gen_init_cpio: generate PWB-type cpio imagesHEADmaster

NOTE: I have been unable to make it generate cpio images that are inline
with the actual cpio utility.  Your mileage may vary when not using this
with your own tools.

2 files changed, 545 insertions, 164 deletions

diff --git a/gen_init_cpio.c b/gen_init_cpio.c
index 694b88c..ea8eb0a 100644
--- a/gen_init_cpio.c
+++ b/gen_init_cpio.c
@@ -18,6 +18,7 @@
 #include <errno.h>
 #include <ctype.h>
 #include <limits.h>
+#include <endian.h>
 
 /*
  * Original work by Jeff Garzik
@@ -29,9 +30,7 @@
 #define xstr(s) #s
 #define str(s) xstr(s)
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
-#define CPIO_HDR_LEN 110
 #define CPIO_TRAILER "TRAILER!!!"
-#define padlen(_off, _align) (((_align) - ((_off) & ((_align) - 1))) % (_align))
 
 /* zero-padding the filename field for data alignment is limited by PATH_MAX */
 static char padding[PATH_MAX];
@@ -39,36 +38,39 @@ static unsigned int offset;
 static unsigned int ino = 721;
 static time_t default_mtime;
 static bool do_file_mtime;
-static bool do_csum = false;
 static int outfd = STDOUT_FILENO;
 static unsigned int dalign;
 
+#pragma pack(1)
+struct header_pwb_cpio {
+    uint16_t h_magic;
+    uint16_t h_dev;
+    uint16_t h_ino;
+    uint16_t h_mode;
+    uint16_t h_uid;
+    uint16_t h_gid;
+    uint16_t h_nlink;
+    uint16_t h_majmin;
+    uint32_t h_mtime;
+    uint16_t h_namesize;
+    uint32_t h_filesize;
+};
+#define CPIO_HDR_LEN sizeof(struct header_pwb_cpio)
+
 struct file_handler {
 	const char *type;
 	int (*handler)(const char *line);
 };
 
-static int push_buf(const char *name, size_t name_len)
-{
-	ssize_t len;
-
-	len = write(outfd, name, name_len);
-	if (len != name_len)
-		return -1;
-
-	offset += name_len;
-	return 0;
-}
-
-static int push_pad(size_t padlen)
+static int push_pad()
 {
 	ssize_t len = 0;
+    size_t padlen = offset % 2;
 
 	if (!padlen)
 		return 0;
 
-	if (padlen < sizeof(padding))
-		len = write(outfd, padding, padlen);
+	len = write(outfd, padding, padlen);
 	if (len != padlen)
 		return -1;
 
@@ -76,7 +78,7 @@ static int push_pad(size_t padlen)
 	return 0;
 }
 
-static int push_rest(const char *name, size_t name_len)
+static int push_buf(const char *name, size_t name_len)
 {
 	ssize_t len;
 
@@ -85,36 +87,32 @@ static int push_rest(const char *name, size_t name_len)
 		return -1;
 
 	offset += name_len;
-
-	return push_pad(padlen(name_len + CPIO_HDR_LEN, 4));
+	return push_pad();
 }
 
 static int cpio_trailer(void)
 {
-	int len;
+    int len;
 	unsigned int namesize = sizeof(CPIO_TRAILER);
 
-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
-	       "%08X%08X%08X%08X%08X%08X%08X",
-		do_csum ? "070702" : "070701", /* magic */
-		0,			/* ino */
-		0,			/* mode */
-		(long) 0,		/* uid */
-		(long) 0,		/* gid */
-		1,			/* nlink */
-		(long) 0,		/* mtime */
-		0,			/* filesize */
-		0,			/* major */
-		0,			/* minor */
-		0,			/* rmajor */
-		0,			/* rminor */
-		namesize,		/* namesize */
-		0);			/* chksum */
+    struct header_pwb_cpio header = {
+        .h_magic = 070707,
+        .h_dev = 0,
+        .h_ino = 0,
+        .h_mode = 0,
+        .h_uid = 0,
+        .h_gid = 0,
+        .h_nlink = 1,
+        .h_majmin = 0,
+        .h_mtime = 0,
+        .h_namesize = namesize,
+        .h_filesize = 0
+    };
+    len = write(outfd, &header, CPIO_HDR_LEN);
 	offset += len;
 
