+#include <sys/wait.h>
+#include <stdio.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <string.h>
+#include <assert.h>
+#include <sys/stat.h>
+#include <stddef.h>
+#include <limits.h>
+#include <sys/param.h>
+
+#include "gcc-compat.h"
+#include "string.h"
+#include "log.h"
+#include "gcc-compat.h"
+#include "error.h"
+
+#if (defined(__GNUC__) && defined(__i386__))
+#define get16bits(d) (*((const uint16_t *) (d)))
+#else
+#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+ +(uint32_t)(((const uint8_t *)(d))[0]) )
+#endif
+
+/*
+ * SuperFastHash, by Paul Hsieh.
+ * http://www.azillionmonkeys.com/qed/hash.html
+ */
+static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash)
+{
+ uint32_t tmp;
+ int rem = len & 3;
+
+ len >>= 2;
+
+ for (;len > 0; len--) {
+ hash += get16bits (data);
+ tmp = (get16bits (data+2) << 11) ^ hash;
+ hash = (hash << 16) ^ tmp;
+ data += 2*sizeof (uint16_t);
+ hash += hash >> 11;
+ }
+
+ /* Handle end cases */
+ switch (rem) {
+ case 3:
+ hash += get16bits (data);
+ hash ^= hash << 16;
+ hash ^= data[sizeof (uint16_t)] << 18;
+ hash += hash >> 11;
+ break;
+ case 2:
+ hash += get16bits (data);
+ hash ^= hash << 11;
+ hash += hash >> 17;
+ break;
+ case 1:
+ hash += *data;
+ hash ^= hash << 10;
+ hash += hash >> 1;
+ }
+ /* Force "avalanching" of final 127 bits */
+ hash ^= hash << 3;
+ hash += hash >> 5;
+ hash ^= hash << 4;
+ hash += hash >> 17;
+ hash ^= hash << 25;
+ hash += hash >> 6;
+ return hash;
+}
+
+/*
+ * Return the canonical absolute name of a given file name.
+ *
+ * Slightly modified version of glibc's realpath, Copyright (C)
+ * 1996-2002,2004,2005,2006,2008 Free Software Foundation, Inc.
+ *
+ * A canonical name does not contain any `.', `..' components nor any repeated
+ * path separators ('/') or symlinks. All path components must exist. The
+ * result is malloc'd and must be freed by the caller.
+ */
+static int dss_realpath(const char *name, char **resolved_path)
+{
+ char *rpath = NULL, *dest, *extra_buf = NULL;
+ const char *start, *end, *rpath_limit;
+ long int path_max;
+ int ret, num_links = 0;
+
+ if (name[0] == '\0') {
+ /*
+ * As per Single Unix Specification V2 we must return an error
+ * if the name argument points to an empty string.
+ */
+ ret = -ERRNO_TO_DSS_ERROR(ENOENT);
+ goto error;
+ }
+#ifdef PATH_MAX
+ path_max = PATH_MAX;
+#else
+ /*
+ * From realpath(3): Asking pathconf(3) does not really help, since on
+ * the one hand POSIX warns that the result of pathconf(3) may be
+ * huge and unsuitable for mallocing memory. And on the other hand
+ * pathconf(3) may return -1 to signify that PATH_MAX is not bounded.
+ */
+ path_max = pathconf(name, _PC_PATH_MAX);
+ if (path_max <= 0 || path_max >= 4096)
+ path_max = 4096;
+#endif
+ rpath = dss_malloc(path_max);
+ rpath_limit = rpath + path_max;
+
+ if (name[0] != '/') {
+ if (!getcwd(rpath, path_max)) {
+ ret = -ERRNO_TO_DSS_ERROR(errno);
+ goto error;
+ }
+ dest = memchr(rpath, '\0', path_max);
+ } else {
+ rpath[0] = '/';
+ dest = rpath + 1;
+ }
+
+ for (start = end = name; *start; start = end) {
+ struct stat st;
+ int n;
+
+ /* Skip sequence of multiple path-separators. */
+ while (*start == '/')
+ ++start;
+
+ /* Find end of path component. */
+ for (end = start; *end && *end != '/'; ++end)
+ /* Nothing. */ ;
+
+ if (end - start == 0)
+ break;
+ else if (end - start == 1 && start[0] == '.')
