Ubuntu Manpage: abidw - serialize the ABI of an ELF file

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 format, named ABIXML, 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.

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.

To generate either ABI or KMI representation, by default abidw uses debug information in the DWARF
format, if present, otherwise it looks for debug information in CTF or BTF formats, if present. Finally,
if no debug info in these formats is found, it only considers ELF symbols and report about their addition
or removal.

This tool uses the libabigail library to analyze the binary as well as its associated debug information.
Here is its general mode of operation.

When instructed to do so, a binary and its associated debug information is read and analyzed. To that
effect, libabigail analyzes by default the descriptions of the types reachable by the interfaces
(functions and variables) that are visible outside of their translation unit. Once that analysis is
done, an Application Binary Interface Corpus is constructed by only considering the subset of types
reachable from interfaces associated to ELF symbols that are defined and exported by the binary. It’s
that final ABI corpus which libabigail considers as representing the ABI of the analyzed binary.

Libabigail then has capabilities to generate textual representations of ABI Corpora, compare them,
analyze their changes and report about them.

INVOCATION

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

OPTIONS

• --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.

• --abixml-version

Display the version of the ABIXML format emitted by this program and exit.

• --add-binaries <bin1,bin2,…>

For each of the comma-separated binaries given in argument to this option, if the binary is found in
the directory specified by the –added-binaries-dir option, then load the ABI corpus of the binary
and add it to a set of ABI corpora (called a ABI Corpus Group) made of the binary denoted by the
Argument of abidw. That corpus group is then serialized out.

• --added-binaries-dir | --abd <dir-path>

This option is to be used in conjunction with the --add-binaries, the --follow-dependencies or the
--list-dependencies option. Binaries listed as arguments of the --add-binaries option or being
dependencies of the input binary in the case of the --follow-dependencies option and found in the
directory <dir-path> are going to be loaded as ABI corpus and added to the set of ABI corpora
(called an ABI corpus group) built and serialized.

• --allow-non-exported-interfaces

When looking at the debug information accompanying a binary, this tool analyzes the descriptions of
the types reachable by the interfaces (functions and variables) that are visible outside of their
translation unit. Once that analysis is done, an ABI corpus is constructed by only considering the
subset of types reachable from interfaces associated to ELF symbols that are defined and exported by
the binary. It’s that final ABI corpus which textual representation is saved as ABIXML.

The problem with that approach however is that analyzing all the interfaces that are visible from
outside their translation unit can amount to a lot of data, especially when those binaries are
applications, as opposed to shared libraries. One example of such applications is the Linux Kernel.
Analyzing massive ABI corpora like these can be extremely slow.

In the presence of an “average sized” binary however one can afford having libabigail analyze all
interfaces that are visible outside of their translation unit, using this option.

Note that this option is turned on by default, unless we are in the presence of the Linux Kernel.

• --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.

• --btf

Extract ABI information from BTF debug information, if present in the given object.

• --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.

• --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.

• --debug-abidiff
Same as --abidiff but in debug mode. In this mode, error messages are emitted for types which
fail type canonicalization.

This is an optional debugging and sanity check option. To enable it the libabigail package needs
to be configured with the –enable-debug-self-comparison option.

• --ctf

Extract ABI information from CTF debug information, if present in the given object.

• --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.

• --debug-type-canonicalization | --debug-tc
Debug the type canonicalization process. This is done by using structural and canonical equality
when canonicalizing every single type. Structural and canonical equality should yield the same
result. If they don’t yield the same result for a given type, then it means that the
canonicalization of that type went wrong. In that case, an error message is emitted and the
execution of the program is aborted.

This option is available only if the package was configured with the
–enable-debug-type-canonicalization option.

• --drop-private-types

This option is implicitly set by option –headers-dir and –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.

This option is provided or compatibility reasons only and should not be explicitly used anymore.

• --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.

• --exported-interfaces-only

By default, when looking at the debug information accompanying a binary, this tool analyzes the
descriptions of the types reachable by the interfaces (functions and variables) that are visible
outside of their translation unit. Once that analysis is done, an ABI corpus is constructed by only
considering the subset of types reachable from interfaces associated to ELF symbols that are defined
and exported by the binary. It’s that final ABI corpus which textual representation is saved as
ABIXML.

