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fadfa1a6f6
This patch teaches the ELF/DWARF reader of libabigail to load special
ELF sections that are specific to Linux Kernel binaries (either
vmlinux or linux kernel modules).
The patch creates a new flag that tells the ELF reader that it needs
to consider the input binary as a Linux Kernel binary. This is the
new 'Linux Kernel mode'.
In this linux kernel mode, the reader expects sections that are named
__ksymtab and/or __ksymtab_gpl sections. Those sections contain
indexes (of ELF symbols described in the normal ELF symbol table) of
exported ELF symbols that are specifically marked by developers using
EXPORT_SYMBOL or EXPORT_SYMBOL_GPL macros. These are symbols of
global variables and functions defined and meant to be used by kernel
modules. They constitute the interface exported by the Linux Kernel
to its modules. So the patch only exports the publicly defined and
exported ELF symbols that are also listed in __ksymtab and
__ksymtab_gpl sections.
The patch also fixes and re-organizes things left and right so that
this new mode works in a well integrated manner with the other parts
of the reader:
- The load address of the binary is no more assumed to be the load
address specified by the program header that is at offset zero.
This is usually the case for user-space programs. To handle Linux
Kernel binaries, the load address is now the one specified by the
program header that is at the smallest offset.
- The patch now tries to populate the various symbol maps only when
necessary. That way, the new symbol maps defined for the ksymtab
and ksymtab_gpl section are also loaded only when necessary; that
is, when in Linux Kernel mode.
- The patch (more) agressively suppresses non-member functions or
variables that are not declarations and that have no associated
ELF symbol.
The patch knows how to recognize and read relevant ELF symbol
information from __ksymtab and __ksymtab_gpl sections.
The patch makes abidiff and abidw detect that a binary is a
Linux Kernel binary (either a vmlinux or a module). It does this by
detecting the presence of the speciall __ksymtab_strings section.
If it detects that a binary is a Linux Kernel binary then it only
considers functions and variables which are defined and exported in
the sense of ELF *AND* which ELF symbols are listed in the __ksymtab
and __ksymtab_gpl sections.
If users want abidiff and abidw to consider their input binaries as
normal ELF binaries then they can use the option --no-linux-kernel-mode.
* include/abg-dwarf-reader.h (create_read_context): Take a new
flag to say if the context is to read an ELF binary in linux
kernel mode.
* src/abg-dwarf-reader.cc (typedef address_set_type)
(address_set_sptr): New typedefs.
(get_binary_load_address): The load address of the binary is
the load address specified by the program header that is at the
smallest offset; not by the program header that is at offset zero.
(read_context::{ksymtab_section_, ksymtab_gpl_section_,
linux_exported_fn_syms_, linux_exported_var_syms_,
linux_exported_gpl_fn_syms_, linux_exported_gpl_var_syms_,
load_in_linux_kernel_mode_}): New data members.
(read_context::read_context): Initialize ksymtab_section_,
ksymtab_gpl_section_ and load_in_linux_kernel_mode_.
(read_context::{find_symbol_table_section, find_opd_section,
lookup_elf_fn_symbol_from_address,
lookup_elf_var_symbol_from_address, get_function_address,
get_variable_address}): Make these const.
(read_context::{find_ksymtab_section, find_ksymtab_gpl_section,
lookup_elf_symbol_from_address, function_symbol_is_exported,
variable_symbol_is_exported, linux_exported_fn_syms,
create_or_get_linux_exported_fn_syms, linux_exported_var_syms,
create_or_get_linux_exported_var_syms, linux_exported_gpl_fn_syms,
linux_exported_gpl_var_syms,
create_or_get_linux_exported_gpl_fn_syms,
linux_exported_gpl_var_syms,
create_or_get_linux_exported_gpl_var_syms, architecture_word_size,
load_kernel_symbol_table, load_ksymtab_symbols,
load_ksymtab_gpl_symbols,
load_linux_specific_exported_symbol_maps,
load_in_linux_kernel_mode}): New member functions.
(read_context::read_int_from_array_of_bytes): Factorize this
new member function out of ...
(read_context::{lookup_ppc64_elf_fn_entry_point_address}):
... this. Make this function const too.
(read_context::read_uint64_from_array_of_bytes): New function.
Uses read_int_from_array_of_bytes above.
(read_context::{fun_entry_addr_sym_map_sptr}): Try to load symbol
maps only when it's necessary.
