From d8f42424ae0b69be7cdc0ddb04c1509219de51ec Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@centraldogma>
Date: Thu, 10 Nov 2011 04:41:32 +0100
Subject: [PATCH] 9boot: fix e820 scan

---
 sys/src/boot/pc/e820.s | 14 ++++++++++++--
 sys/src/boot/pc/sub.c  | 28 ++++++++++++++++++----------
 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/sys/src/boot/pc/e820.s b/sys/src/boot/pc/e820.s
index c830a64e6..71db6c53d 100644
--- a/sys/src/boot/pc/e820.s
+++ b/sys/src/boot/pc/e820.s
@@ -4,17 +4,27 @@
 TEXT e820(SB), $0
 	MOVL bx+4(SP), BX
 	MOVL p+8(SP), DI
-
-	MOVL $0xe820, AX
+	MOVL $0xE820, AX
 	MOVL $0x534D4150, DX
 	CALL rmode16(SB)
 	LWI(24, rCX)
 	BIOSCALL(0x15)
 	JC _bad
 	CALL16(pmode32(SB))
+	CMPB CL, $24
+	JZ _ret
+	MOVL $1, AX
+	MOVL AX, 20(DI)
+_ret:
 	MOVL BX, AX
 	RET
 _bad:
 	CALL16(pmode32(SB))
 	XORL AX, AX
+	MOVL AX, 0(DI)
+	MOVL AX, 4(DI)
+	MOVL AX, 8(DI)
+	MOVL AX, 12(DI)
+	MOVL AX, 16(DI)
+	MOVL AX, 20(DI)
 	RET
diff --git a/sys/src/boot/pc/sub.c b/sys/src/boot/pc/sub.c
index 8140508dc..fafe69ac0 100644
--- a/sys/src/boot/pc/sub.c
+++ b/sys/src/boot/pc/sub.c
@@ -340,27 +340,35 @@ e820conf(void)
 	ulong bx;
 	char *s;
 
-	memset(&e, 0, sizeof(e));
-	if((bx = e820(0, &e)) == 0)
-		return;
-
+	bx=0;
 	s = confend;
-	memmove(confend, "e820=", 5);
-	confend += 5;
 
 	do{
-		if(e.typ == 1 && (e.ext & 1) == 0 && e.len){
+		e.base = 0;
+		e.len = 0;
+		e.typ = 0;
+		e.ext = 1;
+		bx = e820(bx, &e);
+		if(e.typ == 1 && e.len != 0 && (e.ext & 3) == 1){
+			if(confend == s){
+				/* single entry <= 1MB is useless */
+				if(bx == 0 && e.len <= 0x100000)
+					break;
+				memmove(confend, "e820=", 5);
+				confend += 5;
+			}
 			v = e.base;
 			addconfx("", 8, v>>32);
 			addconfx("", 8, v&0xffffffff);
-			v = e.base + e.len;
+			v += e.len;
 			addconfx(" ", 8, v>>32);
 			addconfx("", 8, v&0xffffffff);
 			*confend++ = ' ';
 		}
+	} while(bx);
 
-		memset(&e, 0, sizeof(e));
-	} while(bx = e820(bx, &e));
+	if(confend == s)
+		return;
 
 	*confend = 0;
 	print(s); print(crnl);