 	if (len != CPIO_HDR_LEN ||
-	    push_rest(CPIO_TRAILER, namesize) < 0 ||
-	    push_pad(padlen(offset, 512)) < 0)
+	    push_buf(CPIO_TRAILER, namesize) < 0)
 		return -1;
 
 	if (fsync(outfd) < 0 && errno != EINVAL)
@@ -127,35 +125,31 @@ static int cpio_mkslink(const char *name, const char *target,
 			 unsigned int mode, uid_t uid, gid_t gid)
 {
 	int len;
-	unsigned int namesize, targetsize = strlen(target) + 1;
+	unsigned int namesize, targetsize = strlen(target);
 
 	if (name[0] == '/')
 		name++;
-	namesize = strlen(name) + 1;
-
-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
-	       "%08X%08X%08X%08X%08X%08X%08X",
-		do_csum ? "070702" : "070701", /* magic */
-		ino++,			/* ino */
-		S_IFLNK | mode,		/* mode */
-		(long) uid,		/* uid */
-		(long) gid,		/* gid */
-		1,			/* nlink */
-		(long) default_mtime,	/* mtime */
-		targetsize,		/* filesize */
-		3,			/* major */
-		1,			/* minor */
-		0,			/* rmajor */
-		0,			/* rminor */
-		namesize,		/* namesize */
-		0);			/* chksum */
+	namesize = strlen(name);
+
+    struct header_pwb_cpio header = {
+        .h_magic = 070707,
+        .h_dev = 0,
+        .h_ino = ino++,
+        .h_mode = S_IFLNK | mode,
+        .h_uid = uid,
+        .h_gid = gid,
+        .h_nlink = 1,
+        .h_majmin = 0,
+        .h_mtime = default_mtime,
+        .h_namesize = namesize,
+        .h_filesize = htobe32(targetsize)
+    };
+    len = write(outfd, &header, CPIO_HDR_LEN);
 	offset += len;
 
 	if (len != CPIO_HDR_LEN ||
 	    push_buf(name, namesize) < 0 ||
-	    push_pad(padlen(offset, 4)) < 0 ||
-	    push_buf(target, targetsize) < 0 ||
-	    push_pad(padlen(offset, 4)) < 0)
+	    push_buf(target, targetsize) < 0)
 		return -1;
 
 	return 0;
@@ -190,26 +184,24 @@ static int cpio_mkgeneric(const char *name, unsigned int mode,
 		name++;
 	namesize = strlen(name) + 1;
 
-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
-	       "%08X%08X%08X%08X%08X%08X%08X",
-		do_csum ? "070702" : "070701", /* magic */
-		ino++,			/* ino */
-		mode,			/* mode */
-		(long) uid,		/* uid */
-		(long) gid,		/* gid */
-		2,			/* nlink */
-		(long) default_mtime,	/* mtime */
-		0,			/* filesize */
-		3,			/* major */
-		1,			/* minor */
-		0,			/* rmajor */
-		0,			/* rminor */
-		namesize,		/* namesize */
-		0);			/* chksum */
+    struct header_pwb_cpio header = {
+        .h_magic = 070707,
+        .h_dev = 0,
+        .h_ino = ino++,
+        .h_mode = mode,
+        .h_uid = uid,
+        .h_gid = gid,
+        .h_nlink = 2,
+        .h_majmin = 0,
+        .h_mtime = default_mtime,
+        .h_namesize = namesize,
+        .h_filesize = 0
+    };
+    len = write(outfd, &header, CPIO_HDR_LEN);
 	offset += len;
 
 	if (len != CPIO_HDR_LEN ||
-	    push_rest(name, namesize) < 0)
+	    push_buf(name, namesize) < 0)
 		return -1;
 
 	return 0;
@@ -291,26 +283,24 @@ static int cpio_mknod(const char *name, unsigned int mode,
 		name++;
 	namesize = strlen(name) + 1;
 
