Hello,
I wrote a simple utility to change the label of a swap partition for ubase.
Please tell me what to change should further changes be required for this to be
accepted.
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/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..99467c8
--- /dev/null
+++ b/swaplabel.c
@@ -0,0 +1,94 @@
+/* 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;
+
+ ARGBEGIN {
+ case 'L':
+ setlabel = 1;
+ label = ARGF();
+ break;
+ default:
+ usage();
+ } ARGEND;
+
+ if (argc < 1)
+ usage();
+
+ device = argv[0];
+
+ fd = open(device, O_RDWR);
+
+ if (fd < 0)
+ eprintf("error: could not open device.\n");
+
+ if (lseek(fd, SWAP_MAGIC_OFFSET, SEEK_SET) != SWAP_MAGIC_OFFSET)
+ eprintf("error: failed seeking to magic position.\n");
+
+ if (read(fd, magic, SWAP_MAGIC_LENGTH) != SWAP_MAGIC_LENGTH)
+ eprintf("error: reading magic failed.\n");
+
+ if (memcmp(magic, SWAP_MAGIC1, 10) && memcmp(magic, SWAP_MAGIC2, 10))
+ eprintf("error: %s is not a swap partition.\n", device);
+
+ if (lseek(fd, SWAP_LABEL_OFFSET, SEEK_SET) != SWAP_LABEL_OFFSET)
+ eprintf("error: failed seeking to label position.\n");
+
+ if (!setlabel) {
+ label = malloc(SWAP_LABEL_LENGTH * sizeof(char));
+ if (!label)
+ eprintf("error: malloc failed");
+
+ if (read(fd, label, SWAP_LABEL_LENGTH) != SWAP_LABEL_LENGTH)
+ eprintf("error: reading label failed.\n");
+
+ for (int i = 0; i < SWAP_LABEL_LENGTH && label[i] != '\0'; i++) {
+ if (i == (SWAP_LABEL_LENGTH - 1) && label[i] != '\0')
+ eprintf("error: invalid label.\n");
+ }
+
+ printf("label: %s\n", label);
+
+ free(label);
+ }
+
+ if (setlabel) {
+ if ((strlen(label)+1) > SWAP_LABEL_LENGTH)
+ eprintf("error: label too long.\n");
+
+ if (write(fd, label, (strlen(label)+1)) < 0)
+ eprintf("error: writing label failed.\n");
+ }
+
+ fsync(fd);
+ close(fd);
+}
+
