Re: [PATCH 2/2, RFC] Allow restricting analyzed decls to exported symbols

[Giuliano Procida <gprocida@google.com>]

Hi Dodji.

Sorry for the late reply. I was down with Covid for a while.

I feel this commit deserves some feedback.

My understanding is that the intention here is to make the DWARF
reader do less work (look at fewer type DIEs) than at present.

We are actually hoping that we may be able to make the DWARF reader
look at more type DIEs so that it is more likely to pick up full
definitions of types instead of declarations.

The rationale behind the change appears to be that DWARF processing is
expensive, in particular for kernel ABIs. I would say "measure first".
Here's roughly how I think about things:

1. building the IR is very cheap

A kernel ABI may end up with 40k IR elements. The cost of allocating
memory and calling constructors should be negligible. Any improvements
to this end of things is pointless.

2. reading DWARF information is fairly cheap

We may have 100MB of DWARF but just reading the data (decoding
attribute formats in particular) won't take that long.

Reducing the number of DIEs examined at the top-level by a factor of 2
will speed up this part by a factor of 2, but in the grand scheme of
things that may not be very important.

3. chasing references is a bit more expensive

Cross-references in DWARF are pretty common and the lack of locality
means that chasing cross-references is going to be a constant factor
slower than iterating through the main DWARF tree.

4. deciding whether a DIE needs to be turned into IR is currently very expensive

This is because it involves multiple look-ups and recursive comparison
of DIEs which cannot be unconditionally memoised.

Those are only my thoughts. Some profiling should give a more accurate picture.

I was curious, so I did an analysis of the connectivity of a kernel
ABI (using the STG IR, not libabigail's - there are minor
differences). Here are some fun facts.

The ABI has 34541 nodes.
There are 25196 strongly-connected components.
25053 SCCs are just singleton nodes.
The largest 3 SCCs have sizes: 4960, 784, 343.
1/7 of the ABI nodes are in one SCC!

Completely idle speculation: Perhaps the really huge SCC contributes
significantly to comparison cost.

Regards,
Giuliano.


