- there are no tasks running, we don't need TASK_PRIVILEGE priviledge anymore
- as there is no ring 1 anymore, there is no need for level0() to call sensitive
code from ring 1 in ring 0
- 286 related macros removed as clean up
- copies a mesage from/to userspace without need of translating
addresses
- the assumption is that the address space is installed, i.e. ldt and
cr3 are loaded correctly
- if a pagefault or a general protection occurs while copying from
userland to kernel (or vice versa) and error is returned which gives
the caller a chance to respond in a proper way
- error happens _only_ because of a wrong user pointer if the function
is used correctly
- if the prerequisites of the function do no hold, the function will
most likely fail as the user address becomes random
- switch_address_space() implements a switch of the user address space
for the destination process
- this makes memory of this process easily accessible, e.g. a pointer
valid in the userspace can be used with a little complexity to
access the process's memory
- the switch does not happed only just before we return to userspace,
however, it happens right after we know which process we are going
to schedule. This happens before we start processing the misc flags
of this process so its memory is available
- if the process becomes not runnable while processing the mics flags
we pick a new process and we switch the address space again which
introduces possibly a little bit more overhead, however, it is
hopefully hidden by reducing the overheads when we actually access
the memory
- gas2ack cannot handle all variants of some instructions. Until this issues is
addressed, this patch places a big warning where appropriate. This code is not
supposed to change frequently.
- local APIC timer used as the source of time
- PIC is still used as the hw interrupt controller as we don't have
enough info without ACPI or MPS to set up IO APICs
- remapping of APIC when switching paging on, uses the new mechanism
to tell VM what phys areas to map in kernel's virtual space
- one more step to SMP
based on code by Arun C.
- idle task becomes a pseudo task which is never scheduled. It is never put on
any run queue and never enters userspace. An entry for this task still remains
in the process table for time accounting
- Instead of panicing if there is not process to schedule, pick_proc() returns
NULL which is a signal to put the cpu in an idle state and set everything in
such a way that after receiving and interrupt it looks like idle task was
preempted
- idle task is set non-preemptible to avoid handling in the timer interrupt code
which make userspace scheduling simpler as idle task does not need to be
handled as a special case.
- after a trap to kernel, the code automatically switches to kernel
stack, in the future local to the CPU
- k_reenter variable replaced by a test whether the CS is kernel cs or
not. The information is passed further if needed. Removes a global
variable which would need to be cpu local
- no need for global variables describing the exception or trap
context. This information is kept on stack and a pointer to this
structure is passed to the C code as a single structure
- removed loadedcr3 variable and its use replaced by reading the %cr3
register
- no need to redisable interrupts in restart() as they are already
disabled.
- unified handling of traps that push and don't push errorcode
- removed save() function as the process context is not saved directly
to process table but saved as required by the trap code. Essentially
it means that save() code is inlined everywhere not only in the
exception handling routine
- returning from syscall is more arch independent - it sets the retger
in C
- top of the x86 stack contains the current CPU id and pointer to the
currently scheduled process (the one right interrupted) so the mode
switch code can find where to save the context without need to use
proc_ptr which will be cpu local in the future and therefore
difficult to access in assembler and expensive to access in general
- some more clean up of level0 code. No need to read-back the argument
passed in
%eax from the proc structure. The mode switch code does not clobber
%the general registers and hence we can just call what is in %eax
- many assebly macros in sconst.h as they will be reused by the apic
assembly
- the PIC master and slave irq handlers don't pass the irq hook pointer but just
the irq number. It gives a little bit more information to the C handler as the
irq number is not lost
- the irq code path is more achitecture independent. i386 hw interrupts are
called irq and whereever the code is arch independent enough hw_intr_
functions are called to mask/unmask interrupts
- the legacy PIC is not the only possible interrupt controller in the x86 world,
therefore the intr_(un)mask functions were renamed to signal their
functionality explicitly. APIC will add their own.
- masking and unmasking PIC interrupt lines is removed from assembler and all
the functionality is rewriten in C and moved to i8259.c
- interrupt handlers have to unmask the interrupt line if all irq handlers are
done. Assembler does not do it anymore
