[lttng-tools.git] / src / common / utils.c

/*
 * 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.
 *
 * 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.
 */

#define _LGPL_SOURCE
#include <assert.h>
#include <ctype.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <inttypes.h>
#include <grp.h>
#include <pwd.h>
#include <sys/file.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

/*
 * 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.
 * In case resolved_path is NULL, the string returned was allocated in the
 * function and thus need to be freed by the caller. The size argument allows
 * to specify the size of the resolved_path argument if given, or the size to
 * allocate.
 */
LTTNG_HIDDEN
char *utils_partial_realpath(const char *path, char *resolved_path, size_t size)
{
        char *cut_path = NULL, *try_path = NULL, *try_path_prev = NULL;
        const char *next, *prev, *end;

        /* 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 = 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 if necessary */
        if (resolved_path == NULL) {
                resolved_path = zmalloc(size);
                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, size, "%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, size);
        }

        /* 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 = 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 = 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++] = '/';
                memcpy(&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 = 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 */
                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);
        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;
}
LTTNG_HIDDEN
char *utils_expand_path(const char *path)
{
        return _utils_expand_path(path, true);
}

LTTNG_HIDDEN
char *utils_expand_path_keep_symlink(const char *path)
{
        return _utils_expand_path(path, false);
}
/*
 * Create a pipe in dst.
 */
LTTNG_HIDDEN
int utils_create_pipe(int *dst)
{
        int ret;

        if (dst == NULL) {
                return -1;
        }

        ret = pipe(dst);
        if (ret < 0) {
                PERROR("create pipe");
        }

        return ret;
}

/*
 * Create pipe and set CLOEXEC flag to both fd.
 *
 * Make sure the pipe opened by this function are closed at some point. Use
 * utils_close_pipe().
 */
LTTNG_HIDDEN
int utils_create_pipe_cloexec(int *dst)
{
        int ret, i;

        if (dst == NULL) {
                return -1;
        }

        ret = utils_create_pipe(dst);
        if (ret < 0) {
                goto error;
        }

        for (i = 0; i < 2; i++) {
                ret = fcntl(dst[i], F_SETFD, FD_CLOEXEC);
                if (ret < 0) {
                        PERROR("fcntl pipe cloexec");
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Create pipe and set fd flags to FD_CLOEXEC and O_NONBLOCK.
 *
 * Make sure the pipe opened by this function are closed at some point. Use
 * utils_close_pipe(). Using pipe() and fcntl rather than pipe2() to
 * support OSes other than Linux 2.6.23+.
 */
LTTNG_HIDDEN
int utils_create_pipe_cloexec_nonblock(int *dst)
{
        int ret, i;

        if (dst == NULL) {
                return -1;
        }

        ret = utils_create_pipe(dst);
        if (ret < 0) {
                goto error;
        }

        for (i = 0; i < 2; i++) {
                ret = fcntl(dst[i], F_SETFD, FD_CLOEXEC);
                if (ret < 0) {
                        PERROR("fcntl pipe cloexec");
                        goto error;
                }
                /*
                 * Note: we override any flag that could have been
                 * previously set on the fd.
                 */
                ret = fcntl(dst[i], F_SETFL, O_NONBLOCK);
                if (ret < 0) {
                        PERROR("fcntl pipe nonblock");
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Close both read and write side of the pipe.
 */
LTTNG_HIDDEN
void utils_close_pipe(int *src)
{
        int i, ret;

        if (src == NULL) {
                return;
        }

        for (i = 0; i < 2; i++) {
                /* Safety check */
                if (src[i] < 0) {
                        continue;
                }

                ret = close(src[i]);
                if (ret) {
                        PERROR("close pipe");
                }
        }
}

/*
 * Create a new string using two strings range.
 */
LTTNG_HIDDEN
char *utils_strdupdelim(const char *begin, const char *end)
{
        char *str;

        str = zmalloc(end - begin + 1);
        if (str == NULL) {
                PERROR("zmalloc strdupdelim");
                goto error;
        }

        memcpy(str, begin, end - begin);
        str[end - begin] = '\0';

error:
        return str;
}

/*
 * Set CLOEXEC flag to the give file descriptor.
 */
LTTNG_HIDDEN
int utils_set_fd_cloexec(int fd)
{
        int ret;

        if (fd < 0) {
                ret = -EINVAL;
                goto end;
        }

        ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
        if (ret < 0) {
                PERROR("fcntl cloexec");
                ret = -errno;
        }