On Tue, 6 Sept 2022 at 11:11, Dodji Seketeli <dodji@seketeli.org> wrote:
>
> Hello,
>
> Profiling showed that the DWARF reader scans too much data.
>
> Basically, in build_translation_unit_and_add_to_ir,
> build_ir_node_from_die is called on every single DIE that is seen, for
> a given translation unit.
>
> There are interfaces (function and variable decls) that are not
> associated with exported ELF symbols and that are analyzed by
> build_ir_node_from_die nonetheless.  For instance, interfaces that are
> visible outside of their translation units are analyzed and the types
> that are reachable from those interfaces are analyzed as well.
>
> Once that is done, an ABI corpus is built with the subset of
> interfaces that have exported ELF symbol (strictly those that are part
> of the ABI), but types that are not necessarily reachable from those
> ABI interfaces can also be put into the ABI corpus.
>
> Some tools make use of this "lose" behaviour of libabigail.  For
> instance, abicompat precisely wants to analyze interfaces with
> undefined symbols.  For an application, those interfaces represents
> the interfaces that the application expects to be provided by some
> shared library.
>
> When analyzing the exported interface of the Linux Kernel (or any
> other huge application) however, analyzing more types than necessary
> appears to incur a huge time penalty.
>
> So, this patch introduces an optional behaviour whereby
> build_translation_unit_and_add_to_ir is restricted to analyzing
> interfaces that have exported ELF symbols only.  So only the types
> reachable from those interfaces are analyzed.  This more than halves
> the time spent by "abidw --noout vmlinux".
>
> Strictly speaking, this new behaviour is triggered by a new option named
> --exported-interfaces-only, supported by the tools abidw, abidiff,
> abipkgdiff and kmidiff.
>
> When looking at the Linux Kernel however, this option is enabled by
> default.
>
> Note that an option --allow-non-exported-interfaces is also introduce
> to function under the previous model of operations.  This option is
> enabled by default on all the tools when they are not looking at the
> Linux Kernel.
>
> With this enabled, analyzing the Linux Kernel is back to taking less
> than a minute on a reasonable machine.
>
>         * doc/manuals/tools-use-libabigail.txt: New doc text.
>         * doc/manuals/Makefile.am: Add the new tools-use-libabigail.rst
>         tool to the source distribution.
>         * doc/manuals/abidiff.rst: Include the new
>         tools-use-libabigail.rst.  Document the --exported-interfaces-only
>         and --allow-non-exported-interfaces.
>         * doc/manuals/abidw.rst: Likewise.
>         * doc/manuals/abipkgdiff.rst: Likewise.
>         * doc/manuals/kmidiff.rst: Likewise.
>         * include/abg-ir.h
>         (environment::{user_set_analyze_exported_interfaces_only,
>         analyze_exported_interfaces_only}): Declare new accessors.
>         * src/abg-ir.cc
>         (environment::{user_set_analyze_exported_interfaces_only,
>         analyze_exported_interfaces_only}): Define new accessors.
>         * src/abg-dwarf-reader.cc (die_is_variable_decl)
>         (die_is_function_decl): Define new static functions.
>         (read_context::is_decl_die_with_exported_symbol): Define new
>         member function.
>         (read_context::get_{function,variable}_address): Const-ify the
>         Dwarf_Die* parameter.
>         (build_translation_unit_and_add_to_ir): If the user asks to
>         analyze exported interfaces only,  the analyze only interfaces
>         that have exported ELF symbols.
>         (read_debug_info_into_corpus): If we are looking at the Linux
>         Kernel, then only analyze exported interfaces unless the user asks
>         otherwise.
>         * src/abg-ir-priv.h
>         (environment::priv::analyze_exported_interfaces_only_): Define new
>         data member.
>         * tools/abidiff.cc (options::exported_interfaces_only): Define new
>         data member.
>         (display_usage): Add new help strings for
>         --exported-interfaces-only and --allow-non-exported-interfaces.
>         (parse_command_line): Parse the new options
>         --exported-interfaces-only and --allow-non-exported-interfaces.
>         (main): Pass the value of opts.exported_interfaces_only to the
>         environment.
>         * tools/abidw.cc (options::exported_interfaces_only): Define new
>         data member.
>         (display_usage): Add new help strings for
>         --exported-interfaces-only and --allow-non-exported-interfaces.
>         (parse_command_line): Parse the new options
>         (load_corpus_and_write_abixml)
>         (load_kernel_corpus_group_and_write_abixml): Pass the value of
>         opts.exported_interfaces_only onto the environment.
>         * tools/abipkgdiff.cc (options::exported_interfaces_only): Define new
>         data member.
>         (display_usage): Add new help strings for
>         --exported-interfaces-only and --allow-non-exported-interfaces.