-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
-	       "%08X%08X%08X%08X%08X%08X%08X",
-		do_csum ? "070702" : "070701", /* magic */
-		ino++,			/* ino */
-		mode,			/* mode */
-		(long) uid,		/* uid */
-		(long) gid,		/* gid */
-		1,			/* nlink */
-		(long) default_mtime,	/* mtime */
-		0,			/* filesize */
-		3,			/* major */
-		1,			/* minor */
-		maj,			/* rmajor */
-		min,			/* rminor */
-		namesize,		/* namesize */
-		0);			/* chksum */
+    struct header_pwb_cpio header = {
+        .h_magic = 070707,
+        .h_dev = 0,
+        .h_ino = ino++,
+        .h_mode = mode,
+        .h_uid = uid,
+        .h_gid = gid,
+        .h_nlink = 1,
+        .h_majmin = (maj << 8) | min,
+        .h_mtime = default_mtime,
+        .h_namesize = namesize,
+        .h_filesize = 0
+    };
+    len = write(outfd, &header, CPIO_HDR_LEN);
 	offset += len;
 
 	if (len != CPIO_HDR_LEN ||
-	    push_rest(name, namesize) < 0)
+	    push_buf(name, namesize) < 0)
 		return -1;
 
 	return 0;
@@ -337,29 +327,6 @@ static int cpio_mknod_line(const char *line)
 	return rc;
 }
 
-static int cpio_mkfile_csum(int fd, unsigned long size, uint32_t *csum)
-{
-	while (size) {
-		unsigned char filebuf[65536];
-		ssize_t this_read;
-		size_t i, this_size = MIN(size, sizeof(filebuf));
-
-		this_read = read(fd, filebuf, this_size);
-		if (this_read <= 0 || this_read > this_size)
-			return -1;
-
-		for (i = 0; i < this_read; i++)
-			*csum += filebuf[i];
-
-		size -= this_read;
-	}
-	/* seek back to the start for data segment I/O */
-	if (lseek(fd, 0, SEEK_SET) < 0)
-		return -1;
-
-	return 0;
-}
-
 static int cpio_mkfile(const char *name, const char *location,
 			unsigned int mode, uid_t uid, gid_t gid,
 			unsigned int nlinks)
@@ -369,9 +336,8 @@ static int cpio_mkfile(const char *name, const char *location,
 	int file, retval, len;
 	int rc = -1;
 	time_t mtime;
-	int namesize, namepadlen;
+	int namesize;
 	unsigned int i;
-	uint32_t csum = 0;
 	ssize_t this_read;
 
 	mode |= S_IFREG;
@@ -411,13 +377,7 @@ static int cpio_mkfile(const char *name, const char *location,
 		goto error;
 	}
 
-	if (do_csum && cpio_mkfile_csum(file, buf.st_size, &csum) < 0) {
-		fprintf(stderr, "Failed to checksum file %s\n", location);
-		goto error;
-	}
-
 	size = 0;
-	namepadlen = 0;
 	for (i = 1; i <= nlinks; i++) {
 		if (name[0] == '/')
 			name++;
@@ -427,38 +387,24 @@ static int cpio_mkfile(const char *name, const char *location,
 		if (i == nlinks)
 			size = buf.st_size;
 
