path: root/usr/gen_init_cpio.c

// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <limits.h>

/*
 * 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
#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];
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;

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)
{
	ssize_t len = 0;

	if (!padlen)
		return 0;

	if (padlen < sizeof(padding))
		len = write(outfd, padding, padlen);
	if (len != padlen)
		return -1;

	offset += padlen;
	return 0;
}

static int push_rest(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 push_pad(padlen(name_len + CPIO_HDR_LEN, 4));
}

static int cpio_trailer(void)
{
	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 */
	offset += len;

	if (len != CPIO_HDR_LEN ||
	    push_rest(CPIO_TRAILER, namesize) < 0 ||
	    push_pad(padlen(offset, 512)) < 0)
		return -1;

	if (fsync(outfd) < 0 && errno != EINVAL)
		return -1;

	return 0;
}

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;

	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 */
	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)
		return -1;

	return 0;

}

static int cpio_mkslink_line(const char *line)
{
	char name[PATH_MAX + 1];
	char target[PATH_MAX + 1];
	unsigned int mode;
	int uid;
	int gid;
	int rc = -1;

	if (5 != sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX) "s %o %d %d", name, target, &mode, &uid, &gid)) {
		fprintf(stderr, "Unrecognized dir format '%s'", line);
		goto fail;
	}
	rc = cpio_mkslink(name, target, mode, uid, gid);
 fail:
	return rc;
}

static int cpio_mkgeneric(const char *name, unsigned int mode,
		       uid_t uid, gid_t gid)
{
	int len;
	unsigned int namesize;

	if (name[0] == '/')
		name++;
	namesize