Commit graph

59 commits

Author SHA1 Message Date
David van Moolenbroek
cf9a4ec79b Kernel: clean up include statements a bit
Coverity was flagging a recursive include between kernel.h and
cpulocals.h. As cpulocals.h also included proc.h, we can move that
include statement into kernel.h, and clean up the source files'
include statements accordingly.
2012-08-14 16:29:05 +00:00
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
7336a67dfe retire PUBLIC, PRIVATE and FORWARD 2012-03-25 21:58:14 +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
Arun Thomas
cb54d96eec Remove legacy boot monitor vars 2011-09-16 20:10:47 +02:00
Arun Thomas
92fa3189ab MKSYSDEBUG: conditionally compile more debug code 2011-09-16 15:25:26 +02:00
Ben Gras
ca5e8b2c2d kernel: show segment-adjusted pagefault addr 2011-08-12 15:16:52 +00:00
Ben Gras
01b152d6d9 kernel: add prototype for inkernel_disaster 2011-07-22 15:19:40 +02:00
Ben Gras
7ee78ffb82 kernel: improve exception debug printing
. fold 2 exception-in-kernel cases (pagefault and rest)
	  into 1
	. for exceptions that occur in kernel, don't just print
	  kernel stacktrace (typically that is just the exception
	  handler) but also the stacktrace of when the exception
	  happened
2011-07-22 10:57:08 +00:00
Ben Gras
e785381d4d introduce option to time assert()s
. remove a few asserts in the kernel and 64bi library
    that are not compatible with the timing code
  . change the TIME_BLOCKS code a little to work in-kernel
2011-06-24 16:00:42 +02:00
Ben Gras
515e8d075f kernel: limit stacktrace depth to 50.
- Unlikely to discard useful information and avoids long
    system lockups on machines configured to print system output to serial.
2010-11-02 21:27:04 +00:00
Ben Gras
82d576c9ca enable_fpu_exception() - only write cr0 if bit isn't already on.
(NMI profiling results indicate this both is relatively expensive and
happens a lot unnecessarily if the fpu is in use.)
2010-09-22 14:31:06 +00:00
Tomas Hruby
9e12630d75 SMP - APs are fully enabled
- apic_send_ipi() to send inter-processor interrupts (IPIs)

- APIC IPI schedule and halt handlers to signal x-cpu that a cpu shold
  reschedule or halt

- various little changes to let APs run

- no processes are scheduled at the APs and therefore they are idle
  except being interrupted by a timer time to time
2010-09-15 14:10:30 +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
6c3b981cd6 arch proto.h renamed to arch_proto.h
- the file moved to the arch include dir
2010-09-15 14:09:36 +00:00
Cristiano Giuffrida
03bb1e5750 Don't panic so easily on unexpected pagefault. 2010-07-20 23:51:34 +00:00
Ben Gras
b3a0a2d86f kernel: don't initialize catch_pagefaults at the extern declaration. 2010-06-24 12:23:23 +00:00
Tomas Hruby
cbc9586c13 Lazy FPU
- FPU context is stored only if conflict between 2 FPU users or while
  exporting context of a process to userspace while it is the active
  user of FPU

- FPU has its owner (fpu_owner) which points to the process whose
  state is currently loaded in FPU

- the FPU exception is only turned on when scheduling a process which
  is not the owner of FPU

- FPU state is restored for the process that generated the FPU
  exception. This process runs immediately without letting scheduler
  to pick a new process to resolve the FPU conflict asap, to minimize
  the FPU thrashing and FPU exception hadler execution

- faster all non-FPU-exception kernel entries as FPU state is not
  checked nor saved

- removed MF_USED_FPU flag, only MF_FPU_INITIALIZED remains to signal
  that a process has used FPU in the past
2010-06-07 07:43:17 +00:00
Ben Gras
bfc9c5c3a8 kernel: small ammendment to pagefault-in-kernel panic 2010-05-12 08:56:11 +00:00
Ben Gras
7c5e1d1b29 kernel - don't print info about scheduled process if pagefault happened in kernel. 2010-05-11 15:14:10 +00:00
Tomas Hruby
6e25ad8b0a Use of all NIL_* defines converted to NULL 2010-05-10 13:26:00 +00:00
Tomas Hruby
b528d52ea8 pagefault() is private 2010-04-27 20:30:33 +00:00
Tomas Hruby
f51eea4b32 Changed pagefault delivery to VM
this patch changes the way pagefaults are delivered to VM. It adopts
the same model as the out-of-quantum messages sent by kernel to a
scheduler.

