nova: Makefile: Use `$(MAKE)` instead of `make`

See merge request !35

This allows CLion to correctly parse `make` output and configure
its intellisense, and it's also the recommended way to recursively
invoke `make`.

Viz #260.

Děkuji Petru Pučilovi za upozornění.

Closes #218, #219, #220, #221, #222, #223.

Combining compiler options -fstack-protector and -nostdlib results in
a program which always segfaults. Because some Linux distributions
enable stack protector by default, we should explicitly disable it.

Closes #252

Matěj Kafka authored 3 years ago and Michal Sojka committed 2 years ago

Original masks split the address to 12+20 bits, but we actually want 10+22.

`Ptab::remap` should map a single 4MB page. On x86, that's a 10 bit page directory
index, and 22 bit offset inside the page. The current NOVA code splits the address
as a 12 bit index + 20 bit offset, which is not correct, and afaict only works because
the mapped addresses all have zeros in the 2 bits that are incorrectly split.

Upstream, the whole file is changed significantly, and the method Hptp::map, which
seems to be used for the same temporary mappings as Ptab::remap, uses 4kB pages:
https://github.com/udosteinberg/NOVA/blob/arm/src/x86_64/ptab_hpt.cpp#L58

Matěj Kafka authored 3 years ago and Michal Sojka committed 2 years ago

[Updated by M. Sojka]

This constructor was initially meant to be implemented by students in
task 12, but it's probably simpler to let them implement everything in
Ec::syscall_handler().

Closes #167

Matěj Kafka authored 3 years ago and Michal Sojka committed 2 years ago

In the full NOVA hypervisor, Ec::cont was used to implement
continuation-style switching of execution contexts. For our simplified
version, it is not needed, but it must be understood to correctly use
Ec::make_current(), which many students consider confusing. Therefore,
we remove Ec::cont and make Ec::make_current() to always jump to
Ec::ret_user_sysexit().

As a consequence of Ec::cont removal, this commit also reworks root
task initialization and invocation. This also makes the program flow
during boot easier to understand.

[Code and commit message modified by M. Sojka]

Fixes #217

Zdá se, že definice URL musí být ve stejném "tabu".

Closes #224.