end:
        return ret;
}

/*
 * Create pid file to the given path and filename.
 */
LTTNG_HIDDEN
int utils_create_pid_file(pid_t pid, const char *filepath)
{
        int ret;
        FILE *fp;

        assert(filepath);

        fp = fopen(filepath, "w");
        if (fp == NULL) {
                PERROR("open pid file %s", filepath);
                ret = -1;
                goto error;
        }

        ret = fprintf(fp, "%d\n", (int) pid);
        if (ret < 0) {
                PERROR("fprintf pid file");
                goto error;
        }

        if (fclose(fp)) {
                PERROR("fclose");
        }
        DBG("Pid %d written in file %s", (int) pid, filepath);
        ret = 0;
error:
        return ret;
}

/*
 * Create lock file to the given path and filename.
 * Returns the associated file descriptor, -1 on error.
 */
LTTNG_HIDDEN
int utils_create_lock_file(const char *filepath)
{
        int ret;
        int fd;
        struct flock lock;

        assert(filepath);

        memset(&lock, 0, sizeof(lock));
        fd = open(filepath, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR |
                S_IRGRP | S_IWGRP);
        if (fd < 0) {
                PERROR("open lock file %s", filepath);
                fd = -1;
                goto error;
        }

        /*
         * Attempt to lock the file. If this fails, there is
         * already a process using the same lock file running
         * and we should exit.
         */
        lock.l_whence = SEEK_SET;
        lock.l_type = F_WRLCK;

        ret = fcntl(fd, F_SETLK, &lock);
        if (ret == -1) {
                PERROR("fcntl lock file");
                ERR("Could not get lock file %s, another instance is running.",
                        filepath);
                if (close(fd)) {
                        PERROR("close lock file");
                }
                fd = ret;
                goto error;
        }

error:
        return fd;
}

/*
 * Create directory using the given path and mode.
 *
 * On success, return 0 else a negative error code.
 */
LTTNG_HIDDEN
int utils_mkdir(const char *path, mode_t mode, int uid, int gid)
{
        int ret;
        struct lttng_directory_handle *handle;
        const struct lttng_credentials creds = {
                .uid = (uid_t) uid,
                .gid = (gid_t) gid,
        };

        handle = lttng_directory_handle_create(NULL);
        if (!handle) {
                ret = -1;
                goto end;
        }
        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;
}

/*
 * Recursively create directory using the given path and mode, under the
 * provided uid and gid.
 *
 * On success, return 0 else a negative error code.
 */
LTTNG_HIDDEN
int utils_mkdir_recursive(const char *path, mode_t mode, int uid, int gid)
{
        int ret;
        struct lttng_directory_handle *handle;
        const struct lttng_credentials creds = {
                .uid = (uid_t) uid,
                .gid = (gid_t) gid,
        };

        handle = lttng_directory_handle_create(NULL);
        if (!handle) {
                ret = -1;
                goto end;
        }
        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;
}

/*
 * out_stream_path is the output parameter.
 *
 * Return 0 on success or else a negative value.
 */
LTTNG_HIDDEN
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 count_str[MAX_INT_DEC_LEN(count) + 1] = {};
        const char *path_separator;

        if (path_name && path_name[strlen(path_name) - 1] == '/') {
                path_separator = "";
        } else {
                path_separator = "/";
        }

        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));
        }

        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 {
                ret = 0;
        }
        return ret;
}

/**
 * Parse a string that represents a size in human readable format. It
 * supports decimal integers suffixed by 'k', 'K', 'M' or 'G'.
 *
 * The suffix multiply the integer by:
 * 'k': 1024
 * 'M': 1024^2
 * 'G': 1024^3
 *
 * @param str   The string to parse.
 * @param size  Pointer to a uint64_t that will be filled with the
 *              resulting size.
 *
 * @return 0 on success, -1 on failure.
 */
LTTNG_HIDDEN
int utils_parse_size_suffix(const char * const str, uint64_t * const size)
{
        int ret;
        uint64_t base_size;
        long shift = 0;
        const char *str_end;
        char *num_end;

        if (!str) {
                DBG("utils_parse_size_suffix: received a NULL string.");
                ret = -1;
                goto end;
        }

        /* strtoull will accept a negative number, but we don't want to. */
        if (strchr(str, '-') != NULL) {
                DBG("utils_parse_size_suffix: invalid size string, should not contain '-'.");
                ret = -1;
                goto end;
        }