-		if (dalign && size > dalign) {
-			namepadlen = padlen(offset + CPIO_HDR_LEN + namesize,
-					    dalign);
-			if (namesize + namepadlen > PATH_MAX) {
-				fprintf(stderr,
-					"%s: best-effort alignment %u missed\n",
-					name, dalign);
-				namepadlen = 0;
-			}
-		}
-
-		len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
-		       "%08lX%08X%08X%08X%08X%08X%08X",
-			do_csum ? "070702" : "070701", /* magic */
-			ino,			/* ino */
-			mode,			/* mode */
-			(long) uid,		/* uid */
-			(long) gid,		/* gid */
-			nlinks,			/* nlink */
-			(long) mtime,		/* mtime */
-			size,			/* filesize */
-			3,			/* major */
-			1,			/* minor */
-			0,			/* rmajor */
-			0,			/* rminor */
-			namesize + namepadlen,	/* namesize */
-			size ? csum : 0);	/* chksum */
+        struct header_pwb_cpio header = {
+            .h_magic = 070707,
+            .h_dev = buf.st_dev,
+            .h_ino = buf.st_ino,
+            .h_mode = mode,
+            .h_uid = uid,
+            .h_gid = gid,
+            .h_nlink = 1,
+            .h_majmin = 0,
+            .h_mtime = htobe32(mtime),
+            .h_namesize = namesize,
+            .h_filesize = htobe32(size)
+        };
+        len = write(outfd, &header, CPIO_HDR_LEN);
 		offset += len;
 
 		if (len != CPIO_HDR_LEN ||
-		    push_buf(name, namesize) < 0 ||
-		    push_pad(namepadlen ? namepadlen : padlen(offset, 4)) < 0)
+		    push_buf(name, namesize) < 0)
 			goto error;
 
 		if (size) {
@@ -489,7 +435,7 @@ static int cpio_mkfile(const char *name, const char *location,
 			offset += this_read;
 			size -= this_read;
 		}
-		if (push_pad(padlen(offset, 4)) < 0)
+		if (push_pad() < 0)
 			goto error;
 
 		name += namesize;
@@ -575,7 +521,7 @@ static int cpio_mkfile_line(const char *line)
 static void usage(const char *prog)
 {
 	fprintf(stderr, "Usage:\n"
-		"\t%s [-t <timestamp>] [-c] [-o <output_file>] [-a <data_align>] <cpio_list>\n"
+		"\t%s [-t <timestamp>] [-o <output_file>] [-a <data_align>] <cpio_list>\n"
 		"\n"
 		"<cpio_list> is a file containing newline separated entries that\n"
 		"describe the files to be included in the initramfs archive:\n"
@@ -612,7 +558,6 @@ static void usage(const char *prog)
 		"as mtime for symlinks, directories, regular and special files.\n"
 		"The default is to use the current time for all files, but\n"
 		"preserve modification time for regular files.\n"
-		"-c: calculate and store 32-bit checksums for file data.\n"
 		"<output_file>: write cpio to this file instead of stdout\n"
 		"<data_align>: attempt to align file data by zero-padding the\n"
 		"filename field up to data_align. Must be a multiple of 4.\n"
@@ -656,7 +601,7 @@ int main (int argc, char *argv[])
 	int line_nr = 0;
 	const char *filename;
 
