SoW-2020-0002: Trace Hit Counters: trigger error reporting integration
[lttng-tools.git] / src / common / utils.c
index 08139e5e2cb23d691c92c6800cef841e2362bc57..3497f92dbb00aba9c07186c355f9b881b1a0f619 100644 (file)
@@ -1,22 +1,13 @@
 /*
- * 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) 2012 David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2013 Raphaël Beamonte <raphael.beamonte@gmail.com>
+ * Copyright (C) 2013 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License, version 2 only, as
- * published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 51
- * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "common/macros.h"
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <ctype.h>
 #include <unistd.h>
 
 #include <common/common.h>
+#include <common/readwrite.h>
 #include <common/runas.h>
 #include <common/compat/getenv.h>
 #include <common/compat/string.h>
 #include <common/compat/dirent.h>
+#include <common/compat/directory-handle.h>
+#include <common/dynamic-buffer.h>
+#include <common/string-utils/format.h>
 #include <lttng/constant.h>
 
 #include "utils.h"
 #include "defaults.h"
 #include "time.h"
 
+#define PROC_MEMINFO_PATH               "/proc/meminfo"
+#define PROC_MEMINFO_MEMAVAILABLE_LINE  "MemAvailable:"
+#define PROC_MEMINFO_MEMTOTAL_LINE      "MemTotal:"
+
+/* The length of the longest field of `/proc/meminfo`. */
+#define PROC_MEMINFO_FIELD_MAX_NAME_LEN        20
+
+#if (PROC_MEMINFO_FIELD_MAX_NAME_LEN == 20)
+#define MAX_NAME_LEN_SCANF_IS_A_BROKEN_API "19"
+#else
+#error MAX_NAME_LEN_SCANF_IS_A_BROKEN_API must be updated to match (PROC_MEMINFO_FIELD_MAX_NAME_LEN - 1)
+#endif
+
+#define FALLBACK_USER_BUFLEN 16384
+#define FALLBACK_GROUP_BUFLEN 16384
+
 /*
  * 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
@@ -283,7 +294,7 @@ int expand_double_slashes_dot_and_dotdot(char *path)
                 * Copy the current token which is neither a '.' nor a '..'.
                 */
                path[expanded_path_len++] = '/';
-               memcpy(&path[expanded_path_len], curr_char, curr_token_len);
+               memmove(&path[expanded_path_len], curr_char, curr_token_len);
                expanded_path_len += curr_token_len;
        }
 
@@ -307,7 +318,7 @@ error:
  * The returned string was allocated in the function, it is thus of
  * the responsibility of the caller to free this memory.
  */
-LTTNG_HIDDEN
+static
 char *_utils_expand_path(const char *path, bool keep_symlink)
 {
        int ret;
@@ -362,6 +373,9 @@ char *_utils_expand_path(const char *path, bool keep_symlink)
                /* Resolve partially our path */
                absolute_path = utils_partial_realpath(absolute_path,
                                absolute_path, LTTNG_PATH_MAX);
+               if (!absolute_path) {
+                       goto error;
+               }
        }
 
        ret = expand_double_slashes_dot_and_dotdot(absolute_path);
@@ -527,6 +541,7 @@ void utils_close_pipe(int *src)
                if (ret) {
                        PERROR("close pipe");
                }
+               src[i] = -1;
        }
 }
 