+ /* nothing */ ;
+ else if (end - start == 2 && start[0] == '.' && start[1] == '.') {
+ /* Back up to previous component, ignore if at root already. */
+ if (dest > rpath + 1)
+ while ((--dest)[-1] != '/') ;
+ } else {
+ size_t new_size;
+
+ if (dest[-1] != '/')
+ *dest++ = '/';
+
+ if (dest + (end - start) >= rpath_limit) {
+ ptrdiff_t dest_offset = dest - rpath;
+
+ new_size = rpath_limit - rpath;
+ if (end - start + 1 > path_max)
+ new_size += end - start + 1;
+ else
+ new_size += path_max;
+ rpath = dss_realloc(rpath, new_size);
+ rpath_limit = rpath + new_size;
+ dest = rpath + dest_offset;
+ }
+
+ memcpy(dest, start, end - start);
+ dest += end - start;
+ *dest = '\0';
+
+ if (stat(rpath, &st) < 0) {
+ ret = -ERRNO_TO_DSS_ERROR(errno);
+ goto error;
+ }
+
+ if (S_ISLNK(st.st_mode)) {
+ char *buf = alloca(path_max);
+ size_t len;
+
+ if (++num_links > MAXSYMLINKS) {
+ ret = -ERRNO_TO_DSS_ERROR(ELOOP);
+ goto error;
+ }
+
+ n = readlink(rpath, buf, path_max - 1);
+ if (n < 0) {
+ ret = -ERRNO_TO_DSS_ERROR(errno);
+ goto error;
+ }
+ buf[n] = '\0';
+
+ if (!extra_buf)
+ extra_buf = alloca(path_max);
+
+ len = strlen(end);
+ if ((long int) (n + len) >= path_max) {
+ ret = -ERRNO_TO_DSS_ERROR(ENAMETOOLONG);
+ goto error;
+ }
+
+ /* Careful here, end may be a pointer into extra_buf... */
+ memmove(&extra_buf[n], end, len + 1);
+ name = end = memcpy(extra_buf, buf, n);
+
+ if (buf[0] == '/') /* It's an absolute symlink */
+ dest = rpath + 1;
+ else /* Back up to previous component, ignore if at root already: */
+ if (dest > rpath + 1)
+ while ((--dest)[-1] != '/')
+ ; /* nothing */
+ } else if (!S_ISDIR(st.st_mode) && *end != '\0') {
+ ret = -ERRNO_TO_DSS_ERROR(ENOTDIR);
+ goto error;
+ }
+ }
+ }
+ if (dest > rpath + 1 && dest[-1] == '/')
+ --dest;
+ *dest = '\0';
+ *resolved_path = rpath;
+ return 1;
+error:
+ free(rpath);
+ *resolved_path = NULL;
+ return ret;
+}
+
+static inline int get_key_or_die(char *config_file)
+{
+ int ret;
+ struct stat statbuf;
+ char *rpath;
+
+ assert(config_file);
+ if (stat(config_file, &statbuf) == 0) {
+ ret = dss_realpath(config_file, &rpath);
+ if (ret < 0) {
+ DSS_EMERG_LOG("could not resolve path %s: %s\n", config_file,
+ dss_strerror(-ret));
+ exit(EXIT_FAILURE);
+ }
+ DSS_DEBUG_LOG("resolved path: %s\n", rpath);
+ } else
+ /*
+ * This happens if the user did not specify a config file, and
+ * the default config file does not exist. Another (unlikely)
+ * possibility is that the config file was removed between
+ * startup and this call. We don't care about these corner
+ * cases too much and just use the unresolved path in this
+ * case.
+ */
+ rpath = dss_strdup(config_file);
+ ret = super_fast_hash((uint8_t *)rpath, strlen(rpath), 0) >> 1;
+ free(rpath);
+ return ret;
+}
+
+static int mutex_get(key_t key, int flags)
+{
+ int ret;
+
+ DSS_DEBUG_LOG("getting semaphore 0x%x\n", key);
+ ret = semget(key, 2, flags);
+ if (ret < 0)
+ return -ERRNO_TO_DSS_ERROR(errno);
+ return ret;
+}
+
+static int do_semop(int id, struct sembuf *sops, int num)
+{
+ int ret;
+
+ DSS_DEBUG_LOG("calling semop\n");
+ do {
+ ret = semop(id, sops, num);
+ if (ret >= 0)
+ return 1;
+ } while (errno == EINTR);
+ return -ERRNO_TO_DSS_ERROR(errno);
+}
+
+static int mutex_lock(int id)
+{
+ int ret;
+
+ DSS_DEBUG_LOG("locking\n");
+ struct sembuf sops[4] = {
+ {
+ .sem_num = 0,
+ .sem_op = 0,
+ .sem_flg = SEM_UNDO | IPC_NOWAIT
+ },
+ {
+ .sem_num = 0,
+ .sem_op = 1,
+ .sem_flg = SEM_UNDO | IPC_NOWAIT
+ },
+ {
+ .sem_num = 1,
+ .sem_op = 0,
+ .sem_flg = SEM_UNDO | IPC_NOWAIT
+ },
+ {
+ .sem_num = 1,
+ .sem_op = 1,
+ .sem_flg = SEM_UNDO | IPC_NOWAIT
+ }
+ };
+ ret = do_semop(id, sops, 4);
+ if (ret < 0)
+ return -ERRNO_TO_DSS_ERROR(errno);
+ return 1;
+}
+
+int lock_dss(char *config_file)
+{
+ int ret, key = get_key_or_die(config_file);
+
+ ret = mutex_get(key, IPC_CREAT | 0600);
+ if (ret < 0)
+ return ret;
+ return mutex_lock(ret);
+}
projects / dss.git / commitdiff