>         (parse_command_line): Parse the new options
>         (compare_task::perform, self_compare_task::perform): Pass the
>         value of opts.exported_interfaces_only onto the environment.
>         (compare_prepared_linux_kernel_packages): Likewise.
>         * tools/kmidiff.cc(options::exported_interfaces_only): Define new
>         data member.
>         (display_usage): Add new help strings for
>         --exported-interfaces-only and --allow-non-exported-interfaces.
>         (parse_command_line): Parse the new options
>         (main): Pass the value of opts.exported_interfaces_only onto the
>         environment.
>
> Signed-off-by: Dodji Seketeli <dodji@redhat.com>
> ---
>  doc/manuals/Makefile.am              |   3 +-
>  doc/manuals/abidiff.rst              |  52 ++++++++++++
>  doc/manuals/abidw.rst                |  82 ++++++++++++++++---
>  doc/manuals/abipkgdiff.rst           |  51 ++++++++++++
>  doc/manuals/kmidiff.rst              |  52 +++++++++++-
>  doc/manuals/tools-use-libabigail.txt |  16 ++++
>  include/abg-ir.h                     |   9 +++
>  src/abg-dwarf-reader.cc              | 113 ++++++++++++++++++++++++---
>  src/abg-ir-priv.h                    |   2 +
>  src/abg-ir.cc                        |  36 +++++++++
>  tools/abidiff.cc                     |  12 +++
>  tools/abidw.cc                       |  15 ++++
>  tools/abipkgdiff.cc                  |  21 +++++
>  tools/kmidiff.cc                     |  12 +++
>  14 files changed, 449 insertions(+), 27 deletions(-)
>  create mode 100644 doc/manuals/tools-use-libabigail.txt
>
> diff --git a/doc/manuals/Makefile.am b/doc/manuals/Makefile.am
> index 894b38f1..e2813785 100644
> --- a/doc/manuals/Makefile.am
> +++ b/doc/manuals/Makefile.am
> @@ -14,7 +14,8 @@ libabigail-concepts.rst \
>  libabigail-overview.rst \
>  libabigail-tools.rst \
>  fedabipkgdiff.rst \
> -kmidiff.rst
> +kmidiff.rst \
> +tools-use-libabigail.txt
>
>  # You can set these variables from the command line.
>  SPHINXOPTS    =
> diff --git a/doc/manuals/abidiff.rst b/doc/manuals/abidiff.rst
> index a15515be..0c711d9e 100644
> --- a/doc/manuals/abidiff.rst
> +++ b/doc/manuals/abidiff.rst
> @@ -18,6 +18,8 @@ be accompanied with their debug information in `DWARF`_ format.
>  Otherwise, only `ELF`_ symbols that were added or removed are
>  reported.
>
> +.. include:: tools-use-libabigail.txt
> +
>  .. _abidiff_invocation_label:
>
>  Invocation
> @@ -197,6 +199,56 @@ Options
>      consumption of the tool on binaries with a lot of publicly defined
>      and exported types.
>
> +  * ``--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 those final ABI Corpora
> +    that are compared by this tool.
> +
> +    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.
> +
> +    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.
> +
> +  * ``--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 those final ABI Corpora that are
> +    compared by this tool.
> +
> +    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`_.
> +
>    * ``--stat``
>
>      Rather than displaying the detailed ABI differences between
> diff --git a/doc/manuals/abidw.rst b/doc/manuals/abidw.rst
> index bdd6204d..a3055c7e 100644
> --- a/doc/manuals/abidw.rst
> +++ b/doc/manuals/abidw.rst
> @@ -12,14 +12,19 @@ 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.
> +`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.
> +
> +.. include:: tools-use-libabigail.txt
> +
> +.. _abidiff_invocation_label:
>
>  Invocation
>  ==========
> @@ -92,7 +97,7 @@ Options
>
>    * ``--kmi-whitelist | -kaw`` <*path-to-whitelist*>
>
> -    When analyzing a Linux kernel binary, this option points to the
> +    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
> @@ -105,7 +110,7 @@ Options
>
>      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
> +    exported functions and global variables by the `Linux Kernel`_
>      binaries is emitted.
>
>    * ``--linux-tree | --lt``
> @@ -115,9 +120,10 @@ Options
>      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.
> +    Below is an example of usage of ``abidw`` on a `Linux Kernel`_
> +    tree.
>
> -    First, checkout a Linux kernel source tree and build it.  Then
> +    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``: ::
> @@ -171,6 +177,56 @@ Options
>      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``.
> +
> +    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.
> +
> +    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.
> +
> +  * ``--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`_.
> +
>    * ``--no-linux-kernel-mode``
>
>      Without this option, if abipkgiff detects that the binaries it is
> @@ -308,4 +364,4 @@ standard `here
>  .. _ELF: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
>  .. _DWARF: http://www.dwarfstd.org
>  .. _GNU: http://www.gnu.org
> -
> +.. _Linux Kernel: https://kernel.org/
> diff --git a/doc/manuals/abipkgdiff.rst b/doc/manuals/abipkgdiff.rst
> index 15ea9072..9114775a 100644