- everytime a userspace pagefault occurs, kernel creates a message
  which is sent to VM on behalf of the faulting process

- the process is blocked on delivery to VM in the standard IPC code
  instead of waiting in a spacial in-kernel queue (stack) and is not
  runnable until VM tell kernel that the pagefault is resolved and is
  free to clear the RTS_PAGEFAULT flag.

- VM does not need call kernel and poll the pagefault information
  which saves many (1/2?) calls and kernel calls that return "no more
  data"

- VM notification by kernel does not need to use signals

- each entry in proc table is by 12 bytes smaller (~3k save)
2010-04-26 23:21:26 +00:00
Kees van Reeuwijk
d106968d77 Remove useless symbol declarations from headers, make symbols local where possible, add some explicit initialization to global variables. 2010-04-22 07:49:40 +00:00
Tomas Hruby
25f2145956 Fixed a panic message
- exceptions cannot occur in kernel tasks as we don't have kernel
  tasks anymore
2010-04-07 12:50:43 +00:00
Arun Thomas
4ed3a0cf3a Convert kernel over to bsdmake 2010-04-01 22:22:33 +00:00
Ben Gras
f2b87f5fb7 don't print SYSTEM stacktrace on exceptions as it's not scheduled any more. 2010-03-29 15:32:19 +00:00
Kees van Reeuwijk
c33102ea6b Miscellaneous code cleanup. 2010-03-22 20:43:06 +00:00
Tomas Hruby
a5094f7d7f Kernel dumps its registers when exception
- if an exception occurs in kernel and this exception is not handled
  in an sane way and the kernel crashes, it also dumps what was loaded
  in the general purpose registers exactly at the time of the
  exception to help to debug the problem
2010-03-20 14:59:18 +00:00
Cristiano Giuffrida
cb176df60f New RS and new signal handling for system processes.
UPDATING INFO:
20100317:
        /usr/src/etc/system.conf updated to ignore default kernel calls: copy
        it (or merge it) to /etc/system.conf.
        The hello driver (/dev/hello) added to the distribution:
        # cd /usr/src/commands/scripts && make clean install
        # cd /dev && MAKEDEV hello

KERNEL CHANGES:
- Generic signal handling support. The kernel no longer assumes PM as a signal
manager for every process. The signal manager of a given process can now be
specified in its privilege slot. When a signal has to be delivered, the kernel
performs the lookup and forwards the signal to the appropriate signal manager.
PM is the default signal manager for user processes, RS is the default signal
manager for system processes. To enable ptrace()ing for system processes, it
is sufficient to change the default signal manager to PM. This will temporarily
disable crash recovery, though.
- sys_exit() is now split into sys_exit() (i.e. exit() for system processes,
which generates a self-termination signal), and sys_clear() (i.e. used by PM
to ask the kernel to clear a process slot when a process exits).
- Added a new kernel call (i.e. sys_update()) to swap two process slots and
implement live update.

PM CHANGES:
- Posix signal handling is no longer allowed for system processes. System
signals are split into two fixed categories: termination and non-termination
signals. When a non-termination signaled is processed, PM transforms the signal
into an IPC message and delivers the message to the system process. When a
termination signal is processed, PM terminates the process.
- PM no longer assumes itself as the signal manager for system processes. It now
makes sure that every system signal goes through the kernel before being
actually processes. The kernel will then dispatch the signal to the appropriate
signal manager which may or may not be PM.

SYSLIB CHANGES:
- Simplified SEF init and LU callbacks.
- Added additional predefined SEF callbacks to debug crash recovery and
live update.
- Fixed a temporary ack in the SEF init protocol. SEF init reply is now
completely synchronous.
- Added SEF signal event type to provide a uniform interface for system
processes to deal with signals. A sef_cb_signal_handler() callback is
available for system processes to handle every received signal. A
sef_cb_signal_manager() callback is used by signal managers to process
system signals on behalf of the kernel.
- Fixed a few bugs with memory mapping and DS.

