Fix alignment issues for strict architectures

Fixes two locations where unaligned accesses will cause bus errors on
architectures that are strict about such accesses, namely sparc.

The first is in swab32_into, which is called with an offset of +1 into
an unsigned char array from mklink_fs.

The second is in add2fs_from_tarball when checking the validity of a
tarball, which casts a string from an unaligned position inside a struct
to a long.

After these changes, the test suite passes on sparc.

Author: matoro

genext2fs.c

@@ -2058,11 +2058,14 @@ mkdir_fs(filesystem *fs, uint32 parent_nod, const char *name, uint32 mode,
 
 // byte swapping for symlinks
 static inline void
-swab32_into(uint32 *dst, uint32 *src, size_t n)
+swab32_into(uint32 *dst, uint8 *src, size_t n)
 {
 	size_t i;
-	for(i = 0; i < n; i++)
-		dst[i] = swab32(src[i]);
+	for(i = 0; i < n; i++) {
+		uint32 tmp_buf;
+		memcpy(&tmp_buf, src + i * sizeof(uint32) / sizeof(uint8), sizeof(uint32) / sizeof(uint8));
+		dst[i] = swab32(tmp_buf);
+	}
 }
 
 // make a symlink
@@ -2079,7 +2082,7 @@ mklink_fs(filesystem *fs, uint32 parent_nod, const char *name, size_t size, uint
 
 	if (size < 4 * (EXT2_TIND_BLOCK + 1))
 		if (fs->swapit)
-			swab32_into(node->i_block, (uint32 *)b, EXT2_TIND_BLOCK + 1);
+			swab32_into(node->i_block, b, EXT2_TIND_BLOCK + 1);
 		else
 			memcpy(node->i_block, b, 4 * (EXT2_TIND_BLOCK + 1));
 	else
@@ -2290,7 +2293,7 @@ add2fs_from_tarball(filesystem *fs, uint32 this_nod, FILE * fh, int squash_uids,
 			continue;
 		} else
 			nbnull = 0;
-		if (*(long *)tarhead->ustar != *(long *)"ustar\00000" && strcmp(tarhead->ustar, "ustar  "))
+		if (memcmp(tarhead->ustar, "ustar\00000", sizeof(long)) && strcmp(tarhead->ustar, "ustar  "))
 			error_msg_and_die("not a tarball");
 		signed_checksum = unsigned_checksum = 0;
 		checksum = OCTAL_READ(tarhead->checksum);
@@ -3351,7 +3354,7 @@ print_link(filesystem *fs, uint32 nod)
 			uint32 *buf = malloc(4 * (EXT2_TIND_BLOCK + 1));
 			if (buf == NULL)
 				error_msg_and_die(memory_exhausted);
-			swab32_into(buf, node->i_block, EXT2_TIND_BLOCK + 1);
+			swab32_into(buf, (uint8*)node->i_block, EXT2_TIND_BLOCK + 1);
 			printf("links to '%s'\n", (char*) buf);
 			free(buf);
 		} else {