20060303

1 files changed, 614 insertions, 0 deletions

diff --git a/os/boot/mpc/dosboot.c b/os/boot/mpc/dosboot.c
new file mode 100644
index 00000000..cd8d1276
--- /dev/null
+++ b/os/boot/mpc/dosboot.c
@@ -0,0 +1,614 @@
+#include	"u.h"
+#include	"lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"dosfs.h"
+
+extern char *premature;
+
+/*
+ *  predeclared
+ */
+static void	bootdump(Dosboot*);
+static void	setname(Dosfile*, char*);
+long		dosreadseg(Dosfile*, long, long);
+
+/*
+ *  debugging
+ */
+#define chatty	1
+#define chat	if(chatty)print
+
+/*
+ *  block io buffers
+ */
+enum
+{
+	Nbio=	16,
+};
+typedef struct	Clustbuf	Clustbuf;
+struct Clustbuf
+{
+	int	age;
+	long	sector;
+	uchar	*iobuf;
+	Dos	*dos;
+	int	size;
+};
+Clustbuf	bio[Nbio];
+
+/*
+ *  get an io block from an io buffer
+ */
+Clustbuf*
+getclust(Dos *dos, long sector)
+{
+	Clustbuf *p, *oldest;
+	int size;
+
+	chat("getclust @ %d\n", sector);
+
+	/*
+	 *  if we have it, just return it
+	 */
+	for(p = bio; p < &bio[Nbio]; p++){
+		if(sector == p->sector && dos == p->dos){
+			p->age = m->ticks;
+			chat("getclust %d in cache\n", sector);
+			return p;
+		}
+	}
+
+	/*
+	 *  otherwise, reuse the oldest entry
+	 */
+	oldest = bio;
+	for(p = &bio[1]; p < &bio[Nbio]; p++){
+		if(p->age <= oldest->age)
+			oldest = p;
+	}
+	p = oldest;
+
+	/*
+	 *  make sure the buffer is big enough
+	 */
+	size = dos->clustsize*dos->sectsize;
+	if(p->iobuf==0 || p->size < size)
+		p->iobuf = ialloc(size, 0);
+	p->size = size;
+
+	/*
+	 *  read in the cluster
+	 */
+	chat("getclust addr %d\n", (sector+dos->start)*dos->sectsize);
+	if((*dos->seek)(dos->dev, (sector+dos->start)*dos->sectsize) < 0){
+		chat("can't seek block\n");
+		return 0;
+	}
+	if((*dos->read)(dos->dev, p->iobuf, size) != size){
+		chat("can't read block\n");
+		return 0;
+	}
+
+	p->age = m->ticks;
+	p->dos = dos;
+	p->sector = sector;
+	chat("getclust %d read\n", sector);
+	return p;
+}
+
+/*
+ *  walk the fat one level ( n is a current cluster number ).
+ *  return the new cluster number or -1 if no more.
+ */
+static long
+fatwalk(Dos *dos, int n)
+{
+	ulong k, sect;
+	Clustbuf *p;
+	int o;
+
+	chat("fatwalk %d\n", n);
+
+	if(n < 2 || n >= dos->fatclusters)
+		return -1;
+
+	switch(dos->fatbits){
+	case 12:
+		k = (3*n)/2; break;
+	case 16:
+		k = 2*n; break;
+	default:
+		return -1;
+	}
+	if(k >= dos->fatsize*dos->sectsize)
+		panic("getfat");
+
+	sect = (k/(dos->sectsize*dos->clustsize))*dos->clustsize + dos->fataddr;
+	o = k%(dos->sectsize*dos->clustsize);
+	p = getclust(dos, sect);
+	k = p->iobuf[o++];
+	if(o >= dos->sectsize*dos->clustsize){
+		p = getclust(dos, sect+dos->clustsize);
+		o = 0;
+	}
+	k |= p->iobuf[o]<<8;
+	if(dos->fatbits == 12){
+		if(n&1)
+			k >>= 4;
+		else
+			k &= 0xfff;
+		if(k >= 0xff8)
+			k |= 0xf000;
+	}
+	k = k < 0xfff8 ? k : -1;
+	chat("fatwalk %d -> %d\n", n, k);
+	return k;
+}
+
+/*
+ *  map a file's logical cluster address to a physical sector address
+ */
+static long
+fileaddr(Dosfile *fp, long ltarget)
+{
+	Dos *dos = fp->dos;
+	long l;
+	long p;
+
+	chat("fileaddr %8.8s %d\n", fp->name, ltarget);
+	/*
+	 *  root directory is contiguous and easy
+	 */
+	if(fp->pstart == 0){