@@ -653,44 +668,6 @@ error:
        return fd;
 }
 
-/*
- * On some filesystems (e.g. nfs), mkdir will validate access rights before
- * checking for the existence of the path element. This means that on a setup
- * where "/home/" is a mounted NFS share, and running as an unpriviledged user,
- * recursively creating a path of the form "/home/my_user/trace/" will fail with
- * EACCES on mkdir("/home", ...).
- *
- * Performing a stat(...) on the path to check for existence allows us to
- * work around this behaviour.
- */
-static
-int mkdir_check_exists(const char *path, mode_t mode)
-{
-       int ret = 0;
-       struct stat st;
-
-       ret = stat(path, &st);
-       if (ret == 0) {
-               if (S_ISDIR(st.st_mode)) {
-                       /* Directory exists, skip. */
-                       goto end;
-               } else {
-                       /* Exists, but is not a directory. */
-                       errno = ENOTDIR;
-                       ret = -1;
-                       goto end;
-               }
-       }
-
-       /*
-        * Let mkdir handle other errors as the caller expects mkdir
-        * semantics.
-        */
-       ret = mkdir(path, mode);
-end:
-       return ret;
-}
-
 /*
  * Create directory using the given path and mode.
  *
@@ -700,82 +677,22 @@ LTTNG_HIDDEN
 int utils_mkdir(const char *path, mode_t mode, int uid, int gid)
 {
        int ret;
-
-       if (uid < 0 || gid < 0) {
-               ret = mkdir_check_exists(path, mode);
-       } else {
-               ret = run_as_mkdir(path, mode, uid, gid);
-       }
-       if (ret < 0) {
-               if (errno != EEXIST) {
-                       PERROR("mkdir %s, uid %d, gid %d", path ? path : "NULL",
-                                       uid, gid);
-               } else {
-                       ret = 0;
-               }
-       }
-
-       return ret;
-}
-
-/*
- * Internal version of mkdir_recursive. Runs as the current user.
- * Don't call directly; use utils_mkdir_recursive().
- *
- * This function is ominously marked as "unsafe" since it should only
- * be called by a caller that has transitioned to the uid and gid under which
- * the directory creation should occur.
- */
-LTTNG_HIDDEN
-int _utils_mkdir_recursive_unsafe(const char *path, mode_t mode)
-{
-       char *p, tmp[PATH_MAX];
-       size_t len;
-       int ret;
-
-       assert(path);
-
-       ret = snprintf(tmp, sizeof(tmp), "%s", path);
-       if (ret < 0) {
-               PERROR("snprintf mkdir");
-               goto error;
-       }
-
-       len = ret;
-       if (tmp[len - 1] == '/') {
-               tmp[len - 1] = 0;
-       }
-
-       for (p = tmp + 1; *p; p++) {
-               if (*p == '/') {
-                       *p = 0;
-                       if (tmp[strlen(tmp) - 1] == '.' &&
-                                       tmp[strlen(tmp) - 2] == '.' &&
-                                       tmp[strlen(tmp) - 3] == '/') {
-                               ERR("Using '/../' is not permitted in the trace path (%s)",
-                                               tmp);
-                               ret = -1;
-                               goto error;
-                       }
-                       ret = mkdir_check_exists(tmp, mode);
-                       if (ret < 0) {
-                               if (errno != EACCES) {
-                                       PERROR("mkdir recursive");
-                                       ret = -errno;
-                                       goto error;
-                               }
-                       }
-                       *p = '/';
-               }
-       }
-
-       ret = mkdir_check_exists(tmp, mode);
-       if (ret < 0) {
-               PERROR("mkdir recursive last element");
-               ret = -errno;
+       struct lttng_directory_handle *handle;
+       const struct lttng_credentials creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(gid),
+       };
+
+       handle = lttng_directory_handle_create(NULL);
+       if (!handle) {
+               ret = -1;
+               goto end;
        }
-
-error:
+       ret = lttng_directory_handle_create_subdirectory_as_user(
+                       handle, path, mode,
+                       (uid >= 0 || gid >= 0) ? &creds : NULL);
+end:
+       lttng_directory_handle_put(handle);
        return ret;
 }
 
