Let's adapt this class a bit better to how it's actually being used.
Instead of having valid/invalid states and storing an error in case
it's invalid, a MappedFile is now always valid, and the factory
function that creates it will return an OSError if mapping fails.
Make it possible to bail out of ELF::Image::for_each_program_header()
and then do exactly that if something goes wrong during executable
loading in the kernel.
Also make the errors we return slightly more nuanced than just ENOEXEC.
This commit gets rid of ELF::Loader entirely since its very ambiguous
purpose was actually to load executables for the kernel, and that is
now handled by the kernel itself.
This patch includes some drive-by cleanup in LibDebug and CrashDaemon
enabled by the fact that we no longer need to keep the ref-counted
ELF::Loader around.
The dynamic loader exists as /usr/lib/Loader.so and is loaded by the
kernel when ET_DYN programs are executed.
The dynamic loader is responsible for loading the dependencies of the
main program, allocating TLS storage, preparing all loaded objects for
execution and finally jumping to the entry of the main program.
If a buffer smaller than Elf32_Ehdr was passed to Image, header()
would do an out-of-bounds read.
Make parse() check for that. Make most Image methods assert that the image
is_valid(). For that to work, set m_valid early in Image::parse()
instead of only at its end.
Also reorder a few things so that the fuzzer doesn't hit (valid)
assertions, which were harmless from a security PoV but which still
allowed userspace to crash the kernel with an invalid ELF file.
Make dbgprintf()s configurable at run time so that the fuzzer doesn't
produce lots of logspam.
This function did a const_cast internally which made the call side look
"safe". This method is removed completely and call sites are replaced
with ByteBuffer::wrap(const_cast<void*>(data), size) which makes the
behaviour obvious.
This was supposed to be the foundation for some kind of pre-kernel
environment, but nobody is working on it right now, so let's move
everything back into the kernel and remove all the confusion.
These validate_elf_* methods really had no business being static
methods of ELF::Image. Now that the ELF namespace exists, it makes
sense to just move them to be free functions in the namespace.
