shared with the kernel, mapped into kernel address space;
kernel is notified of its location. kernel segment size is
increased to make it fit.
- map in kernel and other processes that don't have their
own page table using single 4MB (global) mapping.
- new sanity check facility: objects that are allocated with
the slab allocator are, when running with sanity checking on,
marked readonly until they are explicitly unlocked using the USE()
macro.
- another sanity check facility: collect all uses of memory and
see if they don't overlap with (a) eachother and (b) free memory
- own munmap() and munmap_text() functions.
- exec() recovers from out-of-memory conditions properly now; this
solves some weird exec() behaviour
- chew off memory from the same side of the chunk as where we
start scanning, solving some memory fragmentation issues
- use avl trees for freelist and phys_ranges in regions
- implement most useful part of munmap()
- remap() stuff is GQ's for shared memory
addr and taddr don't have to be defined any more, so that <sys/mman.h>
can be included for proper prototypes of munmap() and friends.
- rename our GETPID to MINIX_GETPID to avoid a name conflict with
other sources
- PM needs its own munmap() and munmap_text() to avoid sending messages
to VM at the startup phase. It *does* want to do that, but only
after initialising. So they're called again with unmap_ok set to 1
later.
- getnuid(), getngid() implementation
- If allocation of a new buffer fails, use an already-allocated
unused buffer if available (low memory conditions)
- Allocate buffers dynamically, so memory isn't wasted on wrong-sized
buffers.
- No more _MAX_BLOCK_SIZE.
- 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
remembering the origin and cursor position as that feature didn't
really work properly anyway
- tty: map in video and font memory using a vm call, access it from C,
thereby eliminating pesky weird segment calls and assembly to access it,
and unbreaks loadfont (Roman Ignatov)
- bios_wini: fix bios_wini by allocating a <1MB buffers for it
- memory: preallocate ramdisk, makes it a bit faster (and doesn't
fail halfway if you allocate a huge one)
- floppy: use <1MB buffer
- ramdisk proto: because of the 2x1 page reservations, binaries
got a little fatter and didn't fit on the ramdisk any more.
increase it.
for each symbol, usually answering those "why is does my binary have
such a lot of BSS" questions.
- stop binpackage looking in /var/spool for package files.
- let makewhatis recognize .Sh as heading name
- setup, fsck, df: allow >4kB block sizes painlessly
- mkfs: new #-of-inodes heuristic that depends on kb, not
on blocks; i've run out of inodes on my /usr
- asmconv: don't silently truncate .aligns to 16 bytes
- ipc* commands for shared memory support
- only print a line for every boot process if 'verbose' variable set to
nonzero; reason: with serial output, the long output
significantly slows down frequent reboots, and causes 'scroll damage'
that in some cases is pretty bad. also the verbose output doesn't tell
you the one thing you might want to know about a process: how much memory
is it using? or how much memory is everything using?
- short format does print out total memory allocated for processes
- sys_getbiosbuffer feature is gone (from kernel; available from vm)
- bump version number because munmap() calls that newly compiled binaries
will do trigger an ugly (but harmless) error message in older VM's
- some new VM calls and flags, the new IPC calls
- some new CR0 register bits
- added files for shared memory
- [ABCD]_INDEX are not used anywhere
- value of *_SELECTOR is now calculated using the *_INDEX value so changing the
index does not break the selector
- TSS is now the last of the global selectors. There will be TSS per CPU on SMP
and the number will vary depending on the maximal supported number of CPUs
configured
- pproc_addr is not neccessary to get the address of a process if we know its
number
- local proc variables in system calls implementation (sys_task) conflicts with
the global proc array of all process, therefore the variable were renamed to
proc_nr as they hold the process number