> --- a/doc/manuals/abipkgdiff.rst
> +++ b/doc/manuals/abipkgdiff.rst
> @@ -19,6 +19,7 @@ information directly in a section of said binaries.  In those cases,
>  obviously, no separate debug information package is needed as the tool
>  will find the debug information inside the binaries.
>
> +.. include:: tools-use-libabigail.txt
>
>  .. _abipkgdiff_invocation_label:
>
> @@ -277,6 +278,56 @@ Options
>      global functions and variables are analyzed, so the tool detects
>      and reports changes on these reachable types only.
>
> +  * ``--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 those final ABI Corpora
> +    that are compared by this tool.
> +
> +    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.
> +
> +    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.
> +
> +  * ``--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 those final ABI Corpora that are
> +    compared by this tool.
> +
> +    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`_.
> +
>    *  ``--redundant``
>
>      In the diff reports, do display redundant changes.  A redundant
> diff --git a/doc/manuals/kmidiff.rst b/doc/manuals/kmidiff.rst
> index ce8168ae..53010189 100644
> --- a/doc/manuals/kmidiff.rst
> +++ b/doc/manuals/kmidiff.rst
> @@ -55,6 +55,10 @@ command line looks like: ::
>                        linux/v4.5/build/modules \
>                        linux/v4.6/build/modules
>
> +
> +.. include:: tools-use-libabigail.txt
> +
> +
>  Invocation
>  ==========
>
> @@ -67,8 +71,8 @@ Environment
>
>  By default, ``kmidiff`` compares all the interfaces (exported
>  functions and variables) between the Kernel and its modules.  In
> -practice, though, users want to compare a subset of the those
> -interfaces.
> +practice, though, some users might want to compare a subset of the
> +those interfaces.
>
>  Users can then define a "white list" of the interfaces to compare.
>  Such a white list is a just a file in the "INI" format that looks
> @@ -91,8 +95,11 @@ function or variable.  Only those interfaces along with the types
>  reachable from their signatures are going to be compared by
>  ``kmidiff`` recursively.
>
> -Note that kmidiff compares the interfaces exported by the ``vmlinux``
> -binary and by the all of the compiled modules.
> +Note that by default kmidiff analyzes the types reachable from the
> +interfaces associated with `ELF`_ symbols that are defined and
> +exported by the `Linux Kernel`_ as being the union of the ``vmlinux``
> +binary and all its compiled modules.  It then compares those
> +interfaces (along with their types).
>
>  Options
>  =======
> @@ -180,6 +187,38 @@ Options
>      exported interfaces.  This is the default kind of report emitted
>      by tools like ``abidiff`` or ``abipkgdiff``.
>
> +  * ``--exported-interfaces-only``
> +
> +    When using this option, this tool analyzes the descriptions of the
> +    types reachable by the interfaces (functions and variables)
> +    associated with `ELF`_ symbols that are defined and exported by
> +    the `Linux Kernel`_.
> +
> +    Otherwise, the tool also has the ability to analyze the
> +    descriptions of the types reachable by the interfaces associated
> +    with `ELF`_ symbols that are visible outside their translation
> +    unit.  This later possibility is however much more resource
> +    intensive and results in much slower operations.
> +
> +    That is why this option is enabled by default.
> +
> +
> +  * ``--allow-non-exported-interfaces``
> +
> +    When using this option, 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 is compared against another one.
> +
> +    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, leading to very slow operations.
> +
> +    Note that this option is turned off by default.
> +
>    * ``--show-bytes``
>
>      Show sizes and offsets in bytes, not bits.  This option is
> @@ -198,3 +237,8 @@ Options
>    * ``--show-dec``
>
>      Show sizes and offsets in decimal base.
> +
> +
> +.. _ELF: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
> +.. _ksymtab: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
> +.. _Linux Kernel: https://kernel.org
> diff --git a/doc/manuals/tools-use-libabigail.txt b/doc/manuals/tools-use-libabigail.txt
> new file mode 100644
> index 00000000..43edf296
> --- /dev/null
> +++ b/doc/manuals/tools-use-libabigail.txt
> @@ -0,0 +1,16 @@
> +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.
> diff --git a/include/abg-ir.h b/include/abg-ir.h
> index a857d041..61338edb 100644
> --- a/include/abg-ir.h
> +++ b/include/abg-ir.h
> @@ -197,6 +197,15 @@ public:
>    const config&
>    get_config() const;
>
> +  bool
> +  user_set_analyze_exported_interfaces_only() const;
> +
> +  void
> +  analyze_exported_interfaces_only(bool f);
> +
> +  bool
> +  analyze_exported_interfaces_only() const;
> +
>  #ifdef WITH_DEBUG_SELF_COMPARISON
>    void
>    set_self_comparison_debug_input(const corpus_sptr& corpus);
> diff --git a/src/abg-dwarf-reader.cc b/src/abg-dwarf-reader.cc
