We have many places in the kernel code that we have boolean flags that
are only set once, and never reset again but are checked multiple times
before and after the time they're being set, which matches the purpose
of the SetOnce class.
This removes the allocate_tls syscall and adds an archctl option to set
the fs_base for the current thread on x86-64, since you can't set that
register from userspace. enter_thread_context loads the fs_base for the
next thread on each context switch.
This also moves tpidr_el0 (the thread pointer register on AArch64) to
the register state, so it gets properly saved/restored on context
switches.
The userspace TLS allocation code is kept pretty similar to the original
kernel TLS code, aside from a couple of style changes.
We also have to add a new argument "tls_pointer" to
SC_create_thread_params, as we otherwise can't prevent race conditions
between setting the thread pointer register and signal handling code
that might be triggered before the thread pointer was set, which could
use TLS.
These changes are compatible with clang-format 16 and will be mandatory
when we eventually bump clang-format version. So, since there are no
real downsides, let's commit them now.
About half of the Processor code is common across architectures, so
let's share it with a templated base class. Also, other code that can be
shared in some ways, like FPUState and TrapFrame functions, is adjusted
here. Functions which cannot be shared trivially (without internal
refactoring) are left alone for now.
This commit adds the concept of an InterruptsState to the kernel. This
will be used to make the Spinlock code architecture independent. A new
Processor.cpp file is added such that we don't have to duplicate the
code.
The platform independent Processor.h file includes the shared processor
code and includes the specific platform header file.
All references to the Arch/x86/Processor.h file have been replaced with
a reference to Arch/Processor.h.
