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minix/kernel/main.c
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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/* This file contains the main program of MINIX as well as its shutdown code.
* The routine main() initializes the system and starts the ball rolling by
* setting up the process table, interrupt vectors, and scheduling each task
* to run to initialize itself.
* The routine shutdown() does the opposite and brings down MINIX.
*
* The entries into this file are:
* main: MINIX main program
* prepare_shutdown: prepare to take MINIX down
*/
#include "kernel.h"
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <a.out.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include <minix/endpoint.h>
#include "proc.h"
#include "debug.h"
/* Prototype declarations for PRIVATE functions. */
FORWARD _PROTOTYPE( void announce, (void));
/*===========================================================================*
* main *
*===========================================================================*/
PUBLIC void main()
{
/* Start the ball rolling. */
struct boot_image *ip; /* boot image pointer */
register struct proc *rp; /* process pointer */
register struct priv *sp; /* privilege structure pointer */
register int i, j, s;
int hdrindex; /* index to array of a.out headers */
phys_clicks text_base;
vir_clicks text_clicks, data_clicks, st_clicks;
reg_t ktsb; /* kernel task stack base */
struct exec e_hdr; /* for a copy of an a.out header */
/* Architecture-dependent initialization. */
arch_init();
/* Clear the process table. Anounce each slot as empty and set up mappings
* for proc_addr() and proc_nr() macros. Do the same for the table with
* privilege structures for the system processes.
*/
for (rp = BEG_PROC_ADDR, i = -NR_TASKS; rp < END_PROC_ADDR; ++rp, ++i) {
rp->p_rts_flags = SLOT_FREE; /* initialize free slot */
#if DEBUG_SCHED_CHECK
rp->p_magic = PMAGIC;
#endif
rp->p_nr = i; /* proc number from ptr */
rp->p_endpoint = _ENDPOINT(0, rp->p_nr); /* generation no. 0 */
}
for (sp = BEG_PRIV_ADDR, i = 0; sp < END_PRIV_ADDR; ++sp, ++i) {
sp->s_proc_nr = NONE; /* initialize as free */
sp->s_id = i; /* priv structure index */
ppriv_addr[i] = sp; /* priv ptr from number */
}
/* Set up proc table entries for processes in boot image. The stacks of the
* kernel tasks are initialized to an array in data space. The stacks
* of the servers have been added to the data segment by the monitor, so
* the stack pointer is set to the end of the data segment. All the
* processes are in low memory on the 8086. On the 386 only the kernel
* is in low memory, the rest is loaded in extended memory.
*/
/* Task stacks. */
ktsb = (reg_t) t_stack;
for (i=0; i < NR_BOOT_PROCS; ++i) {
int ci;
bitchunk_t fv;
ip = &image[i]; /* process' attributes */
rp = proc_addr(ip->proc_nr); /* get process pointer */
ip->endpoint = rp->p_endpoint; /* ipc endpoint */
rp->p_max_priority = ip->priority; /* max scheduling priority */
rp->p_priority = ip->priority; /* current priority */
rp->p_quantum_size = ip->quantum; /* quantum size in ticks */
rp->p_ticks_left = ip->quantum; /* current credit */
strncpy(rp->p_name, ip->proc_name, P_NAME_LEN); /* set process name */
(void) get_priv(rp, (ip->flags & SYS_PROC)); /* assign structure */
priv(rp)->s_flags = ip->flags; /* process flags */
priv(rp)->s_trap_mask = ip->trap_mask; /* allowed traps */
/* Warn about violations of the boot image table order consistency. */
if (priv_id(rp) != s_nr_to_id(ip->proc_nr))
kprintf("Warning: boot image table has wrong process order\n");
/* Initialize call mask bitmap from unordered set.
* A single SYS_ALL_CALLS is a special case - it
* means all calls are allowed.
*/
if(ip->nr_k_calls == 1 && ip->k_calls[0] == SYS_ALL_CALLS)
fv = ~0; /* fill call mask */
else
fv = 0; /* clear call mask */
for(ci = 0; ci < CALL_MASK_SIZE; ci++) /* fill or clear call mask */
priv(rp)->s_k_call_mask[ci] = fv;
if(!fv) /* not all full? enter calls bit by bit */
for(ci = 0; ci < ip->nr_k_calls; ci++)
SET_BIT(priv(rp)->s_k_call_mask,
ip->k_calls[ci]-KERNEL_CALL);
for (j = 0; j < NR_SYS_PROCS && j < BITCHUNK_BITS; j++)
if (ip->ipc_to & (1 << j))
set_sendto_bit(rp, j); /* restrict targets */
if (iskerneln(proc_nr(rp))) { /* part of the kernel? */
if (ip->stksize > 0) { /* HARDWARE stack size is 0 */
rp->p_priv->s_stack_guard = (reg_t *) ktsb;
*rp->p_priv->s_stack_guard = STACK_GUARD;
}
ktsb += ip->stksize; /* point to high end of stack */
rp->p_reg.sp = ktsb; /* this task's initial stack ptr */
hdrindex = 0; /* all use the first a.out header */
} else {
hdrindex = 1 + i-NR_TASKS; /* servers, drivers, INIT */
}
/* Architecture-specific way to find out aout header of this
* boot process.
