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kernel: add support for sticky segments (cached, preallocated, never paged)

--- a/sys/src/9/port/devproc.c

+++ b/sys/src/9/port/devproc.c

@@ -138,7 +138,7 @@

 };

 /* Segment type from portdat.h */

-static char *sname[]={ "Text", "Data", "Bss", "Stack", "Shared", "Phys", "Fixed", };

+static char *sname[]={ "Text", "Data", "Bss", "Stack", "Shared", "Phys", "Fixed", "Sticky" };

 /*

  * Qids are, in path:

--- a/sys/src/9/port/devsegment.c

+++ b/sys/src/9/port/devsegment.c

@@ -284,6 +284,8 @@

 		if((g->s->type&SG_TYPE) == SG_FIXED)

 			snprint(buf, sizeof(buf), "va %#p %#p fixed %#p\n", g->s->base, g->s->top-g->s->base,

 				g->s->map[0]->pages[0]->pa);

+		else if((g->s->type&SG_TYPE) == SG_STICKY)

+			snprint(buf, sizeof(buf), "va %#p %#p sticky\n", g->s->base, g->s->top-g->s->base);

 		else

 			snprint(buf, sizeof(buf), "va %#p %#p\n", g->s->base, g->s->top-g->s->base);

 		return readstr(voff, a, n, buf);

@@ -331,6 +333,20 @@

 				if(!iseve())

 					error(Eperm);

 				g->s = fixedseg(va, len/BY2PG);

+			} else if(cb->nf >= 4 && strcmp(cb->f[3], "sticky") == 0){

+				Segment *s;

+

+				if(!iseve())

+					error(Eperm);

+				s = newseg(SG_STICKY, va, len/BY2PG);

+				if(waserror()){

+					putseg(s);

+					nexterror();

+				}

+				for(; va < s->top; va += BY2PG)

+					segpage(s, newpage(1, nil, va));

+				poperror();

+				g->s = s;

 			} else

 				g->s = newseg(SG_SHARED, va, len/BY2PG);

 		} else

--- a/sys/src/9/port/fault.c

+++ b/sys/src/9/port/fault.c

@@ -270,6 +270,8 @@

 			copypage(old, *pg);

 			putpage(old);

 		}

+		/* wet floor */

+	case SG_STICKY:			/* Never paged out */

 		mmuphys = PPN((*pg)->pa) | PTEWRITE | PTEVALID;

 		(*pg)->modref = PG_MOD|PG_REF;

 		break;

--- a/sys/src/9/port/portdat.h

+++ b/sys/src/9/port/portdat.h

@@ -368,6 +368,7 @@

 	SG_SHARED	= 04,

 	SG_PHYSICAL	= 05,

 	SG_FIXED	= 06,

+	SG_STICKY	= 07,

 	SG_RONLY	= 0040,		/* Segment is read only */

 	SG_CEXEC	= 0100,		/* Detach at exec */

--- a/sys/src/9/port/proc.c

+++ b/sys/src/9/port/proc.c

@@ -1595,6 +1595,7 @@

 		case SG_SHARED:

 		case SG_PHYSICAL:

 		case SG_FIXED:

+		case SG_STICKY:

 			continue;

 		}

 		qlock(s);

--- a/sys/src/9/port/segment.c

+++ b/sys/src/9/port/segment.c

@@ -155,6 +155,7 @@

 	case SG_SHARED:

 	case SG_PHYSICAL:

 	case SG_FIXED:

+	case SG_STICKY:

 		goto sameseg;

 	case SG_STACK:

@@ -499,6 +500,7 @@

 	switch(s->type&SG_TYPE){

 	case SG_PHYSICAL:

 	case SG_FIXED:

+	case SG_STICKY:

 		return;

 	}

--- a/sys/src/9/port/sysproc.c

+++ b/sys/src/9/port/sysproc.c

@@ -773,6 +773,7 @@

 		case SG_STACK:

 		case SG_PHYSICAL:

 		case SG_FIXED:

+		case SG_STICKY:

 			error(Ebadarg);

 		default:

 			return ibrk(va_arg(list, uintptr), i);