-	default_mtime = time(NULL);
+	default_mtime = htobe32(time(NULL));
 	while (1) {
 		int opt = getopt(argc, argv, "t:cho:a:");
 		char *invalid;
@@ -665,7 +610,7 @@ int main (int argc, char *argv[])
 			break;
 		switch (opt) {
 		case 't':
-			default_mtime = strtol(optarg, &invalid, 10);
+			default_mtime = htobe32(strtol(optarg, &invalid, 10));
 			if (!*optarg || *invalid) {
 				fprintf(stderr, "Invalid timestamp: %s\n",
 						optarg);
@@ -674,9 +619,6 @@ int main (int argc, char *argv[])
 			}
 			do_file_mtime = true;
 			break;
-		case 'c':
-			do_csum = true;
-			break;
 		case 'o':
 			outfd = open(optarg,
 				     O_WRONLY | O_CREAT | O_LARGEFILE | O_TRUNC,
diff --git a/gen_init_cpio.c.diff b/gen_init_cpio.c.diff
new file mode 100644
index 0000000..4673a7c
--- /dev/null
+++ b/gen_init_cpio.c.diff
@@ -0,0 +1,439 @@
+--- gen_init_cpio.c.orig	2026-01-05 01:58:57.204608452 -0600
++++ gen_init_cpio.c	2026-01-05 02:48:04.693026062 -0600
+@@ -18,6 +18,7 @@
+ #include <errno.h>
+ #include <ctype.h>
+ #include <limits.h>
++#include <endian.h>
+ 
+ /*
+  * Original work by Jeff Garzik
+@@ -29,9 +30,7 @@
+ #define xstr(s) #s
+ #define str(s) xstr(s)
+ #define MIN(a, b) ((a) < (b) ? (a) : (b))
+-#define CPIO_HDR_LEN 110
+ #define CPIO_TRAILER "TRAILER!!!"
+-#define padlen(_off, _align) (((_align) - ((_off) & ((_align) - 1))) % (_align))
+ 
+ /* zero-padding the filename field for data alignment is limited by PATH_MAX */
+ static char padding[PATH_MAX];
+@@ -39,36 +38,39 @@
+ static unsigned int ino = 721;
+ static time_t default_mtime;
+ static bool do_file_mtime;
+-static bool do_csum = false;
+ static int outfd = STDOUT_FILENO;
+ static unsigned int dalign;
+ 
++#pragma pack(1)
++struct header_pwb_cpio {
++    uint16_t h_magic;
++    uint16_t h_dev;
++    uint16_t h_ino;
++    uint16_t h_mode;
++    uint16_t h_uid;
++    uint16_t h_gid;
++    uint16_t h_nlink;
++    uint16_t h_majmin;
++    uint32_t h_mtime;
++    uint16_t h_namesize;
++    uint32_t h_filesize;
++};
++#define CPIO_HDR_LEN sizeof(struct header_pwb_cpio)
++
+ struct file_handler {
+ 	const char *type;
+ 	int (*handler)(const char *line);
+ };
+ 
+-static int push_buf(const char *name, size_t name_len)
+-{
+-	ssize_t len;
+-
+-	len = write(outfd, name, name_len);
+-	if (len != name_len)
+-		return -1;
+-
+-	offset += name_len;
+-	return 0;
+-}
+-
+-static int push_pad(size_t padlen)
++static int push_pad()
+ {
+ 	ssize_t len = 0;
++    size_t padlen = offset % 2;
+ 
+ 	if (!padlen)
+ 		return 0;
+ 
+-	if (padlen < sizeof(padding))
+-		len = write(outfd, padding, padlen);
++	len = write(outfd, padding, padlen);
+ 	if (len != padlen)
+ 		return -1;
+ 
+@@ -76,7 +78,7 @@
+ 	return 0;
+ }
+ 
+-static int push_rest(const char *name, size_t name_len)
++static int push_buf(const char *name, size_t name_len)
+ {
+ 	ssize_t len;
+ 
+@@ -85,36 +87,32 @@
+ 		return -1;
+ 
+ 	offset += name_len;
+-
+-	return push_pad(padlen(name_len + CPIO_HDR_LEN, 4));
++	return push_pad();
+ }
+ 
+ static int cpio_trailer(void)
+ {
+-	int len;
++    int len;
+ 	unsigned int namesize = sizeof(CPIO_TRAILER);
+ 