*/
arch_get_aout_headers(hdrindex, &e_hdr);
/* Convert addresses to clicks and build process memory map */
text_base = e_hdr.a_syms >> CLICK_SHIFT;
text_clicks = (e_hdr.a_text + CLICK_SIZE-1) >> CLICK_SHIFT;
data_clicks = (e_hdr.a_data+e_hdr.a_bss + CLICK_SIZE-1) >> CLICK_SHIFT;
st_clicks= (e_hdr.a_total + CLICK_SIZE-1) >> CLICK_SHIFT;
if (!(e_hdr.a_flags & A_SEP))
{
data_clicks= (e_hdr.a_text+e_hdr.a_data+e_hdr.a_bss +
CLICK_SIZE-1) >> CLICK_SHIFT;
text_clicks = 0; /* common I&D */
}
rp->p_memmap[T].mem_phys = text_base;
rp->p_memmap[T].mem_len = text_clicks;
rp->p_memmap[D].mem_phys = text_base + text_clicks;
rp->p_memmap[D].mem_len = data_clicks;
rp->p_memmap[S].mem_phys = text_base + text_clicks + st_clicks;
rp->p_memmap[S].mem_vir = st_clicks;
rp->p_memmap[S].mem_len = 0;
/* Set initial register values. The processor status word for tasks
* is different from that of other processes because tasks can
* access I/O; this is not allowed to less-privileged processes
*/
rp->p_reg.pc = (reg_t) ip->initial_pc;
rp->p_reg.psw = (iskernelp(rp)) ? INIT_TASK_PSW : INIT_PSW;
/* Initialize the server stack pointer. Take it down one word
* to give crtso.s something to use as "argc".
*/
if (isusern(proc_nr(rp))) { /* user-space process? */
rp->p_reg.sp = (rp->p_memmap[S].mem_vir +
rp->p_memmap[S].mem_len) << CLICK_SHIFT;
rp->p_reg.sp -= sizeof(reg_t);
}
/* scheduling functions depend on proc_ptr pointing somewhere. */
if(!proc_ptr) proc_ptr = rp;
/* If this process has its own page table, VM will set the
* PT up and manage it. VM will signal the kernel when it has
* done this; until then, don't let it run.
*/
if(priv(rp)->s_flags & PROC_FULLVM)
RTS_SET(rp, VMINHIBIT);
/* Set ready. The HARDWARE task is never ready. */
if (rp->p_nr == HARDWARE) RTS_SET(rp, NO_PRIORITY);
RTS_UNSET(rp, SLOT_FREE); /* remove SLOT_FREE and schedule */
alloc_segments(rp);
}
#if SPROFILE
sprofiling = 0; /* we're not profiling until instructed to */
#endif /* SPROFILE */
cprof_procs_no = 0; /* init nr of hash table slots used */
vm_running = 0;
krandom.random_sources = RANDOM_SOURCES;
krandom.random_elements = RANDOM_ELEMENTS;
/* MINIX is now ready. All boot image processes are on the ready queue.
* Return to the assembly code to start running the current process.
*/
bill_ptr = proc_addr(IDLE); /* it has to point somewhere */
announce(); /* print MINIX startup banner */
/* Warnings for sanity checks that take time. These warnings are printed
* so it's a clear warning no full release should be done with them
* enabled.
*/
#if DEBUG_SCHED_CHECK
FIXME("DEBUG_SCHED_CHECK enabled");
#endif
#if DEBUG_VMASSERT
FIXME("DEBUG_VMASSERT enabled");
#endif
#if DEBUG_PROC_CHECK
FIXME("PROC check enabled");
#endif
restart();
}
/*===========================================================================*
* announce *
*===========================================================================*/
PRIVATE void announce(void)
{
/* Display the MINIX startup banner. */
kprintf("\nMINIX %s.%s. "
#ifdef _SVN_REVISION
"(" _SVN_REVISION ")\n"
#endif
"Copyright 2009, Vrije Universiteit, Amsterdam, The Netherlands\n",
OS_RELEASE, OS_VERSION);
kprintf("MINIX is open source software, see http://www.minix3.org\n");
FIXME("pm, vfs, etc own page table");
}
/*===========================================================================*
* prepare_shutdown *
*===========================================================================*/
PUBLIC void prepare_shutdown(how)
int how;
{
/* This function prepares to shutdown MINIX. */
static timer_t shutdown_timer;
register struct proc *rp;
message m;
/* Continue after 1 second, to give processes a chance to get scheduled to
* do shutdown work. Set a watchog timer to call shutdown(). The timer
* argument passes the shutdown status.
*/
kprintf("MINIX will now be shut down ...\n");
tmr_arg(&shutdown_timer)->ta_int = how;
set_timer(&shutdown_timer, get_uptime() + system_hz, minix_shutdown);
}
/*===========================================================================*
* shutdown *
*===========================================================================*/
PUBLIC void minix_shutdown(tp)
timer_t *tp;
{
/* This function is called from prepare_shutdown or stop_sequence to bring
* down MINIX. How to shutdown is in the argument: RBT_HALT (return to the
* monitor), RBT_MONITOR (execute given code), RBT_RESET (hard reset).
*/
intr_init(INTS_ORIG);
clock_stop();
arch_shutdown(tp ? tmr_arg(tp)->ta_int : RBT_PANIC);
}
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