+/*
+ * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2013 Raphaël Beamonte <raphael.beamonte@gmail.com>
+ * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ * Copyright (C) 2021 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ */
+
+#define _LGPL_SOURCE
+#include <common/macros.h>
+#include <common/common.h>
+#include <common/path.h>
+
+/*
+ * Return a partial realpath(3) of the path even if the full path does not
+ * exist. For instance, with /tmp/test1/test2/test3, if test2/ does not exist
+ * but the /tmp/test1 does, the real path for /tmp/test1 is concatened with
+ * /test2/test3 then returned. In normal time, realpath(3) fails if the end
+ * point directory does not exist.
+ *
+ * Return a newly-allocated string.
+ */
+static
+char *utils_partial_realpath(const char *path)
+{
+ char *cut_path = NULL, *try_path = NULL, *try_path_prev = NULL;
+ const char *next, *prev, *end;
+ char *resolved_path = NULL;
+
+ /* Safety net */
+ if (path == NULL) {
+ goto error;
+ }
+
+ /*
+ * Identify the end of the path, we don't want to treat the
+ * last char if it is a '/', we will just keep it on the side
+ * to be added at the end, and return a value coherent with
+ * the path given as argument
+ */
+ end = path + strlen(path);
+ if (*(end-1) == '/') {
+ end--;
+ }
+
+ /* Initiate the values of the pointers before looping */
+ next = path;
+ prev = next;
+ /* Only to ensure try_path is not NULL to enter the while */
+ try_path = (char *)next;
+
+ /* Resolve the canonical path of the first part of the path */
+ while (try_path != NULL && next != end) {
+ char *try_path_buf = NULL;
+
+ /*
+ * If there is not any '/' left, we want to try with
+ * the full path
+ */
+ next = strpbrk(next + 1, "/");
+ if (next == NULL) {
+ next = end;
+ }
+
+ /* Cut the part we will be trying to resolve */
+ cut_path = lttng_strndup(path, next - path);
+ if (cut_path == NULL) {
+ PERROR("lttng_strndup");
+ goto error;
+ }
+
+ try_path_buf = (char *) zmalloc(LTTNG_PATH_MAX);
+ if (!try_path_buf) {
+ PERROR("zmalloc");
+ goto error;
+ }
+
+ /* Try to resolve this part */
+ try_path = realpath((char *) cut_path, try_path_buf);
+ if (try_path == NULL) {
+ free(try_path_buf);
+ /*
+ * There was an error, we just want to be assured it
+ * is linked to an unexistent directory, if it's another
+ * reason, we spawn an error
+ */
+ switch (errno) {
+ case ENOENT:
+ /* Ignore the error */
+ break;
+ default:
+ PERROR("realpath (partial_realpath)");
+ goto error;
+ break;
+ }
+ } else {
+ /* Save the place we are before trying the next step */
+ try_path_buf = NULL;
+ free(try_path_prev);
+ try_path_prev = try_path;
+ prev = next;
+ }
+
+ /* Free the allocated memory */
+ free(cut_path);
+ cut_path = NULL;
+ }
+
+ /* Allocate memory for the resolved path. */
+ resolved_path = (char *) zmalloc(LTTNG_PATH_MAX);
+ if (resolved_path == NULL) {
+ PERROR("zmalloc resolved path");
+ goto error;
+ }
+
+ /*
+ * If we were able to solve at least partially the path, we can concatenate
+ * what worked and what didn't work
+ */
+ if (try_path_prev != NULL) {
+ /* If we risk to concatenate two '/', we remove one of them */
+ if (try_path_prev[strlen(try_path_prev) - 1] == '/' && prev[0] == '/') {
+ try_path_prev[strlen(try_path_prev) - 1] = '\0';
+ }
+
+ /*
+ * Duplicate the memory used by prev in case resolved_path and
+ * path are pointers for the same memory space
+ */
+ cut_path = strdup(prev);
+ if (cut_path == NULL) {
+ PERROR("strdup");
+ goto error;
+ }
+
+ /* Concatenate the strings */
+ snprintf(resolved_path, LTTNG_PATH_MAX, "%s%s",
+ try_path_prev, cut_path);
+
+ /* Free the allocated memory */
+ free(cut_path);
+ free(try_path_prev);
+ cut_path = NULL;
+ try_path_prev = NULL;
+ /*
+ * Else, we just copy the path in our resolved_path to
+ * return it as is
+ */
+ } else {
+ strncpy(resolved_path, path, LTTNG_PATH_MAX);
+ }
+
+ /* Then we return the 'partially' resolved path */
+ return resolved_path;
+
+error:
+ free(resolved_path);
+ free(cut_path);
+ free(try_path);
+ if (try_path_prev != try_path) {
+ free(try_path_prev);
+ }
+ return NULL;
+}
+
+static
+int expand_double_slashes_dot_and_dotdot(char *path)
+{
+ size_t expanded_path_len, path_len;
+ const char *curr_char, *path_last_char, *next_slash, *prev_slash;
+
+ path_len = strlen(path);
+ path_last_char = &path[path_len];
+
+ if (path_len == 0) {
+ goto error;
+ }
+
+ expanded_path_len = 0;
+
+ /* We iterate over the provided path to expand the "//", "../" and "./" */
+ for (curr_char = path; curr_char <= path_last_char; curr_char = next_slash + 1) {
+ /* Find the next forward slash. */
+ size_t curr_token_len;
+
+ if (curr_char == path_last_char) {
+ expanded_path_len++;
+ break;
+ }
+
+ next_slash = (const char *) memchr(curr_char, '/', path_last_char - curr_char);
+ if (next_slash == NULL) {
+ /* Reached the end of the provided path. */
+ next_slash = path_last_char;
+ }
+
+ /* Compute how long is the previous token. */
+ curr_token_len = next_slash - curr_char;
+ switch(curr_token_len) {
+ case 0:
+ /*
+ * The pointer has not move meaning that curr_char is
+ * pointing to a slash. It that case there is no token
+ * to copy, so continue the iteration to find the next
+ * token
+ */
+ continue;
+ case 1:
+ /*
+ * The pointer moved 1 character. Check if that
+ * character is a dot ('.'), if it is: omit it, else
+ * copy the token to the normalized path.