@@ -789,221 +706,66 @@ LTTNG_HIDDEN
 int utils_mkdir_recursive(const char *path, mode_t mode, int uid, int gid)
 {
        int ret;
-
-       if (uid < 0 || gid < 0) {
-               /* Run as current user. */
-               ret = _utils_mkdir_recursive_unsafe(path, mode);
-       } else {
-               ret = run_as_mkdir_recursive(path, mode, uid, gid);
-       }
-       if (ret < 0) {
-               PERROR("mkdir %s, uid %d, gid %d", path ? path : "NULL",
-                               uid, gid);
-       }
-
-       return ret;
-}
-
-/*
- * path is the output parameter. It needs to be PATH_MAX len.
- *
- * Return 0 on success or else a negative value.
- */
-static int utils_stream_file_name(char *path,
-               const char *path_name, const char *file_name,
-               uint64_t size, uint64_t count,
-               const char *suffix)
-{
-       int ret;
-       char full_path[PATH_MAX];
-       char *path_name_suffix = NULL;
-       char *extra = NULL;
-
-       ret = snprintf(full_path, sizeof(full_path), "%s/%s",
-                       path_name, file_name);
-       if (ret < 0) {
-               PERROR("snprintf create output file");
-               goto error;
-       }
-
-       /* Setup extra string if suffix or/and a count is needed. */
-       if (size > 0 && suffix) {
-               ret = asprintf(&extra, "_%" PRIu64 "%s", count, suffix);
-       } else if (size > 0) {
-               ret = asprintf(&extra, "_%" PRIu64, count);
-       } else if (suffix) {
-               ret = asprintf(&extra, "%s", suffix);
-       }
-       if (ret < 0) {
-               PERROR("Allocating extra string to name");
-               goto error;
-       }
-
-       /*
-        * If we split the trace in multiple files, we have to add the count at
-        * the end of the tracefile name.
-        */
-       if (extra) {
-               ret = asprintf(&path_name_suffix, "%s%s", full_path, extra);
-               if (ret < 0) {
-                       PERROR("Allocating path name with extra string");
-                       goto error_free_suffix;
-               }
-               strncpy(path, path_name_suffix, PATH_MAX - 1);
-               path[PATH_MAX - 1] = '\0';
-       } else {
-               ret = lttng_strncpy(path, full_path, PATH_MAX);
-               if (ret) {
-                       ERR("Failed to copy stream file name");
-                       goto error_free_suffix;
-               }
-       }
-       path[PATH_MAX - 1] = '\0';
-       ret = 0;
-
-       free(path_name_suffix);
-error_free_suffix:
-       free(extra);
-error:
-       return ret;
-}
-
-/*
- * Create the stream file on disk.
- *
- * Return 0 on success or else a negative value.
- */
-LTTNG_HIDDEN
-int utils_create_stream_file(const char *path_name, char *file_name, uint64_t size,
-               uint64_t count, int uid, int gid, char *suffix)
-{
-       int ret, flags, mode;
-       char path[PATH_MAX];
-
-       ret = utils_stream_file_name(path, path_name, file_name,
-                       size, count, suffix);
-       if (ret < 0) {
-               goto error;
-       }
-
-       /*
-        * With the session rotation feature on the relay, we might need to seek
-        * and truncate a tracefile, so we need read and write access.
-        */
-       flags = O_RDWR | O_CREAT | O_TRUNC;
-       /* Open with 660 mode */
-       mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
-
-       if (uid < 0 || gid < 0) {
-               ret = open(path, flags, mode);
-       } else {
-               ret = run_as_open(path, flags, mode, uid, gid);
-       }
-       if (ret < 0) {
-               PERROR("open stream path %s", path);
+       struct lttng_directory_handle *handle;
+       const struct lttng_credentials creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(gid),
+       };
+
+       handle = lttng_directory_handle_create(NULL);
+       if (!handle) {
+               ret = -1;
+               goto end;
        }
-error:
+       ret = lttng_directory_handle_create_subdirectory_recursive_as_user(
+                       handle, path, mode,
+                       (uid >= 0 || gid >= 0) ? &creds : NULL);
+end:
+       lttng_directory_handle_put(handle);
        return ret;
 }
 
 /*
- * Unlink the stream tracefile from disk.
+ * out_stream_path is the output parameter.
  *
  * Return 0 on success or else a negative value.
  */
 LTTNG_HIDDEN
-int utils_unlink_stream_file(const char *path_name, char *file_name, uint64_t size,
-               uint64_t count, int uid, int gid, char *suffix)
+int utils_stream_file_path(const char *path_name, const char *file_name,
+               uint64_t size, uint64_t count, const char *suffix,
+               char *out_stream_path, size_t stream_path_len)
 {
        int ret;
-       char path[PATH_MAX];
+       char count_str[MAX_INT_DEC_LEN(count) + 1] = {};
+       const char *path_separator;
 