To mitigate that performance issue, this option allows libabigail to only analyze types that are
reachable from interfaces associated with defined and exported ELF symbols.

Note that this option is turned on by default when analyzing the Linux Kernel. Otherwise, it’s
turned off by default.

• --follow-dependencies

For each dependency of the input binary of abidw, if it is found in the directory specified by the
--added-binaries-dir option, then construct an ABI corpus out of the dependency and add it to a set
of ABI corpora (called an ABI Corpus Group) along with the ABI corpus of the input binary of the
program. The ABI Corpus Group is then serialized out.

• --force-early-suppression

This option must be used alongside option –suppression.

It forces suppression specifications to be applied in early suppression mode. Artifacts of the
internal representation that are matched by suppression specifications are thus suppressed from
memory.

If this option is not used then only suppression specifications with the drop property set to ‘yes’
are effective. All other suppression specification directives will appear to be ignored.

• --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. This option implicitly sets
option –drop-private-types.

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.

This option implicitly sets option –drop-private-types.

• --help | -h

Display a short help about the command and exit.

• --kmi-whitelist | --kmi-stablelist |-w <path-to-stablelist>

When analyzing a Linux Kernel binary, this option points to the list of names of ELF symbols of
functions and variables which ABI must be written out. Any function or variable with a name that is
not included in that list will not ignored. That list is called a “ Kernel Module Interface stable
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 KABI.

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

If this option is not provided – thus if no stable 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.

• --list-dependencies

For each dependency of the input binary of``abidw``, if it’s found in the directory specified by the
--added-binaries-dir option, then the name of the dependency is printed out.

• --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.

• --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

• --no-assume-odr-for-cplusplus

When analysing a binary originating from C++ code using DWARF debug information, libabigail assumes
the One Definition Rule to speed-up the analysis. In that case, when several types have the same
name in the binary, they are assumed to all be equal.

This option disables that assumption and instructs libabigail to actually actually compare the types
to determine if they are equal.

• --no-corpus-path

Do not emit the path attribute for the ABI corpus.

• --no-elf-needed

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

• --no-leverage-dwarf-factorization

When analysing a binary which DWARF debug information was processed with the DWZ tool, the type
information is supposed to be already factorized. That context is used by libabigail to perform
some speed optimizations.

This option disables those optimizations.

• --no-load-undefined-interfaces

By default, libabigail (and thus abidw) loads information about undefined function and variable
symbols as well as functions and variables that are associated with those undefined symbols. Those
are called undefined interfaces. This option however makes makes abidw avoid loading information
about undefined interfaces. The resulting XML file thus doesn’t contain information about those
undefined interfaces.

• --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.

• --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-parameter-names

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

• --no-show-locs
In the emitted ABI representation, do not show file, line or column where ABI artifacts are
defined.

• --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.

• --out-file | -o <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.

• --stats

Emit statistics about various internal things.

• --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.

Only suppression specifications that have the drop property set to ‘yes’ are going to be effective.
All other suppression specification directives will appear as being ignored, unless the command line
option –force-early-suppression is provided.

• --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.

• --verbose

Emit verbose logs about the progress of miscellaneous internal things.

• --version | -v

Display the version of the program and exit.

USAGE EXAMPLES

          1. Emitting an ABIXML representation of a binary:

                 $ abidw binary > binary.abi

          2. Emitting an ABIXML representation of a set of binaries specified on the command line:

                 $ abidw --added-binaries=bin1,bin2,bin3  \
                         --added-binaries-dir /some/where \
                         binary > binaries.abi

             Note  that  the  binaries  bin1,  bin2  and  bin3  are to be found in the directory /some/where.  A
             representation of the ABI of the set of binaries binary, bin1, bin2 and bin3 called an  ABI  corpus
             group is serialized in the file binaries.abi.

          3. Emitting an ABIXML representation of a binary and its dependencies:

                 $ abidw --follow-dependencies              \
                         --added-binaries-dir /some/where   \
                         binary > binary.abi

             Note  that  only  the dependencies that are found in the directory /some/where are analysed.  Their
             ABIs, along with the ABI the binary named binary  are  represented  as  an  ABI  corpus  group  and
             serialized in the file binary.abi, in the ABIXML format.

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

COPYRIGHT

       2014-2025, Red Hat, Inc.

                                                  Jul 31, 2025                                          ABIDW(1)