add symlink follow counter

config.h

@@ -26,8 +26,8 @@
 #define FS_MAX_PATH_LEN 512
 #define FS_MAX_OPEN_FD 32
 #define FS_MAX_FNAME_LEN 11
-#define FS_MAX_DIRECTORY_DEPTH 512
-#define FS_MAX_SYMLINK_FOLLOWING_DEPTH 1024
+#define FS_MAX_DIRECTORY_DEPTH 2048
+#define FS_MAX_SYMLINK_FOLLOWS 1024
 
 
 #endif

src/fs.c

@@ -24,6 +24,7 @@ static unsigned int fs_cwd_inode_ptr;
 static struct fs_file_description fs_file_descriptions[FS_MAX_OPEN_FD];
 
 static int extract_basename(char *path, char *name);
+static int read_symlink(int symlink_inode_ptr, char *path);
 
 
 static int read_block(unsigned int block_no, void *data)
@@ -907,18 +908,21 @@ fs_remove_fname_from_directory_finish:
 	return 0;
 }
 
-static void resolve_path(struct resolved_path *rp, char *path, unsigned int params)
+static void resolve_path(struct resolved_path * const rp, const char * const original_path, const unsigned int params)
 {
 	rp->parent_inode_ptr = -1;
 	rp->target_inode_ptr = -1;
 
-	int path_len = strlen(path);
+	int path_len = strlen(original_path);
 
 	if (!path_len) {
 		pr_err("no path specified\n");
 		return;
 	}
 
+	char path[FS_MAX_PATH_LEN+1];
+	strcpy(path, original_path);
+
 	if (!strcmp(path, "/")) {
 		rp->parent_inode_ptr = 0;
 		rp->target_inode_ptr = 0;
@@ -931,6 +935,8 @@ static void resolve_path(struct resolved_path *rp, char *path, unsigned int para
 	int current_inode_ptr;
 	int i;
 
+	unsigned int symlinks_followed = 0;
+
 	if (path[0] == '/') {
 		current_inode_ptr = 0;
 		rp->parent_inode_ptr = 0;
@@ -950,65 +956,149 @@ static void resolve_path(struct resolved_path *rp, char *path, unsigned int para
 		if (path[i] != '/') {
 			next_fname[next_fname_ptr] = path[i];
 			next_fname_ptr++;
-			continue;
 		}
 
-		// path[i] == '/', trying to change current directory
+		if ((path[i] != '/') && (i+1 < path_len))
+			continue;
 
 		if (!next_fname_ptr)
 			continue;
 
-		if (i+1 == path_len)
-			continue;
-
-		{
-			int res = find_fname_in_directory(current_inode_ptr, next_fname);
-			if (res < 0) {
-				pr_warn("directory '%s' does not exist\n", next_fname);
-				rp->parent_inode_ptr = -1;
-				break;
-			}
-
-			{
-				struct fs_inode d;
-				read_block(read_inode_ptr(res), &d);
-
-				if (d.ftype == REGULAR) {
-					pr_warn("'%s' is a regular file\n", next_fname);
-					rp->parent_inode_ptr = -1;
-					break;
-				}
-			}
-
-			pr("Found directory '%s'\n", next_fname);
-			current_inode_ptr = res;
-			rp->parent_inode_ptr = res;
-		}
-
-		next_fname_ptr = 0;
-		strcpy(current_fname, next_fname);
-		memset(next_fname, 0, FS_MAX_FNAME_LEN);
-	}
-
-	if (rp->parent_inode_ptr < 0) {
-		rp->target_inode_ptr = -1;
-		return;
-	}
-
-	strcpy(rp->parent_fname, current_fname);
-
-	{
 		int res = find_fname_in_directory(current_inode_ptr, next_fname);
 		if (res < 0) {
-			pr_warn("target fname '%s' does not exist\n", next_fname);
-			rp->target_inode_ptr = -1;
-		} else {
-			rp->target_inode_ptr = res;
-			strcpy(rp->target_fname, next_fname);
-		}
-	}
+			if (i+1 < path_len) {
+				pr_warn("parent '%s' does not exist\n", next_fname);
+				rp->parent_inode_ptr = -1;
+			}
 
