| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "util/log.h" |
| #include "util/rand.h" |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <inttypes.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <sys/stat.h> |
| #include <sys/types.h> |
| #include <unistd.h> |
| |
| #define URANDOM_PATH "/dev/urandom" |
| |
| #define PSAMP_THREAD_LOCAL_BUF_LEN 256 |
| |
| /** |
| * @file rand_linux.c |
| * |
| * A Linux implementation of a random number source. This implementation reads |
| * random numbers from /dev/urandom. To avoid reading from /dev/urandom too |
| * often, we have a thread-local cache of random data. This is done using ELF |
| * TLS. |
| */ |
| |
| struct random_src { |
| /** |
| * The HTrace log. |
| */ |
| struct htrace_log *lg; |
| |
| /** |
| * File descriptor for /dev/urandom. |
| */ |
| int urandom_fd; |
| }; |
| |
| /** |
| * A thread-local cache of random bits. |
| */ |
| static __thread uint32_t g_rnd_cache[PSAMP_THREAD_LOCAL_BUF_LEN]; |
| |
| /** |
| * An index into our thread-local cache of random bits. |
| */ |
| static __thread int g_rnd_cache_idx = PSAMP_THREAD_LOCAL_BUF_LEN; |
| |
| static void refill_rand_cache(struct random_src *rnd) |
| { |
| size_t total = 0; |
| |
| while (1) { |
| ssize_t res; |
| ssize_t rem = (PSAMP_THREAD_LOCAL_BUF_LEN * sizeof(uint32_t)) - total; |
| if (rem == 0) { |
| break; |
| } |
| res = read(rnd->urandom_fd, ((uint8_t*)&g_rnd_cache) + total, rem); |
| if (res < 0) { |
| int err = errno; |
| if (err == EINTR) { |
| continue; |
| } |
| htrace_log(rnd->lg, "refill_rand_cache: error refilling " |
| "random cache: %d (%s)\n", err, |
| terror(err)); |
| return; |
| } |
| total += res; |
| } |
| g_rnd_cache_idx = 0; |
| } |
| |
| struct random_src *random_src_alloc(struct htrace_log *lg) |
| { |
| struct random_src *rnd; |
| int err; |
| |
| rnd = calloc(1, sizeof(*rnd)); |
| if (!rnd) { |
| htrace_log(lg, "random_src_alloc: OOM\n"); |
| return NULL; |
| } |
| rnd->urandom_fd = open(URANDOM_PATH, O_RDONLY); |
| if (rnd->urandom_fd < 0) { |
| err = errno; |
| htrace_log(lg, "random_src_alloc: failed to open " |
| URANDOM_PATH ": error %d (%s)\n", err, |
| terror(err)); |
| free(rnd); |
| return NULL; |
| } |
| rnd->lg = lg; |
| return rnd; |
| } |
| |
| void random_src_free(struct random_src *rnd) |
| { |
| if (!rnd) { |
| return; |
| } |
| if (close(rnd->urandom_fd)) { |
| int err = errno; |
| htrace_log(rnd->lg, "linux_prob_sampler_free: close error: " |
| "%d (%s)\n", err, terror(err)); |
| } |
| free(rnd); |
| } |
| |
| uint32_t random_u32(struct random_src *rnd) |
| { |
| if (g_rnd_cache_idx >= PSAMP_THREAD_LOCAL_BUF_LEN) { |
| refill_rand_cache(rnd); |
| } |
| return g_rnd_cache[g_rnd_cache_idx++]; |
| } |
| |
| uint64_t random_u64(struct random_src *rnd) |
| { |
| uint64_t val = random_u32(rnd); |
| val <<= 32; |
| return val | random_u32(rnd); |
| } |
| |
| // vim: ts=4:sw=4:tw=79:et |