-       ret = utils_stream_file_name(path, path_name, file_name,
-                       size, count, suffix);
-       if (ret < 0) {
-               goto error;
-       }
-       if (uid < 0 || gid < 0) {
-               ret = unlink(path);
+       if (path_name && (path_name[0] == '\0' ||
+                       path_name[strlen(path_name) - 1] == '/')) {
+               path_separator = "";
        } else {
-               ret = run_as_unlink(path, uid, gid);
+               path_separator = "/";
        }
-       if (ret < 0) {
-               goto error;
-       }
-error:
-       DBG("utils_unlink_stream_file %s returns %d", path, ret);
-       return ret;
-}
-
-/*
- * Change the output tracefile according to the given size and count The
- * new_count pointer is set during this operation.
- *
- * From the consumer, the stream lock MUST be held before calling this function
- * because we are modifying the stream status.
- *
- * Return 0 on success or else a negative value.
- */
-LTTNG_HIDDEN
-int utils_rotate_stream_file(char *path_name, char *file_name, uint64_t size,
-               uint64_t count, int uid, int gid, int out_fd, uint64_t *new_count,
-               int *stream_fd)
-{
-       int ret;
-
-       assert(stream_fd);
 
-       ret = close(out_fd);
-       if (ret < 0) {
-               PERROR("Closing tracefile");
-               goto error;
+       path_name = path_name ? : "";
+       suffix = suffix ? : "";
+       if (size > 0) {
+               ret = snprintf(count_str, sizeof(count_str), "_%" PRIu64,
+                               count);
+               assert(ret > 0 && ret < sizeof(count_str));
        }
-       *stream_fd = -1;
 
-       if (count > 0) {
-               /*
-                * In tracefile rotation, for the relay daemon we need
-                * to unlink the old file if present, because it may
-                * still be open in reading by the live thread, and we
-                * need to ensure that we do not overwrite the content
-                * between get_index and get_packet. Since we have no
-                * way to verify integrity of the data content compared
-                * to the associated index, we need to ensure the reader
-                * has exclusive access to the file content, and that
-                * the open of the data file is performed in get_index.
-                * Unlinking the old file rather than overwriting it
-                * achieves this.
-                */
-               if (new_count) {
-                       *new_count = (*new_count + 1) % count;
-               }
-               ret = utils_unlink_stream_file(path_name, file_name, size,
-                               new_count ? *new_count : 0, uid, gid, 0);
-               if (ret < 0 && errno != ENOENT) {
-                       goto error;
-               }
+       ret = snprintf(out_stream_path, stream_path_len, "%s%s%s%s%s",
+                       path_name, path_separator, file_name, count_str,
+                       suffix);
+       if (ret < 0 || ret >= stream_path_len) {
+               ERR("Truncation occurred while formatting stream path");
+               ret = -1;
        } else {
-               if (new_count) {
-                       (*new_count)++;
-               }
-       }
-
-       ret = utils_create_stream_file(path_name, file_name, size,
-                       new_count ? *new_count : 0, uid, gid, 0);
-       if (ret < 0) {
-               goto error;
+               ret = 0;
        }
-       *stream_fd = ret;
-
-       /* Success. */
-       ret = 0;
-
-error:
        return ret;
 }
 
-
 /**
  * Parse a string that represents a size in human readable format. It
  * supports decimal integers suffixed by 'k', 'K', 'M' or 'G'.
@@ -1104,12 +866,19 @@ end:
 
 /**
  * Parse a string that represents a time in human readable format. It
- * supports decimal integers suffixed by 's', 'u', 'm', 'us', and 'ms'.
+ * supports decimal integers suffixed by:
+ *     "us" for microsecond,
+ *     "ms" for millisecond,
+ *     "s"  for second,
+ *     "m"  for minute,
+ *     "h"  for hour
  *
  * The suffix multiply the integer by:
- * 'u'/'us': 1
- * 'm'/'ms': 1000
- * 's': 1000000
+ *     "us" : 1
+ *     "ms" : 1000
+ *     "s"  : 1000000
+ *     "m"  : 60000000
+ *     "h"  : 3600000000
  *
  * Note that unit-less numbers are assumed to be microseconds.
  *
@@ -1124,7 +893,7 @@ int utils_parse_time_suffix(char const * const str, uint64_t * const time_us)
 {
        int ret;
        uint64_t base_time;
-       long multiplier = 1;
+       uint64_t multiplier = 1;
        const char *str_end;
        char *num_end;
 
