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minix/kernel/system.h
Ben Gras cd8b915ed9 Primary goal for these changes is: 
- no longer have kernel have its own page table that is loaded
    on every kernel entry (trap, interrupt, exception). the primary
    purpose is to reduce the number of required reloads.
Result:
  - kernel can only access memory of process that was running when
    kernel was entered
  - kernel must be mapped into every process page table, so traps to
    kernel keep working
Problem:
  - kernel must often access memory of arbitrary processes (e.g. send
    arbitrary processes messages); this can't happen directly any more;
    usually because that process' page table isn't loaded at all, sometimes
    because that memory isn't mapped in at all, sometimes because it isn't
    mapped in read-write.
So:
  - kernel must be able to map in memory of any process, in its own
    address space.
Implementation:
  - VM and kernel share a range of memory in which addresses of
    all page tables of all processes are available. This has two purposes:
      . Kernel has to know what data to copy in order to map in a range
      . Kernel has to know where to write the data in order to map it in
    That last point is because kernel has to write in the currently loaded
    page table.
  - Processes and kernel are separated through segments; kernel segments
    haven't changed.
  - The kernel keeps the process whose page table is currently loaded
    in 'ptproc.'
  - If it wants to map in a range of memory, it writes the value of the
    page directory entry for that range into the page directory entry
    in the currently loaded map. There is a slot reserved for such
    purposes. The kernel can then access this memory directly.
  - In order to do this, its segment has been increased (and the
    segments of processes start where it ends).
  - In the pagefault handler, detect if the kernel is doing
    'trappable' memory access (i.e. a pagefault isn't a fatal
     error) and if so,
       - set the saved instruction pointer to phys_copy_fault,
	 breaking out of phys_copy
       - set the saved eax register to the address of the page
	 fault, both for sanity checking and for checking in
	 which of the two ranges that phys_copy was called
	 with the fault occured
  - Some boot-time processes do not have their own page table,
    and are mapped in with the kernel, and separated with
    segments. The kernel detects this using HASPT. If such a
    process has to be scheduled, any page table will work and
    no page table switch is done.

Major changes in kernel are
  - When accessing user processes memory, kernel no longer
    explicitly checks before it does so if that memory is OK.
    It simply makes the mapping (if necessary), tries to do the
    operation, and traps the pagefault if that memory isn't present;
    if that happens, the copy function returns EFAULT.
    So all of the CHECKRANGE_OR_SUSPEND macros are gone.
  - Kernel no longer has to copy/read and parse page tables.
  - A message copying optimisation: when messages are copied, and
    the recipient isn't mapped in, they are copied into a buffer
    in the kernel. This is done in QueueMess. The next time
    the recipient is scheduled, this message is copied into
    its memory. This happens in schedcheck().
    This eliminates the mapping/copying step for messages, and makes
    it easier to deliver messages. This eliminates soft_notify.
  - Kernel no longer creates a page table at all, so the vm_setbuf
    and pagetable writing in memory.c is gone.

Minor changes in kernel are
  - ipc_stats thrown out, wasn't used
  - misc flags all renamed to MF_*
  - NOREC_* macros to enter and leave functions that should not
    be called recursively; just sanity checks really
  - code to fully decode segment selectors and descriptors
    to print on exceptions
  - lots of vmassert()s added, only executed if DEBUG_VMASSERT is 1
2009-09-21 14:31:52 +00:00

