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27 commits

Author SHA1 Message Date
Ben Gras
50e2064049 No more intel/minix segments.
This commit removes all traces of Minix segments (the text/data/stack
memory map abstraction in the kernel) and significance of Intel segments
(hardware segments like CS, DS that add offsets to all addressing before
page table translation). This ultimately simplifies the memory layout
and addressing and makes the same layout possible on non-Intel
architectures.

There are only two types of addresses in the world now: virtual
and physical; even the kernel and processes have the same virtual
address space. Kernel and user processes can be distinguished at a
glance as processes won't use 0xF0000000 and above.

No static pre-allocated memory sizes exist any more.

Changes to booting:
        . The pre_init.c leaves the kernel and modules exactly as
          they were left by the bootloader in physical memory
        . The kernel starts running using physical addressing,
          loaded at a fixed location given in its linker script by the
          bootloader.  All code and data in this phase are linked to
          this fixed low location.
        . It makes a bootstrap pagetable to map itself to a
          fixed high location (also in linker script) and jumps to
          the high address. All code and data then use this high addressing.
        . All code/data symbols linked at the low addresses is prefixed by
          an objcopy step with __k_unpaged_*, so that that code cannot
          reference highly-linked symbols (which aren't valid yet) or vice
          versa (symbols that aren't valid any more).
        . The two addressing modes are separated in the linker script by
          collecting the unpaged_*.o objects and linking them with low
          addresses, and linking the rest high. Some objects are linked
          twice, once low and once high.
        . The bootstrap phase passes a lot of information (e.g. free memory
          list, physical location of the modules, etc.) using the kinfo
          struct.
        . After this bootstrap the low-linked part is freed.
        . The kernel maps in VM into the bootstrap page table so that VM can
          begin executing. Its first job is to make page tables for all other
          boot processes. So VM runs before RS, and RS gets a fully dynamic,
          VM-managed address space. VM gets its privilege info from RS as usual
          but that happens after RS starts running.
        . Both the kernel loading VM and VM organizing boot processes happen
	  using the libexec logic. This removes the last reason for VM to
	  still know much about exec() and vm/exec.c is gone.

Further Implementation:
        . All segments are based at 0 and have a 4 GB limit.
        . The kernel is mapped in at the top of the virtual address
          space so as not to constrain the user processes.
        . Processes do not use segments from the LDT at all; there are
          no segments in the LDT any more, so no LLDT is needed.
        . The Minix segments T/D/S are gone and so none of the
          user-space or in-kernel copy functions use them. The copy
          functions use a process endpoint of NONE to realize it's
          a physical address, virtual otherwise.
        . The umap call only makes sense to translate a virtual address
          to a physical address now.
        . Segments-related calls like newmap and alloc_segments are gone.
        . All segments-related translation in VM is gone (vir2map etc).
        . Initialization in VM is simpler as no moving around is necessary.
        . VM and all other boot processes can be linked wherever they wish
          and will be mapped in at the right location by the kernel and VM
          respectively.

Other changes:
        . The multiboot code is less special: it does not use mb_print
          for its diagnostics any more but uses printf() as normal, saving
          the output into the diagnostics buffer, only printing to the
          screen using the direct print functions if a panic() occurs.
        . The multiboot code uses the flexible 'free memory map list'
          style to receive the list of free memory if available.
        . The kernel determines the memory layout of the processes to
          a degree: it tells VM where the kernel starts and ends and
          where the kernel wants the top of the process to be. VM then
          uses this entire range, i.e. the stack is right at the top,
          and mmap()ped bits of memory are placed below that downwards,
          and the break grows upwards.

