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authorDr. David von Oheimb <David.von.Oheimb@siemens.com>2020-06-10 14:15:28 +0200
committerDr. David von Oheimb <David.von.Oheimb@siemens.com>2020-07-05 11:29:43 +0200
commit036cbb6bbf30955abdcffaf6e52cd926d8d8ee75 (patch)
tree1929b9d33c7041858cbbed980f8c981d8eb77c3c /NOTES.UNIX
parent915e7e75a49343ff5ddd23a54219eb32f57aa01c (diff)
downloadopenssl-new-036cbb6bbf30955abdcffaf6e52cd926d8d8ee75.tar.gz
Rename NOTES*, README*, VERSION, HACKING, LICENSE to .md or .txt
Reviewed-by: Tim Hudson <tjh@openssl.org> (Merged from https://github.com/openssl/openssl/pull/12109)
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-
- NOTES FOR UNIX LIKE PLATFORMS
- =============================
-
- For Unix/POSIX runtime systems on Windows, please see NOTES.WIN.
-
-
- OpenSSL uses the compiler to link programs and shared libraries
- ---------------------------------------------------------------
-
- OpenSSL's generated Makefile uses the C compiler command line to
- link programs, shared libraries and dynamically loadable shared
- objects. Because of this, any linking option that's given to the
- configuration scripts MUST be in a form that the compiler can accept.
- This varies between systems, where some have compilers that accept
- linker flags directly, while others take them in '-Wl,' form. You need
- to read your compiler documentation to figure out what is acceptable,
- and ld(1) to figure out what linker options are available.
-
-
- Shared libraries and installation in non-default locations
- ----------------------------------------------------------
-
- Every Unix system has its own set of default locations for shared
- libraries, such as /lib, /usr/lib or possibly /usr/local/lib. If
- libraries are installed in non-default locations, dynamically linked
- binaries will not find them and therefore fail to run, unless they get
- a bit of help from a defined runtime shared library search path.
-
- For OpenSSL's application (the 'openssl' command), our configuration
- scripts do NOT generally set the runtime shared library search path for
- you. It's therefore advisable to set it explicitly when configuring,
- unless the libraries are to be installed in directories that you know
- to be in the default list.
-
- Runtime shared library search paths are specified with different
- linking options depending on operating system and versions thereof, and
- are talked about differently in their respective documentation;
- variations of RPATH are the most usual (note: ELF systems have two such
- tags, more on that below).
-
- Possible options to set the runtime shared library search path include
- the following:
-
- -Wl,-rpath,/whatever/path # Linux, *BSD, etc.
- -R /whatever/path # Solaris
- -Wl,-R,/whatever/path # AIX (-bsvr4 is passed internally)
- -Wl,+b,/whatever/path # HP-UX
- -rpath /whatever/path # Tru64, IRIX
-
- OpenSSL's configuration scripts recognise all these options and pass
- them to the Makefile that they build. (In fact, all arguments starting
- with '-Wl,' are recognised as linker options.)
-
- Please do not use verbatim directories in your runtime shared library
- search path! Some OpenSSL config targets add an extra directory level
- for multilib installations. To help with that, the produced Makefile
- includes the variable LIBRPATH, which is a convenience variable to be
- used with the runtime shared library search path options, as shown in
- this example:
-
- $ ./Configure --prefix=/usr/local/ssl --openssldir=/usr/local/ssl \
- '-Wl,-rpath,$(LIBRPATH)'
-
- On modern ELF based systems, there are two runtime search paths tags to
- consider, DT_RPATH and DT_RUNPATH. Shared objects are searched for in
- this order:
-
- 1. Using directories specified in DT_RPATH, unless DT_RUNPATH is
- also set.
- 2. Using the environment variable LD_LIBRARY_PATH
- 3. Using directories specified in DT_RUNPATH.
- 4. Using system shared object caches and default directories.
-
- This means that the values in the environment variable LD_LIBRARY_PATH
- won't matter if the library is found in the paths given by DT_RPATH
- (and DT_RUNPATH isn't set).
-
- Exactly which of DT_RPATH or DT_RUNPATH is set by default appears to
- depend on the system. For example, according to documentation,
- DT_RPATH appears to be deprecated on Solaris in favor of DT_RUNPATH,
- while on Debian GNU/Linux, either can be set, and DT_RPATH is the
- default at the time of writing.
-
- How to choose which runtime search path tag is to be set depends on
- your system, please refer to ld(1) for the exact information on your
- system. As an example, the way to ensure the DT_RUNPATH is set on
- Debian GNU/Linux systems rather than DT_RPATH is to tell the linker to
- set new dtags, like this:
-
- $ ./Configure --prefix=/usr/local/ssl --openssldir=/usr/local/ssl \
- '-Wl,--enable-new-dtags,-rpath,$(LIBRPATH)'
-
- It might be worth noting that some/most ELF systems implement support
- for runtime search path relative to the directory containing current
- executable, by interpreting $ORIGIN along with some other internal
- variables. Consult your system documentation.
-
- Linking your application
- ------------------------
-
- Third-party applications dynamically linked with OpenSSL (or any other)
- shared library face exactly the same problem with non-default locations.
- The OpenSSL config options mentioned above might or might not have bearing
- on linking of the target application. "Might" means that under some
- circumstances it would be sufficient to link with OpenSSL shared library
- "naturally", i.e. with -L/whatever/path -lssl -lcrypto. But there are
- also cases when you'd have to explicitly specify runtime search path
- when linking your application. Consult your system documentation and use
- above section as inspiration...
-
- Shared OpenSSL builds also install static libraries. Linking with the
- latter is likely to require special care, because linkers usually look
- for shared libraries first and tend to remain "blind" to static OpenSSL
- libraries. Referring to system documentation would suffice, if not for
- a corner case. On AIX static libraries (in shared build) are named
- differently, add _a suffix to link with them, e.g. -lcrypto_a.