+		if(ltarget*dos->sectsize*dos->clustsize >= dos->rootsize*sizeof(Dosdir))
+			return -1;
+		l = dos->rootaddr + ltarget*dos->clustsize;
+		chat("fileaddr %d -> %d\n", ltarget, l);
+		return l;
+	}
+
+	/*
+	 *  anything else requires a walk through the fat
+	 */
+	if(ltarget >= fp->lcurrent && fp->pcurrent){
+		/* start at the currrent point */
+		l = fp->lcurrent;
+		p = fp->pcurrent;
+	} else {
+		/* go back to the beginning */
+		l = 0;
+		p = fp->pstart;
+	}
+	while(l != ltarget){
+		/* walk the fat */
+		p = fatwalk(dos, p);
+		if(p < 0)
+			return -1;
+		l++;
+	}
+	fp->lcurrent = l;
+	fp->pcurrent = p;
+
+	/*
+	 *  clusters start at 2 instead of 0 (why? - presotto)
+	 */
+	l =  dos->dataaddr + (p-2)*dos->clustsize;
+	chat("fileaddr %d -> %d\n", ltarget, l);
+	return l;
+}
+
+/*
+ *  read from a dos file
+ */
+long
+dosread(Dosfile *fp, void *a, long n)
+{
+	long addr;
+	long rv;
+	int i;
+	int off;
+	Clustbuf *p;
+	uchar *from, *to;
+
+	if((fp->attr & DDIR) == 0){
+		if(fp->offset >= fp->length)
+			return 0;
+		if(fp->offset+n > fp->length)
+			n = fp->length - fp->offset;
+	}
+
+	to = a;
+	for(rv = 0; rv < n; rv+=i){
+		/*
+		 *  read the cluster
+		 */
+		addr = fileaddr(fp, fp->offset/fp->dos->clustbytes);
+		if(addr < 0)
+			return -1;
+		p = getclust(fp->dos, addr);
+		if(p == 0)
+			return -1;
+
+		/*
+		 *  copy the bytes we need
+		 */
+		off = fp->offset % fp->dos->clustbytes;
+		from = &p->iobuf[off];
+		i = n - rv;
+		if(i > fp->dos->clustbytes - off)
+			i = fp->dos->clustbytes - off;
+		memmove(to, from, i);
+		to += i;
+		fp->offset += i;
+	}
+
+	return rv;
+}
+
+/*
+ *  walk a directory returns
+ * 	-1 if something went wrong
+ *	 0 if not found
+ *	 1 if found
+ */
+int
+doswalk(Dosfile *file, char *name)
+{
+	Dosdir d;
+	long n;
+
+	if((file->attr & DDIR) == 0){
+		chat("walking non-directory!\n");
+		return -1;
+	}
+
+	setname(file, name);
+
+	file->offset = 0;	/* start at the beginning */
+	while((n = dosread(file, &d, sizeof(d))) == sizeof(d)){
+		chat("comparing to %8.8s.%3.3s\n", d.name, d.ext);
+		if(memcmp(file->name, d.name, sizeof(d.name)) != 0)
+			continue;
+		if(memcmp(file->ext, d.ext, sizeof(d.ext)) != 0)
+			continue;
+		if(d.attr & DVLABEL){
+			chat("%8.8s.%3.3s is a LABEL\n", d.name, d.ext);
+			continue;
+		}
+		file->attr = d.attr;
+		file->pstart = GSHORT(d.start);
+		file->length = GLONG(d.length);
+		file->pcurrent = 0;
+		file->lcurrent = 0;
+		file->offset = 0;
+		return 1;
+	}
+	return n >= 0 ? 0 : -1;
+}
+
+
+/*
+ *  instructions that boot blocks can start with
+ */
+#define	JMPSHORT	0xeb
+#define JMPNEAR		0xe9
+
+/*
+ *  read dos file system properties
+ */
+int
+dosinit(Dos *dos, int start, int ishard)
+{
+	Dosboot *b;
+	int i;
+	Clustbuf *p;
+	Dospart *dp;
+	ulong mbroffset, offset;
+
+	/* defaults till we know better */
+	dos->start = start;
+	dos->sectsize = 512;
+	dos->clustsize = 1;
+	mbroffset = 0;
+
+dmddo:
+	/* get first sector */
+	p = getclust(dos, mbroffset);
+	if(p == 0){
+		chat("can't read boot block\n");
+		return -1;
+	}
+
+	/*
+	 * If it's a hard disc then look for an MBR and pick either an
+	 * active partition or the FAT with the lowest starting LBA.