+ */
+ if (curr_char[0] == '.') {
+ continue;
+ }
+ break;
+ case 2:
+ /*
+ * The pointer moved 2 characters. Check if these
+ * characters are double dots ('..'). If that is the
+ * case, we need to remove the last token of the
+ * normalized path.
+ */
+ if (curr_char[0] == '.' && curr_char[1] == '.') {
+ /*
+ * Find the previous path component by
+ * using the memrchr function to find the
+ * previous forward slash and substract that
+ * len to the resulting path.
+ */
+ prev_slash = (const char *) lttng_memrchr(path, '/', expanded_path_len);
+ /*
+ * If prev_slash is NULL, we reached the
+ * beginning of the path. We can't go back any
+ * further.
+ */
+ if (prev_slash != NULL) {
+ expanded_path_len = prev_slash - path;
+ }
+ continue;
+ }
+ break;
+ default:
+ break;
+ }
+
+ /*
+ * Copy the current token which is neither a '.' nor a '..'.
+ */
+ path[expanded_path_len++] = '/';
+ memmove(&path[expanded_path_len], curr_char, curr_token_len);
+ expanded_path_len += curr_token_len;
+ }
+
+ if (expanded_path_len == 0) {
+ path[expanded_path_len++] = '/';
+ }
+
+ path[expanded_path_len] = '\0';
+ return 0;
+error:
+ return -1;
+}
+
+/*
+ * Make a full resolution of the given path even if it doesn't exist.
+ * This function uses the utils_partial_realpath function to resolve
+ * symlinks and relatives paths at the start of the string, and
+ * implements functionnalities to resolve the './' and '../' strings
+ * in the middle of a path. This function is only necessary because
+ * realpath(3) does not accept to resolve unexistent paths.
+ * The returned string was allocated in the function, it is thus of
+ * the responsibility of the caller to free this memory.
+ */
+static
+char *_utils_expand_path(const char *path, bool keep_symlink)
+{
+ int ret;
+ char *absolute_path = NULL;
+ char *last_token;
+ bool is_dot, is_dotdot;
+
+ /* Safety net */
+ if (path == NULL) {
+ goto error;
+ }
+
+ /* Allocate memory for the absolute_path */
+ absolute_path = (char *) zmalloc(LTTNG_PATH_MAX);
+ if (absolute_path == NULL) {
+ PERROR("zmalloc expand path");
+ goto error;
+ }
+
+ if (path[0] == '/') {
+ ret = lttng_strncpy(absolute_path, path, LTTNG_PATH_MAX);
+ if (ret) {
+ ERR("Path exceeds maximal size of %i bytes", LTTNG_PATH_MAX);
+ goto error;
+ }
+ } else {
+ /*
+ * This is a relative path. We need to get the present working
+ * directory and start the path walk from there.
+ */
+ char current_working_dir[LTTNG_PATH_MAX];
+ char *cwd_ret;
+
+ cwd_ret = getcwd(current_working_dir, sizeof(current_working_dir));
+ if (!cwd_ret) {
+ goto error;
+ }
+ /*
+ * Get the number of character in the CWD and allocate an array
+ * to can hold it and the path provided by the caller.
+ */
+ ret = snprintf(absolute_path, LTTNG_PATH_MAX, "%s/%s",
+ current_working_dir, path);
+ if (ret >= LTTNG_PATH_MAX) {
+ ERR("Concatenating current working directory %s and path %s exceeds maximal size of %i bytes",
+ current_working_dir, path, LTTNG_PATH_MAX);
+ goto error;
+ }
+ }
+
+ if (keep_symlink) {
+ /* Resolve partially our path */
+ char *new_absolute_path = utils_partial_realpath(absolute_path);
+ if (!new_absolute_path) {
+ goto error;
+ }
+
+ free(absolute_path);
+ absolute_path = new_absolute_path;
+ }
+
+ ret = expand_double_slashes_dot_and_dotdot(absolute_path);
+ if (ret) {
+ goto error;
+ }
+
+ /* Identify the last token */
+ last_token = strrchr(absolute_path, '/');
+
+ /* Verify that this token is not a relative path */
+ is_dotdot = (strcmp(last_token, "/..") == 0);
+ is_dot = (strcmp(last_token, "/.") == 0);
+
+ /* If it is, take action */
+ if (is_dot || is_dotdot) {
+ /* For both, remove this token */
+ *last_token = '\0';
+
+ /* If it was a reference to parent directory, go back one more time */
+ if (is_dotdot) {
+ last_token = strrchr(absolute_path, '/');
+
+ /* If there was only one level left, we keep the first '/' */
+ if (last_token == absolute_path) {
+ last_token++;
+ }
+
+ *last_token = '\0';
+ }
+ }
+
+ return absolute_path;
+
+error:
+ free(absolute_path);
+ return NULL;
+}
+char *utils_expand_path(const char *path)
+{
+ return _utils_expand_path(path, true);
+}
+
+char *utils_expand_path_keep_symlink(const char *path)
+{
+ return _utils_expand_path(path, false);
+}
projects / lttng-tools.git / commitdiff