(read_context::elf_architecture_is_big_endian): Fix logic.
(read_context::{var_addr_sym_map}): Express the const variant in
terms of the non-const one. In the non-const one, load the map
only when necessary.
(read_context::load_symbol_maps_from_symtab_section): Renamed
load_symbol_maps into this.
(read_context::is_linux_kernel_binary): Define new member
function.
(read_context::{function, variable}_symbol_is_exported): If we are
not prevented from considering loading in linux kernel mode, then
just looking at a linux kernel binary makes us consider the
special kernel sections.
(read_debug_info_into_corpus): Likewise.
(build_ir_node_from_die): Take a new flag that says if the ir node
is a declaration required by another concrete IR node.
(enum read_context::kernel_symbol_table_kind): New enum.
(read_context::load_symbol_maps): Support loading linux kernel
specific sections too.
(build_var_decl): Use the new
read_context::variable_symbol_is_exported.
(function_is_suppressed): Suppress non-member functions or
variables that are not declarations and that have no symbol.
(variable_is_suppressed, build_var_decl_if_not_suppressed): Take a
new flag that says if the variable is a declaration required by a
concrete variable. If non member variable that is a declaration
is not the specification of another concrete variable, then it's
suppressed.
(add_fn_symbols_to_map, add_var_symbols_to_map): New function
definitions.
(read_debug_info_into_corpus): If we are reading linux kernel or
linux kernel modules, only set explicitely exported symbols (in
the linux kernel binary sense) as exported function or variable
symbols.
(create_read_context): Take a new flag to say if the context is to
read an ELF binary in linux kernel mode.
* tools/abidiff.cc (options::options): Initialize
options::linux_kernel_mode to true.
(display_usage): Display usage of the --no-linux-kernel-mode option.
(parse_command_line): Parse the --no-linux-kernel-mode option.
* tools/abidw.cc (options::options): Initialize
options::linux_kernel_mode to true.
(display_usage): Display usage of --no-linux-kernel-mode option.
(parse_command_line): Parse the --no-linux-kernel-mode option.
* doc/manuals/abidiff.rst: Document the new --no-linux-kernel-mode
options.
* doc/manuals/abidw.rst: Likewise.
* tests/data/test-diff-dwarf-abixml/test0-pr19026-libvtkIOSQL-6.1.so.1.abi:
Adjust.
* tests/data/test-read-dwarf/test9-pr18818-clang.so.abi: Adjust.
* tests/data/test-read-dwarf/test10-pr18818-gcc.so.abi: Adjust.
* tests/data/test-read-dwarf/test11-pr18828.so.abi: Adjust.
* tests/data/test-read-dwarf/test12-pr18844.so.abi: Likewise.
* tests/data/test-read-dwarf/test13-pr18894.so.abi: Likewise.
* tests/data/test-read-dwarf/test14-pr18893.so.abi: Likewise.
* tests/data/test-read-dwarf/test15-pr18892.so.abi: Likewise.
* tests/data/test-read-dwarf/test16-pr18904.so.abi: Likewise.
* tests/data/test-read-dwarf/test17-pr19027.so.abi: Likewise.
* tests/data/test-read-dwarf/test18-pr19037-libvtkRenderingLIC-6.1.so.abi:
Likewise.
* tests/data/test-read-dwarf/test19-pr19023-libtcmalloc_and_profiler.so.abi:
Likewise.
* tests/data/test-read-dwarf/test20-pr19025-libvtkParallelCore-6.1.so.abi:
Likewise.
* tests/data/test-read-dwarf/test21-pr19092.so.abi: Likewise.
* tests/data/test-read-dwarf/test22-pr19097-libstdc++.so.6.0.17.so.abi: Likewise.
* tests/data/test-read-dwarf/libtest23.so.abi: Adjust.
* tests/data/test-read-dwarf/libtest24-drop-fns-2.so.abi: Adjust.
* tests/data/test-read-dwarf/libtest24-drop-fns.so.abi: Adjust.
Signed-off-by: Dodji Seketeli <dodji@redhat.com>
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======
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abidw
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======
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abidw reads a shared library in `ELF`_ format and emits an XML
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representation of its ABI to standard output. The emitted
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representation includes all the globally defined functions and
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variables, along with a complete representation of their types. It
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also includes a representation of the globally defined ELF symbols of
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the file. The input shared library must contain associated debug
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information in `DWARF`_ format.