+-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
+-	       "%08X%08X%08X%08X%08X%08X%08X",
+-		do_csum ? "070702" : "070701", /* magic */
+-		0,			/* ino */
+-		0,			/* mode */
+-		(long) 0,		/* uid */
+-		(long) 0,		/* gid */
+-		1,			/* nlink */
+-		(long) 0,		/* mtime */
+-		0,			/* filesize */
+-		0,			/* major */
+-		0,			/* minor */
+-		0,			/* rmajor */
+-		0,			/* rminor */
+-		namesize,		/* namesize */
+-		0);			/* chksum */
++    struct header_pwb_cpio header = {
++        .h_magic = 070707,
++        .h_dev = 0,
++        .h_ino = 0,
++        .h_mode = 0,
++        .h_uid = 0,
++        .h_gid = 0,
++        .h_nlink = 1,
++        .h_majmin = 0,
++        .h_mtime = 0,
++        .h_namesize = namesize,
++        .h_filesize = 0
++    };
++    len = write(outfd, &header, CPIO_HDR_LEN);
+ 	offset += len;
+ 
+ 	if (len != CPIO_HDR_LEN ||
+-	    push_rest(CPIO_TRAILER, namesize) < 0 ||
+-	    push_pad(padlen(offset, 512)) < 0)
++	    push_buf(CPIO_TRAILER, namesize) < 0)
+ 		return -1;
+ 
+ 	if (fsync(outfd) < 0 && errno != EINVAL)
+@@ -127,35 +125,31 @@
+ 			 unsigned int mode, uid_t uid, gid_t gid)
+ {
+ 	int len;
+-	unsigned int namesize, targetsize = strlen(target) + 1;
++	unsigned int namesize, targetsize = strlen(target);
+ 
+ 	if (name[0] == '/')
+ 		name++;
+-	namesize = strlen(name) + 1;
++	namesize = strlen(name);
+ 
+-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
+-	       "%08X%08X%08X%08X%08X%08X%08X",
+-		do_csum ? "070702" : "070701", /* magic */
+-		ino++,			/* ino */
+-		S_IFLNK | mode,		/* mode */
+-		(long) uid,		/* uid */
+-		(long) gid,		/* gid */
+-		1,			/* nlink */
+-		(long) default_mtime,	/* mtime */
+-		targetsize,		/* filesize */
+-		3,			/* major */
+-		1,			/* minor */
+-		0,			/* rmajor */
+-		0,			/* rminor */
+-		namesize,		/* namesize */
+-		0);			/* chksum */
++    struct header_pwb_cpio header = {
++        .h_magic = 070707,
++        .h_dev = 0,
++        .h_ino = ino++,
++        .h_mode = S_IFLNK | mode,
++        .h_uid = uid,
++        .h_gid = gid,
++        .h_nlink = 1,
++        .h_majmin = 0,
++        .h_mtime = default_mtime,
++        .h_namesize = namesize,
++        .h_filesize = htobe32(targetsize)
++    };
++    len = write(outfd, &header, CPIO_HDR_LEN);
+ 	offset += len;
+ 
+ 	if (len != CPIO_HDR_LEN ||
+ 	    push_buf(name, namesize) < 0 ||
+-	    push_pad(padlen(offset, 4)) < 0 ||
+-	    push_buf(target, targetsize) < 0 ||
+-	    push_pad(padlen(offset, 4)) < 0)
++	    push_buf(target, targetsize) < 0)
+ 		return -1;
+ 
+ 	return 0;
+@@ -190,26 +184,24 @@
+ 		name++;
+ 	namesize = strlen(name) + 1;
+ 
+-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
+-	       "%08X%08X%08X%08X%08X%08X%08X",
+-		do_csum ? "070702" : "070701", /* magic */
+-		ino++,			/* ino */
+-		mode,			/* mode */
+-		(long) uid,		/* uid */
+-		(long) gid,		/* gid */
+-		2,			/* nlink */
+-		(long) default_mtime,	/* mtime */
+-		0,			/* filesize */
+-		3,			/* major */
+-		1,			/* minor */
+-		0,			/* rmajor */
+-		0,			/* rminor */
+-		namesize,		/* namesize */
+-		0);			/* chksum */
++    struct header_pwb_cpio header = {