@@ -1161,17 +930,37 @@ int utils_parse_time_suffix(char const * const str, uint64_t * const time_us)
        /* Check if a prefix is present. */
        switch (*num_end) {
        case 'u':
-               multiplier = 1;
-               /* Skip another letter in the 'us' case. */
-               num_end += (*(num_end + 1) == 's') ? 2 : 1;
+               /*
+                * Microsecond (us)
+                *
+                * Skip the "us" if the string matches the "us" suffix,
+                * otherwise let the check for the end of the string handle
+                * the error reporting.
+                */
+               if (*(num_end + 1) == 's') {
+                       num_end += 2;
+               }
                break;
        case 'm':
-               multiplier = 1000;
-               /* Skip another letter in the 'ms' case. */
-               num_end += (*(num_end + 1) == 's') ? 2 : 1;
+               if (*(num_end + 1) == 's') {
+                       /* Millisecond (ms) */
+                       multiplier = USEC_PER_MSEC;
+                       /* Skip the 's' */
+                       num_end++;
+               } else {
+                       /* Minute (m) */
+                       multiplier = USEC_PER_MINUTE;
+               }
+               num_end++;
                break;
        case 's':
-               multiplier = 1000000;
+               /* Second */
+               multiplier = USEC_PER_SEC;
+               num_end++;
+               break;
+       case 'h':
+               /* Hour */
+               multiplier = USEC_PER_HOURS;
                num_end++;
                break;
        case '\0':
@@ -1223,7 +1012,7 @@ static inline unsigned int fls_u32(uint32_t x)
 #define HAS_FLS_U32
 #endif
 
-#if defined(__x86_64)
+#if defined(__x86_64) && defined(__LP64__)
 static inline
 unsigned int fls_u64(uint64_t x)
 {
@@ -1341,7 +1130,7 @@ int utils_get_count_order_u64(uint64_t x)
  * Otherwise returns the value of HOME.
  */
 LTTNG_HIDDEN
-char *utils_get_home_dir(void)
+const char *utils_get_home_dir(void)
 {
        char *val = NULL;
        struct passwd *pwd;
@@ -1436,24 +1225,83 @@ size_t utils_get_current_time_str(const char *format, char *dst, size_t len)
 }
 
 /*
- * Return the group ID matching name, else 0 if it cannot be found.
+ * Return 0 on success and set *gid to the group_ID matching the passed name.
+ * Else -1 if it cannot be found or an error occurred.
  */
 LTTNG_HIDDEN
-gid_t utils_get_group_id(const char *name)
+int utils_get_group_id(const char *name, bool warn, gid_t *gid)
 {
-       struct group *grp;
+       static volatile int warn_once;
+       int ret;
+       long sys_len;
+       size_t len;
+       struct group grp;
+       struct group *result;
+       struct lttng_dynamic_buffer buffer;
+
+       /* Get the system limit, if it exists. */
+       sys_len = sysconf(_SC_GETGR_R_SIZE_MAX);
+       if (sys_len == -1) {
+               len = 1024;
+       } else {
+               len = (size_t) sys_len;
+       }
+
+       lttng_dynamic_buffer_init(&buffer);
+       ret = lttng_dynamic_buffer_set_size(&buffer, len);
+       if (ret) {
+               ERR("Failed to allocate group info buffer");
+               ret = -1;
+               goto error;
+       }
 
-       grp = getgrnam(name);
-       if (!grp) {
-               static volatile int warn_once;
+       while ((ret = getgrnam_r(name, &grp, buffer.data, buffer.size, &result)) == ERANGE) {
+               const size_t new_len = 2 * buffer.size;
 
