(obj => "PATH/TO/objectfile",
srcs => [ "PATH/TO/sourcefile", ... ],
deps => [ "dep1", ... ],
incs => [ "INCL/PATH", ... ]
intent => one of "lib", "dso", "bin" );

'obj' has the intended object file with '.o'
extension, src2obj() is expected to change it to
something more suitable for the platform.
'srcs' has the list of source files to build the
object file, with the first item being the source
file that directly corresponds to the object file.
'deps' is a list of explicit dependencies. 'incs'
is a list of include file directories. Finally,
'intent' indicates what this object file is going
to be used for.

obj2lib - function that produces build file lines to build a
static library file ("libfoo.a" in Unix terms) from
object files.

called like this:

obj2lib(lib => "PATH/TO/libfile",
objs => [ "PATH/TO/objectfile", ... ]);

'lib' has the intended library file name *without*
extension, obj2lib is expected to add that. 'objs'
has the list of object files to build this library.

libobj2shlib - backward compatibility function that's used the
same way as obj2shlib (described next), and was
expected to build the shared library from the
corresponding static library when that was suitable.
NOTE: building a shared library from a static
library is now DEPRECATED, as they no longer share
object files. Attempting to do this will fail.

obj2shlib - function that produces build file lines to build a
shareable object library file ("libfoo.so" in Unix
terms) from the corresponding object files.

called like this:

obj2shlib(shlib => "PATH/TO/shlibfile",
lib => "PATH/TO/libfile",
objs => [ "PATH/TO/objectfile", ... ],
deps => [ "PATH/TO/otherlibfile", ... ]);

'lib' has the base (static) library ffile name
*without* extension. This is useful in case
supporting files are needed (such as import
libraries on Windows).
'shlib' has the corresponding shared library name
*without* extension. 'deps' has the list of other
libraries (also *without* extension) this library
needs to be linked with. 'objs' has the list of
object files to build this library.

obj2dso - function that produces build file lines to build a
dynamic shared object file from object files.

called like this:

obj2dso(lib => "PATH/TO/libfile",
objs => [ "PATH/TO/objectfile", ... ],
deps => [ "PATH/TO/otherlibfile",
... ]);

This is almost the same as obj2shlib, but the
intent is to build a shareable library that can be
loaded in runtime (a "plugin"...).

obj2bin - function that produces build file lines to build an
executable file from object files.

called like this:

obj2bin(bin => "PATH/TO/binfile",
objs => [ "PATH/TO/objectfile", ... ],
deps => [ "PATH/TO/libfile", ... ]);

'bin' has the intended executable file name
*without* extension, obj2bin is expected to add
that. 'objs' has the list of object files to build
this library. 'deps' has the list of library files
(also *without* extension) that the programs needs
to be linked with.

in2script - function that produces build file lines to build a
script file from some input.

called like this:

in2script(script => "PATH/TO/scriptfile",
sources => [ "PATH/TO/infile", ... ]);

'script' has the intended script file name.
'sources' has the list of source files to build the
resulting script from.

In all cases, file file paths are relative to the build tree top, and
the build file actions run with the build tree top as current working
directory.

Make sure to end the section with these functions with a string that
you thing is appropriate for the resulting build file. If nothing
else, end it like this:

""; # Make sure no lingering values end up in the Makefile
-}


Configure helper scripts
========================

Configure uses helper scripts in this directory:

Checker scripts
---------------

These scripts are per platform family, to check the integrity of the
tools used for configuration and building. The checker script used is
either {build_platform}-{build_file}-checker.pm or
{build_platform}-checker.pm, where {build_platform} is the second
'build_scheme' list element from the configuration target data, and
{build_file} is 'build_file' from the same target data.

If the check succeeds, the script is expected to end with a non-zero
expression. If the check fails, the script can end with a zero, or
with a `die`.