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This is the public release of libelf-0.8.13, a free ELF object
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file access library. If you have problems with applications
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that use libelf and work with the commercial (SVR4, Solaris)
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version but not with this one, please contact me.
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IMPORTANT NOTE: If you have libelf-0.5.2 installed, you probably
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have a file .../include/elf.h that contains the single line
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``#include <libelf/elf.h>''. REMOVE THIS FILE BEFORE YOU RUN
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configure.
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Installation is straightforward - the package is autoconf'ed. Just do
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``cd libelf-0.8.13; ./configure; make; make install''. Header files
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will be installed in .../include/libelf/. If your system does not
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provide its own versions of libelf.h, nlist.h or gelf.h, ``make
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install'' will add the missing headers. If you prefer not to have
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these files installed in /usr/include, use ``--disable-compat'' and
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add ``-I /usr/include/libelf'' to your CFLAGS when compiling
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libelf-based programs.
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Note to distribution makers: You can install libelf in a separate root
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hierarchy by using the command ``make instroot=/my/root install''.
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You should also use the ``--enable-compat'' configure option in that
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case, or run ``make instroot=/my/root install-compat'' manually, to
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install all the required header files.
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If you are running Linux with libc 5.* as the default C library,
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and you plan to use the 64-bit functions, you must either use
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``-I.../include/libelf'', or remove /usr/include/libelf.h and use
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``--enable-compat'' when running configure. Libc 6.* (aka glibc2)
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doesn't have its own <libelf.h>, <nlist.h> or <gelf.h>.
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You need an ANSI/ISO C compiler to build libelf. Gcc is optimal.
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On some systems (in particular, Solaris and all variants of Linux),
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``make'' will try to build a shared library. If you run into problems
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on your system, please pass ``--disable-shared'' to configure.
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If you build a shared library and want it to be installed as
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``libelf-0.8.13.so'' rather than ``libelf.so.0.8.13'', please use
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``./configure --enable-gnu-names''. Other files, e.g. ``libelf.so'' and
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``libelf.so.0'' are NOT affected.
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Another configure option, ``--enable-debug'', adds debugging code to
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libelf; if you don't run into problems, you will probably not need it.
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When creating an ELF shared library, it is possible to add references
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to other shared libraries in the DYNAMIC section of the resulting
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file. The make variable DEPSHLIBS contains a list of libraries to add.
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It is set to ``-lc'' on Linux systems, and empty otherwise. To
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override this setting, use something like ``make DEPSHLIBS="-la -lb"''.
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For Linux, `-lc' is included automagically.
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NLS is available and enabled by default. To turn it off, pass the
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``--disable-nls'' option to configure.
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Libelf can use gettext or catgets for accessing message
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catalogs. If gettext is available AND is part of libc (i.e. not
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in a separate library), it will be used. Otherwise, configure
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will look for catgets. If you have gettext in a separate
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library and want to use it, you should pass the library's name
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to configure, e.g. ``LIBS=-lintl ./configure''. Note that you
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MUST link your libelf-based applications with -lintl then,
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which is probably not what you want, or change the DEPSHLIBS variable
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described above (in case you're building a shared library).
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If you have GNU gettext 0.10 installed on your system, and if GNU gettext
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runs on top of the catgets interface (rather old Linux systems, using
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libc5), configure will refuse to use it and use catgets instead. If you
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absolutely want to use GNU gettext, go ahead and rebuild it (which is
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IMHO a good idea in general in this case):
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cd .../gettext-0.10
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ac_cv_func_catgets=no ac_cv_func_gettext=no ./configure
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make
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make install
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After that, return to the libelf build directory, remove
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config.cache, and start over.
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*** Large File Support (LFS) applications ***
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Some 32-bit systems support files that are larger than the address space
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of the architecture. On these, the `off_t' data type may have 32 or
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64 bits, depending on the API you choose. Since off_t is also part of
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the libelf API, in particular the Elf_Data and Elf_Arhdr structures,
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an application compiled with large file support will need a version of
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libelf that has also been compiled with LFS; otherwise, it won't work
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correctly. Similarly, a program compiled without LFS needs a library
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compiled without LFS.
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Note that libelf is currently unable to process large files on 32-bit
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architectures, whether you compile it for LFS or not, for the simple
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reason that the files won't fit into the processes' address space.
