algorith -> algorithm
occured -> occurred

Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

dwelf_elf_begin was slightly different from elf_begin in case the file
turned out to not be an ELF file. elf_begin would return an Elf handle
with ELF_K_NONE. But dwelf_elf_begin would return NULL. This made it
impossible to tell the difference between a file or decompression error
and a (decompressed) file not being an ELF file.

Since dwelf_elf_begin could still return different kinds of ELF files
(ELF_K_ELF or ELF_K_AR - and theoretically ELF_K_COFF) this was not
really useful anyway. So make it so that dwelf_elf_begin always returns
an Elf handle unless there was a real error reading or decompressing
the file. Otherwise return NULL to make clear there was a real error.

Make sure that the decompression function returns DWFL_E_BADELF only
when the file isn't compressed. In which case the Elf handle won't
be replaced and can be returned (as ELF_K_NONE).

Add a new version to dwelf_elf_begin so programs can rely on it
returning NULL only for real errors.

Signed-off-by: Mark Wielaard <mark@klomp.org>

To print eh human readable description of the ELF e_machine header field
we used the ebl name. But this is not set for most EM constants. Introduce
a new function dwelf_elf_e_machine_string that does work for all known
EM values. Use that in eu-readelf to print a string representation of the
e_machine value.

Since this was the only usage of ebl->name, remove that from struct ebl.

Also add a testcase that makes sure dwelf_elf_e_machine_string works for
all EM values in the libelf/elf.h header so we will immediately notice
when a new value appears.

Signed-off-by: Mark Wielaard <mark@klomp.org>

This introduces a new function dwelf_elf_begin which creates a (read-only)
ELF handle from a possibly compressed file handle or a file that start
with a linux kernel header. This can be used in eu-readelf to (re)open a
(pure) ELF.

eu-readelf uses libdwfl to relocate addresses in the original file in
case it is ET_REL. But to show the "raw" data it might need to (re)open
the file. Which could fail if the file was compressed. And produced an
obscure error message: "cannot create EBL handle".

This rewrites __libdw_open_file a little so that the given file handle
will never be closed (whether on success or failure) and introduces a
new internal function __libdw_open_elf that dwelf_elf_begin wraps.

Signed-off-by: Mark Wielaard <mark@klomp.org>

Move the strtab functions from libebl to libdw. Programs often want to
create ELF/DWARF string tables. We don't want (static) linking against
ebl since those are internal functions that might change.

This introduces dwelf_strtab_init, dwelf_strtab_add,
dwelf_strtab_add_len, dwelf_strtab_finalize, dwelf_strent_off,
dwelf_strent_str and dwelf_strtab_free. Documentation for each has
been added to libdwelf.h. The add fucntion got a variant that takes
the length explicitly and finalize was changed to return NULL on
out of memory instead of aborting. All code and tests now uses the
new functions.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

Helper function to get the size of a GNU compressed zdebug section.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

Move internal function __libdwfl_find_build_id to libdwelf and use it to
add a public dwelf_elf_gnu_build_id function to extract the NT_GNU_BUILD_ID
from an ELF file using either the shdrs or phdrs. Adjust internal callers
and add a testcase.

Signed-off-by: Mark Wielaard <mjw@redhat.com>

Signed-off-by: Florian Weimer <fweimer@redhat.com>

New public header elfutils/libdwelf.h for low-level DWARF/ELF helper
functions.  The new function dwelf_elf_gnu_debuglink returns the name and
crc as found in the .gnu_debuglink section of an ELF file.

Signed-off-by: Mark Wielaard <mjw@redhat.com>