> index e41172c1..cba89664 100644
> --- a/src/abg-dwarf-reader.cc
> +++ b/src/abg-dwarf-reader.cc
> @@ -402,6 +402,12 @@ die_is_decl(const Dwarf_Die* die);
>  static bool
>  die_is_declaration_only(Dwarf_Die* die);
>
> +static bool
> +die_is_variable_decl(const Dwarf_Die *die);
> +
> +static bool
> +die_is_function_decl(const Dwarf_Die *die);
> +
>  static bool
>  die_has_size_attribute(const Dwarf_Die *die);
>
> @@ -5303,6 +5309,44 @@ public:
>      return symbol;
>    }
>
> +  /// Test if a DIE represents a decl (function or variable) that has
> +  /// a symbol that is exported, whatever that means.  This is
> +  /// supposed to work for Linux Kernel binaries as well.
> +  ///
> +  /// This is useful to limit the amount of DIEs taken into account to
> +  /// the strict limit of what an ABI actually means.  Limiting the
> +  /// volume of DIEs analyzed this way is an important optimization to
> +  /// keep big binaries "manageable" by libabigail.
> +  ///
> +  /// @param DIE the die to consider.
> +  bool
> +  is_decl_die_with_exported_symbol(const Dwarf_Die *die)
> +  {
> +    if (!die || !die_is_decl(die))
> +      return false;
> +
> +    bool result = false, address_found = false, symbol_is_exported = false;;
> +    Dwarf_Addr decl_symbol_address = 0;
> +
> +    if (die_is_variable_decl(die))
> +      {
> +       if ((address_found = get_variable_address(die, decl_symbol_address)))
> +         symbol_is_exported =
> +           !!variable_symbol_is_exported(decl_symbol_address);
> +      }
> +    else if (die_is_function_decl(die))
> +      {
> +       if ((address_found = get_function_address(die, decl_symbol_address)))
> +         symbol_is_exported =
> +           !!function_symbol_is_exported(decl_symbol_address);
> +      }
> +
> +    if (address_found)
> +      result = symbol_is_exported;
> +
> +    return result;
> +  }
> +
>    /// Getter for the symtab reader. Will load the symtab from the elf handle if
>    /// not yet set.
>    ///
> @@ -5580,16 +5624,18 @@ public:
>    ///
>    /// @return true if the function address was found.
>    bool
> -  get_function_address(Dwarf_Die* function_die, Dwarf_Addr& address) const
> +  get_function_address(const Dwarf_Die* function_die, Dwarf_Addr& address) const
>    {
> -    if (!die_address_attribute(function_die, DW_AT_low_pc, address))
> +    if (!die_address_attribute(const_cast<Dwarf_Die*>(function_die),
> +                              DW_AT_low_pc, address))
>        // So no DW_AT_low_pc was found.  Let's see if the function DIE
>        // has got a DW_AT_ranges attribute instead.  If it does, the
>        // first address of the set of addresses represented by the
>        // value of that DW_AT_ranges represents the function (symbol)
>        // address we are looking for.
> -      if (!get_first_exported_fn_address_from_DW_AT_ranges(function_die,
> -                                                          address))
> +      if (!get_first_exported_fn_address_from_DW_AT_ranges
> +         (const_cast<Dwarf_Die*>(function_die),
> +          address))
>         return false;
>
>      address = maybe_adjust_fn_sym_address(address);
> @@ -5611,11 +5657,12 @@ public:
>    ///
>    /// @return true if the variable address was found.
>    bool
> -  get_variable_address(Dwarf_Die*      variable_die,
> +  get_variable_address(const Dwarf_Die* variable_die,
>                        Dwarf_Addr&      address) const
>    {
>      bool is_tls_address = false;
> -    if (!die_location_address(variable_die, address, is_tls_address))
> +    if (!die_location_address(const_cast<Dwarf_Die*>(variable_die),
> +                             address, is_tls_address))
>        return false;
>      if (!is_tls_address)
>        address = maybe_adjust_var_sym_address(address);
> @@ -7155,6 +7202,40 @@ die_is_declaration_only(Dwarf_Die* die)
>    return false;
>  }
>
> +/// Test if a DIE is for a function decl.
> +///
> +/// @param die the DIE to consider.
> +///
> +/// @return true iff @p die represents a function decl.
> +static bool
> +die_is_function_decl(const Dwarf_Die *die)
> +{
> +  if (!die)
> +    return false;
> +
> +  int tag = dwarf_tag(const_cast<Dwarf_Die*>(die));
> +  if (tag == DW_TAG_subprogram)
> +    return true;
> +  return false;
> +}
> +
> +/// Test if a DIE is for a variable decl.
> +///
> +/// @param die the DIE to consider.
> +///
> +/// @return true iff @p die represents a variable decl.
> +static bool
> +die_is_variable_decl(const Dwarf_Die *die)
> +{
> +    if (!die)
> +    return false;
> +
> +  int tag = dwarf_tag(const_cast<Dwarf_Die*>(die));
> +  if (tag == DW_TAG_variable)
> +    return true;
> +  return false;
> +}
> +
>  /// Test if a DIE has size attribute.
>  ///
>  /// @param die the DIE to consider.
> @@ -12690,9 +12771,13 @@ build_translation_unit_and_add_to_ir(read_context&     ctxt,
>    result->set_is_constructed(false);
>
>    do
> -    build_ir_node_from_die(ctxt, &child,
> -                          die_is_public_decl(&child),
> -                          dwarf_dieoffset(&child));