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Therefore, libelf is compiled without LFS by default. It can of course
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read and write ELF files for 64-bit architectures, but they will be
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limited in length on a 32-bit system.
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You may compile libelf with large file support by setting CPPFLAGS at
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configuration time:
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CPPFLAGS=`getconf LFS_CFLAGS` ./configure
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But I really, really recommend you don't, because it breaks binary
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compatibility with existing libelf based applications.
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*** 64-bit support ***
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Starting with libelf-0.7.0, libelf also supports 64-bit ELF files.
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This is enabled by default unless your system (or your compiler) does
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not support 64-bit integers, or lacks 64-bit declarations in <elf.h>.
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If you have problems building with 64-bit support, please do
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./configure --disable-elf64
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for the moment, and contact me. Please note that I haven't tested 64-bit
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support much. There are still some unresolved problems, e.g. IRIX
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uses different Elf64_Rel and Elf64_Rela structures (they replaced the
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r_info member), and the enumeration values for Elf_Type differ from
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the commercial (SVR4) implementation of libelf - they broke binary
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compatibility for no good reason, and I'm not willing to follow their
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footsteps. The result is that libelf-0.7.* ist upward compatible with
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libelf-0.6.4 (as it should be) but INCOMPATIBLE WITH SVR4 LIBELF. If you
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have both versions installed, you'd better make sure that you link with
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the library that matches the <libelf.h> you're #include'ing.
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*** Symbol Versioning ***
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Libelf >= 0.8.0 supports the data structures and definitions used for
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symbol versioning on Solaris and Linux, in particular, the Elfxx_Verdef,
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Elfxx_Verdaux, Elfxx_Verneed, Elfxx_Vernaux and Elfxx_Versym structures
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and the SHT_XXX_verdef, SHT_XXX_verneed and SHT_XXX_versym section types
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(where `xx' is either `32' or `64', and `XXX' is either `SUNW' or `GNU').
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Libelf now translates versioning sections to/from their external
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representation properly (earlier versions left them in `raw' format,
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with the data type set to ELF_T_BYTE). This may cause problems on
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systems which use the same (OS-specific) section types for different
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purposes. The configure program tries to figure out if your OS uses
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versioning; if that check fails, you can use
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./configure --disable-versioning
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to turn off versioning translation support.
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*** W32 Support ***
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There is now some support for building on W32 systems (requires Microsoft
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VC++). In order to build a W32 DLL, cd into the `lib' subdirectory, edit
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build.bat if necessary (it needs the path to your compiler binaries) and
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run it. If you're lucky, libelf.dll and the import/export libraries will
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be built. If not, please drop me a line.
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I tested it on XP Pro (SP2), using VC++ 2005 Express Edition.
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Apparently, Visual Studio .NET 2003 works fine as well.
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Various notes regarding the W32 port:
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- When you open() an ELF file, remember to use the O_BINARY flag.
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- You may have to add /MD to the linker command line.
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*** Missing things ***
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* There is no documentation. You can use the Solaris
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manpages instead (available at http://docs.sun.com/).
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The ELF file format is described in several places;
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among them Suns "Linker and Libraries Guide" and the
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"System V Application Binary Interface" documents;
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http://www.caldera.com/developer/devspecs/gabi41.pdf and
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http://www.caldera.com/developer/gabi/ are probably good
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starting points. Processor-specific documentation is spread
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across a number of `Processor Supplement' documents, one
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for each architecture; you'll have to use a search engine to
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find them.
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* The COFF file format is not understood. This is so obsolete
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that it will probably never be implemented.
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* nlist(3) is incomplete; the n_type and n_sclass
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members of struct nl are set to zero even if type
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(that is, debug) information is available.
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* Libelf does not translate Solaris' `Move' and `Syminfo'
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sections. You can read them using elf_getdata(), but you'll
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only get raw (untranslated) bytes.
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Changes since 0.8.12:
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* New function elf_getaroff().
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* Build fixes.
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Changes since 0.8.11:
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* Due to some unfortunate confusion, the elf_getphnum(),
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elf_getshnum() and elf_getshstrndx() are not compatible
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between libelf implementations. Therefore, the developers
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decided to replace them with new functions: elf_getphdrnum(),
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elf_getshdrnum() and elf_getshdrstrndx(), which will always
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return -1 on failure and 0 on success. Code using the old
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interface should be upgraded to increase portability.