+	 * Things are tricky because we could be pointing to, amongst others:
+	 *	1) a floppy BPB;
+	 *	2) a hard disc MBR;
+	 *	3) a hard disc extended partition table;
+	 *	4) a logical drive on a hard disc;
+	 *	5) a disc-manager boot block.
+	 * They all have the same magic at the end of the block.
+	 */
+	if(p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA) {
+		chat("not DOS\n");
+		return -1;
+	}
+	p->dos = 0;
+	b = (Dosboot *)p->iobuf;
+	if(ishard && b->mediadesc != 0xF8){
+		dp = (Dospart*)&p->iobuf[0x1BE];
+		offset = 0xFFFFFFFF;
+		for(i = 0; i < 4; i++, dp++){
+			if(dp->type == DMDDO){
+				mbroffset = 63;
+				goto dmddo;
+			}
+			if(dp->type != FAT12 && dp->type != FAT16 && dp->type != FATHUGE)
+				continue;
+			if(dp->flag & 0x80){
+				offset = GLONG(dp->start);
+				break;
+			}
+			if(GLONG(dp->start) < offset)
+				offset = GLONG(dp->start);
+		}
+		if(i != 4 || offset != 0xFFFFFFFF){
+			dos->start = mbroffset+offset;
+			p = getclust(dos, 0);
+			if(p == 0 || p->iobuf[0x1FE] != 0x55 || p->iobuf[0x1FF] != 0xAA)
+				return -1;
+		}
+		p->dos = 0;
+	}
+
+	b = (Dosboot *)p->iobuf;
+	if(b->magic[0] != JMPNEAR && (b->magic[0] != JMPSHORT || b->magic[2] != 0x90)){
+		chat("no dos file system\n");
+		return -1;
+	}
+
+	if(chatty)
+		bootdump(b);
+
+	/*
+	 *  determine the systems' wondersous properties
+	 */
+	dos->sectsize = GSHORT(b->sectsize);
+	dos->clustsize = b->clustsize;
+	dos->clustbytes = dos->sectsize*dos->clustsize;
+	dos->nresrv = GSHORT(b->nresrv);
+	dos->nfats = b->nfats;
+	dos->rootsize = GSHORT(b->rootsize);
+	dos->volsize = GSHORT(b->volsize);
+	if(dos->volsize == 0)
+		dos->volsize = GLONG(b->bigvolsize);
+	dos->mediadesc = b->mediadesc;
+	dos->fatsize = GSHORT(b->fatsize);
+	dos->fataddr = dos->nresrv;
+	dos->rootaddr = dos->fataddr + dos->nfats*dos->fatsize;
+	i = dos->rootsize*sizeof(Dosdir) + dos->sectsize - 1;
+	i = i/dos->sectsize;
+	dos->dataaddr = dos->rootaddr + i;
+	dos->fatclusters = 2+(dos->volsize - dos->dataaddr)/dos->clustsize;
+	if(dos->fatclusters < 4087)
+		dos->fatbits = 12;
+	else
+		dos->fatbits = 16;
+	dos->freeptr = 2;
+
+	/*
+	 *  set up the root
+	 */
+	dos->root.dos = dos;
+	dos->root.pstart = 0;
+	dos->root.pcurrent = dos->root.lcurrent = 0;
+	dos->root.offset = 0;
+	dos->root.attr = DDIR;
+	dos->root.length = dos->rootsize*sizeof(Dosdir);
+
+	return 0;
+}
+
+static void
+bootdump(Dosboot *b)
+{
+	if(chatty == 0)
+		return;
+	print("magic: 0x%2.2x 0x%2.2x 0x%2.2x\n",
+		b->magic[0], b->magic[1], b->magic[2]);
+	print("version: \"%8.8s\"\n", b->version);
+	print("sectsize: %d\n", GSHORT(b->sectsize));
+	print("allocsize: %d\n", b->clustsize);
+	print("nresrv: %d\n", GSHORT(b->nresrv));
+	print("nfats: %d\n", b->nfats);
+	print("rootsize: %d\n", GSHORT(b->rootsize));
+	print("volsize: %d\n", GSHORT(b->volsize));
+	print("mediadesc: 0x%2.2x\n", b->mediadesc);
+	print("fatsize: %d\n", GSHORT(b->fatsize));
+	print("trksize: %d\n", GSHORT(b->trksize));
+	print("nheads: %d\n", GSHORT(b->nheads));
+	print("nhidden: %d\n", GLONG(b->nhidden));
+	print("bigvolsize: %d\n", GLONG(b->bigvolsize));
+	print("driveno: %d\n", b->driveno);
+	print("reserved0: 0x%2.2x\n", b->reserved0);
+	print("bootsig: 0x%2.2x\n", b->bootsig);
+	print("volid: 0x%8.8x\n", GLONG(b->volid));
+	print("label: \"%11.11s\"\n", b->label);
+}
+
+/*
+ *  grab next element from a path, return the pointer to unprocessed portion of
+ *  path.