-               if (!warn_once) {
-                       WARN("No tracing group detected");
-                       warn_once = 1;
+               /* Buffer is not big enough, increase its size. */
+               if (new_len < buffer.size) {
+                       ERR("Group info buffer size overflow");
+                       ret = -1;
+                       goto error;
                }
-               return 0;
+
+               ret = lttng_dynamic_buffer_set_size(&buffer, new_len);
+               if (ret) {
+                       ERR("Failed to grow group info buffer to %zu bytes",
+                                       new_len);
+                       ret = -1;
+                       goto error;
+               }
+       }
+       if (ret) {
+               if (ret == ESRCH) {
+                       DBG("Could not find group file entry for group name '%s'",
+                                       name);
+               } else {
+                       PERROR("Failed to get group file entry for group name '%s'",
+                                       name);
+               }
+
+               ret = -1;
+               goto error;
+       }
+
+       /* Group not found. */
+       if (!result) {
+               ret = -1;
+               goto error;
+       }
+
+       *gid = result->gr_gid;
+       ret = 0;
+
+error:
+       if (ret && warn && !warn_once) {
+               WARN("No tracing group detected");
+               warn_once = 1;
        }
-       return grp->gr_gid;
+       lttng_dynamic_buffer_reset(&buffer);
+       return ret;
 }
 
 /*
@@ -1508,79 +1356,17 @@ end:
 LTTNG_HIDDEN
 int utils_recursive_rmdir(const char *path)
 {
-       DIR *dir;
-       size_t path_len;
-       int dir_fd, ret = 0, closeret, is_empty = 1;
-       struct dirent *entry;
-
-       /* Open directory */
-       dir = opendir(path);
-       if (!dir) {
-               PERROR("Cannot open '%s' path", path);
-               return -1;
-       }
-       dir_fd = lttng_dirfd(dir);
-       if (dir_fd < 0) {
-               PERROR("lttng_dirfd");
-               return -1;
-       }
-
-       path_len = strlen(path);
-       while ((entry = readdir(dir))) {
-               struct stat st;
-               size_t name_len;
-               char filename[PATH_MAX];
-
-               if (!strcmp(entry->d_name, ".")
-                               || !strcmp(entry->d_name, "..")) {
-                       continue;
-               }
-
-               name_len = strlen(entry->d_name);
-               if (path_len + name_len + 2 > sizeof(filename)) {
-                       ERR("Failed to remove file: path name too long (%s/%s)",
-                               path, entry->d_name);
-                       continue;
-               }
-               if (snprintf(filename, sizeof(filename), "%s/%s",
-                               path, entry->d_name) < 0) {
-                       ERR("Failed to format path.");
-                       continue;
-               }
-
-               if (stat(filename, &st)) {
-                       PERROR("stat");
-                       continue;
-               }
+       int ret;
+       struct lttng_directory_handle *handle;
 
-               if (S_ISDIR(st.st_mode)) {
-                       char subpath[PATH_MAX];
-
-                       strncpy(subpath, path, PATH_MAX);
-                       subpath[PATH_MAX - 1] = '\0';
-                       strncat(subpath, "/",
-                               PATH_MAX - strlen(subpath) - 1);
-                       strncat(subpath, entry->d_name,
-                               PATH_MAX - strlen(subpath) - 1);
-                       if (utils_recursive_rmdir(subpath)) {
-                               is_empty = 0;
-                       }
-               } else if (S_ISREG(st.st_mode)) {
-                       is_empty = 0;
-               } else {
-                       ret = -EINVAL;
-                       goto end;
-               }
+       handle = lttng_directory_handle_create(NULL);
+       if (!handle) {
+               ret = -1;
+               goto end;
        }
+       ret = lttng_directory_handle_remove_subdirectory(handle, path);
 end:
-       closeret = closedir(dir);
-       if (closeret) {
-               PERROR("closedir");
-       }
-       if (is_empty) {
-               DBG3("Attempting rmdir %s", path);
-               ret = rmdir(path);
-       }
+       lttng_directory_handle_put(handle);
        return ret;
 }
 