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Changes since 0.8.10:
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* Fixed a bug in elf_rawfile().
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* If you use ELF_F_LAYOUT together with ELF_F_LAYOUT_OVERLAP,
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elf_update() will now tolerate overlapping sections.
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Changes since 0.8.9:
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* Ported to QNX Neutrino.
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* Fixed Windows build errors.
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* Parallel (make -j) installation should work now.
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* It's now possible to enable and disable select sanity checks
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libelf performs. Currently, this affects the "NUL terminated
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string table entry" check performed in elf_strptr(). By
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default, the function will return an error if the string
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requested is not properly terminated - because some
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applications might dump core otherwise. If you configure
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libelf with `--disable-sanity-checks', however, the check
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(and, in the future, probably others as well) is disabled
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by default. You can still turn it on and off at runtime by
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setting the LIBELF_SANITY_CHECKS environment variable to
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an integer value:
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# disable all sanity checks
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export LIBELF_SANITY_CHECKS=0
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# enable all sanity checks
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export LIBELF_SANITY_CHECKS=-1
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Each bit of the value corresponds to a particular check,
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so you could use LIBELF_SANITY_CHECKS=1 to enable only
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the elf_strptr() check. You may also use a value in hex
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(0x...) or octal (0...) format.
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Changes since 0.8.8:
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* Improved translator for symbol versioning sections.
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* The W32 library is now built in the `lib' subdirectory.
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* Windows DLLs should work now.
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Changes since 0.8.6:
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* added elf_getphnum().
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* added elf_getshnum().
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* added elf_getshstrndx().
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* added elfx_update_shstrndx().
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* handle interrupted reads/writes more gracefully.
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* added (partial) support for unusual e_[ps]hentsize values.
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* fixed the bugs introduced in 0.8.7.
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Changes since 0.8.5:
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* added W32 support.
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* added workaround for alignment errors in archive members.
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* my email address has changed again ;)
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Changes since 0.8.4:
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* elf_strptr() should now work more safely with fragmented
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or badly formatted string tables.
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Changes since 0.8.3:
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* Fixed a bug in elf_update() that was introduced in 0.8.3.
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Changes since 0.8.2:
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* Should compile on MacOSX now.
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* Can read and write files with more than 65280 sections
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* Tries to handle 64-bit ELF files that use 8-byte hash table
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entries. In particular, libelf tries to guess the data type in
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elf_getdata(), and doesn't override sh_entsize in elf_update()
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any longer. If you want the library to pick the entry size,
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you must set its value to 0 before you call elf_update().
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* No longer dumps core in elf_update() when a versioning section
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has no data. Instead, it returns an error message. Note that
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you're supposed to provide a valid d_buf for any section, unless
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it's empty or has SHT_NOBITS type.
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* Building a shared library is now the default (if supported).
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Changes since 0.8.0:
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* Corrected typo in lib/{32,64}.xlatetof.c that sometimes
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caused a compilation failure.
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* Use open(name, O_RDONLY|O_BINARY) in lib/nlist.c.
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Changes since 0.7.0:
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* I implemented the gelf_* interface, as found on Solaris.
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I don't know whether it's compatible -- the Solaris manpage
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isn't very specific, so I had to guess return values etc. in
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some cases.
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* Added elf{32,64}_checksum (supposed to be compatible with
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Solaris).
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* Added symbol versioning support.
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Changes since 0.6.4:
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* Fixed configure for IRIX systems
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* Added check for truncated archive members
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* Added check for misaligned SHDR/PHDR tables
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* Support for building libelf together with GNU libc
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* Added elf_memory(3)
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* Added 64-bit support
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Changes since 0.5.2:
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* some bug fixes
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* mmap support
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* new directory layout
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* There is a new function, elf_delscn(), that deletes
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a section from an ELF file. It also adjusts the
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sh_link and sh_info members in the section header
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table, if (and ONLY if) the ELF standard indicates
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that these values are section indices. References
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to the deleted section will be cleared, so be careful.
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* my email address has changed ;)
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Where to get libelf:
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ftp://ftp.ibiblio.org/pub/Linux/libs/
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http://www.mr511.de/software/
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Michael "Tired" Riepe
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<libelf@mr511.de>
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