1 files changed, 108 insertions, 0 deletions
diff --git a/os/boot/pc/bootld.c b/os/boot/pc/bootld.c
new file mode 100644
index 00000000..e60b2389
--- /dev/null
+++ b/os/boot/pc/bootld.c
@@ -0,0 +1,108 @@
+#include "u.h"
+#include "lib.h"
+#include "mem.h"
+#include "dat.h"
+#include "fns.h"
+#include "io.h"
+
+static int
+addbytes(char **dbuf, char *edbuf, char **sbuf, char *esbuf)
+{
+	int n;
+
+	n = edbuf - *dbuf;
+	if(n <= 0)
+		return 0;
+	if(n > esbuf - *sbuf)
+		n = esbuf - *sbuf;
+	if(n <= 0)
+		return -1;
+
+	memmove(*dbuf, *sbuf, n);
+	*sbuf += n;
+	*dbuf += n;
+	return edbuf - *dbuf;
+}
+
+extern void origin(void);
+
+int
+bootpass(Boot *b, void *vbuf, int nbuf)
+{
+	char *buf, *ebuf, *p, *q;
+	ulong size;
+
+	if(b->state == FAILED)
+		return FAIL;
+
+	if(nbuf == 0)
+		goto Endofinput;
+
+	buf = vbuf;
+	ebuf = buf+nbuf;
+	while(addbytes(&b->wp, b->ep, &buf, ebuf) == 0) {
+		switch(b->state) {
+		case INIT9LOAD:
+			b->state = READ9LOAD;
+			b->bp = (char*)0x10000;
+			b->wp = b->bp;
+			b->ep = b->bp + 256*1024;
+			break;
+
+		case READ9LOAD:
+			return ENOUGH;
+
+		default:
+			panic("bootstate");
+		}
+	}
+	return MORE;
+
+
+Endofinput:
+	/* end of input */
+	print("\n");
+	switch(b->state) {
+	case INIT9LOAD:
+		print("premature EOF\n");
+		b->state = FAILED;
+		return FAIL;
+	
+	case READ9LOAD:
+		size = b->wp - b->bp;
+		if(memcmp(b->bp, origin, 16) != 0) {
+			print("beginning of file does not look right\n");
+			b->state = FAILED;
+			return FAIL;
+		}
+		if(size < 32*1024 || size > 256*1024) {
+			print("got %lud byte loader; not likely\n", size);
+			b->state = FAILED;
+			return FAIL;
+		}
+
+		p = b->bp;
+		q = b->wp;
+		if(q - p > 10000)	/* don't search much past l.s */
+			q = p+10000;
+
+		/*
+		 * The string `JUMP' appears right before
+		 * tokzero, which is where we want to jump.
+		 */
+		for(; p<q; p++) {
+			if(strncmp(p, "JUMP", 4) == 0) {
+				p += 4;
+				warp9((ulong)p);
+			}
+		}
+		print("could not find jump destination\n");
+		b->state = FAILED;
+		return FAIL;
+
+	default:
+		panic("bootdone");
+	}
+	b->state = FAILED;
+	return FAIL;
+}