++        .h_magic = 070707,
++        .h_dev = 0,
++        .h_ino = ino++,
++        .h_mode = mode,
++        .h_uid = uid,
++        .h_gid = gid,
++        .h_nlink = 2,
++        .h_majmin = 0,
++        .h_mtime = default_mtime,
++        .h_namesize = namesize,
++        .h_filesize = 0
++    };
++    len = write(outfd, &header, CPIO_HDR_LEN);
+ 	offset += len;
+ 
+ 	if (len != CPIO_HDR_LEN ||
+-	    push_rest(name, namesize) < 0)
++	    push_buf(name, namesize) < 0)
+ 		return -1;
+ 
+ 	return 0;
+@@ -291,26 +283,24 @@
+ 		name++;
+ 	namesize = strlen(name) + 1;
+ 
+-	len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
+-	       "%08X%08X%08X%08X%08X%08X%08X",
+-		do_csum ? "070702" : "070701", /* magic */
+-		ino++,			/* ino */
+-		mode,			/* mode */
+-		(long) uid,		/* uid */
+-		(long) gid,		/* gid */
+-		1,			/* nlink */
+-		(long) default_mtime,	/* mtime */
+-		0,			/* filesize */
+-		3,			/* major */
+-		1,			/* minor */
+-		maj,			/* rmajor */
+-		min,			/* rminor */
+-		namesize,		/* namesize */
+-		0);			/* chksum */
++    struct header_pwb_cpio header = {
++        .h_magic = 070707,
++        .h_dev = 0,
++        .h_ino = ino++,
++        .h_mode = mode,
++        .h_uid = uid,
++        .h_gid = gid,
++        .h_nlink = 1,
++        .h_majmin = (maj << 8) | min,
++        .h_mtime = default_mtime,
++        .h_namesize = namesize,
++        .h_filesize = 0
++    };
++    len = write(outfd, &header, CPIO_HDR_LEN);
+ 	offset += len;
+ 
+ 	if (len != CPIO_HDR_LEN ||
+-	    push_rest(name, namesize) < 0)
++	    push_buf(name, namesize) < 0)
+ 		return -1;
+ 
+ 	return 0;
+@@ -337,29 +327,6 @@
+ 	return rc;
+ }
+ 
+-static int cpio_mkfile_csum(int fd, unsigned long size, uint32_t *csum)
+-{
+-	while (size) {
+-		unsigned char filebuf[65536];
+-		ssize_t this_read;
+-		size_t i, this_size = MIN(size, sizeof(filebuf));
+-
+-		this_read = read(fd, filebuf, this_size);
+-		if (this_read <= 0 || this_read > this_size)
+-			return -1;
+-
+-		for (i = 0; i < this_read; i++)
+-			*csum += filebuf[i];
+-
+-		size -= this_read;
+-	}
+-	/* seek back to the start for data segment I/O */
+-	if (lseek(fd, 0, SEEK_SET) < 0)
+-		return -1;
+-
+-	return 0;
+-}
+-
+ static int cpio_mkfile(const char *name, const char *location,
+ 			unsigned int mode, uid_t uid, gid_t gid,
+ 			unsigned int nlinks)
+@@ -369,9 +336,8 @@
+ 	int file, retval, len;
+ 	int rc = -1;
+ 	time_t mtime;
+-	int namesize, namepadlen;
++	int namesize;
+ 	unsigned int i;
+-	uint32_t csum = 0;
+ 	ssize_t this_read;
+ 
+ 	mode |= S_IFREG;
+@@ -411,13 +377,7 @@
+ 		goto error;
+ 	}
+ 
+-	if (do_csum && cpio_mkfile_csum(file, buf.st_size, &csum) < 0) {
+-		fprintf(stderr, "Failed to checksum file %s\n", location);
+-		goto error;
+-	}
+-
+ 	size = 0;
+-	namepadlen = 0;
+ 	for (i = 1; i <= nlinks; i++) {
+ 		if (name[0] == '/')
+ 			name++;
+@@ -427,38 +387,24 @@
+ 		if (i == nlinks)
+ 			size = buf.st_size;
+ 
+-		if (dalign && size > dalign) {
+-			namepadlen = padlen(offset + CPIO_HDR_LEN + namesize,
+-					    dalign);
+-			if (namesize + namepadlen > PATH_MAX) {
