shithub: riscv

Download patch

ref: 529082d34d2bafd81d5987a2ed646c3a3c88a0a2
parent: 5a6131ea0919726bee4cba03a7a5361e6ea6df92
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Thu Nov 20 14:05:43 EST 2014 

pc, pc64: preserve last KB of conventional memory (might contain bios tables)

we add new function convmemsize() that returns the size of
*usable* conventional memory that does some sanity checking
and reserves the last KB below the top of memory pointer.

this avoids lowraminit() overriding potential bios tables
and sigsearch() going off the rails looking for tables
at above 640K.


--- a/sys/src/9/pc/memory.c
+++ b/sys/src/9/pc/memory.c
@@ -340,6 +340,24 @@
 	return nil;
 }
 
+static uintptr
+convmemsize(void)
+{
+	uintptr top;
+	uchar *bda;
+
+	bda = KADDR(0x400);
+	top = ((bda[0x14]<<8) | bda[0x13])*KB;
+
+	if(top < 64*KB || top > 640*KB)
+		top = 640*KB;	/* sanity */
+
+	/* reserved for bios tables (EBDA) */
+	top -= 1*KB;
+
+	return top;
+}
+
 void*
 sigsearch(char* signature)
 {
@@ -362,11 +380,9 @@
 				return r;
 		}
 	}
+	if((r = sigscan(KADDR(convmemsize()), 1024, signature)) != nil)
+		return r;
 
-	if((p = ((bda[0x14]<<8)|bda[0x13])*1024) != 0){
-		if((r = sigscan(KADDR(p-1024), 1024, signature)) != nil)
-			return r;
-	}
 	/* hack for virtualbox: look in KiB below 0xa0000 */
 	if((r = sigscan(KADDR(0xa0000-1024), 1024, signature)) != nil)
 		return r;
@@ -377,8 +393,7 @@
 static void
 lowraminit(void)
 {
-	ulong pa, x;
-	uchar *bda;
+	uintptr pa, x;
 
 	/*
 	 * Initialise the memory bank information for conventional memory
@@ -387,16 +402,13 @@
 	 * the BIOS data area.
 	 */
 	x = PADDR(CPU0END);
-	bda = (uchar*)KADDR(0x400);
-	pa = ((bda[0x14]<<8)|bda[0x13])*KB;
-	if(pa > 640*KB)
-		pa = 640*KB;
+	pa = convmemsize();
 	if(x < pa){
 		mapfree(&rmapram, x, pa-x);
 		memset(KADDR(x), 0, pa-x);		/* keep us honest */
 	}
 
-	x = PADDR(PGROUND((ulong)end));
+	x = PADDR(PGROUND((uintptr)end));
 	pa = MemMin;
 	if(x > pa)
 		panic("kernel too big");
--- a/sys/src/9/pc64/memory.c
+++ b/sys/src/9/pc64/memory.c
@@ -337,6 +337,24 @@
 	return nil;
 }
 
+static uintptr
+convmemsize(void)
+{
+	uintptr top;
+	uchar *bda;
+
+	bda = KADDR(0x400);
+	top = ((bda[0x14]<<8) | bda[0x13])*KB;
+
+	if(top < 64*KB || top > 640*KB)
+		top = 640*KB;	/* sanity */
+
+	/* reserved for bios tables (EBDA) */
+	top -= 1*KB;
+
+	return top;
+}
+
 void*
 sigsearch(char* signature)
 {
@@ -359,11 +377,9 @@
 				return r;
 		}
 	}
+	if((r = sigscan(KADDR(convmemsize()), 1024, signature)) != nil)
+		return r;
 
-	if((p = ((bda[0x14]<<8)|bda[0x13])*1024) != 0){
-		if((r = sigscan(KADDR(p-1024), 1024, signature)) != nil)
-			return r;
-	}
 	/* hack for virtualbox: look in KiB below 0xa0000 */
 	if((r = sigscan(KADDR(0xa0000-1024), 1024, signature)) != nil)
 		return r;
@@ -375,7 +391,6 @@
 lowraminit(void)
 {
 	uintptr pa, x;
-	uchar *bda;
 
 	/*
 	 * Initialise the memory bank information for conventional memory
@@ -384,10 +399,7 @@
 	 * the BIOS data area.
 	 */
 	x = PADDR(CPU0END);
-	bda = (uchar*)KADDR(0x400);
-	pa = ((bda[0x14]<<8)|bda[0x13])*KB;
-	if(pa > 640*KB)
-		pa = 640*KB;
+	pa = convmemsize();
 	if(x < pa){
 		mapfree(&rmapram, x, pa-x);
 		memset(KADDR(x), 0, pa-x);		/* keep us honest */