-	return;
+			rp->target_inode_ptr = -1;
+			break;
+		}
+
+		struct fs_inode d;
+		read_block(read_inode_ptr(res), &d);
+
+		if (d.ftype == SYMLINK) {
+			if (i+1 < path_len) {
+				symlinks_followed++;
+				if (symlinks_followed > FS_MAX_SYMLINK_FOLLOWS) {
+					pr_err("too many symlink follows\n");
+					rp->parent_inode_ptr = -1;
+					rp->target_inode_ptr = -1;
+					break;
+				}
+
+				char symlink_path[FS_MAX_PATH_LEN+1];
+				int symlink_path_len = read_symlink(res, symlink_path);
+
+				if (symlink_path_len < 0) {
+					pr_warn("broken symlink\n");
+					rp->parent_inode_ptr = -1;
+					rp->target_inode_ptr = -1;
+					break;
+				}
+
+				if (symlink_path[0] == '/') {
+					memmove(&(path[symlink_path_len]), &(path[i+1]), path_len-i-1);
+					strcpy(path, &(symlink_path[1]));
+					path[symlink_path_len-1] = '/';
+					path_len = symlink_path_len + path_len - i - 1;
+					i = -1;
+
+					next_fname_ptr = 0;
+					strcpy(current_fname, "/");
+					memset(next_fname, 0, FS_MAX_FNAME_LEN);
+				} else {
+					memmove(&(path[symlink_path_len+1]), &(path[i+1]), path_len-i-1);
+					strcpy(path, symlink_path);
+					path[symlink_path_len] = '/';
+					path_len = symlink_path_len + path_len - i;
+					i = -1;
+
+					next_fname_ptr = 0;
+					strcpy(current_fname, next_fname);
+					memset(next_fname, 0, FS_MAX_FNAME_LEN);
+				}
+			} else {
+				if (!(params & FOLLOW_LAST_SYMLINK)) {
+					rp->target_inode_ptr = res;
+					strcpy(rp->parent_fname, current_fname);
+					strcpy(rp->target_fname, next_fname);
+					break;
+				}
+
+				symlinks_followed++;
+				if (symlinks_followed > FS_MAX_SYMLINK_FOLLOWS) {
+					pr_err("too many symlink follows\n");
+					rp->parent_inode_ptr = -1;
+					rp->target_inode_ptr = -1;
+					break;
+				}
+
+				char symlink_path[FS_MAX_PATH_LEN+1];
+				int symlink_path_len = read_symlink(res, symlink_path);
+
+				if (symlink_path_len < 0) {
+					pr_warn("broken symlink\n");
+					rp->parent_inode_ptr = -1;
+					rp->target_inode_ptr = -1;
+					break;
+				}
+
+				if (!strcmp(symlink_path, "/")) {
+					rp->parent_inode_ptr = 0;
+					rp->target_inode_ptr = 0;
+					strcpy(rp->parent_fname, "/");
+					strcpy(rp->target_fname, "/");
+					break;
+				}
+
+				if (symlink_path[0] == '/') {
+					strcpy(path, &(symlink_path[1]));
+					path_len = symlink_path_len - 1;
+					i = -1;
+
+					next_fname_ptr = 0;
+					strcpy(current_fname, "/");
+					memset(next_fname, 0, FS_MAX_FNAME_LEN);
+				} else {
+					strcpy(path, symlink_path);
+					path_len = symlink_path_len;
+					i = -1;
+
+					next_fname_ptr = 0;
+					strcpy(current_fname, next_fname);
+					memset(next_fname, 0, FS_MAX_FNAME_LEN);
+				}
+			}
+		} else if (d.ftype == REGULAR) {
+			if (i+1 < path_len) {
+				pr_warn("'%s': regular file not in the end of a path\n", next_fname);
+				rp->parent_inode_ptr = -1;
+				rp->target_inode_ptr = -1;
+				break;
+			} else {
+				rp->target_inode_ptr = res;
+				strcpy(rp->parent_fname, current_fname);
+				strcpy(rp->target_fname, next_fname);
+			}
+		} else if (d.ftype == DIRECTORY) {
+			if (i+1 < path_len) {
+				pr("Found directory '%s'\n", next_fname);
+				current_inode_ptr = res;
+				rp->parent_inode_ptr = res;
+
+				next_fname_ptr = 0;
+				strcpy(current_fname, next_fname);
+				memset(next_fname, 0, FS_MAX_FNAME_LEN);
+			} else {
+				rp->target_inode_ptr = res;
+				strcpy(rp->parent_fname, current_fname);
+				strcpy(rp->target_fname, next_fname);
+			}
+		}
+
+	}
 }
 
 
@@ -1631,6 +1721,73 @@ int fs_ln(void *d)
 	return 0;
 }
 
+static int read_symlink(int symlink_inode_ptr, char *path)
+{
+	struct fs_inode i;
+	read_block(read_inode_ptr(symlink_inode_ptr), &i);
+
+	path[0] = '\0';
+	int bytes_read = 0;
+
+	for (int j = 0; j < BLOCK_ADDRESSES_PER_INODE; j++) {
+		if (!i.blocks[j]) {
+			pr_err("inode size (%d) indicates existing block but it's address is absent in inode, symlink at inode_ptr=%d might be broken\n",
+					i.size, symlink_inode_ptr);
+			return -1;
+		}
+
+		char data[FS_BLOCK_SIZE];
+		read_block(i.blocks[j], data);
+
+		if (i.size - bytes_read < FS_BLOCK_SIZE) {
+			memcpy(&(path[bytes_read]), data, i.size - bytes_read);
+			bytes_read = i.size;
+			path[bytes_read] = '\0';
+		} else {
+			memcpy(&(path[bytes_read]), data, FS_BLOCK_SIZE);
+			bytes_read += FS_BLOCK_SIZE;
+			path[bytes_read] = '\0';
+		}
+
+		if (i.size == bytes_read)
+			goto finish_reading;
+	}
+
+	for (unsigned int next_ext = i.next_extension; ; ) {
+		struct fs_inode_extension ext;
+		read_block(next_ext, &ext);
+
+		for (int j = 0; j < BLOCK_ADDRESSES_PER_INODE_EXTENSION; j++) {
+			if (!ext.blocks[j]) {
+				pr_err("inode size (%d) indicates existing block but it's address is absent in inode extension, symlink at inode_ptr=%d might be broken\n",
+						i.size, symlink_inode_ptr);
+				return -1;
+			}
+
+			char data[FS_BLOCK_SIZE];
+			read_block(ext.blocks[j], data);
+
+			if (i.size - bytes_read < FS_BLOCK_SIZE) {
+				memcpy(&(path[bytes_read]), data, i.size - bytes_read);
+				bytes_read = i.size;
+				path[bytes_read] = '\0';
+			} else {
+				memcpy(&(path[bytes_read]), data, FS_BLOCK_SIZE);
+				bytes_read += FS_BLOCK_SIZE;
+				path[bytes_read] = '\0';
+			}
+
+			if (i.size == bytes_read)
+				goto finish_reading;
+		}
+
+		next_ext = ext.next_extension;
+	}
+
+finish_reading:
+	return bytes_read;
+}
+
 int fs_symlink(void *d)
 {
 	char *target_path = ((char **) d)[0];