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Invocation
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==========
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::
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abidw [options] [<path-to-elf-file>]
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Options
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=======
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* ``--help | -h``
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Display a short help about the command and exit.
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* `--version | -v`
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Display the version of the program and exit.
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* ``--debug-info-dir | -d`` <*dir-path*>
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In cases where the debug info for *path-to-elf-file* is in a
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separate file that is located in a non-standard place, this tells
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``abidw`` where to look for that debug info file.
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Note that *dir-path* must point to the root directory under which
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the debug information is arranged in a tree-like manner. Under
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Red Hat based systems, that directory is usually
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``<root>/usr/lib/debug``.
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Note that this option is not mandatory for split debug information
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installed by your system's package manager because then
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``abidw`` knows where to find it.
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* ``--out-file`` <*file-path*>
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This option instructs ``abidw`` to emit the XML representation of
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*path-to-elf-file* into the file *file-path*, rather than emitting
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it to its standard output.
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* ``--noout``
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This option instructs ``abidw`` to not emit the XML representation
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of the ABI. So it only reads the ELF and debug information,
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builds the internal representation of the ABI and exits. This
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option is usually useful for debugging purposes.
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* ``--suppressions | suppr`` <*path-to-suppression-specifications-file*>
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Use a :ref:`suppression specification <suppr_spec_label>` file
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located at *path-to-suppression-specifications-file*. Note that
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this option can appear multiple times on the command line. In
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that case, all of the provided suppression specification files are
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taken into account. ABI artifacts matched by the suppression
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specifications are suppressed from the output of this tool.
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* ``--headers-dir | --hd`` <headers-directory-path-1>
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Specifies where to find the public headers of the first shared
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library that the tool has to consider. The tool will thus filter
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out types that are not defined in public headers.
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* ``--no-linux-kernel-mode``
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Without this option, if abipkgiff detects that the binaries it is
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looking at are Linux Kernel binaries (either vmlinux or modules)
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then it only considers functions and variables which ELF symbols
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are listed in the __ksymtab and __ksymtab_gpl sections.
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With this option, abipkgdiff considers the binary as a non-special
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ELF binary. It thus considers functions and variables which are
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defined and exported in the ELF sense.
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* ``--check-alternate-debug-info`` <*elf-path*>
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If the debug info for the file *elf-path* contains a reference to
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an `alternate debug info <alt-di-label>`_ file, ``abidw`` checks
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that it can find that alternate debug info file. In that case, it
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emits a meaningful success message mentioning the full path to the
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alternate debug info file found. Otherwise, it emits an error
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code.
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* ``--no-show-locs``
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Do not show information about where in the *second shared library*
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the respective type was changed.
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* ``--check-alternate-debug-info-base-name`` <*elf-path*>
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Like ``--check-alternate-debug-info``, but in the success message,
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only mention the base name of the debug info file; not its full path.
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* ``--load-all-types``
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By default, ``libabigail`` (and thus ``abidw``) only loads types
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that are reachable from functions and variables declarations that
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are publicly defined and exported by the binary. So only those
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types are present in the output of ``abidw``. This option however
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makes ``abidw`` load *all* the types defined in the binaries, even
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those that are not reachable from public declarations.
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* ``--abidiff``
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Load the ABI of the ELF binary given in argument, save it in
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libabigail's XML format in a temporary file; read the ABI from the
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temporary XML file and compare the ABI that has been read back
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against the ABI of the ELF binary given in argument. The ABIs
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should compare equal. If they don't, the program emits a
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diagnostic and exits with a non-zero code.
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This is a debugging and sanity check option.
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* ``--stats``
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Emit statistics about various internal things.
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* ``--verbose``
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Emit verbose logs about the progress of miscellaneous internal
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things.
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Notes
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=====
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.. _alt-di-label:
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Alternate debug info files
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--------------------------
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As of the version 4 of the DWARF specification, `Alternate debug
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information <http://www.dwarfstd.org/ShowIssue.php?issue=120604.1>`_
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is a `GNU`_ extension to the DWARF specification. It has however been
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proposed for inclusion into the upcoming version 5 of the DWARF
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standard. You can read more about the GNU extensions to the DWARF
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standard `here
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<https://fedorahosted.org/elfutils/wiki/DwarfExtensions>`_.
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.. _ELF: http://en.wikipedia.org/wiki/Executable_and_Linkable_Format
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.. _DWARF: http://www.dwarfstd.org
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.. _GNU: http://www.gnu.org
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