Since SYSCALL/SYSRET rely on MSRs to control their function, split out
syscall_enable() into syscall_initialize() and syscall_enable(), the
latter being called on all CPUs. This affects not just syscalls but also
the kernel_to_user_trampoline.
Additionally, do away with the max syscalls, and just make a single page
of syscall pointers and name pointers. Max syscalls was fragile and
needed to be kept in sync in multiple places.
In preparation for moving things to the init process, move process
loading out of the scheduler. memory_bootstrap now has a
load_simple_process function for mapping an args::program into memory,
and the stack setup has been simplified (though all the initv values are
still being added by the kernel - this needs rework) and normalized to
use the thread::add_thunk_user code path.
The rcx register is used by the function call ABI for the 4th argument,
but is also clobbered by SYSCALL to hold the IP. The r10 register is
caller-saved but not part of the ABI, so stash rcx there when crossing
the syscall boundary.
The vm_space allow() functionality was a bit janky; using VMAs for all
regions would be a lot cleaner. To that end, this change:
- Adds a "static array" ctor to kutil::vector for setting the kernel
address space's VMA list. This way a kernel heap VMA can be created
without the heap already existing.
- Splits vm_area into different subclasses depending on desired behavior
- Splits out the concept of vm_mapper which maps vm_areas to vm_spaces,
so that some kinds of VMA can be inherently single-space
- Implements VMA resizing so that userspace can grow allocations.
- Obsolete page_table_indices is removed
Also, the following bugs were fixed:
- kutil::map iterators on empty maps no longer break
- memory::page_count was doing page-align, not page-count
See: Github bug #242
See: [frobozz blog post](https://jsix.dev/posts/frobozz/)
Tags:
There are a lot of under the hood changes here:
- Move syscalls to be a dispatch table, defined by syscalls.inc
- Don't need a full process state (push_all) in syscalls now
- In push_all, define REGS instead of using offsets
- Save TWO stack pointers as well as current saved stack pointer in TCB:
- rsp0 is the base of the kernel stack for interrupts
- rsp3 is the saved user stack from cpu_data
- Update syscall numbers in nulldrv
- Some asm-debugging enhancements to the gdb script
- fork() still not working
