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kernel: fixed segment support (for fpga experiments)

fixed segments are continuous in physical memory but
allocated in user pages. unlike shared segments, they
are not allocated on demand but the pages are allocated
on creation time (devsegment). fixed segments are
never swapped out, segfreed or resized and can only be
destroyed as a whole.

the physical base address can be discovered by userspace
reading the ctl file in devsegment.

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

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

@@ -134,7 +134,7 @@

 };

 /* Segment type from portdat.h */

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

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

 /*

  * Qids are, in path:

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

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

@@ -56,6 +56,7 @@

 static	int	cmddone(void*);

 static	void	segmentkproc(void*);

 static	void	docmd(Globalseg *g, int cmd);

+static	Segment* fixedseg(uintptr va, ulong len);

 /*

  *  returns with globalseg incref'd

@@ -98,7 +99,7 @@

 {

 	Qid q;

 	Globalseg *g;

-	ulong size;

+	uintptr size;

 	switch(TYPE(c)) {

 	case Qtopdir:

@@ -328,7 +329,11 @@

 		g = c->aux;

 		if(g->s == nil)

 			error("segment not yet allocated");

-		sprint(buf, "va %#lux %#lux\n", g->s->base, g->s->top-g->s->base);

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

+			sprint(buf, "va %#p %#p fixed %#p\n", g->s->base, g->s->top-g->s->base,

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

+		else

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

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

 	case Qdata:

 		g = c->aux;

@@ -362,7 +367,7 @@

 {

 	Cmdbuf *cb;

 	Globalseg *g;

-	ulong va, len, top;

+	uintptr va, top, len;

 	if(c->qid.type == QTDIR)

 		error(Eperm);

@@ -376,14 +381,19 @@

 				error("already has a virtual address");

 			if(cb->nf < 3)

 				error(Ebadarg);

-			va = strtoul(cb->f[1], 0, 0);

-			len = strtoul(cb->f[2], 0, 0);

+			va = strtoull(cb->f[1], 0, 0);

+			len = strtoull(cb->f[2], 0, 0);

 			top = PGROUND(va + len);

 			va = va&~(BY2PG-1);

-			len = (top - va) / BY2PG;

-			if(len == 0)

+			if(va == 0 || top > USTKTOP || top <= va)

 				error(Ebadarg);

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

+			len = (top - va) / BY2PG;

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

+				if(!iseve())

+					error(Eperm);

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

+			} else

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

 		} else

 			error(Ebadctl);

 		break;

@@ -559,6 +569,73 @@

 	}

 	pexit("done", 1);

+}

+

+/*

+ * allocate a fixed segment with sequential run of of adjacent

+ * user memory pages.

+ */

+static Segment*

+fixedseg(uintptr va, ulong len)

+{

+	KMap *k;

+	Segment *s;

+	Page **f, *p;

+	ulong n, i, j;

+	int color;

+

+	s = newseg(SG_FIXED, va, len);

+	if(waserror()){

+		putseg(s);

+		nexterror();

+	}

+	lock(&palloc);

+	i = 0;

+	p = palloc.pages;

+	color = getpgcolor(va);

+	for(n = palloc.user; n >= len; n--, p++){

+		if(p->ref != 0 || i != 0 && (p[-1].pa+BY2PG) != p->pa || i == 0 && p->color != color){

+		Retry:

+			i = 0;

+			continue;

+		}

+		if(++i < len)

+			continue;

+		for(j = 0; j < i; j++, p--){

+			for(f = &palloc.head; *f != nil; f = &((*f)->next)){

+				if(*f == p){

+					*f = p->next;

+					goto Freed;

+				}

+			}

+			while(j-- > 0)

+				pagechainhead(++p);

+			goto Retry;

+		Freed:

+			palloc.freecount--;

+		}

+		unlock(&palloc);

+

+		while(i-- > 0){

+			p++;

+			p->ref = 1;

+			p->va = va;

+			p->modref = 0;

+			p->txtflush = ~0;

+			

+			k = kmap(p);

+			memset((void*)VA(k), 0, BY2PG);

+			kunmap(k);

+			

+			segpage(s, p);

+			va += BY2PG;

+		}

+		poperror();

+		return s;

+	}

+	unlock(&palloc);

+	error(Enomem);

+	return nil;

 }

 Dev segmentdevtab = {

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

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

@@ -267,6 +267,7 @@

 			copypage(old, *pg);

 			putpage(old);

 		}

+	case SG_FIXED:			/* 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

@@ -341,6 +341,7 @@

 	SG_STACK	= 03,

 	SG_SHARED	= 04,

 	SG_PHYSICAL	= 05,

+	SG_FIXED	= 06,

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

 	SG_CEXEC	= 0100,		/* Detach at exec */

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

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

@@ -156,6 +156,7 @@

 	case SG_TEXT:		/* New segment shares pte set */

 	case SG_SHARED:

 	case SG_PHYSICAL:

+	case SG_FIXED:

 		goto sameseg;

 	case SG_STACK:

@@ -489,8 +490,11 @@

 	if(pages == 0)

 		return;

-	if((s->type&SG_TYPE) == SG_PHYSICAL)

+	switch(s->type&SG_TYPE){

+	case SG_PHYSICAL:

+	case SG_FIXED:

 		return;

+	}

 	/*

 	 * we have to make sure other processors flush the

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

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

@@ -751,6 +751,7 @@

 		case SG_DATA:

 		case SG_STACK:

 		case SG_PHYSICAL:

+		case SG_FIXED:

 			error(Ebadarg);

 		default:

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