cd8b915ed9
- 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
82 lines
3 KiB
C
Executable file
82 lines
3 KiB
C
Executable file
#ifndef GLO_H
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#define GLO_H
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#include <minix/sysutil.h>
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/* Global variables used in the kernel. This file contains the declarations;
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* storage space for the variables is allocated in table.c, because EXTERN is
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* defined as extern unless the _TABLE definition is seen. We rely on the
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* compiler's default initialization (0) for several global variables.
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*/
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#ifdef _TABLE
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#undef EXTERN
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#define EXTERN
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#endif
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#include <minix/config.h>
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#include <archtypes.h>
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#include "config.h"
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#include "debug.h"
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/* Variables relating to shutting down MINIX. */
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EXTERN char kernel_exception; /* TRUE after system exceptions */
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EXTERN char shutdown_started; /* TRUE after shutdowns / reboots */
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/* Kernel information structures. This groups vital kernel information. */
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EXTERN struct kinfo kinfo; /* kernel information for users */
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EXTERN struct machine machine; /* machine information for users */
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EXTERN struct kmessages kmess; /* diagnostic messages in kernel */
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EXTERN struct k_randomness krandom; /* gather kernel random information */
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EXTERN struct loadinfo kloadinfo; /* status of load average */
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/* Process scheduling information and the kernel reentry count. */
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EXTERN struct proc *proc_ptr; /* pointer to currently running process */
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EXTERN struct proc *next_ptr; /* next process to run after restart() */
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EXTERN struct proc *prev_ptr;
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EXTERN struct proc *bill_ptr; /* process to bill for clock ticks */
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EXTERN struct proc *vmrestart; /* first process on vmrestart queue */
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EXTERN struct proc *vmrequest; /* first process on vmrequest queue */
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EXTERN struct proc *pagefaults; /* first process on pagefault queue */
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EXTERN char k_reenter; /* kernel reentry count (entry count less 1) */
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EXTERN unsigned lost_ticks; /* clock ticks counted outside clock task */
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/* Interrupt related variables. */
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EXTERN irq_hook_t irq_hooks[NR_IRQ_HOOKS]; /* hooks for general use */
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EXTERN int irq_actids[NR_IRQ_VECTORS]; /* IRQ ID bits active */
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EXTERN int irq_use; /* map of all in-use irq's */
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EXTERN u32_t system_hz; /* HZ value */
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/* Miscellaneous. */
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EXTERN reg_t mon_ss, mon_sp; /* boot monitor stack */
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EXTERN int mon_return; /* true if we can return to monitor */
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EXTERN int do_serial_debug;
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EXTERN endpoint_t who_e; /* message source endpoint */
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EXTERN int who_p; /* message source proc */
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EXTERN int sys_call_code; /* kernel call number in SYSTEM */
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EXTERN time_t boottime;
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EXTERN char params_buffer[512]; /* boot monitor parameters */
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EXTERN int minix_panicing;
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EXTERN int locklevel;
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#if DEBUG_TRACE
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EXTERN int verboseflags;
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#endif
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/* VM */
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EXTERN int vm_running;
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EXTERN int catch_pagefaults;
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EXTERN struct proc *ptproc;
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/* Timing */
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EXTERN util_timingdata_t timingdata[TIMING_CATEGORIES];
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/* Variables that are initialized elsewhere are just extern here. */
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extern struct boot_image image[]; /* system image processes */
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extern char *t_stack[]; /* task stack space */
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extern struct segdesc_s gdt[]; /* global descriptor table */
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EXTERN _PROTOTYPE( void (*level0_func), (void) );
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#endif /* GLO_H */
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