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/* Function prototypes for the system library. The prototypes in this file
* are undefined to do_unused if the kernel call is not enabled in config.h.
* The implementation is contained in src/kernel/system/.
*
* The system library allows to access system services by doing a kernel call.
* System calls are transformed into request messages to the SYS task that is
* responsible for handling the call. By convention, sys_call() is transformed
* into a message with type SYS_CALL that is handled in a function do_call().
*
* Changes:
* Jul 30, 2005 created SYS_INT86 to support BIOS driver (Philip Homburg)
* Jul 13, 2005 created SYS_PRIVCTL to manage services (Jorrit N. Herder)
* Jul 09, 2005 updated SYS_KILL to signal services (Jorrit N. Herder)
* Jun 21, 2005 created SYS_NICE for nice(2) kernel call (Ben J. Gras)
* Jun 21, 2005 created SYS_MEMSET to speed up exec(2) (Ben J. Gras)
* Apr 12, 2005 updated SYS_VCOPY for virtual_copy() (Jorrit N. Herder)
* Jan 20, 2005 updated SYS_COPY for virtual_copy() (Jorrit N. Herder)
* Oct 24, 2004 created SYS_GETKSIG to support PM (Jorrit N. Herder)
* Oct 10, 2004 created handler for unused calls (Jorrit N. Herder)
* Sep 09, 2004 updated SYS_EXIT to let services exit (Jorrit N. Herder)
* Aug 25, 2004 rewrote SYS_SETALARM to clean up code (Jorrit N. Herder)
* Jul 13, 2004 created SYS_SEGCTL to support drivers (Jorrit N. Herder)
* May 24, 2004 created SYS_SDEVIO to support drivers (Jorrit N. Herder)
* May 24, 2004 created SYS_GETINFO to retrieve info (Jorrit N. Herder)
* Apr 18, 2004 created SYS_VDEVIO to support drivers (Jorrit N. Herder)
* Feb 24, 2004 created SYS_IRQCTL to support drivers (Jorrit N. Herder)
* Feb 02, 2004 created SYS_DEVIO to support drivers (Jorrit N. Herder)
*/
#ifndef SYSTEM_H
#define SYSTEM_H
/* Common includes for the system library. */
#include "debug.h"
#include "kernel.h"
#include "proto.h"
#include "proc.h"
/* Default handler for unused kernel calls. */
_PROTOTYPE( int do_unused, (message *m_ptr) );
_PROTOTYPE( int do_exec, (message *m_ptr) );
#if ! USE_EXEC
#define do_exec do_unused
#endif
_PROTOTYPE( int do_fork, (message *m_ptr) );
#if ! USE_FORK
#define do_fork do_unused
#endif
_PROTOTYPE( int do_newmap, (message *m_ptr) );
#if ! USE_NEWMAP
#define do_newmap do_unused
#endif
_PROTOTYPE( int do_exit, (message *m_ptr) );
#if ! USE_EXIT
#define do_exit do_unused
#endif
_PROTOTYPE( int do_trace, (message *m_ptr) );
#if ! USE_TRACE
#define do_trace do_unused
#endif
_PROTOTYPE( int do_nice, (message *m_ptr) );
#if ! USE_NICE
#define do_nice do_unused
#endif
_PROTOTYPE( int do_copy, (message *m_ptr) );
#define do_vircopy do_copy
#if ! (USE_VIRCOPY || USE_PHYSCOPY)
#define do_copy do_unused
#endif
_PROTOTYPE( int do_vcopy, (message *m_ptr) );
#define do_virvcopy do_vcopy
#if ! (USE_VIRVCOPY || USE_PHYSVCOPY)
#define do_vcopy do_unused
#endif
_PROTOTYPE( int do_umap, (message *m_ptr) );
#if ! USE_UMAP
#define do_umap do_unused
#endif
_PROTOTYPE( int do_memset, (message *m_ptr) );
#if ! USE_MEMSET
#define do_memset do_unused
#endif
_PROTOTYPE( int do_abort, (message *m_ptr) );
#if ! USE_ABORT
#define do_abort do_unused
#endif
_PROTOTYPE( int do_getinfo, (message *m_ptr) );
#if ! USE_GETINFO
#define do_getinfo do_unused
#endif
_PROTOTYPE( int do_privctl, (message *m_ptr) );
#if ! USE_PRIVCTL
#define do_privctl do_unused
#endif
_PROTOTYPE( int do_segctl, (message *m_ptr) );
#if ! USE_SEGCTL
#define do_segctl do_unused
#endif
_PROTOTYPE( int do_irqctl, (message *m_ptr) );
#if ! USE_IRQCTL
#define do_irqctl do_unused
#endif
_PROTOTYPE( int do_devio, (message *m_ptr) );
#if ! USE_DEVIO
#define do_devio do_unused
#endif
_PROTOTYPE( int do_vdevio, (message *m_ptr) );
#if ! USE_VDEVIO
#define do_vdevio do_unused
#endif
_PROTOTYPE( int do_int86, (message *m_ptr) );
_PROTOTYPE( int do_sdevio, (message *m_ptr) );
#if ! USE_SDEVIO
#define do_sdevio do_unused
#endif
_PROTOTYPE( int do_kill, (message *m_ptr) );
#if ! USE_KILL
#define do_kill do_unused
#endif
_PROTOTYPE( int do_getksig, (message *m_ptr) );
#if ! USE_GETKSIG
#define do_getksig do_unused
#endif
_PROTOTYPE( int do_endksig, (message *m_ptr) );
#if ! USE_ENDKSIG
#define do_endksig do_unused
#endif
_PROTOTYPE( int do_sigsend, (message *m_ptr) );
#if ! USE_SIGSEND
#define do_sigsend do_unused
#endif
_PROTOTYPE( int do_sigreturn, (message *m_ptr) );
#if ! USE_SIGRETURN
#define do_sigreturn do_unused
#endif
_PROTOTYPE( int do_times, (message *m_ptr) );
#if ! USE_TIMES
#define do_times do_unused
#endif
_PROTOTYPE( int do_setalarm, (message *m_ptr) );
#if ! USE_SETALARM
#define do_setalarm do_unused
#endif
_PROTOTYPE( int do_stime, (message *m_ptr) );
_PROTOTYPE( int do_vtimer, (message *m_ptr) );
#if ! USE_VTIMER
#define do_vtimer do_unused
#endif
_PROTOTYPE( int do_safecopy, (message *m_ptr) );
_PROTOTYPE( int do_vsafecopy, (message *m_ptr) );
_PROTOTYPE( int do_iopenable, (message *m_ptr) );
_PROTOTYPE( int do_vmctl, (message *m_ptr) );
_PROTOTYPE( int do_setgrant, (message *m_ptr) );
_PROTOTYPE( int do_readbios, (message *m_ptr) );
_PROTOTYPE( int do_mapdma, (message *m_ptr) );
_PROTOTYPE( int do_sprofile, (message *m_ptr) );
#if ! SPROFILE
#define do_sprofile do_unused
#endif
_PROTOTYPE( int do_cprofile, (message *m_ptr) );
_PROTOTYPE( int do_profbuf, (message *m_ptr) );
_PROTOTYPE( int do_mapdma, (message *m_ptr) );
#endif /* SYSTEM_H */
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