VM CHANGES:
- Page faults and memory requests coming from the kernel are now implemented
using signals.
- Added a new VM call to swap two process slots and implement live update.
- The call is used by RS at update time and in turn invokes the kernel call
sys_update().

RS CHANGES:
- RS has been reworked with a better functional decomposition.
- Better kernel call masks. com.h now defines the set of very basic kernel calls
every system service is allowed to use. This makes system.conf simpler and
easier to maintain. In addition, this guarantees a higher level of isolation
for system libraries that use one or more kernel calls internally (e.g. printf).
- RS is the default signal manager for system processes. By default, RS
intercepts every signal delivered to every system process. This makes crash
recovery possible before bringing PM and friends in the loop.
- RS now supports fast rollback when something goes wrong while initializing
the new version during a live update.
- Live update is now implemented by keeping the two versions side-by-side and
swapping the process slots when the old version is ready to update.
- Crash recovery is now implemented by keeping the two versions side-by-side
and cleaning up the old version only when the recovery process is complete.

DS CHANGES:
- Fixed a bug when the process doing ds_publish() or ds_delete() is not known
by DS.
- Fixed the completely broken support for strings. String publishing is now
implemented in the system library and simply wraps publishing of memory ranges.
Ideally, we should adopt a similar approach for other data types as well.
- Test suite fixed.

DRIVER CHANGES:
- The hello driver has been added to the Minix distribution to demonstrate basic
live update and crash recovery functionalities.
- Other drivers have been adapted to conform the new SEF interface.
2010-03-17 01:15:29 +00:00
Ben Gras
0937d6c367 re-establish kernel assert()s.
use the regular <assert.h> assert() instead of vmassert() in
kernel. throw out some #if 0 code. fix a few assert() conditions.
enable by default.
2010-03-10 13:00:05 +00:00
Ben Gras
35a108b911 panic() cleanup.
this change
   - makes panic() variadic, doing full printf() formatting -
     no more NO_NUM, and no more separate printf() statements
     needed to print extra info (or something in hex) before panicing
   - unifies panic() - same panic() name and usage for everyone -
     vm, kernel and rest have different names/syntax currently
     in order to implement their own luxuries, but no longer
   - throws out the 1st argument, to make source less noisy.
     the panic() in syslib retrieves the server name from the kernel
     so it should be clear enough who is panicing; e.g.
         panic("sigaction failed: %d", errno);
     looks like:
         at_wini(73130): panic: sigaction failed: 0
         syslib:panic.c: stacktrace: 0x74dc 0x2025 0x100a
   - throws out report() - printf() is more convenient and powerful
   - harmonizes/fixes the use of panic() - there were a few places
     that used printf-style formatting (didn't work) and newlines
     (messes up the formatting) in panic()
   - throws out a few per-server panic() functions
   - cleans up a tie-in of tty with panic()

merging printf() and panic() statements to be done incrementally.
2010-03-05 15:05:11 +00:00
Ben Gras
e6cb76a2e2 no more kprintf - kernel uses libsys printf now, only kputc is special
to the kernel.
2010-03-03 15:45:01 +00:00
David van Moolenbroek
e306663455 fix the somehow newly introduced warnings 2010-02-14 18:39:47 +00:00
Tomas Hruby
c6fec6866f No locking in kernel code
- No locking in RTS_(UN)SET macros

- No lock_notify()

- Removed unused lock_send()

- No lock/unlock macros anymore
2010-02-09 15:26:58 +00:00
Tomas Hruby
728f0f0c49 Removal of the system task
* Userspace change to use the new kernel calls

	- _taskcall(SYSTASK...) changed to _kernel_call(...)

