This commit fixes the following issues regarding cache maintainance
under ARM:
* read out I-, and D-cache line size at runtime and use the correct one
* remove 'update_data_region' call from unprivileged syscalls
* rename 'update_instr_region' syscall to 'cache_coherent_region' to
reflect what it doing, namely make I-, and D-cache coherent
* restrict 'cache_coherent_region' syscall to one page at a time
* lookup the region given in a 'cache_coherent_region' syscall in the
page-table of the PD to prevent machine exceptions in the kernel
* only clean D-cache lines, do not invalidate them when pages where
added on Cortex-A8 and ARMv6 (MMU sees phys. memory here)
* remove unused code relicts of cache maintainance
In addition it introduces per architecture memory clearance functions
used by core, when preparing new dataspaces. Thereby, it optimizes:
* on ARMv7 using per-word assignments
* on ARMv8 using cacheline zeroing
* on x86_64 using 'rept stosq' assembler instruction
Fix#3685
Since gcc 8.3.0 generates SSE instructions into kernel code, the
kernel itself may raise FPU exceptions and/or corrupt user level FPU
contexts thereby. Both things are not feasible, and therefore, lazy FPU
switching becomes a no go for base-hw because we cannot avoid FPU
instructions because of the entanglement of base-hw, base, and the tool
chain (libgcc_eh.a).
issue #3365
Instead of changing the attributes (e.g., Xd bit) of the top-level page-tables,
set them to allow everything. Only leafs of the paging hierarchy are set
according to the paging attributes given by core. Otherwise, top-level page-
table attributes are changed during lifetime, which requires a TLB flush
operation (not intended in the semantic of the kernel/core).
This led to problems when using the non-executable features introduced by
issue #1723 in the recent past.
Recent work related to issue 1723 showed that there is potential
to get rid of code duplication in MMU fault handling especially
with regard to ARM cpus.
* Instead of always re-load page-tables when a thread context is switched
only do this when another user PD's thread is the next target,
core-threads are always executed within the last PD's page-table set
* remove the concept of the mode transition
* instead map the exception vector once in bootstrap code into kernel's
memory segment
* when a new page directory is constructed for a user PD, copy over the
top-level kernel segment entries on RISCV and X86, on ARM we use a designated
page directory register for the kernel segment
* transfer the current CPU id from bootstrap to core/kernel in a register
to ease first stack address calculation
* align cpu context member of threads and vms, because of x86 constraints
regarding the stack-pointer loading
* introduce Align_at template for members with alignment constraints
* let the x86 hardware do part of the context saving in ISS, by passing
the thread context into the TSS before leaving to user-land
* use one exception vector for all ARM platforms including Arm_v6
Fix#2091
* introduce new syscall (core-only) to create privileged threads
* take the privilege level of the thread into account
when doing a context switch
* map kernel segment as accessable for privileged code only
Ref #2091
* introduces central memory map for core/kernel
* on 32-bit platforms the kernel/core starts at 0x80000000
* on 64-bit platforms the kernel/core starts at 0xffffffc000000000
* mark kernel/core mappings as global ones (tagged TLB)
* move the exception vector to begin of core's binary,
thereby bootstrap knows from where to map it appropriately
* do not map boot modules into core anymore
* constrain core's virtual heap memory area
* differentiate in between user's and core's main thread's UTCB,
which now resides inside the kernel segment
Ref #2091
Put the initialization of the cpu cores, setup of page-tables, enabling of
MMU and caches into a separate component that is only used to bootstrap
the kernel resp. core.
Ref #2092
