add unified sigsearch() function to look for bios data structures

replace the various functions that searched for bios data structures by
a single sigsearch() one in pc/memory.c that will probe the various bios
data areas.

also, a new checksum() function was added that is to be used to validate
the structures found.

1 files changed, 3 insertions, 59 deletions

diff --git a/sys/src/9/pc/archmp.c b/sys/src/9/pc/archmp.c
index 7d72e0462..3247e04f5 100644
--- a/sys/src/9/pc/archmp.c
+++ b/sys/src/9/pc/archmp.c
@@ -354,51 +354,6 @@ pcmpinit(void)
 	mpinit();
 }
 
-static _MP_*
-mpscan(uchar *addr, int len)
-{
-	uchar *e, *p, sum;
-	int i;
-
-	e = addr+len;
-	for(p = addr; p < e; p += sizeof(_MP_)){
-		if(memcmp(p, "_MP_", 4))
-			continue;
-		sum = 0;
-		for(i = 0; i < sizeof(_MP_); i++)
-			sum += p[i];
-		if(sum == 0)
-			return (_MP_*)p;
-	}
-	return 0;
-}
-
-static _MP_*
-mpsearch(void)
-{
-	uchar *bda;
-	ulong p;
-	_MP_ *mp;
-
-	/*
-	 * Search for the MP Floating Pointer Structure:
-	 * 1) in the first KB of the EBDA;
-	 * 2) in the last KB of system base memory;
-	 * 3) in the BIOS ROM between 0xE0000 and 0xFFFFF.
-	 */
-	bda = KADDR(0x400);
-	if((p = (bda[0x0F]<<8)|bda[0x0E])){
-		if(mp = mpscan(KADDR(p<<4), 1024))
-			return mp;
-	}
-	else{
-		p = ((bda[0x14]<<8)|bda[0x13])*1024;
-		if(mp = mpscan(KADDR(p-1024), 1024))
-			return mp;
-	}
-	return mpscan(KADDR(0xF0000), 0x10000);
-}
-
 static int identify(void);
 
 PCArch archmp = {
@@ -418,8 +373,6 @@ identify(void)
 {
 	char *cp;
 	_MP_ *_mp_;
-	uchar *p, sum;
-	ulong length;
 
 	if((cp = getconf("*nomp")) != nil && strcmp(cp, "0") != 0)
 		return 1;
@@ -431,21 +384,12 @@ identify(void)
 	 * if correct, check the version.
 	 * To do: check extended table checksum.
 	 */
-	if((_mp_ = mpsearch()) == 0 || _mp_->physaddr == 0)
+	if((_mp_ = sigsearch("_MP_")) == 0 || _mp_->physaddr == 0)
 		return 1;
 
 	pcmp = KADDR(_mp_->physaddr);
-	if(memcmp(pcmp, "PCMP", 4)){
-		pcmp = nil;
-		return 1;
-	}
-
-	length = pcmp->length;
-	sum = 0;
-	for(p = (uchar*)pcmp; length; length--)
-		sum += *p++;
-
-	if(sum || (pcmp->version != 1 && pcmp->version != 4)){
+	if(memcmp(pcmp, "PCMP", 4) || checksum(pcmp, pcmp->length) || 
+	   (pcmp->version != 1 && pcmp->version != 4)) {
 		pcmp = nil;
 		return 1;
 	}