1 files changed, 90 insertions, 0 deletions
diff --git a/mount/mount_guess_rootdev.c b/mount/mount_guess_rootdev.c
new file mode 100644
index 000000000..072c09fc4
--- /dev/null
+++ b/mount/mount_guess_rootdev.c
@@ -0,0 +1,90 @@
+/*
+ * Having the wrong rootdevice listed in mtab is slightly inconvenient.
+ * Try to guess what it could be...
+ * In case /proc/cmdline exists, and has the format
+ *	stuff root=R more stuff...
+ * and we think we understand the number R, decode it as a root device.
+ *
+ * Another possibility:
+ * Erik Andersen writes:
+ *  I did a similar find_real_root_device_name() in busybox some time back.  
+ *  Basically, do a stat("/", &rootstat) then walk /dev stat'ing each file
+ *  and if (statbuf.st_rdev == rootstat.st_rdev) then you have a match.
+ *  Works fine.
+ */
+#include <stdio.h>
+#include <string.h>
+#include "mount_guess_rootdev.h"
+
+#define PROC_CMDLINE	"/proc/cmdline"
+
+static char *
+rootdev(char *p) {
+	unsigned long devno;
+	char *ep;
+	char *type = "hd";
+	char let;
+	int ma, mi;
+	char devname[8];
+
+	devno = strtoul(p, &ep, 16);
+	if ((ep == p+3 || ep == p+4) && (*ep == ' ' || *ep == 0)) {
+		ma = (devno >> 8);
+		mi = (devno & 0xff);
+		switch(ma) {
+		case 8:
+			type = "sd";
+			let = 'a'+(mi/16);
+			mi = mi%16;
+			break;
+		case 3:
+			let = 'a'; break;
+		case 0x16:
+			let = 'c'; break;
+		case 0x21:
+			let = 'e'; break;
+		case 0x22:
+			let = 'g'; break;
+		case 0x38:
+			let = 'i'; break;
+		case 0x39:
+			let = 'k'; break;
+		default:
+			return NULL;
+		}
+		if (mi & 0x40) {
+			mi -= 0x40;
+			let++;
+		}
+		if (mi == 0)
+			sprintf(devname, "/dev/%s%c", type, let);
+		else
+			sprintf(devname, "/dev/%s%c%d", type, let, mi);
+		return strdup(devname);
+	}
+	return NULL;
+}
+
+char *
+mount_guess_rootdev() {
+	FILE *cf;
+	char line[1024];
+	char *p;
+
+	cf = fopen(PROC_CMDLINE, "r");
+	if (cf && fgets(line, sizeof(line), cf)) {
+		for (p = line; *p; p++)
+			if (!strncmp(p, " root=", 6))
+				return rootdev(p+6);
+	}
+	return NULL;
+}
+
+#if 0
+main(){
+	char *p = mount_guess_rootdev();
+	if (!p)
+		p = "/dev/root";
+	printf("%s\n", p);
+}
+#endif