There were some recent bug reports where we trusted the ELF section header
to be sane and divided the sh_size by the sh_entsize to get the number of
objects in the section. This would cause a divide by zero if the file was
corrupt and the sh_entsize was zero. Add checks for any such code.

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

error.h isn't standard and so isn't part of the musl C library.
To easy future porting, consolidate the inclusion of error.h into system.h.

https://sourceware.org/bugzilla/show_bug.cgi?id=21008

Signed-off-by: Ross Burton <ross.burton@intel.com>

Those flags are not available on all platforms, and omitting them when
not available will not cause any harm. In particular:

-z,defs disallows undefined symbols in object files. This option is
unsupported if the target binary format enforces the same condition
already. Furthermore it is only a compile time sanity check. When it is
omitted, the same binary is produced.

-z,relro instructs the loader to mark sections read-only after loading
the library, where possible. This is a hardening mechanism. If it is
unavailable, the functionality of the code is not affected in any way.

-fPIC instructs the compiler to produce position independent code. While
this is preferable to relocatable code, relocatable code also works and
may even be faster. Relocatable code might just be loaded into memory
multiple times for different processes.

-fPIE is the same thing as -fPIC for executables rather than shared
libraries.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>

Link them all with -z,defs,-z,relro,--no-undefined, provide complete
dependencies for the link steps, and add libeu.a to each one. libeu.a
contains useful library functionality that each of them might use. The
linker will strip unneeded symbols, so linking it in won't hurt even if
none of the functions are used.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>

The way it was before it didn't actually test if elf_update failed, but
rather did something random. !!(<some number>) is a boolean and boolean
true can be represented as anything non-0, including negative numbers.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>

Make sure that if we have really lots of labels the tempsym doesn't get
truncated because it is too small to hold the whole name.

This doesn't enable -Wformat-truncation=2 or fix other "issues" pointed
out by enabling this warning because there are currently some issues
with it. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79448

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

If it doesn't exist, provide a definition based on memcpy.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>

This change also creates a new header file libeu.h to provide the
prototypes for the function of libeu. That hides the definition of function
crc32, which can conflict with zlib, from libelf. It also prevents mistakes
to refer those functions from a component which doesn't link with libeu,
such as libelf.

Signed-off-by: Akihiko Odaki <akihiko.odaki.4i@stu.hosei.ac.jp>

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>

Signed-off-by: Richard Henderson <rth@redhat.com>