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
                       '<unistd.h>'.  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_<version>' rather than
                       the default 'OPENSSL_<version>'. 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 indicates 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.