        /* str_end will point to the \0 */
        str_end = str + strlen(str);
        errno = 0;
        base_size = strtoull(str, &num_end, 0);
        if (errno != 0) {
                PERROR("utils_parse_size_suffix strtoull");
                ret = -1;
                goto end;
        }

        if (num_end == str) {
                /* strtoull parsed nothing, not good. */
                DBG("utils_parse_size_suffix: strtoull had nothing good to parse.");
                ret = -1;
                goto end;
        }

        /* Check if a prefix is present. */
        switch (*num_end) {
        case 'G':
                shift = GIBI_LOG2;
                num_end++;
                break;
        case 'M': /*  */
                shift = MEBI_LOG2;
                num_end++;
                break;
        case 'K':
        case 'k':
                shift = KIBI_LOG2;
                num_end++;
                break;
        case '\0':
                break;
        default:
                DBG("utils_parse_size_suffix: invalid suffix.");
                ret = -1;
                goto end;
        }

        /* Check for garbage after the valid input. */
        if (num_end != str_end) {
                DBG("utils_parse_size_suffix: Garbage after size string.");
                ret = -1;
                goto end;
        }

        *size = base_size << shift;

        /* Check for overflow */
        if ((*size >> shift) != base_size) {
                DBG("utils_parse_size_suffix: oops, overflow detected.");
                ret = -1;
                goto end;
        }

        ret = 0;
end:
        return ret;
}

/**
 * Parse a string that represents a time in human readable format. It
 * 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:
 *     "us" : 1
 *     "ms" : 1000
 *     "s"  : 1000000
 *     "m"  : 60000000
 *     "h"  : 3600000000
 *
 * Note that unit-less numbers are assumed to be microseconds.
 *
 * @param str           The string to parse, assumed to be NULL-terminated.
 * @param time_us       Pointer to a uint64_t that will be filled with the
 *                      resulting time in microseconds.
 *
 * @return 0 on success, -1 on failure.
 */
LTTNG_HIDDEN
int utils_parse_time_suffix(char const * const str, uint64_t * const time_us)
{
        int ret;
        uint64_t base_time;
        uint64_t multiplier = 1;
        const char *str_end;
        char *num_end;

        if (!str) {
                DBG("utils_parse_time_suffix: received a NULL string.");
                ret = -1;
                goto end;
        }

        /* strtoull will accept a negative number, but we don't want to. */
        if (strchr(str, '-') != NULL) {
                DBG("utils_parse_time_suffix: invalid time string, should not contain '-'.");
                ret = -1;
                goto end;
        }

        /* str_end will point to the \0 */
        str_end = str + strlen(str);
        errno = 0;
        base_time = strtoull(str, &num_end, 10);
        if (errno != 0) {
                PERROR("utils_parse_time_suffix strtoull on string \"%s\"", str);
                ret = -1;
                goto end;
        }

        if (num_end == str) {
                /* strtoull parsed nothing, not good. */
                DBG("utils_parse_time_suffix: strtoull had nothing good to parse.");
                ret = -1;
                goto end;
        }

        /* Check if a prefix is present. */
        switch (*num_end) {
        case 'u':
                /*
                 * 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':
                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':
                /* Second */
                multiplier = USEC_PER_SEC;
                num_end++;
                break;
        case 'h':
                /* Hour */
                multiplier = USEC_PER_HOURS;
                num_end++;
                break;
        case '\0':
                break;
        default:
                DBG("utils_parse_time_suffix: invalid suffix.");
                ret = -1;
                goto end;
        }

        /* Check for garbage after the valid input. */
        if (num_end != str_end) {
                DBG("utils_parse_time_suffix: Garbage after time string.");
                ret = -1;
                goto end;
        }

        *time_us = base_time * multiplier;

        /* Check for overflow */
        if ((*time_us / multiplier) != base_time) {
                DBG("utils_parse_time_suffix: oops, overflow detected.");
                ret = -1;
                goto end;
        }

        ret = 0;
end:
        return ret;
}

/*
 * fls: returns the position of the most significant bit.
 * Returns 0 if no bit is set, else returns the position of the most
 * significant bit (from 1 to 32 on 32-bit, from 1 to 64 on 64-bit).
 */
#if defined(__i386) || defined(__x86_64)
static inline unsigned int fls_u32(uint32_t x)
{
        int r;

        asm("bsrl %1,%0\n\t"
                "jnz 1f\n\t"
                "movl $-1,%0\n\t"
                "1:\n\t"
                : "=r" (r) : "rm" (x));
        return r + 1;
}
#define HAS_FLS_U32
#endif

