sparc: refactor piggy_32.c

Refactoring to increase readability (a little).
- sort includes
- spaces around operators
- small helpers introduced
- added a few comments
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/boot/piggyback_32.c

@@ -19,14 +19,15 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
 
-#include <stdio.h>
+#include <dirent.h>
+#include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
-#include <dirent.h>
-#include <unistd.h>
-#include <stdlib.h>
+#include <stdio.h>
+
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ -35,16 +36,19 @@
  * as PROM looks for a.out image only.
  */
 
+/* read two bytes as big endian */
 static unsigned short ld2(char *p)
 {
 	return (p[0] << 8) | p[1];
 }
 
+/* read 4 bytes as big endian */
 static unsigned int ld4(char *p)
 {
 	return (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
 }
 
+/* save 4 bytes as big endian */
 static void st4(char *p, unsigned int x)
 {
 	p[0] = x >> 24;
@@ -53,6 +57,12 @@ static void st4(char *p, unsigned int x)
 	p[3] = x;
 }
 
+static void die(const char *str)
+{
+	perror(str);
+	exit(1);
+}
+
 static void usage(void)
 {
 	/* fs_img.gz is an image of initial ramdisk. */
@@ -61,10 +71,57 @@ static void usage(void)
 	exit(1);
 }
 
-static void die(char *str)
+static int start_line(const char *line)
 {
-	perror (str);
-	exit(1);
+	if (strcmp(line + 8, " T start\n") == 0)
+		return 1;
+	else if (strcmp(line + 16, " T start\n") == 0)
+		return 1;
+	return 0;
+}
+
+static int end_line(const char *line)
+{
+	if (strcmp(line + 8, " A _end\n") == 0)
+		return 1;
+	else if (strcmp (line + 16, " A _end\n") == 0)
+		return 1;
+	return 0;
+}
+
+/*
+ * Find address for start and end in System.map.
+ * The file looks like this:
+ * f0004000 T start
+ * f0379f79 A _end
+ * 1234567890123456
+ * ^coloumn 1
+ * There is support for 64 bit addresses too.
+ *
+ * Return 0 if either start or end is not found
+ */
+static int get_start_end(const char *filename, unsigned int *start, unsigned int *end)
+{
+	FILE *map;
+	char buffer[1024];
+
+	*start = 0;
+	*end = 0;
+	map = fopen(filename, "r");
+	if (!map)
+		die(filename);
+	while (fgets(buffer, 1024, map)) {
+		if (start_line(buffer))
+			*start = strtoul(buffer, NULL, 16);
+		else if (end_line(buffer))
+			*end = strtoul(buffer, NULL, 16);
+	}
+	fclose (map);
+
+	if (*start == 0 || *end == 0)
+		return 0;
+
+	return 1;
 }
 
 int main(int argc,char **argv)
@@ -72,33 +129,29 @@ int main(int argc,char **argv)
 	static char aout_magic[] = { 0x01, 0x03, 0x01, 0x07 };
 	char buffer[1024], *q, *r;
 	unsigned int i, j, k, start, end, offset;
-	FILE *map;
 	struct stat s;
 	int image, tail;
 
-	if (argc != 4) usage();
-	start = end = 0;
-	if (stat (argv[3], &s) < 0) die (argv[3]);
-	map = fopen (argv[2], "r");
-	if (!map) die(argv[2]);
-	while (fgets (buffer, 1024, map)) {
-		if (!strcmp (buffer + 8, " T start\n") || !strcmp (buffer + 16, " T start\n"))
-			start = strtoul (buffer, NULL, 16);
-		else if (!strcmp (buffer + 8, " A _end\n") || !strcmp (buffer + 16, " A _end\n"))
-			end = strtoul (buffer, NULL, 16);
-	}
-	fclose (map);
-	if (!start || !end) {
-		fprintf (stderr, "Could not determine start and end from System.map\n");
+	if (argc != 4)
+		usage();
+	if (stat (argv[3], &s) < 0)
+		die(argv[3]);
+
+	if (!get_start_end(argv[2], &start, &end)) {
+		fprintf (stderr, "Could not determine start and end from %s\n", argv[2]);
 		exit(1);
 	}
-	if ((image = open(argv[1],O_RDWR)) < 0) die(argv[1]);
-	if (read(image,buffer,512) != 512) die(argv[1]);
+	if ((image = open(argv[1], O_RDWR)) < 0)
+		die(argv[1]);
+	if (read(image, buffer, 512) != 512)
+		die(argv[1]);
 	if (memcmp (buffer, "\177ELF", 4) == 0) {
 		q = buffer + ld4(buffer + 28);
 		i = ld4(q + 4) + ld4(buffer + 24) - ld4(q + 8);
-		if (lseek(image,i,0) < 0) die("lseek");
-		if (read(image,buffer,512) != 512) die(argv[1]);
+		if (lseek(image, i, 0) < 0)
+			die("lseek");
+		if (read(image, buffer, 512) != 512)
+			die(argv[1]);
 		j = 0;
 	} else if (memcmp(buffer, aout_magic, 4) == 0) {
 		i = j = 32;
@@ -107,9 +160,11 @@ int main(int argc,char **argv)
 		exit(1);
 	}
 	k = i;
-	i += (ld2(buffer + j + 2)<<2) - 512;
-	if (lseek(image,i,0) < 0) die("lseek");
-	if (read(image,buffer,1024) != 1024) die(argv[1]);
+	i += (ld2(buffer + j + 2) << 2) - 512;
+	if (lseek(image, i, 0) < 0)
+		die("lseek");
+	if (read(image, buffer, 1024) != 1024)
+		die(argv[1]);
 	for (q = buffer, r = q + 512; q < r; q += 4) {
 		if (*q == 'H' && q[1] == 'd' && q[2] == 'r' && q[3] == 'S')
 			break;
@@ -119,19 +174,26 @@ int main(int argc,char **argv)
 		exit(1);
 	}
 	offset = i + (q - buffer) + 10;
-	if (lseek(image, offset, 0) < 0) die ("lseek");
+	if (lseek(image, offset, 0) < 0)
+		die("lseek");
 
 	st4(buffer, 0);
 	st4(buffer + 4, 0x01000000);
 	st4(buffer + 8, (end + 32 + 4095) & ~4095);
 	st4(buffer + 12, s.st_size);
 
-	if (write(image,buffer+2,14) != 14) die (argv[1]);
-	if (lseek(image, k - start + ((end + 32 + 4095) & ~4095), 0) < 0) die ("lseek");
-	if ((tail = open(argv[3],O_RDONLY)) < 0) die(argv[3]);
-	while ((i = read (tail,buffer,1024)) > 0)
-		if (write(image,buffer,i) != i) die (argv[1]);
-	if (close(image) < 0) die("close");
-	if (close(tail) < 0) die("close");
+	if (write(image, buffer + 2, 14) != 14)
+		die(argv[1]);
+	if (lseek(image, k - start + ((end + 32 + 4095) & ~4095), 0) < 0)
+		die("lseek");
+	if ((tail = open(argv[3],O_RDONLY)) < 0)
+		die(argv[3]);
+	while ((i = read (tail, buffer, 1024)) > 0)
+		if (write(image, buffer, i) != i)
+			die(argv[1]);
+	if (close(image) < 0)
+		die("close");
+	if (close(tail) < 0)
+		die("close");
 	return 0;
 }