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e820: handle duplicate and overlapping e820 entries, handle overflows

new algorithm:

sort entries by top address first. then for each entry we use:

base = max(base, last)

so we'll never map the same addresses twice.

--- a/sys/src/9/pc/memory.c

+++ b/sys/src/9/pc/memory.c

@@ -568,7 +568,7 @@

 {

 	int type;

 	uvlong base;

-	uvlong len;

+	uvlong top;

 };

 static Emap emap[128];

 int nemap;

@@ -580,11 +580,15 @@

 	a = (Emap*)va;

 	b = (Emap*)vb;

+	if(a->top < b->top)

+		return -1;

+	if(a->top > b->top)

+		return 1;

 	if(a->base < b->base)

 		return -1;

 	if(a->base > b->base)

 		return 1;

-	return a->len - b->len;

+	return 0;

 }

 static void

@@ -592,7 +596,7 @@

 {

 	ulong e, n;

 	ulong *table, flags, maxkpa;

-	

+

 	/*

 	 * Split any call crossing MemMin to make below simpler.

 	 */

@@ -611,7 +615,7 @@

 	/*

 	 * Any non-memory below 16*MB is used as upper mem blocks.

 	 */

-	if(type == MemUPA && base < 16*MB && base+len > 16*MB){

+	if(type == MemUPA && base < 16*MB && len > 16*MB-base){

 		map(base, 16*MB-base, MemUMB);

 		map(16*MB, len-(16*MB-base), MemUPA);

 		return;

@@ -633,7 +637,7 @@

 	 * Memory between KTZERO and end is the kernel itself

 	 * and is already mapped.

 	 */

-	if(base < PADDR(KTZERO) && base+len > PADDR(KTZERO)){

+	if(base < PADDR(KTZERO) && len > PADDR(KTZERO)-base){

 		map(base, PADDR(KTZERO)-base, type);

 		return;

 	}

@@ -697,8 +701,7 @@

 static int

 e820scan(void)

 {

-	ulong base, len;

-	uvlong last;

+	ulong base, len, last;

 	Emap *e;

 	char *s;

 	int i;

@@ -707,7 +710,8 @@

 	if((s = getconf("*e820")) == nil)

 		if((s = getconf("e820")) == nil)

 			return -1;

-	for(nemap = 0; nemap < nelem(emap); nemap++){

+	nemap = 0;

+	while(nemap < nelem(emap)){

 		while(*s == ' ')

 			s++;

 		if(*s == 0)

@@ -721,10 +725,11 @@

 		e->base = strtoull(s, &s, 16);

 		if(*s != ' ')

 			break;

-		e->len = strtoull(s, &s, 16);

-		if(*s != ' ' && *s != 0 || e->len <= e->base)

+		e->top  = strtoull(s, &s, 16);

+		if(*s != ' ' && *s != 0)

 			break;

-		e->len -= e->base;

+		if(e->base < e->top)

+			nemap++;

 	}

 	if(nemap == 0)

 		return -1;

@@ -735,23 +740,30 @@

 		/*

 		 * pull out the info but only about the low 32 bits...

 		 */

-		if(e->base >= (1LL<<32))

+		if(e->base >= (1ULL<<32))

 			break;

-		base = e->base;

-		if(base+e->len > (1LL<<32))

+		if(e->top <= last)

+			continue;

+		if(e->base < last)

+			base = last;

+		else

+			base = e->base;

+		if(e->top > (1ULL<<32))

 			len = -base;

 		else

-			len = e->len;

+			len = e->top - base;

 		/*

 		 * If the map skips addresses, mark them available.

 		 */

-		if(last < e->base)

-			map(last, e->base-last, MemUPA);

-		last = base+len;

+		if(last < base)

+			map(last, base-last, MemUPA);

 		map(base, len, (e->type == 1) ? MemRAM : MemReserved);

+		last = base + len;

+		if(last == 0)

+			break;

 	}

-	if(last < (1LL<<32))

-		map(last, (u32int)-last, MemUPA);

+	if(last != 0)

+		map(last, -last, MemUPA);

 	return 0;

 }

-- 

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