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.
abidw [options] [<path-to-elf-file>]
- --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.
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.
Do not emit the path attribute for the ABI corpus.
- --suppressions | suppr
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.
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.
Do not include the list of DT_NEEDED dependency names in the corpus.
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.
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.
In the emitted ABI representation, do not show names of function parameters, just the types.
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.
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.
This is a debugging and sanity check option.
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.
Emit statistics about various internal things.
Emit verbose logs about the progress of miscellaneous internal things.
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.
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|October 11, 2021|