From aed9e3f6fa85851a35ad7bfb1b925e4feeb1a240 Mon Sep 17 00:00:00 2001
From: Jan Tatje <jan@jnt.io>
Date: Sat, 29 Nov 2014 21:09:39 +0000
Subject: [PATCH] Add swaplabel(8)

---
 LICENSE     |  1 +
 Makefile    |  2 ++
 TODO        |  1 -
 swaplabel.8 | 11 ++++++++
 swaplabel.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 swaplabel.8
 create mode 100644 swaplabel.c

diff --git a/LICENSE b/LICENSE
index 29531aa..3a661ad 100644
--- a/LICENSE
+++ b/LICENSE
@@ -9,6 +9,7 @@ MIT/X Consortium License
 © 2014 Hiltjo Posthuma <hiltjo@codemadness.org>
 © 2014 Laslo Hunhold <dev@frign.de>
 © 2014 Roberto E. Vargas Caballero <k0ga@shike2.com>
+© 2014 Jan Tatje <jan@jnt.io>
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
diff --git a/Makefile b/Makefile
index d267535..150ca13 100644
--- a/Makefile
+++ b/Makefile
@@ -70,6 +70,7 @@ SRC = \
 	rmmod.c             \
 	stat.c              \
 	su.c                \
+	swaplabel.c         \
 	swapoff.c           \
 	swapon.c            \
 	switch_root.c       \
@@ -125,6 +126,7 @@ MAN8 = \
 	pivot_root.8        \
 	readahead.8         \
 	rmmod.8             \
+	swaplabel.8         \
 	swapoff.8           \
 	swapon.8            \
 	switch_root.8       \
diff --git a/TODO b/TODO
index 681e77d..c33c2ec 100644
--- a/TODO
+++ b/TODO
@@ -4,7 +4,6 @@ Tools
 vmstat
 top
 Better ps support
-swaplabel
 losetup
 lspci
 mkswap [-L]
diff --git a/swaplabel.8 b/swaplabel.8
new file mode 100644
index 0000000..d442626
--- /dev/null
+++ b/swaplabel.8
@@ -0,0 +1,11 @@
+.TH SWAPLABEL 8 ubase-VERSION
+.SH NAME
+\fBswaplabel\fR - set the label of a swap filesystem
+.SH SYNOPSIS
+\fBswaplabel\fR [\fB-L\fI label\fR] \fIdevice\fR
+.SH DESCRIPTION
+\fBswaplabel\fR is used to change the label of a swap device or file.
+.SH OPTIONS
+.TP
+\fB-L\fR
+Change the label.
diff --git a/swaplabel.c b/swaplabel.c
new file mode 100644
index 0000000..9f89b21
--- /dev/null
+++ b/swaplabel.c
@@ -0,0 +1,80 @@
+/* See LICENSE file for copyright and license details. */
+#include <sys/types.h>
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "util.h"
+
+#define SWAP_MAGIC1 "SWAPSPACE2"
+#define SWAP_MAGIC2 "SWAP-SPACE"
+#define SWAP_MAGIC_LENGTH (10)
+#define SWAP_MAGIC_OFFSET (sysconf(_SC_PAGESIZE) - SWAP_MAGIC_LENGTH)
+#define SWAP_LABEL_LENGTH (16)
+#define SWAP_LABEL_OFFSET (1024 + 4 + 4 + 4 + 16)
+
+static void
+usage(void)
+{
+	eprintf("usage: %s [-L label] device\n", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+	int setlabel = 0;
+	int fd = -1;
+	char magic[10] = { 0 };
+	char *label = NULL;
+	char *device = NULL;
+	int i;
+
+	ARGBEGIN {
+	case 'L':
+		setlabel = 1;
+		label = EARGF(usage());
+		break;
+	default:
+		usage();
+	} ARGEND;
+
+	if (argc < 1)
+		usage();
+	device = argv[0];
+
+	fd = open(device, O_RDWR);
+	if (fd < 0)
+		eprintf("open %s:", device);
+
+	if (lseek(fd, SWAP_MAGIC_OFFSET, SEEK_SET) != SWAP_MAGIC_OFFSET)
+		eprintf("failed seeking to magic position:");
+	if (read(fd, magic, SWAP_MAGIC_LENGTH) != SWAP_MAGIC_LENGTH)
+		eprintf("reading magic failed:");
+	if (memcmp(magic, SWAP_MAGIC1, 10) && memcmp(magic, SWAP_MAGIC2, 10))
+		eprintf("%s: is not a swap partition\n", device);
+	if (lseek(fd, SWAP_LABEL_OFFSET, SEEK_SET) != SWAP_LABEL_OFFSET)
+		eprintf("failed seeking to label position:");
+
+	if (!setlabel) {
+		label = emalloc(SWAP_LABEL_LENGTH);
+		if (read(fd, label, SWAP_LABEL_LENGTH) != SWAP_LABEL_LENGTH)
+			eprintf("reading label failed:");
+		for (i = 0; i < SWAP_LABEL_LENGTH && label[i] != '\0'; i++)
+			if (i == (SWAP_LABEL_LENGTH - 1) && label[i] != '\0')
+				eprintf("invalid label\n");
+		printf("label: %s\n", label);
+		free(label);
+	} else {
+		if (strlen(label) + 1 > SWAP_LABEL_LENGTH)
+			eprintf("label too long\n");
+		if (write(fd, label, strlen(label) + 1) != (ssize_t)strlen(label) + 1)
+			eprintf("writing label failed:");
+	}
+
+	fsync(fd);
+	close(fd);
+	return 0;
+}