+ */
+static char *
+nextelem(char *path, char *elem)
+{
+	int i;
+
+	while(*path == '/')
+		path++;
+	if(*path==0 || *path==' ')
+		return 0;
+	for(i=0; *path!='\0' && *path!='/' && *path!=' '; i++){
+		if(i==28){
+			print("name component too long\n");
+			return 0;
+		}
+		*elem++ = *path++;
+	}
+	*elem = '\0';
+	return path;
+}
+
+int
+dosstat(Dos *dos, char *path, Dosfile *f)
+{
+	char element[NAMELEN];
+
+	*f = dos->root;
+	while(path = nextelem(path, element)){
+		switch(doswalk(f, element)){
+		case -1:
+			return -1;
+		case 0:
+			return 0;
+		}
+	}
+	return 1;
+}
+
+/*
+ *  boot
+ */
+int
+dosboot(Dos *dos, char *path)
+{
+	Dosfile file;
+	long n;
+	long addr;
+	Exec *ep;
+	void (*b)(void);
+
+	switch(dosstat(dos, path, &file)){
+
+	case -1:
+		print("error walking to %s\n", path);
+		return -1;
+	case 0:
+		print("%s not found\n", path);
+		return -1;
+	case 1:
+		print("found %8.8s.%3.3s attr 0x%ux start 0x%lux len %d\n", file.name,
+			file.ext, file.attr, file.pstart, file.length);
+		break;
+	}
+
+	/*
+	 *  read header
+	 */
+	ep = (Exec*)ialloc(sizeof(Exec), 0);
+	n = sizeof(Exec);
+	if(dosreadseg(&file, n, (ulong) ep) != n){
+		print(premature);
+		return -1;
+	}
+	if(GLLONG(ep->magic) != Q_MAGIC){
+		print("bad magic 0x%lux not a plan 9 executable!\n", GLLONG(ep->magic));
+		return -1;
+	}
+
+	/*
+	 *  read text
+	 */
+	addr = PADDR(GLLONG(ep->entry));
+	n = GLLONG(ep->text);
+	print("+%d", n);
+	if(dosreadseg(&file, n, addr) != n){
+		print(premature);
+		return -1;
+	}
+
+	/*
+	 *  read data (starts at first page after kernel)
+	 */
+	addr = PGROUND(addr+n);
+	n = GLLONG(ep->data);
+	print("+%d", n);
+	if(dosreadseg(&file, n, addr) != n){
+		print(premature);
+		return -1;
+	}
+
+	/*
+	 *  bss and entry point
+	 */
+	print("+%d\nstart at 0x%lux\n", GLLONG(ep->bss), GLLONG(ep->entry));
+
+	/*
+	 *  Go to new code. It's up to the program to get its PC relocated to
+	 *  the right place.
+	 */
+	b = (void (*)(void))(PADDR(GLLONG(ep->entry)));
+	(*b)();
+	return 0;
+}
+
+/*
+ *  read in a segment
+ */
+long
+dosreadseg(Dosfile *fp, long len, long addr)
+{
+	char *a;
+	long n, sofar;
+
+	a = (char *)addr;
+	for(sofar = 0; sofar < len; sofar += n){
+		n = 8*1024;
+		if(len - sofar < n)
+			n = len - sofar;
+		n = dosread(fp, a + sofar, n);
+		if(n <= 0)
+			break;
+		print(".");
+	}
+	return sofar;
+}
+
+/*
+ *  set up a dos file name
+ */
+static void
+setname(Dosfile *fp, char *from)
+{
+	char *to;
+
+	to = fp->name;
+	for(; *from && to-fp->name < 8; from++, to++){
+		if(*from == '.'){
+			from++;
+			break;
+		}
+		if(*from >= 'a' && *from <= 'z')
+			*to = *from + 'A' - 'a';
+		else
+			*to = *from;
+	}
+	while(to - fp->name < 8)
+		*to++ = ' ';
+	
+	to = fp->ext;
+	for(; *from && to-fp->ext < 3; from++, to++){
+		if(*from >= 'a' && *from <= 'z')
+			*to = *from + 'A' - 'a';
+		else
+			*to = *from;
+	}
+	while(to-fp->ext < 3)
+		*to++ = ' ';
+
+	chat("name is %8.8s %3.3s\n", fp->name, fp->ext);
+}