	- int 32 reused for the kernel calls

	- _do_kernel_call() to make the trap to kernel

	- kernel_call() to make the actuall kernel call from C using
	  _do_kernel_call()

	- unlike ipc call the kernel call always succeeds as kernel is
	  always available, however, kernel may return an error

* Kernel side implementation of kernel calls

	- the SYSTEm task does not run, only the proc table entry is
	  preserved

	- every data_copy(SYSTEM is no data_copy(KERNEL

	- "locking" is an empty operation now as everything runs in
	  kernel

	- sys_task() is replaced by kernel_call() which copies the
	  message into kernel, dispatches the call to its handler and
	  finishes by either copying the results back to userspace (if
	  need be) or by suspending the process because of VM

	- suspended processes are later made runnable once the memory
	  issue is resolved, picked up by the scheduler and only at
	  this time the call is resumed (in fact restarted) which does
	  not need to copy the message from userspace as the message
	  is already saved in the process structure.

	- no ned for the vmrestart queue, the scheduler will restart
	  the system calls

	- no special case in do_vmctl(), all requests remove the
	  RTS_VMREQUEST flag
2010-02-09 15:20:09 +00:00
Tomas Hruby
5e57818431 copy_msg_from_user() and copy_msg_to_user()
- 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
2010-02-09 15:15:45 +00:00
Kees van Reeuwijk
b67f788eea Removed a number of useless #includes 2010-01-26 10:59:01 +00:00
Kees van Reeuwijk
a7cee5bec4 Removed unused symbols.
Minor cleanups.
2010-01-22 22:01:08 +00:00
Tomas Hruby
5efa92f754 NMI watchdog is an awesome feature for debugging locked up kernels.
There is not that much use for it on a single CPU, however, deadlock
between kernel and system task can be delected. Or a runaway loop.

If a kernel gets locked up the timer interrupts don't occure (as all
interrupts are disabled in kernel mode). The only chance is to
interrupt the kernel by a non-maskable interrupt.

This patch generates NMIs using performance counters. It uses the most
widely available performace counters. As the performance counters are 
highly model-specific this patch is not guaranteed to work on every
machine.  Unfortunately this is also true for KVM :-/ On the other
hand adding this feature for other models is not extremely difficult
and the framework makes it hopefully easy enough.

Depending on the frequency of the CPU an NMI is generated at most
about every 0.5s If the cpu's speed is less then 2Ghz it is generated
at most every 1s. In general an NMI is generated much less often as
the performance counter counts down only if the cpu is not idle.
Therefore the overhead of this feature is fairly minimal even if the
load is high.

Uppon detecting that the kernel is locked up the kernel dumps the 
state of the kernel registers and panics.

Local APIC must be enabled for the watchdog to work.

The code is _always_ compiled in, however, it is only enabled if  
watchdog=<non-zero> is set in the boot monitor.

One corner case is serial console debugging. As dumping a lot of stuff
to the serial link may take a lot of time, the watchdog does not 
detect lockups during this time!!! as it would result in too many
false positives. 10 nmi have to be handled before the lockup is
detected. This means something between ~5s to 10s.

Another corner case is that the watchdog is enabled only after the
paging is enabled as it would be pure madness to try to get it right.
2010-01-16 20:53:55 +00:00
David van Moolenbroek
bac0e91705 typo (Bug#376, reported by Kees van Reeuwijk) 2010-01-04 12:29:51 +00:00
Ben Gras
bd42705433 FPU context switching support by Evgeniy Ivanov. 2009-12-02 13:01:48 +00:00
David van Moolenbroek
fce9fd4b4e Add 'getidle' CPU utilization measurement infrastructure 2009-12-02 11:52:26 +00:00
Tomas Hruby
a972f4bacc All macros defining rts flags are prefixed with RTS_
- macros used with RTS_SET group of macros to define struct proc p_rts_flags are
  now prefixed with RTS_ to make things clear
2009-11-10 09:11:13 +00:00
Tomas Hruby
ae75f9d4e5 Removal of the executable flag from files that cannot be executed
- 755 -> 644
2009-11-09 10:26:00 +00:00
Tomas Hruby
ebbce7507b Complete ovehaul of mode switching code
- 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
2009-11-06 09:08:26 +00:00
Ben Gras
88a12c70d2 little more info in pagefault exception handler. 2009-10-03 12:23:02 +00:00
David van Moolenbroek
b423d7b477 Merge of David's ptrace branch. Summary:
o Support for ptrace T_ATTACH/T_DETACH and T_SYSCALL
o PM signal handling logic should now work properly, even with debuggers
  being present
o Asynchronous PM/VFS protocol, full IPC support for senda(), and
  AMF_NOREPLY senda() flag

