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Primary goal for these changes is:

Browse Source 
- 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
This commit is contained in:
Ben Gras
2009-09-21 14:31:52 +00:00
parent f5b04e1881
commit cd8b915ed9
39 changed files with 2149 additions and 1319 deletions
Download Patch File Download Diff File Expand all files Collapse all files

124
kernel/system.c
View File

@@ -40,6 +40,7 @@
#include <sys/sigcontext.h>
#include <minix/endpoint.h>
#include <minix/safecopies.h>
#include <minix/portio.h>
#include <minix/u64.h>
#include <sys/vm_i386.h>
@@ -58,7 +59,6 @@ char *callnames[NR_SYS_CALLS];
call_vec[(call_nr-KERNEL_CALL)] = (handler)
FORWARD _PROTOTYPE( void initialize, (void));
FORWARD _PROTOTYPE( void softnotify_check, (void));
FORWARD _PROTOTYPE( struct proc *vmrestart_check, (message *));
/*===========================================================================*
@@ -77,26 +77,18 @@ PUBLIC void sys_task()
/* Initialize the system task. */
initialize();
while (TRUE) {
struct proc *restarting;
restarting = vmrestart_check(&m);
softnotify_check();
if(softnotify)
minix_panic("softnotify non-NULL before receive (1)", NO_NUM);
if(!restarting) {
int r;
/* Get work. Block and wait until a request message arrives. */
if(softnotify)
minix_panic("softnotify non-NULL before receive (2)", NO_NUM);
if((r=receive(ANY, &m)) != OK)
minix_panic("receive() failed", r);
if(m.m_source == SYSTEM)
continue;
if(softnotify)
minix_panic("softnotify non-NULL after receive", NO_NUM);
}
}
sys_call_code = (unsigned) m.m_type;
call_nr = sys_call_code - KERNEL_CALL;
@@ -104,37 +96,13 @@ PUBLIC void sys_task()
okendpt(who_e, &who_p);
caller_ptr = proc_addr(who_p);
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.total= add64u(sys_stats.total, 1);
/* See if the caller made a valid request and try to handle it. */
if (call_nr < 0 || call_nr >= NR_SYS_CALLS) { /* check call number */
#if DEBUG_ENABLE_IPC_WARNINGS
kprintf("SYSTEM: illegal request %d from %d.\n",
call_nr,m.m_source);
#endif
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.bad_req++;
result = EBADREQUEST; /* illegal message type */
}
else if (!GET_BIT(priv(caller_ptr)->s_k_call_mask, call_nr)) {
#if DEBUG_ENABLE_IPC_WARNINGS
static int curr= 0, limit= 100, extra= 20;
if (curr < limit+extra)
{
kprintf("SYSTEM: request %d from %d denied.\n",
call_nr, m.m_source);
} else if (curr == limit+extra)
{
kprintf("sys_task: no debug output for a while\n");
}
else if (curr == 2*limit-1)
limit *= 2;
curr++;
#endif
if (caller_ptr->p_endpoint == ipc_stats_target)
sys_stats.not_allowed++;
result = ECALLDENIED; /* illegal message type */
}
else {
@@ -146,15 +114,20 @@ PUBLIC void sys_task()
* until VM tells us it's allowed. VM has been notified
* and we must wait for its reply to restart the call.
*/
vmassert(RTS_ISSET(caller_ptr, VMREQUEST));
vmassert(caller_ptr->p_vmrequest.type == VMSTYPE_KERNELCALL);
memcpy(&caller_ptr->p_vmrequest.saved.reqmsg, &m, sizeof(m));
caller_ptr->p_vmrequest.type = VMSTYPE_SYS_MESSAGE;
} else if (result != EDONTREPLY) {
/* Send a reply, unless inhibited by a handler function.
* Use the kernel function lock_send() to prevent a system
* call trap.
*/
if(restarting)
RTS_LOCK_UNSET(restarting, VMREQUEST);
if(restarting) {
vmassert(!RTS_ISSET(restarting, VMREQUEST));
#if 0
vmassert(!RTS_ISSET(restarting, VMREQTARGET));
#endif
}
m.m_type = result; /* report status of call */
if(WILLRECEIVE(caller_ptr, SYSTEM)) {
if (OK != (s=lock_send(m.m_source, &m))) {
@@ -222,7 +195,6 @@ PRIVATE void initialize(void)
map(SYS_NEWMAP, do_newmap); /* set up a process memory map */
map(SYS_SEGCTL, do_segctl); /* add segment and get selector */
map(SYS_MEMSET, do_memset); /* write char to memory area */
map(SYS_VM_SETBUF, do_vm_setbuf); /* PM passes buffer for page tables */
