We now map most shared library text segments shared, read+exec only.
This reduces our memory footprint at system startup by 16 MB which is
pretty neat! :^)
Problem:
- C functions with no arguments require a single `void` in the argument list.
Solution:
- Put the `void` in the argument list of functions in C header files.
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.
We now configure the gcc spec files to use a different crt files for
static & PIE binaries.
This relieves us from the need to explicitly specify the desired crt0
file in cmake scripts.
Problem:
- `(void)` simply casts the expression to void. This is understood to
indicate that it is ignored, but this is really a compiler trick to
get the compiler to not generate a warning.
Solution:
- Use the `[[maybe_unused]]` attribute to indicate the value is unused.
Note:
- Functions taking a `(void)` argument list have also been changed to
`()` because this is not needed and shows up in the same grep
command.
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.
This should catch more malformed ELF files earlier than simply
checking the ELF header alone. Also change the API of
validate_program_headers to take the interpreter_path by pointer. This
makes it less awkward to call when we don't care about the interpreter,
and just want the validation.
ELF::DynamicLoader now validates the ELF header and the program headers
in its constructor. The requested program interpreter from the
PT_INTERP program header is now avaiable via a getter. The dynamic
loader program will want to check that this matches its name, for extra
shenanigans checking.