Other Consequences:
        . Every process gets its own page table as address spaces
          can't be separated any more by segments.
        . As all segments are 0-based, there is no distinction between
          virtual and linear addresses, nor between userspace and
          kernel addresses.
        . Less work is done when context switching, leading to a net
          performance increase. (8% faster on my machine for 'make servers'.)
	. The layout and configuration of the GDT makes sysenter and syscall
	  possible.
2012-07-15 22:30:15 +02:00
Ben Gras
769af57274 further libexec generalization
. new mode for sys_memset: include process so memset can be
	  done in physical or virtual address space.
	. add a mode to mmap() that lets a process allocate uninitialized
	  memory.
	. this allows an exec()er (RS, VFS, etc.) to request uninitialized
	  memory from VM and selectively clear the ranges that don't come
	  from a file, leaving no uninitialized memory left for the process
	  to see.
	. use callbacks for clearing the process, clearing memory in the
	  process, and copying into the process; so that the libexec code
	  can be used from rs, vfs, and in the future, kernel (to load vm)
	  and vm (to load boot-time processes)
2012-06-07 15:15:02 +02:00
Ben Gras
1daf36038c kernel: compact utility functions 2012-06-07 11:25:32 +02:00
Ben Gras
b41df2eb0d kernel: mon_return cleanup
cleanup of boot monitor related code.
2012-04-25 17:59:43 +02:00
Arun Thomas
b0666ba6b6 kernel: Remove unnecessary ACK conditionals 2012-03-29 13:29:09 +02:00
David van Moolenbroek
0a8a2ecfb5 Kernel: pass FPU restore exception to user process
Previously, user processes could cause a kernel panic upon FPU state
restore, by passing bogus FPU state to the kernel (through e.g.
sigreturn). With this patch, the process is now sent a SIGFPE signal
instead.
2012-03-05 22:32:14 +01:00
Ben Gras
ca47635d0a try multiple reset methods
. fixes reboot-hang under vbox
	. makes experience nicer under vmware
	. taken from netbsd reset code
2012-02-20 23:46:38 +01:00
Ben Gras
35cc7fbeb8 kernel: invlpg facility
. only use for single-page invalidations initially
	. shows tiny but statistically significant performance
	  improvement; will be more helpful in certain VM debug
	  modes
2011-08-12 13:08:27 +00:00
Arun Thomas
93ae43f577 boot: Add multiboot support
Not yet fully spec-compliant; work in progress
2011-06-24 17:21:51 +02:00
Tomas Hruby
9e01a83636 SMP - reduced TLB flushing
- flush TLB of processes only if the page tables has been changed and
  the page tables of this process are already loaded on this cpu which
  means that there might be stale entries in TLB. Until now SMP was
  always flushing TLB to make sure everything is consistent.
2010-10-25 16:21:23 +00:00
Tomas Hruby
8145b458d6 A klib.S include fix
- by Antoine Leca
2010-10-15 22:21:01 +00:00
Tomas Hruby
ef92583c3a Busy idle loop when profiling
- the Intel architecture cycle counter (performance counter) does not
  count when the CPU is idle therefore we use busy loop instead of
  halting the cpu when there is nothing to schedule

- the downside is that handling interrupts may be accounted as idle
  time if a sample is taken before we get out of the nested trap and
  pick a new process
2010-09-23 10:49:52 +00:00
Tomas Hruby
2d1c8849d8 Remove unnecessary TLB flushes
- this should be only for SMP
2010-09-22 08:01:36 +00:00
Tomas Hruby
e4283176ae SMP - Force TLB flush before scheduling a process
- this makes sure that each process always run with updated TLB

- this is the simplest way how to achieve the consistency. As it means
  significant performace degradation when not require, this is nto the
  final solution and will be refined
2010-09-15 14:11:17 +00:00
Tomas Hruby
e87d29171f SMP - Compiles for both single and multi processor again
- this patch adds various fixes as some of the previous patches break
  compilations without CONFIG_SMP being set
2010-09-15 14:11:03 +00:00
Tomas Hruby
9b6d66c787 SMP - BSP waits until the APs finish their booting
- APs configure local timers

- while configuring local APIC timer the CPUs fiddle with the interrupt
  handlers. As the interrupt table is shared the BSP must not run
2010-09-15 14:10:12 +00:00
Tomas Hruby
6aa26565e6 SMP - Big kernel lock (BKL)
- to isolate execution inside kernel we use a big kernel lock
  implemented as a spinlock

- the lock is acquired asap after entering kernel mode and released as
  late as possible. Only one CPU as a time can execute the core kernel
  code

- measurement son real hw show that the overhead of this lock is close
  to 0% of kernel time for the currnet system

- the overhead of this lock may be as high as 45% of kernel time in
  virtual machines depending on the ratio between physical CPUs
  available and emulated CPUs. The performance degradation is
  significant
2010-09-15 14:10:03 +00:00
Tomas Hruby
62c666566e SMP - We boot APs
- kernel detects CPUs by searching ACPI tables for local apic nodes

- each CPU has its own TSS that points to its own stack. All cpus boot
  on the same boot stack (in sequence) but switch to its private stack
  as soon as they can.