> +    // Analyze all the DIEs we encounter unless we are asked to only
> +    // analyze exported interfaces and the types reachables from them.
> +    if (!ctxt.env()->analyze_exported_interfaces_only()
> +       || ctxt.is_decl_die_with_exported_symbol(&child))
> +      build_ir_node_from_die(ctxt, &child,
> +                            die_is_public_decl(&child),
> +                            dwarf_dieoffset(&child));
>    while (dwarf_siblingof(&child, &child) == 0);
>
>    if (!ctxt.var_decls_to_re_add_to_tree().empty())
> @@ -15699,6 +15784,16 @@ read_debug_info_into_corpus(read_context& ctxt)
>      origin |= corpus::LINUX_KERNEL_BINARY_ORIGIN;
>    ctxt.current_corpus()->set_origin(origin);
>
> +  if (origin & corpus::LINUX_KERNEL_BINARY_ORIGIN
> +      && !ctxt.env()->user_set_analyze_exported_interfaces_only())
> +    // So we are looking at the Linux Kernel and the user has not set
> +    // any particular option regarding the amount of types to analyse.
> +    // In that case, we need to only analyze types that are reachable
> +    // from exported interfaces otherwise we get such a massive amount
> +    // of type DIEs to look at that things are just too slow down the
> +    // road.
> +    ctxt.env()->analyze_exported_interfaces_only(true);
> +
>    ctxt.current_corpus()->set_soname(ctxt.dt_soname());
>    ctxt.current_corpus()->set_needed(ctxt.dt_needed());
>    ctxt.current_corpus()->set_architecture_name(ctxt.elf_architecture());
> diff --git a/src/abg-ir-priv.h b/src/abg-ir-priv.h
> index 45b711b7..21734b25 100644
> --- a/src/abg-ir-priv.h
> +++ b/src/abg-ir-priv.h
> @@ -26,6 +26,7 @@ namespace ir
>  {
>
>  using std::string;
> +using abg_compat::optional;
>
>  /// The result of structural comparison of type ABI artifacts.
>  enum comparison_result
> @@ -443,6 +444,7 @@ struct environment::priv
>    bool                                 decl_only_class_equals_definition_;
>    bool                                 use_enum_binary_only_equality_;
>    bool                                 allow_type_comparison_results_caching_;
> +  optional<bool>                       analyze_exported_interfaces_only_;
>  #ifdef WITH_DEBUG_SELF_COMPARISON
>    bool                                 self_comparison_debug_on_;
>  #endif
> diff --git a/src/abg-ir.cc b/src/abg-ir.cc
> index 91c8e99b..02d68e63 100644
> --- a/src/abg-ir.cc
> +++ b/src/abg-ir.cc
> @@ -3674,6 +3674,42 @@ const config&
>  environment::get_config() const
>  {return priv_->config_;}
>
> +/// Getter for a property that says if the user actually did set the
> +/// analyze_exported_interfaces_only() property.  If not, it means
> +/// the default behaviour prevails.
> +///
> +/// @return tru iff the user did set the
> +/// analyze_exported_interfaces_only() property.
> +bool
> +environment::user_set_analyze_exported_interfaces_only() const
> +{return priv_->analyze_exported_interfaces_only_.has_value();}
> +
> +/// Setter for the property that controls if we are to restrict the
> +/// analysis to the types that are only reachable from the exported
> +/// interfaces only, or if the set of types should be more broad than
> +/// that.  Typically, we'd restrict the analysis to types reachable
> +/// from exported interfaces only (stricto sensu, that would really be
> +/// only the types that are part of the ABI of well designed
> +/// libraries) for performance reasons.
> +///
> +/// @param f the value of the flag.
> +void
> +environment::analyze_exported_interfaces_only(bool f)
> +{priv_->analyze_exported_interfaces_only_ = f;}
> +
> +/// Getter for the property that controls if we are to restrict the
> +/// analysis to the types that are only reachable from the exported
> +/// interfaces only, or if the set of types should be more broad than
> +/// that.  Typically, we'd restrict the analysis to types reachable
> +/// from exported interfaces only (stricto sensu, that would really be
> +/// only the types that are part of the ABI of well designed
> +/// libraries) for performance reasons.
> +///
> +/// @param f the value of the flag.
> +bool
> +environment::analyze_exported_interfaces_only() const
> +{return priv_->analyze_exported_interfaces_only_.value_or(false);}
> +
>  #ifdef WITH_DEBUG_SELF_COMPARISON
>  /// Setter of the corpus of the input corpus of the self comparison
>  /// that takes place when doing "abidw --debug-abidiff <binary>".
> diff --git a/tools/abidiff.cc b/tools/abidiff.cc
> index 97b036cb..e0bb35ac 100644
> --- a/tools/abidiff.cc
> +++ b/tools/abidiff.cc
> @@ -29,6 +29,7 @@ using std::ostream;
>  using std::cout;
>  using std::cerr;
>  using std::shared_ptr;
> +using abg_compat::optional;
>  using abigail::ir::environment;
>  using abigail::ir::environment_sptr;
>  using abigail::translation_unit;
> @@ -74,6 +75,7 @@ struct options
>    vector<string>       headers_dirs2;
>    vector<string>        header_files2;
>    bool                 drop_private_types;
> +  optional<bool>       exported_interfaces_only;
>    bool                 linux_kernel_mode;