@@ -1647,37 +1433,276 @@ end:
        return ret;
 }
 
+static
+int read_proc_meminfo_field(const char *field, size_t *value)
+{
+       int ret;
+       FILE *proc_meminfo;
+       char name[PROC_MEMINFO_FIELD_MAX_NAME_LEN] = {};
+
+       proc_meminfo = fopen(PROC_MEMINFO_PATH, "r");
+       if (!proc_meminfo) {
+               PERROR("Failed to fopen() " PROC_MEMINFO_PATH);
+               ret = -1;
+               goto fopen_error;
+        }
+
+       /*
+        * Read the contents of /proc/meminfo line by line to find the right
+        * field.
+        */
+       while (!feof(proc_meminfo)) {
+               unsigned long value_kb;
+
+               ret = fscanf(proc_meminfo,
+                               "%" MAX_NAME_LEN_SCANF_IS_A_BROKEN_API "s %lu kB\n",
+                               name, &value_kb);
+               if (ret == EOF) {
+                       /*
+                        * fscanf() returning EOF can indicate EOF or an error.
+                        */
+                       if (ferror(proc_meminfo)) {
+                               PERROR("Failed to parse " PROC_MEMINFO_PATH);
+                       }
+                       break;
+               }
+
+               if (ret == 2 && strcmp(name, field) == 0) {
+                       /*
+                        * This number is displayed in kilo-bytes. Return the
+                        * number of bytes.
+                        */
+                       *value = ((size_t) value_kb) * 1024;
+                       ret = 0;
+                       goto found;
+               }
+       }
+       /* Reached the end of the file without finding the right field. */
+       ret = -1;
+
+found:
+       fclose(proc_meminfo);
+fopen_error:
+       return ret;
+}
+
+/*
+ * Returns an estimate of the number of bytes of memory available based on the
+ * the information in `/proc/meminfo`. The number returned by this function is
+ * a best guess.
+ */
 LTTNG_HIDDEN
-int timespec_to_ms(struct timespec ts, unsigned long *ms)
+int utils_get_memory_available(size_t *value)
 {
-       unsigned long res, remain_ms;
+       return read_proc_meminfo_field(PROC_MEMINFO_MEMAVAILABLE_LINE, value);
+}
 