- final booting code in main() placed in bsp_finish_booting() which is
  executed only after the BSP switches to its final stack

- apic functions to send startup interrupts

- assembler functions to handle CPU features not needed for single cpu
  mode like memory barries, HT detection etc.

- new files kernel/smp.[ch], kernel/arch/i386/arch_smp.c and
  kernel/arch/i386/include/arch_smp.h

- 16-bit trampoline code for the APs. It is executed by each AP after
  receiving startup IPIs it brings up the CPUs to 32bit mode and let
  them spin in an infinite loop so they don't do any damage.

- implementation of kernel spinlock

- CONFIG_SMP and CONFIG_MAX_CPUS set by the build system
2010-09-15 14:09:52 +00:00
Tomas Hruby
13a0d5fa5e SMP - Cpu local variables
- most global variables carry information which is specific to the
  local CPU and each CPU must have its own copy

- cpu local variable must be declared in cpulocal.h between
  DECLARE_CPULOCAL_START and DECLARE_CPULOCAL_END markers using
  DECLARE_CPULOCAL macro

- to access the cpu local data the provided macros must be used

	get_cpu_var(cpu, name)
	get_cpu_var_ptr(cpu, name)

	get_cpulocal_var(name)
	get_cpulocal_var_ptr(name)

- using this macros makes future changes in the implementation
  possible

- switching to ELF will make the declaration of cpu local data much
  simpler, e.g.

  CPULOCAL int blah;

  anywhere in the kernel source code
2010-09-15 14:09:46 +00:00
Tomas Hruby
e6ebac015d APIC mode uses IO APICs
- kernel turns on IO APICs if no_apic is _not_ set or is equal 0

- pci driver must use the acpi driver to setup IRQ routing otherwise
  the system cannot work correctly except systems like KVM that use
  only legacy (E)ISA IRQs 0-15
2010-09-07 07:18:11 +00:00
Arun Thomas
9a21d1a2fd Macros for symbols used in both ASM and C
-The macros take care of prepending the leading underscore when
 necessary.
2010-08-17 16:44:07 +00:00
Erik van der Kouwe
df0ba02a38 Multiboot support (contributed by Feiran "Fam" Zheng);
keep in mind that GRUB needs to be patched to read MFS for now;
use /boot/image_latest to boot the last compiled image in GRUB
2010-07-23 14:24:34 +00:00
Ben Gras
a09a8d4f3e kernel: fix for vm_init that triggered assert(ptproc == newptproc)
- zero cr3 in vm_init() to avoid switch_address_space() not doing anything.

 - add vm_stop() to disable paging on shutdown.
2010-06-07 22:21:45 +00:00
Ben Gras
2f892aca91 kernel fpu context switching: fix race condition
There seems to have been a broken assumption in the fpu context
restoring code.  It restores the context of the running process, without
guarantee that the current process is the one that will be scheduled.
This caused fpu saving for a different process to be triggered without
fpu hardware being enabled, causing an fpu exception in the kernel. This
practically only shows up with DEBUG_RACE on. Fix my thruby+me.

The fix
 . is to only set the fpu-in-use-by-this-process flag in the
   exception handler, and then take care of fpu restoring when
   actually returning to userspace

And the patch
 . translates fpu saving and restoring to c in arch_system.c,
   getting rid of a juicy chunk of assembly
 . makes osfxsr_feature private to arch_system.c
 . removes most of the arch dependent code from do_sigsend
2010-06-03 11:32:22 +00:00
Arun Thomas
007104d60e GCC build fixes/updates
-Set stack sizes for boot image processes
-Increase RS stack size
-Reduce ramdisk size
-HARDWARE task should use kernel stack
-Minor asm tweaks for leading underscores
2010-05-26 18:45:55 +00:00
Arun Thomas
b0159ad168 Buildsystem changes for GCC
-Makefile updates
-Update mkdep
-Build fixes/warning cleanups for some programs
-Restore leading underscores on global syms in kernel asm files
-Increase ramdisk size
2010-05-19 13:24:15 +00:00
Arun Thomas
4ed3a0cf3a Convert kernel over to bsdmake 2010-04-01 22:22:33 +00:00
Renamed from kernel/arch/i386/klib386.S (Browse further)