>    bool                 no_default_supprs;
>    bool                 no_arch;
> @@ -197,6 +199,9 @@ display_usage(const string& prog_name, ostream& out)
>      << " --header-file2|--hf2 <path>  the path to one header of file2\n"
>      << " --drop-private-types  drop private types from "
>      "internal representation\n"
> +    << "  --exported-interfaces-only  analyze exported interfaces only\n"
> +    << "  --allow-non-exported-interfaces  analyze interfaces that "
> +    "might not be exported\n"
>      << " --no-linux-kernel-mode  don't consider the input binaries as "
>         "linux kernel binaries\n"
>      << " --kmi-whitelist|-w  path to a "
> @@ -403,6 +408,10 @@ parse_command_line(int argc, char* argv[], options& opts)
>         }
>        else if (!strcmp(argv[i], "--drop-private-types"))
>         opts.drop_private_types = true;
> +      else if (!strcmp(argv[i], "--exported-interfaces-only"))
> +       opts.exported_interfaces_only = true;
> +      else if (!strcmp(argv[i], "--allow-non-exported-interfaces"))
> +       opts.exported_interfaces_only = false;
>        else if (!strcmp(argv[i], "--no-default-suppression"))
>         opts.no_default_supprs = true;
>        else if (!strcmp(argv[i], "--no-architecture"))
> @@ -1130,6 +1139,9 @@ main(int argc, char* argv[])
>        t2_type = guess_file_type(opts.file2);
>
>        environment_sptr env(new environment);
> +      if (opts.exported_interfaces_only.has_value())
> +       env->analyze_exported_interfaces_only(*opts.exported_interfaces_only);
> +
>  #ifdef WITH_DEBUG_SELF_COMPARISON
>             if (opts.do_debug)
>               env->self_comparison_debug_is_on(true);
> diff --git a/tools/abidw.cc b/tools/abidw.cc
> index 9a27a029..f38d6048 100644
> --- a/tools/abidw.cc
> +++ b/tools/abidw.cc
> @@ -40,6 +40,7 @@ using std::ostream;
>  using std::ofstream;
>  using std::vector;
>  using std::shared_ptr;
> +using abg_compat::optional;
>  using abigail::tools_utils::emit_prefix;
>  using abigail::tools_utils::temp_file;
>  using abigail::tools_utils::temp_file_sptr;
> @@ -114,6 +115,7 @@ struct options
>    bool                 do_log;
>    bool                 drop_private_types;
>    bool                 drop_undefined_syms;
> +  optional<bool>       exported_interfaces_only;
>    type_id_style_kind   type_id_style;
>  #ifdef WITH_DEBUG_SELF_COMPARISON
>    string               type_id_file_path;
> @@ -187,6 +189,9 @@ display_usage(const string& prog_name, ostream& out)
>      << "  --short-locs  only print filenames rather than paths\n"
>      << "  --drop-private-types  drop private types from representation\n"
>      << "  --drop-undefined-syms  drop undefined symbols from representation\n"
> +    << "  --exported-interfaces-only  analyze exported interfaces only\n"
> +    << "  --allow-non-exported-interfaces  analyze interfaces that "
> +    "might not be exported\n"
>      << "  --no-comp-dir-path  do not show compilation path information\n"
>      << "  --no-elf-needed  do not show the DT_NEEDED information\n"
>      << "  --no-write-default-sizes  do not emit pointer size when it equals"
> @@ -368,6 +373,10 @@ parse_command_line(int argc, char* argv[], options& opts)
>         opts.drop_private_types = true;
>        else if (!strcmp(argv[i], "--drop-undefined-syms"))
>         opts.drop_undefined_syms = true;
> +      else if (!strcmp(argv[i], "--exported-interfaces-only"))
> +       opts.exported_interfaces_only = true;
> +      else if (!strcmp(argv[i], "--allow-non-exported-interfaces"))
> +       opts.exported_interfaces_only = false;
>        else if (!strcmp(argv[i], "--no-linux-kernel-mode"))
>         opts.linux_kernel_mode = false;
>        else if (!strcmp(argv[i], "--abidiff"))
> @@ -606,6 +615,9 @@ load_corpus_and_write_abixml(char* argv[],
>              }
>          }
>
> +      if (opts.exported_interfaces_only.has_value())
> +       env->analyze_exported_interfaces_only(*opts.exported_interfaces_only);
> +
>        t.start();
>        corp = dwarf_reader::read_corpus_from_elf(ctxt, s);
>        t.stop();
> @@ -813,6 +825,9 @@ load_kernel_corpus_group_and_write_abixml(char* argv[],
>    timer t, global_timer;
>    suppressions_type supprs;
>
> +  if (opts.exported_interfaces_only.has_value())
> +    env->analyze_exported_interfaces_only(*opts.exported_interfaces_only);
> +
>    if (opts.do_log)
>      emit_prefix(argv[0], cerr)
>        << "going to build ABI representation of the Linux Kernel ...\n";
> diff --git a/tools/abipkgdiff.cc b/tools/abipkgdiff.cc
> index 551080b9..656d5882 100644
> --- a/tools/abipkgdiff.cc
> +++ b/tools/abipkgdiff.cc
> @@ -106,6 +106,7 @@ using std::set;
>  using std::ostringstream;
>  using std::shared_ptr;
>  using std::dynamic_pointer_cast;
> +using abg_compat::optional;
>  using abigail::workers::task;
>  using abigail::workers::task_sptr;
>  using abigail::workers::queue;
> @@ -205,6 +206,7 @@ public:
>    bool         fail_if_no_debug_info;
>    bool         show_identical_binaries;