+-				fprintf(stderr,
+-					"%s: best-effort alignment %u missed\n",
+-					name, dalign);
+-				namepadlen = 0;
+-			}
+-		}
+-
+-		len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
+-		       "%08lX%08X%08X%08X%08X%08X%08X",
+-			do_csum ? "070702" : "070701", /* magic */
+-			ino,			/* ino */
+-			mode,			/* mode */
+-			(long) uid,		/* uid */
+-			(long) gid,		/* gid */
+-			nlinks,			/* nlink */
+-			(long) mtime,		/* mtime */
+-			size,			/* filesize */
+-			3,			/* major */
+-			1,			/* minor */
+-			0,			/* rmajor */
+-			0,			/* rminor */
+-			namesize + namepadlen,	/* namesize */
+-			size ? csum : 0);	/* chksum */
++        struct header_pwb_cpio header = {
++            .h_magic = 070707,
++            .h_dev = buf.st_dev,
++            .h_ino = buf.st_ino,
++            .h_mode = mode,
++            .h_uid = uid,
++            .h_gid = gid,
++            .h_nlink = 1,
++            .h_majmin = 0,
++            .h_mtime = htobe32(mtime),
++            .h_namesize = namesize,
++            .h_filesize = htobe32(size)
++        };
++        len = write(outfd, &header, CPIO_HDR_LEN);
+ 		offset += len;
+ 
+ 		if (len != CPIO_HDR_LEN ||
+-		    push_buf(name, namesize) < 0 ||
+-		    push_pad(namepadlen ? namepadlen : padlen(offset, 4)) < 0)
++		    push_buf(name, namesize) < 0)
+ 			goto error;
+ 
+ 		if (size) {
+@@ -489,7 +435,7 @@
+ 			offset += this_read;
+ 			size -= this_read;
+ 		}
+-		if (push_pad(padlen(offset, 4)) < 0)
++		if (push_pad() < 0)
+ 			goto error;
+ 
+ 		name += namesize;
+@@ -575,7 +521,7 @@
+ static void usage(const char *prog)
+ {
+ 	fprintf(stderr, "Usage:\n"
+-		"\t%s [-t <timestamp>] [-c] [-o <output_file>] [-a <data_align>] <cpio_list>\n"
++		"\t%s [-t <timestamp>] [-o <output_file>] [-a <data_align>] <cpio_list>\n"
+ 		"\n"
+ 		"<cpio_list> is a file containing newline separated entries that\n"
+ 		"describe the files to be included in the initramfs archive:\n"
+@@ -612,7 +558,6 @@
+ 		"as mtime for symlinks, directories, regular and special files.\n"
+ 		"The default is to use the current time for all files, but\n"
+ 		"preserve modification time for regular files.\n"
+-		"-c: calculate and store 32-bit checksums for file data.\n"
+ 		"<output_file>: write cpio to this file instead of stdout\n"
+ 		"<data_align>: attempt to align file data by zero-padding the\n"
+ 		"filename field up to data_align. Must be a multiple of 4.\n"
+@@ -656,7 +601,7 @@
+ 	int line_nr = 0;
+ 	const char *filename;
+ 
+-	default_mtime = time(NULL);
++	default_mtime = htobe32(time(NULL));
+ 	while (1) {
+ 		int opt = getopt(argc, argv, "t:cho:a:");
+ 		char *invalid;
+@@ -665,7 +610,7 @@
+ 			break;
+ 		switch (opt) {
+ 		case 't':
+-			default_mtime = strtol(optarg, &invalid, 10);
++			default_mtime = htobe32(strtol(optarg, &invalid, 10));
+ 			if (!*optarg || *invalid) {
+ 				fprintf(stderr, "Invalid timestamp: %s\n",
+ 						optarg);
+@@ -674,9 +619,6 @@
+ 			}
+ 			do_file_mtime = true;
+ 			break;
+-		case 'c':
+-			do_csum = true;
+-			break;
+ 		case 'o':
+ 			outfd = open(optarg,
+ 				     O_WRONLY | O_CREAT | O_LARGEFILE | O_TRUNC,