#if defined(__x86_64) && defined(__LP64__)
static inline
unsigned int fls_u64(uint64_t x)
{
        long r;

        asm("bsrq %1,%0\n\t"
            "jnz 1f\n\t"
            "movq $-1,%0\n\t"
            "1:\n\t"
            : "=r" (r) : "rm" (x));
        return r + 1;
}
#define HAS_FLS_U64
#endif

#ifndef HAS_FLS_U64
static __attribute__((unused))
unsigned int fls_u64(uint64_t x)
{
        unsigned int r = 64;

        if (!x)
                return 0;

        if (!(x & 0xFFFFFFFF00000000ULL)) {
                x <<= 32;
                r -= 32;
        }
        if (!(x & 0xFFFF000000000000ULL)) {
                x <<= 16;
                r -= 16;
        }
        if (!(x & 0xFF00000000000000ULL)) {
                x <<= 8;
                r -= 8;
        }
        if (!(x & 0xF000000000000000ULL)) {
                x <<= 4;
                r -= 4;
        }
        if (!(x & 0xC000000000000000ULL)) {
                x <<= 2;
                r -= 2;
        }
        if (!(x & 0x8000000000000000ULL)) {
                x <<= 1;
                r -= 1;
        }
        return r;
}
#endif

#ifndef HAS_FLS_U32
static __attribute__((unused)) unsigned int fls_u32(uint32_t x)
{
        unsigned int r = 32;

        if (!x) {
                return 0;
        }
        if (!(x & 0xFFFF0000U)) {
                x <<= 16;
                r -= 16;
        }
        if (!(x & 0xFF000000U)) {
                x <<= 8;
                r -= 8;
        }
        if (!(x & 0xF0000000U)) {
                x <<= 4;
                r -= 4;
        }
        if (!(x & 0xC0000000U)) {
                x <<= 2;
                r -= 2;
        }
        if (!(x & 0x80000000U)) {
                x <<= 1;
                r -= 1;
        }
        return r;
}
#endif

/*
 * Return the minimum order for which x <= (1UL << order).
 * Return -1 if x is 0.
 */
LTTNG_HIDDEN
int utils_get_count_order_u32(uint32_t x)
{
        if (!x) {
                return -1;
        }

        return fls_u32(x - 1);
}

/*
 * Return the minimum order for which x <= (1UL << order).
 * Return -1 if x is 0.
 */
LTTNG_HIDDEN
int utils_get_count_order_u64(uint64_t x)
{
        if (!x) {
                return -1;
        }

        return fls_u64(x - 1);
}

/**
 * Obtain the value of LTTNG_HOME environment variable, if exists.
 * Otherwise returns the value of HOME.
 */
LTTNG_HIDDEN
const char *utils_get_home_dir(void)
{
        char *val = NULL;
        struct passwd *pwd;

        val = lttng_secure_getenv(DEFAULT_LTTNG_HOME_ENV_VAR);
        if (val != NULL) {
                goto end;
        }
        val = lttng_secure_getenv(DEFAULT_LTTNG_FALLBACK_HOME_ENV_VAR);
        if (val != NULL) {
                goto end;
        }

        /* Fallback on the password file entry. */
        pwd = getpwuid(getuid());
        if (!pwd) {
                goto end;
        }
        val = pwd->pw_dir;

        DBG3("Home directory is '%s'", val);

end:
        return val;
}

/**
 * Get user's home directory. Dynamically allocated, must be freed
 * by the caller.
 */
LTTNG_HIDDEN
char *utils_get_user_home_dir(uid_t uid)
{
        struct passwd pwd;
        struct passwd *result;
        char *home_dir = NULL;
        char *buf = NULL;
        long buflen;
        int ret;

        buflen = sysconf(_SC_GETPW_R_SIZE_MAX);
        if (buflen == -1) {
                goto end;
        }
retry:
        buf = zmalloc(buflen);
        if (!buf) {
                goto end;
        }

        ret = getpwuid_r(uid, &pwd, buf, buflen, &result);
        if (ret || !result) {
                if (ret == ERANGE) {
                        free(buf);
                        buflen *= 2;
                        goto retry;
                }
                goto end;
        }

        home_dir = strdup(pwd.pw_dir);
end:
        free(buf);
        return home_dir;
}

/*
 * With the given format, fill dst with the time of len maximum siz.
 *
 * Return amount of bytes set in the buffer or else 0 on error.
 */
LTTNG_HIDDEN
size_t utils_get_current_time_str(const char *format, char *dst, size_t len)
{
        size_t ret;
        time_t rawtime;
        struct tm *timeinfo;

        assert(format);
        assert(dst);