>    bool         self_check;
> +  optional<bool> exported_interfaces_only;
>  #ifdef WITH_CTF
>    bool         use_ctf;
>  #endif
> @@ -868,6 +870,9 @@ display_usage(const string& prog_name, ostream& out)
>      "full impact analysis report rather than the default leaf changes reports\n"
>      << " --non-reachable-types|-t  consider types non reachable"
>      " from public interfaces\n"
> +    << "  --exported-interfaces-only  analyze exported interfaces only\n"
> +    << "  --allow-non-exported-interfaces  analyze interfaces that "
> +    "might not be exported\n"
>      << " --no-linkage-name             do not display linkage names of "
>      "added/removed/changed\n"
>      << " --redundant                    display redundant changes\n"
> @@ -2076,6 +2081,10 @@ public:
>      abigail::elf_reader::status detailed_status =
>        abigail::elf_reader::STATUS_UNKNOWN;
>
> +    if (args->opts.exported_interfaces_only.has_value())
> +      env->analyze_exported_interfaces_only
> +       (*args->opts.exported_interfaces_only);
> +
>      status |= compare(args->elf1, args->debug_dir1, args->private_types_suppr1,
>                       args->elf2, args->debug_dir2, args->private_types_suppr2,
>                       args->opts, env, diff, ctxt, &detailed_status);
> @@ -2142,6 +2151,10 @@ public:
>      diff_context_sptr ctxt;
>      corpus_diff_sptr diff;
>
> +    if (args->opts.exported_interfaces_only.has_value())
> +      env->analyze_exported_interfaces_only
> +       (*args->opts.exported_interfaces_only);
> +
>      abigail::elf_reader::status detailed_status =
>        abigail::elf_reader::STATUS_UNKNOWN;
>
> @@ -3024,6 +3037,10 @@ compare_prepared_linux_kernel_packages(package& first_package,
>    string dist_root2 = second_package.extracted_dir_path();
>
>    abigail::ir::environment_sptr env(new abigail::ir::environment);
> +  if (opts.exported_interfaces_only.has_value())
> +    env->analyze_exported_interfaces_only
> +      (*opts.exported_interfaces_only);
> +
>    suppressions_type supprs;
>    corpus_group_sptr corpus1, corpus2;
>    corpus1 = build_corpus_group_from_kernel_dist_under(dist_root1,
> @@ -3326,6 +3343,10 @@ parse_command_line(int argc, char* argv[], options& opts)
>        else if (!strcmp(argv[i], "--full-impact")
>                ||!strcmp(argv[i], "-f"))
>         opts.show_full_impact_report = true;
> +      else if (!strcmp(argv[i], "--exported-interfaces-only"))
> +       opts.exported_interfaces_only = true;
> +      else if (!strcmp(argv[i], "--allow-non-exported-interfaces"))
> +       opts.exported_interfaces_only = false;
>        else if (!strcmp(argv[i], "--no-linkage-name"))
>         opts.show_linkage_names = false;
>        else if (!strcmp(argv[i], "--redundant"))
> diff --git a/tools/kmidiff.cc b/tools/kmidiff.cc
> index 8fd3fed9..f3332765 100644
> --- a/tools/kmidiff.cc
> +++ b/tools/kmidiff.cc
> @@ -29,6 +29,7 @@ using std::vector;
>  using std::ostream;
>  using std::cout;
>  using std::cerr;
> +using abg_compat::optional;
>
>  using namespace abigail::tools_utils;
>  using namespace abigail::dwarf_reader;
> @@ -60,6 +61,7 @@ struct options
>    bool                 show_hexadecimal_values;
>    bool                 show_offsets_sizes_in_bits;
>    bool                 show_impacted_interfaces;
> +  optional<bool>       exported_interfaces_only;
>  #ifdef WITH_CTF
>    bool                 use_ctf;
>  #endif
> @@ -120,6 +122,9 @@ display_usage(const string& prog_name, ostream& out)
>      << " --impacted-interfaces|-i  show interfaces impacted by ABI changes\n"
>      << " --full-impact|-f  show the full impact of changes on top-most "
>          "interfaces\n"
> +    << "  --exported-interfaces-only  analyze exported interfaces only\n"
> +    << "  --allow-non-exported-interfaces  analyze interfaces that "
> +    "might not be exported\n"
>      << " --show-bytes  show size and offsets in bytes\n"
>      << " --show-bits  show size and offsets in bits\n"
>      << " --show-hex  show size and offset in hexadecimal\n"
> @@ -262,6 +267,10 @@ parse_command_line(int argc, char* argv[], options& opts)
>        else if (!strcmp(argv[i], "--full-impact")
>                || !strcmp(argv[i], "-f"))
>         opts.leaf_changes_only = false;
> +      else if (!strcmp(argv[i], "--exported-interfaces-only"))
> +       opts.exported_interfaces_only = true;
> +      else if (!strcmp(argv[i], "--allow-non-exported-interfaces"))
> +       opts.exported_interfaces_only = false;
>        else if (!strcmp(argv[i], "--show-bytes"))
>         opts.show_offsets_sizes_in_bits = false;
>        else if (!strcmp(argv[i], "--show-bits"))
> @@ -408,6 +417,9 @@ main(int argc, char* argv[])
>
>    environment_sptr env(new environment);
>
> +  if (opts.exported_interfaces_only.has_value())
> +    env->analyze_exported_interfaces_only(*opts.exported_interfaces_only);
> +
>    corpus_group_sptr group1, group2;
>    string debug_info_root_dir;
>    corpus::origin origin =
> --
> 2.37.2
>
>
>
> --
>                 Dodji