abidw - Man Page

Name

abidw — serialize the ABI of an ELF file

abidw reads a shared library in ELF format and emits an XML representation of its ABI to standard output.  The emitted representation includes all the globally defined functions and variables, along with a complete representation of their types.  It also includes a representation of the globally defined ELF symbols of the file.  The input shared library must contain associated debug information in DWARF format.

When given the --linux-tree option, this program can also handle a Linux kernel tree.  That is, a directory tree that contains both the vmlinux binary and Linux kernel modules.  It analyses those Linux kernel binaries and emits an XML representation of the interface between the kernel and its module, to standard output.  In this case, we don’t call it an ABI, but a KMI (Kernel Module Interface).  The emitted KMI includes all the globally defined functions and variables, along with a complete representation of their types.  The input binaries must contain associated debug information in DWARF format.

Invocation

abidw [options] [<path-to-elf-file>]

Options

  • --help | -h

    Display a short help about the command and exit.

  • –version | -v

    Display the version of the program and exit.

  • --debug-info-dir | -d <dir-path>

    In cases where the debug info for path-to-elf-file is in a separate file that is located in a non-standard place, this tells abidw where to look for that debug info file.

    Note that dir-path must point to the root directory under which the debug information is arranged in a tree-like manner.  Under Red Hat based systems, that directory is usually <root>/usr/lib/debug.

    This option can be provided several times with different root directories.  In that case, abidw will potentially look into all those root directories to find the split debug info for the elf file.

    Note that this option is not mandatory for split debug information installed by your system’s package manager because then abidw knows where to find it.

  • --out-file <file-path>

    This option instructs abidw to emit the XML representation of path-to-elf-file into the file file-path, rather than emitting it to its standard output.

  • --noout

    This option instructs abidw to not emit the XML representation of the ABI.  So it only reads the ELF and debug information, builds the internal representation of the ABI and exits.  This option is usually useful for debugging purposes.

  • --no-corpus-path

    Do not emit the path attribute for the ABI corpus.

  • --suppressions | suppr <path-to-suppression-specifications-file>

    Use a suppression specification file located at path-to-suppression-specifications-file.  Note that this option can appear multiple times on the command line.  In that case, all of the provided suppression specification files are taken into account.  ABI artifacts matched by the suppression specifications are suppressed from the output of this tool.

  • --kmi-whitelist | -kaw <path-to-whitelist>

    When analyzing a Linux kernel binary, this option points to the white list of names of ELF symbols of functions and variables which ABI must be written out.  That white list is called a ” Kernel Module Interface white list”.  This is because for the Kernel, we don’t talk about the ABI; we rather talk about the interface between the Kernel and its module. Hence the term KMI rather than ABI

    Any other function or variable which ELF symbol are not present in that white list will not be considered by the KMI writing process.

    If this option is not provided – thus if no white list is provided – then the entire KMI, that is, all publicly defined and exported functions and global variables by the Linux Kernel binaries is emitted.

  • --linux-tree | --lt

    Make abidw to consider the input path as a path to a directory containing the vmlinux binary as several kernel modules binaries. In that case, this program emits the representation of the Kernel Module Interface (KMI) on the standard output.

    Below is an example of usage of abidw on a Linux Kernel tree.

    First, checkout a Linux kernel source tree and build it.  Then install the kernel modules in a directory somewhere.  Copy the vmlinux binary into that directory too.  And then serialize the KMI of that kernel to disk, using abidw:

    $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
    $ cd linux && git checkout v4.5
    $ make allyesconfig all
    $ mkdir build-output
    $ make INSTALL_MOD_PATH=./build-output modules_install
    $ cp vmlinux build-output/modules/4.5.0
    $ abidw --linux-tree build-output/modules/4.5.0 > build-output/linux-4.5.0.kmi
  • --headers-dir | --hd <headers-directory-path-1>

    Specifies where to find the public headers of the binary that the tool has to consider.  The tool will thus filter out types that are not defined in public headers.