        /* Get date and time for session path */
        time(&rawtime);
        timeinfo = localtime(&rawtime);
        ret = strftime(dst, len, format, timeinfo);
        if (ret == 0) {
                ERR("Unable to strftime with format %s at dst %p of len %zu", format,
                                dst, len);
        }

        return ret;
}

/*
 * 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
int utils_get_group_id(const char *name, bool warn, gid_t *gid)
{
        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;
        }

        while ((ret = getgrnam_r(name, &grp, buffer.data, buffer.size, &result)) == ERANGE) {
                const size_t new_len = 2 * buffer.size;

                /* Buffer is not big enough, increase its size. */
                if (new_len < buffer.size) {
                        ERR("Group info buffer size overflow");
                        ret = -1;
                        goto error;
                }

                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) {
                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;
        }
        lttng_dynamic_buffer_reset(&buffer);
        return ret;
}

/*
 * Return a newly allocated option string. This string is to be used as the
 * optstring argument of getopt_long(), see GETOPT(3). opt_count is the number
 * of elements in the long_options array. Returns NULL if the string's
 * allocation fails.
 */
LTTNG_HIDDEN
char *utils_generate_optstring(const struct option *long_options,
                size_t opt_count)
{
        int i;
        size_t string_len = opt_count, str_pos = 0;
        char *optstring;

        /*
         * Compute the necessary string length. One letter per option, two when an
         * argument is necessary, and a trailing NULL.
         */
        for (i = 0; i < opt_count; i++) {
                string_len += long_options[i].has_arg ? 1 : 0;
        }

        optstring = zmalloc(string_len);
        if (!optstring) {
                goto end;
        }

        for (i = 0; i < opt_count; i++) {
                if (!long_options[i].name) {
                        /* Got to the trailing NULL element */
                        break;
                }

                if (long_options[i].val != '\0') {
                        optstring[str_pos++] = (char) long_options[i].val;
                        if (long_options[i].has_arg) {
                                optstring[str_pos++] = ':';
                        }
                }
        }

end:
        return optstring;
}

/*
 * Try to remove a hierarchy of empty directories, recursively. Don't unlink
 * any file. Try to rmdir any empty directory within the hierarchy.
 */
LTTNG_HIDDEN
int utils_recursive_rmdir(const char *path)
{
        int ret;
        struct lttng_directory_handle *handle;

        handle = lttng_directory_handle_create(NULL);
        if (!handle) {
                ret = -1;
                goto end;
        }
        ret = lttng_directory_handle_remove_subdirectory(handle, path);
end:
        lttng_directory_handle_put(handle);
        return ret;
}

LTTNG_HIDDEN
int utils_truncate_stream_file(int fd, off_t length)
{
        int ret;
        off_t lseek_ret;

        ret = ftruncate(fd, length);
        if (ret < 0) {
                PERROR("ftruncate");
                goto end;
        }
        lseek_ret = lseek(fd, length, SEEK_SET);
        if (lseek_ret < 0) {
                PERROR("lseek");
                ret = -1;
                goto end;
        }
end:
        return ret;
}

static const char *get_man_bin_path(void)
{
        char *env_man_path = lttng_secure_getenv(DEFAULT_MAN_BIN_PATH_ENV);

        if (env_man_path) {
                return env_man_path;
        }

        return DEFAULT_MAN_BIN_PATH;
}

LTTNG_HIDDEN
int utils_show_help(int section, const char *page_name,
                const char *help_msg)
{
        char section_string[8];
        const char *man_bin_path = get_man_bin_path();
        int ret = 0;

        if (help_msg) {
                printf("%s", help_msg);
                goto end;
        }

        /* Section integer -> section string */
        ret = sprintf(section_string, "%d", section);
        assert(ret > 0 && ret < 8);

        /*
         * Execute man pager.
         *
         * We provide -M to man here because LTTng-tools can
         * be installed outside /usr, in which case its man pages are
         * not located in the default /usr/share/man directory.
         */
        ret = execlp(man_bin_path, "man", "-M", MANPATH,
                section_string, page_name, NULL);

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 utils_get_memory_available(size_t *value)
{
        return read_proc_meminfo_field(PROC_MEMINFO_MEMAVAILABLE_LINE, value);
}

/*
 * 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;
        }

        /* 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);
                }
        }

end:
        return ret;
}