[PATCH] usr/gen_init_cpio.c: support for hard links

Extend usr/gen_init_cpio.c "file" entry, adding support for hard links.

Previous format:
file <name> <location> <mode> <uid> <gid>

New format:
file <name> <location> <mode> <uid> <gid> [<hard links>]

The hard links specification is optional, keeping the previous
behaviour.

All hard links are defined sequentially in the resulting cpio and the
file data is present only in the last link. This is the behaviour of
GNU's cpio and is supported by the kernel initramfs extractor.
Signed-off-by: Luciano Rocha <strange@nsk.no-ip.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

usr/gen_init_cpio.c

@@ -14,6 +14,7 @@
  * Original work by Jeff Garzik
  *
  * External file lists, symlink, pipe and fifo support by Thayne Harbaugh
+ * Hard link support by Luciano Rocha
  */
 
 #define xstr(s) #s
@@ -286,16 +287,19 @@ static int cpio_mknod_line(const char *line)
 	return rc;
 }
 
-/* Not marked static to keep the compiler quiet, as no one uses this yet... */
 static int cpio_mkfile(const char *name, const char *location,
-			unsigned int mode, uid_t uid, gid_t gid)
+			unsigned int mode, uid_t uid, gid_t gid,
+			unsigned int nlinks)
 {
 	char s[256];
 	char *filebuf = NULL;
 	struct stat buf;
+	long size;
 	int file = -1;
 	int retval;
 	int rc = -1;
+	int namesize;
+	int i;
 
 	mode |= S_IFREG;
 
@@ -323,29 +327,41 @@ static int cpio_mkfile(const char *name, const char *location,
 		goto error;
 	}
 
+	size = 0;
+	for (i = 1; i <= nlinks; i++) {
+		/* data goes on last link */
+		if (i == nlinks) size = buf.st_size;
+
+		namesize = strlen(name) + 1;
 		sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX"
-	       "%08X%08X%08X%08X%08X%08X%08X",
+		       "%08lX%08X%08X%08X%08X%08X%08X",
 			"070701",		/* magic */
-		ino++,			/* ino */
+			ino,			/* ino */
 			mode,			/* mode */
 			(long) uid,		/* uid */
 			(long) gid,		/* gid */
-		1,			/* nlink */
+			nlinks,			/* nlink */
 			(long) buf.st_mtime,	/* mtime */
-		(int) buf.st_size,	/* filesize */
+			size,			/* filesize */
 			3,			/* major */
 			1,			/* minor */
 			0,			/* rmajor */
 			0,			/* rminor */
-		(unsigned)strlen(name) + 1,/* namesize */
+			namesize,		/* namesize */
 			0);			/* chksum */
 		push_hdr(s);
 		push_string(name);
 		push_pad();
 
-	fwrite(filebuf, buf.st_size, 1, stdout);
-	offset += buf.st_size;
+		if (size) {
+			fwrite(filebuf, size, 1, stdout);
+			offset += size;
 			push_pad();
+		}
+
+		name += namesize;
+	}
+	ino++;
 	rc = 0;
 	
 error:
@@ -357,18 +373,51 @@ error:
 static int cpio_mkfile_line(const char *line)
 {
 	char name[PATH_MAX + 1];
+	char *dname = NULL; /* malloc'ed buffer for hard links */
 	char location[PATH_MAX + 1];
 	unsigned int mode;
 	int uid;
 	int gid;
+	int nlinks = 1;
+	int end = 0, dname_len = 0;
 	int rc = -1;
 
-	if (5 != sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX) "s %o %d %d", name, location, &mode, &uid, &gid)) {
+	if (5 > sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX)
+				"s %o %d %d %n",
+				name, location, &mode, &uid, &gid, &end)) {
 		fprintf(stderr, "Unrecognized file format '%s'", line);
 		goto fail;
 	}
-	rc = cpio_mkfile(name, location, mode, uid, gid);
+	if (end && isgraph(line[end])) {
+		int len;
+		int nend;
+
+		dname = malloc(strlen(line));
+		if (!dname) {
+			fprintf (stderr, "out of memory (%d)\n", dname_len);
+			goto fail;
+		}
+
+		dname_len = strlen(name) + 1;
+		memcpy(dname, name, dname_len);
+
+		do {
+			nend = 0;
+			if (sscanf(line + end, "%" str(PATH_MAX) "s %n",
+					name, &nend) < 1)
+				break;
+			len = strlen(name) + 1;
+			memcpy(dname + dname_len, name, len);
+			dname_len += len;
+			nlinks++;
+			end += nend;
+		} while (isgraph(line[end]));
+	} else {
+		dname = name;
+	}
+	rc = cpio_mkfile(dname, location, mode, uid, gid, nlinks);
  fail:
+	if (dname_len) free(dname);
 	return rc;
 }
 
@@ -381,7 +430,7 @@ void usage(const char *prog)
 		"describe the files to be included in the initramfs archive:\n"
 		"\n"
 		"# a comment\n"
-		"file <name> <location> <mode> <uid> <gid>\n"
+		"file <name> <location> <mode> <uid> <gid> [<hard links>]\n"
 		"dir <name> <mode> <uid> <gid>\n"
 		"nod <name> <mode> <uid> <gid> <dev_type> <maj> <min>\n"
 		"slink <name> <target> <mode> <uid> <gid>\n"
@@ -397,6 +446,7 @@ void usage(const char *prog)
 		"<dev_type>   device type (b=block, c=character)\n"
 		"<maj>        major number of nod\n"
 		"<min>        minor number of nod\n"
+		"<hard links> space separated list of other links to file\n"
 		"\n"
 		"example:\n"
 		"# A simple initramfs\n"