    Note that several public header directories can be specified for the binary to consider.  In that case the --header-dir option should be present several times on the command line, like in the following example:

    $ abidw --header-dir /some/path       \
            --header-dir /some/other/path \
            binary > binary.abi
  • --header-file | --hf <header-file-path>

    Specifies where to find one of the public headers of the abi file that the tool has to consider.  The tool will thus filter out types that are not defined in public headers.

  • --drop-private-types

    This option is to be used with the --headers-dir and/or header-file options.  With this option, types that are NOT defined in the headers are entirely dropped from the internal representation build by Libabigail to represent the ABI and will not end up in the abi XML file.

  • --no-elf-needed

    Do not include the list of DT_NEEDED dependency names in the corpus.

  • --drop-undefined-syms

    With this option functions or variables for which the (exported) ELF symbol is undefined are dropped from the internal representation build by Libabigail to represent the ABI and will not end up in the abi XML file.

  • --no-linux-kernel-mode

    Without this option, if abipkgiff detects that the binaries it is looking at are Linux Kernel binaries (either vmlinux or modules) then it only considers functions and variables which ELF symbols are listed in the __ksymtab and __ksymtab_gpl sections.

    With this option, abipkgdiff considers the binary as a non-special ELF binary.  It thus considers functions and variables which are defined and exported in the ELF sense.

  • --check-alternate-debug-info <elf-path>

    If the debug info for the file elf-path contains a reference to an alternate debug info file, abidw checks that it can find that alternate debug info file.  In that case, it emits a meaningful success message mentioning the full path to the alternate debug info file found.  Otherwise, it emits an error code.

  • --no-show-locs

    In the emitted ABI representation, do not show file, line or column where ABI artifacts are defined.

  • --no-parameter-names

    In the emitted ABI representation, do not show names of function parameters, just the types.

  • --no-write-default-sizes

    In the XML ABI representation, do not write the size-in-bits for pointer type definitions, reference type definitions, function declarations and function types when they are equal to the default address size of the translation unit.  Note that libabigail before 1.8 will not set the default size and will interpret types without a size-in-bits attribute as zero sized.

  • --type-id-style <sequence``|``hash>

    This option controls how types are idenfied in the generated XML files.  The default sequence style just numbers (with type-id- as prefix) the types in the order they are encountered.  The hash style uses a (stable, portable) hash of libabigail’s internal type names and is intended to make the XML files easier to diff.

  • --check-alternate-debug-info-base-name <elf-path>

    Like --check-alternate-debug-info, but in the success message, only mention the base name of the debug info file; not its full path.

  • --load-all-types

    By default, libabigail (and thus abidw) only loads types that are reachable from functions and variables declarations that are publicly defined and exported by the binary.  So only those types are present in the output of abidw.  This option however makes abidw load all the types defined in the binaries, even those that are not reachable from public declarations.

  • --abidiff

    Load the ABI of the ELF binary given in argument, save it in libabigail’s XML format in a temporary file; read the ABI from the temporary XML file and compare the ABI that has been read back against the ABI of the ELF binary given in argument.  The ABIs should compare equal.  If they don’t, the program emits a diagnostic and exits with a non-zero code.

    This is a debugging and sanity check option.

  • --annotate

    Annotate the ABIXML output with comments above most elements.  The comments are made of the pretty-printed form types, declaration or even ELF symbols.  The purpose is to make the ABIXML output more human-readable for debugging or documenting purposes.

  • --stats

    Emit statistics about various internal things.

  • --verbose

    Emit verbose logs about the progress of miscellaneous internal things.

Notes

Alternate debug info files

As of the version 4 of the DWARF specification, Alternate debug information is a GNU extension to the DWARF specification.  It has however been proposed for inclusion into the upcoming version 5 of the DWARF standard.  You can read more about the GNU extensions to the DWARF standard here.

Author

Dodji Seketeli

Info

Feb 25, 2021 Libabigail