Stefan Kalkowski 4e97a6511b hw: switch page-tables only when necessary
* 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
2017-10-19 13:31:18 +02:00
..

This is generic part of the Genode implementation. It consists of two parts:

:_Core_: is the ultimate root of the Genode application tree
  and provides abstractions for the lowest-level hardware resources
  such as RAM, ROM, CPU, and generic device access. All generic parts of Core
  can be found here - for system-specific implementations refer to the
  appropriate 'base-<system>' directory.

:_Base libraries and protocols_: that are used by each Genode component
  to interact with other components. This is the glue that holds everything
  together.

_Core_ may export information about the hardware platform by an ROM
called 'platform_info'. Depending on the platform, e.g. ARM or x86 or riscv,
and depending on the boot mode and boot loader and kernel, some nodes may not
be populated.

!<platform_info>
! <acpi revision="2" rsdt="0x1fe93074" xsdt="0x1fe930e8"/>
! <boot>
!   <framebuffer phys="0x7300000" width="1024" height="768" bpp="32"/>
! </boot>
!</platform_info>

If the ACPI RSDT and XSDT physical pointer is reported by the used kernel
and/or bootloader, _Core_ may provide this information by the ROM.

If the graphic device is initialised and can be directly used by a framebuffer
driver, _Core_ may provide the physical pointer to the framebuffer, the
resolution and color depth in bits.