map(SYS_VMCTL, do_vmctl); /* various VM process settings */
/* Copying. */
@@ -350,7 +322,11 @@ PUBLIC void send_sig(int proc_nr, int sig_nr)
rp = proc_addr(proc_nr);
sigaddset(&priv(rp)->s_sig_pending, sig_nr);
soft_notify(rp->p_endpoint);
if(!intr_disabled()) {
lock_notify(SYSTEM, rp->p_endpoint);
} else {
mini_notify(proc_addr(SYSTEM), rp->p_endpoint);
}
}
/*===========================================================================*
@@ -467,7 +443,9 @@ register struct proc *rc; /* slot of process to clean up */
if(isemptyp(rc)) minix_panic("clear_proc: empty process", rc->p_endpoint);
if(rc->p_endpoint == PM_PROC_NR || rc->p_endpoint == VFS_PROC_NR) {
if(rc->p_endpoint == PM_PROC_NR || rc->p_endpoint == VFS_PROC_NR ||
rc->p_endpoint == VM_PROC_NR)
{
/* This test is great for debugging system processes dying,
* but as this happens normally on reboot, not good permanent code.
*/
@@ -543,13 +521,6 @@ register struct proc *rc; /* slot of process to clean up */
#endif
}
}
/* No pending soft notifies. */
for(np = softnotify; np; np = np->next_soft_notify) {
if(np == rc) {
minix_panic("dying proc was on next_soft_notify", np->p_endpoint);
}
}
}
/*===========================================================================*
@@ -583,28 +554,6 @@ int access; /* does grantee want to CPF_READ or _WRITE? */
return umap_virtual(proc_addr(proc_nr), D, v_offset, bytes);
}
/*===========================================================================*
* softnotify_check *
*===========================================================================*/
PRIVATE void softnotify_check(void)
{
struct proc *np, *nextnp;
if(!softnotify)
return;
for(np = softnotify; np; np = nextnp) {
if(!np->p_softnotified)
minix_panic("softnotify but no p_softnotified", NO_NUM);
lock_notify(SYSTEM, np->p_endpoint);
nextnp = np->next_soft_notify;
np->next_soft_notify = NULL;
np->p_softnotified = 0;
}
softnotify = NULL;
}
/*===========================================================================*
* vmrestart_check *
*===========================================================================*/
@@ -618,23 +567,18 @@ PRIVATE struct proc *vmrestart_check(message *m)
if(!(restarting = vmrestart))
return NULL;
if(restarting->p_rts_flags & SLOT_FREE)
minix_panic("SYSTEM: VMREQUEST set for empty process", NO_NUM);
vmassert(!RTS_ISSET(restarting, SLOT_FREE));
vmassert(RTS_ISSET(restarting, VMREQUEST));
type = restarting->p_vmrequest.type;
restarting->p_vmrequest.type = VMSTYPE_SYS_NONE;
vmrestart = restarting->p_vmrequest.nextrestart;
if(!RTS_ISSET(restarting, VMREQUEST))
minix_panic("SYSTEM: VMREQUEST not set for process on vmrestart queue",
restarting->p_endpoint);
switch(type) {
case VMSTYPE_SYS_MESSAGE:
case VMSTYPE_KERNELCALL:
memcpy(m, &restarting->p_vmrequest.saved.reqmsg, sizeof(*m));
if(m->m_source != restarting->p_endpoint)
minix_panic("SYSTEM: vmrestart source doesn't match",
NO_NUM);
restarting->p_vmrequest.saved.reqmsg.m_source = NONE;
vmassert(m->m_source == restarting->p_endpoint);
/* Original caller could've disappeared in the meantime. */
if(!isokendpt(m->m_source, &who_p)) {
kprintf("SYSTEM: ignoring call %d from dead %d\n",
@@ -653,26 +597,6 @@ PRIVATE struct proc *vmrestart_check(message *m)
}
}
return restarting;
case VMSTYPE_SYS_CALL:
kprintf("SYSTEM: restart sys_call\n");
/* Restarting a kernel trap. */
sys_call_restart(restarting);
/* Handled; restart system loop. */
return NULL;
case VMSTYPE_MSGCOPY:
/* Do delayed message copy. */
if((r=data_copy(SYSTEM,
(vir_bytes) &restarting->p_vmrequest.saved.msgcopy.msgbuf,
restarting->p_vmrequest.saved.msgcopy.dst->p_endpoint,
(vir_bytes) restarting->p_vmrequest.saved.msgcopy.dst_v,
sizeof(message))) != OK) {
minix_panic("SYSTEM: delayed msgcopy failed", r);
}
RTS_LOCK_UNSET(restarting, VMREQUEST);
/* Handled; restart system loop. */
return NULL;
default:
minix_panic("strange restart type", type);
}