-       if (ts.tv_sec > ULONG_MAX / MSEC_PER_SEC) {
-               errno = EOVERFLOW;
-               return -1;      /* multiplication overflow */
+/*
+ * Returns the total size of the memory on the system in bytes based on the
+ * the information in `/proc/meminfo`.
+ */
+LTTNG_HIDDEN
+int utils_get_memory_total(size_t *value)
+{
+       return read_proc_meminfo_field(PROC_MEMINFO_MEMTOTAL_LINE, value);
+}
+
+LTTNG_HIDDEN
+int utils_change_working_directory(const char *path)
+{
+       int ret;
+
+       assert(path);
+
+       DBG("Changing working directory to \"%s\"", path);
+       ret = chdir(path);
+       if (ret) {
+               PERROR("Failed to change working directory to \"%s\"", path);
+               goto end;
        }
-       res = ts.tv_sec * MSEC_PER_SEC;
-       remain_ms = ULONG_MAX - res;
-       if (ts.tv_nsec / NSEC_PER_MSEC > remain_ms) {
-               errno = EOVERFLOW;
-               return -1;      /* addition overflow */
+
+       /* Check for write access */
+       if (access(path, W_OK)) {
+               if (errno == EACCES) {
+                       /*
+                        * Do not treat this as an error since the permission
+                        * might change in the lifetime of the process
+                        */
+                       DBG("Working directory \"%s\" is not writable", path);
+               } else {
+                       PERROR("Failed to check if working directory \"%s\" is writable",
+                                       path);
+               }
        }
-       res += ts.tv_nsec / NSEC_PER_MSEC;
-       *ms = res;
-       return 0;
+
+end:
+       return ret;
+}
+
+LTTNG_HIDDEN
+enum lttng_error_code utils_user_id_from_name(const char *user_name, uid_t *uid)
+{
+       struct passwd p, *pres;
+       int ret;
+       enum lttng_error_code ret_val = LTTNG_OK;
+       char *buf = NULL;
+       ssize_t buflen;
+
+       buflen = sysconf(_SC_GETPW_R_SIZE_MAX);
+       if (buflen < 0) {
+               buflen = FALLBACK_USER_BUFLEN;
+       }
+
+       buf = zmalloc(buflen);
+       if (!buf) {
+               ret_val = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       for (;;) {
+               ret = getpwnam_r(user_name, &p, buf, buflen, &pres);
+               switch (ret) {
+               case EINTR:
+                       continue;
+               case ERANGE:
+                       buflen *= 2;
+                       free(buf);
+                       buf = zmalloc(buflen);
+                       if (!buf) {
+                               ret_val = LTTNG_ERR_NOMEM;
+                               goto end;
+                       }
+                       continue;
+               default:
+                       goto end_loop;
+               }
+       }
+end_loop:
+
+       switch (ret) {
+       case 0:
+               if (pres == NULL) {
+                       ret_val = LTTNG_ERR_USER_NOT_FOUND;
+               } else {
+                       *uid = p.pw_uid;
+                       DBG("Lookup of tracker UID/VUID: name '%s' maps to uid %" PRId64,
+                                       user_name, (int64_t) *uid);
+                       ret_val = LTTNG_OK;
+               }
+               break;
+       case ENOENT:
+       case ESRCH:
+       case EBADF:
+       case EPERM:
+               ret_val = LTTNG_ERR_USER_NOT_FOUND;
+               break;
+       default:
+               ret_val = LTTNG_ERR_NOMEM;
+       }
+end:
+       free(buf);
+       return ret_val;
+}
+
+LTTNG_HIDDEN
+enum lttng_error_code utils_group_id_from_name(
+               const char *group_name, gid_t *gid)
+{
+       struct group g, *gres;
+       int ret;
+       enum lttng_error_code ret_val = LTTNG_OK;
+       char *buf = NULL;
+       ssize_t buflen;
+
+       buflen = sysconf(_SC_GETGR_R_SIZE_MAX);
+       if (buflen < 0) {
+               buflen = FALLBACK_GROUP_BUFLEN;
+       }
+
+       buf = zmalloc(buflen);
+       if (!buf) {
+               ret_val = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       for (;;) {
+               ret = getgrnam_r(group_name, &g, buf, buflen, &gres);
+               switch (ret) {
+               case EINTR:
+                       continue;
+               case ERANGE:
+                       buflen *= 2;
+                       free(buf);
+                       buf = zmalloc(buflen);
+                       if (!buf) {
+                               ret_val = LTTNG_ERR_NOMEM;
+                               goto end;
+                       }
+                       continue;
+               default:
+                       goto end_loop;
+               }
+       }
+end_loop:
+
+       switch (ret) {
+       case 0:
+               if (gres == NULL) {
+                       ret_val = LTTNG_ERR_GROUP_NOT_FOUND;
+               } else {
+                       *gid = g.gr_gid;
+                       DBG("Lookup of tracker GID/GUID: name '%s' maps to gid %" PRId64,
+                                       group_name, (int64_t) *gid);
+                       ret_val = LTTNG_OK;
+               }
+               break;
+       case ENOENT:
+       case ESRCH:
+       case EBADF:
+       case EPERM:
+               ret_val = LTTNG_ERR_GROUP_NOT_FOUND;
+               break;
+       default:
+               ret_val = LTTNG_ERR_NOMEM;
+       }
+end:
+       free(buf);
+       return ret_val;
 }
 
 LTTNG_HIDDEN
-struct timespec timespec_abs_diff(struct timespec t1, struct timespec t2)
+int utils_parse_unsigned_long_long(const char *str,
+               unsigned long long *value)
 {
-       uint64_t ts1 = (uint64_t) t1.tv_sec * (uint64_t) NSEC_PER_SEC +
-                       (uint64_t) t1.tv_nsec;
-       uint64_t ts2 = (uint64_t) t2.tv_sec * (uint64_t) NSEC_PER_SEC +
-                       (uint64_t) t2.tv_nsec;
-       uint64_t diff = max(ts1, ts2) - min(ts1, ts2);
-       struct timespec res;
-
-       res.tv_sec = diff / (uint64_t) NSEC_PER_SEC;
-       res.tv_nsec = diff % (uint64_t) NSEC_PER_SEC;
-       return res;
+       int ret;
+       char *endptr;
+
+       assert(str);
+       assert(value);
+
+       errno = 0;
+       *value = strtoull(str, &endptr, 10);
+
+       /* Conversion failed.  Out of range? */
+       if (errno != 0) {
+               ret = -1;
+               goto end;
+       }
+
+       /* Not the end of the string? */
+       if (*endptr) {
+               ret = -1;
+               goto end;
+       }
+
+       /* Empty string? */
+       if (endptr == str) {
+               ret = -1;
+               goto end;
+       }
+
+       ret = 0;
+
+end:
+       return ret;
 }
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