We explicitly test (with system-elf-libelf) that our include headers
work with the system elf.h header. But it might be helpful to install
the elf.h file for a private install. Our elf.h header really is just
a copy of the latest glibc elf.h. But it might be newer and include
more constants than the system installed elf.h.

Add a new configure option --enable-install-elfh to install elf.h.
But warn when it is enabled for the default /usr or /usr/local prefix
because it might clash with the glibc/system elf.h header in that case.

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

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>

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

Elf_Data of a compressed section has type ELF_T_CHDR. This type can be
xlated to the file or memory representation. This will make sure the Chdr
is in the correct endianess. The compressed data following the Chdr isn't
translated.

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

Explicitly link libelf and libdw with -lz.

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

Note, elfutils does not explicitly enable AM_SILENT_RULES.  It's only
available starting from automake 1.11, but starting from automake 1.13
silent rules are always generated, defaulting to verbose.  $(AM_V_foo)
additions should be no-ops on systems that don't support silent rules.

To be silent, use "./configure --enable-silent-rules" or "make V=0".

Signed-off-by: Josh Stone <jistone@redhat.com>

This avoids relocation overflows in sparc/sparc64 targets while
linking,  where the reachable data using -fpic is only 4kb.

Signed-off-by: Jose E. Marchesi <jose.marchesi@oracle.com>

The commands to check for invalid text relocations in the generated DSOs
shouldn't be displayed.  They contain an echo which prints the text.
This patch suppresses the commands from being printed.

Using american fuzzy lop has found a lot of issues. It would be nice to
make using it a bit easier. Our build files make sure that no shared
library uses text relocations, but afl-gcc will insert some on i686.
http://www.akkadia.org/drepper/textrelocs.html

Now CC=afl-gcc ./configure --disable-textrelcheck will allow them so
that afl can instrument the libraries.

Don't try to use or install them except with afl-fuzz. When selinux is
enabled it might prevent loading the libraries with DT_TEXTREL set.

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