DETAILS

Process stop and delay call handling of PM:
o Added sys_runctl() kernel call with sys_stop() and sys_resume()
  aliases, for PM to stop and resume a process
o Added exception for sending/syscall-traced processes to sys_runctl(),
  and matching SIGKREADY pseudo-signal to PM
o Fixed PM signal logic to deal with requests from a process after
  stopping it (so-called "delay calls"), using the SIGKREADY facility
o Fixed various PM panics due to race conditions with delay calls versus
  VFS calls
o Removed special PRIO_STOP priority value
o Added SYS_LOCK RTS kernel flag, to stop an individual process from
  running while modifying its process structure

Signal and debugger handling in PM:
o Fixed debugger signals being dropped if a second signal arrives when
  the debugger has not retrieved the first one
o Fixed debugger signals being sent to the debugger more than once
o Fixed debugger signals unpausing process in VFS; removed PM_UNPAUSE_TR
  protocol message
o Detached debugger signals from general signal logic and from being
  blocked on VFS calls, meaning that even VFS can now be traced
o Fixed debugger being unable to receive more than one pending signal in
  one process stop
o Fixed signal delivery being delayed needlessly when multiple signals
  are pending
o Fixed wait test for tracer, which was returning for children that were
  not waited for
o Removed second parallel pending call from PM to VFS for any process
o Fixed process becoming runnable between exec() and debugger trap
o Added support for notifying the debugger before the parent when a
  debugged child exits
o Fixed debugger death causing child to remain stopped forever
o Fixed consistently incorrect use of _NSIG

Extensions to ptrace():
o Added T_ATTACH and T_DETACH ptrace request, to attach and detach a
  debugger to and from a process
o Added T_SYSCALL ptrace request, to trace system calls
o Added T_SETOPT ptrace request, to set trace options
o Added TO_TRACEFORK trace option, to attach automatically to children
  of a traced process
o Added TO_ALTEXEC trace option, to send SIGSTOP instead of SIGTRAP upon
  a successful exec() of the tracee
o Extended T_GETUSER ptrace support to allow retrieving a process's priv
  structure
o Removed T_STOP ptrace request again, as it does not help implementing
  debuggers properly
o Added MINIX3-specific ptrace test (test42)
o Added proper manual page for ptrace(2)

Asynchronous PM/VFS interface:
o Fixed asynchronous messages not being checked when receive() is called
  with an endpoint other than ANY
o Added AMF_NOREPLY senda() flag, preventing such messages from
  satisfying the receive part of a sendrec()
o Added asynsend3() that takes optional flags; asynsend() is now a
  #define passing in 0 as third parameter
o Made PM/VFS protocol asynchronous; reintroduced tell_fs()
o Made PM_BASE request/reply number range unique
o Hacked in a horrible temporary workaround into RS to deal with newly
  revealed RS-PM-VFS race condition triangle until VFS is asynchronous

System signal handling:
o Fixed shutdown logic of device drivers; removed old SIGKSTOP signal
o Removed is-superuser check from PM's do_procstat() (aka getsigset())
o Added sigset macros to allow system processes to deal with the full
  signal set, rather than just the POSIX subset

Miscellaneous PM fixes:
o Split do_getset into do_get and do_set, merging common code and making
  structure clearer
o Fixed setpriority() being able to put to sleep processes using an
  invalid parameter, or revive zombie processes
o Made find_proc() global; removed obsolete proc_from_pid()
o Cleanup here and there

Also included:
o Fixed false-positive boot order kernel warning
o Removed last traces of old NOTIFY_FROM code

THINGS OF POSSIBLE INTEREST

o It should now be possible to run PM at any priority, even lower than
  user processes
o No assumptions are made about communication speed between PM and VFS,
  although communication must be FIFO
o A debugger will now receive incoming debuggee signals at kill time
  only; the process may not yet be fully stopped
o A first step has been made towards making the SYSTEM task preemptible
2009-09-30 09:57:22 +00:00
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