mkswap: fix help text to not lie about supported options.

mkswap: use uint32, not int, to match kernel.
mkswap: optimization: use pre-zeroed buffer

include/usage.h

@@ -2335,14 +2335,17 @@ USE_FEATURE_BRCTL_FANCY("\n" \
        "$ mknod -m 644 /tmp/pipe p\n"
 
 #define mkswap_trivial_usage \
-       "[-c] [-v0|-v1] device [block-count]"
+       "DEVICE"
 #define mkswap_full_usage \
-       "Prepare a disk partition to be used as swap partition" \
+       "Prepare block device to be used as swap partition"
-       "\n\nOptions:\n" \
+#if 0
-       "	-c		Check for read-ability\n" \
+       "[-c] [-v0|-v1] DEVICE [BLOCKS]"
-       "	-v0		Make version 0 swap [max 128 Megs]\n" \
+       "\n\nOptions:"
-       "	-v1		Make version 1 swap [big!] (default for kernels > 2.1.117)\n" \
+     "\n	-c	Check for readability"
-       "	block-count	Number of block to use (default is entire partition)"
+     "\n	-v0	Make swap version 0 (max 128M)"
+     "\n	-v1	Make swap version 1 (default for kernels > 2.1.117)"
+     "\n	BLOCKS	Number of blocks to use (default is entire partition)"
+#endif
 
 #define mktemp_trivial_usage \
        "[-dt] [-p DIR] TEMPLATE"
@@ -3312,34 +3315,36 @@ USE_FEATURE_RUN_PARTS_FANCY("\n	-l	Prints names of all matching files even when
 
 #define sort_trivial_usage \
        "[-nru" \
-	USE_FEATURE_SORT_BIG("gMcszbdfimSTokt] [-o outfile] [-k start[.offset][opts][,end[.offset][opts]] [-t char") \
+	USE_FEATURE_SORT_BIG("gMcszbdfimSTokt] [-o FILE] [-k start[.offset][opts][,end[.offset][opts]] [-t CHAR") \
        "] [FILE]..."
 #define sort_full_usage \
        "Sort lines of text in the specified files" \
-       "\n\nOptions:\n" \
+       "\n\nOptions:" \
 	USE_FEATURE_SORT_BIG( \
-       "	-b	Ignore leading blanks\n" \
+     "\n	-b	Ignore leading blanks" \
-       "	-c	Check whether input is sorted\n" \
+     "\n	-c	Check whether input is sorted" \
-       "	-d	Dictionary order (blank or alphanumeric only)\n" \
+     "\n	-d	Dictionary order (blank or alphanumeric only)" \
-       "	-f	Ignore case\n" \
+     "\n	-f	Ignore case" \
-       "	-g	General numerical sort\n" \
+     "\n	-g	General numerical sort" \
-       "	-i	Ignore unprintable characters\n" \
+     "\n	-i	Ignore unprintable characters" \
-       "	-k	Sort key\n" \
+     "\n	-k	Sort key" \
-       "	-M	Sort month\n") \
+     "\n	-M	Sort month" \
-       "	-n	Sort numbers\n" \
+	) \
+     "\n	-n	Sort numbers" \
 	USE_FEATURE_SORT_BIG( \
-       "	-o	Output to file\n" \
+     "\n	-o	Output to file" \
-       "	-k	Sort by key\n" \
+     "\n	-k	Sort by key" \
-       "	-t	Use key separator other than whitespace\n") \
+     "\n	-t CHAR	Key separator" \
-       "	-r	Reverse sort order\n" \
+	) \
+     "\n	-r	Reverse sort order" \
 	USE_FEATURE_SORT_BIG( \
-       "	-s	Stable (don't sort ties alphabetically)\n") \
+     "\n	-s	Stable (don't sort ties alphabetically)" \
-       "	-u	Suppress duplicate lines" \
+	) \
+     "\n	-u	Suppress duplicate lines" \
 	USE_FEATURE_SORT_BIG( \
-       "\n	-z	Input terminated by nulls, not newlines\n") \
+     "\n	-z	Lines are terminated by NUL, not newline" \
-	USE_FEATURE_SORT_BIG( \
+     "\n	-mST	Ignored for GNU compatibility") \
-       "	-mST	Ignored for GNU compatibility") \
+
-       ""
 #define sort_example_usage \
        "$ echo -e \"e\\nf\\nb\\nd\\nc\\na\" | sort\n" \
        "a\n" \

util-linux/mkswap.c

@@ -50,12 +50,47 @@ static void mkswap_selinux_setcontext(int fd, const char *path)
 #define mkswap_selinux_setcontext(fd, path) ((void)0)
 #endif
 
+#if 0 /* from Linux 2.6.23 */
+/*
+ * Magic header for a swap area. The first part of the union is
+ * what the swap magic looks like for the old (limited to 128MB)
+ * swap area format, the second part of the union adds - in the
+ * old reserved area - some extra information. Note that the first
+ * kilobyte is reserved for boot loader or disk label stuff...
+ */
+union swap_header {
+	struct {
+		char reserved[PAGE_SIZE - 10];
+		char magic[10];			/* SWAP-SPACE or SWAPSPACE2 */
+	} magic;
+	struct {
+		char            bootbits[1024];	/* Space for disklabel etc. */
+		__u32           version;        /* second kbyte, word 0 */
+		__u32           last_page;      /* 1 */
+		__u32           nr_badpages;    /* 2 */
+		unsigned char   sws_uuid[16];   /* 3,4,5,6 */
+		unsigned char   sws_volume[16]; /* 7,8,9,10  */
+		__u32           padding[117];   /* 11..127 */
+		__u32           badpages[1];    /* 128, total 129 32-bit words */
+	} info;
+};
+#endif
+
+#define NWORDS 129
+#define hdr ((uint32_t*)(&bb_common_bufsiz1))
+
+struct BUG_bufsiz1_is_too_small {
+	char BUG_bufsiz1_is_too_small[COMMON_BUFSIZE < (NWORDS * 4) ? -1 : 1];
+};
+
+/* Stored without terminating NUL */
+static const char SWAPSPACE2[sizeof("SWAPSPACE2")-1] ALIGN1 = "SWAPSPACE2";
+
 int mkswap_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int mkswap_main(int argc, char **argv)
 {
 	int fd, pagesize;
 	off_t len;
-	unsigned int hdr[129];
 
 	// No options supported.
 
@@ -74,9 +109,7 @@ int mkswap_main(int argc, char **argv)
 			len - pagesize);
 	mkswap_selinux_setcontext(fd, argv[1]);
 
-	// Make a header.
+	// Make a header. hdr is zero-filled so far...
-
-	memset(hdr, 0, sizeof(hdr));
 	hdr[0] = 1;
 	hdr[1] = (len / pagesize) - 1;
 
@@ -84,9 +117,9 @@ int mkswap_main(int argc, char **argv)
 	// signature on disk (not in cache) during swapon.
 
 	xlseek(fd, 1024, SEEK_SET);
-	xwrite(fd, hdr, sizeof(hdr));
+	xwrite(fd, hdr, NWORDS * 4);
 	xlseek(fd, pagesize - 10, SEEK_SET);
-	xwrite(fd, "SWAPSPACE2", 10);
+	xwrite(fd, SWAPSPACE2, 10);
 	fsync(fd);
 
 	if (ENABLE_FEATURE_CLEAN_UP) close(fd);