mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-01 03:53:33 +00:00
046c7ebd4a
- Introduce fast spinlock API - Double rand64() perf w/ spinlock - Improve raise() on New Technology - Support gettid() across platforms - Implement SA_NODEFER on New Technology - Move the lock intrinsics into LIBC_INTRIN - Make SIGTRAP recoverable on New Technology - Block SIGCHLD in wait4() on New Technology - Add threading prototypes for XNU and FreeBSD - Rewrite abort() fixing its minor bugs on XNU/NT - Shave down a lot of the content in libc/bits/bits.h - Let signal handlers modify CPU registers on New Technology
80 lines
3.7 KiB
C
80 lines
3.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=8 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/bits/bits.h"
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#include "libc/bits/weaken.h"
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#include "libc/calls/calls.h"
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#include "libc/intrin/spinlock.h"
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#include "libc/nexgen32e/rdtsc.h"
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#include "libc/nt/thread.h"
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#include "libc/rand/rand.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/auxv.h"
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#include "libc/thread/create.h"
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extern int __pid;
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static int thepid;
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static uint128_t thepool;
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static cthread_spinlock_t rand64_lock;
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/**
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* Returns nondeterministic random data.
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*
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* This function is similar to lemur64() except it'thepool intended to
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* be unpredictable. This PRNG automatically seeds itself on startup
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* using a much stronger and faster random source than `srand(time(0))`.
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* This function will automatically reseed itself when new processes and
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* threads are spawned. This function is thread safe in the sense that a
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* race condition can't happen where two threads return the same result.
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*
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* @see rdseed(), rdrand(), rand(), random(), rngset()
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* @note this function is not intended for cryptography
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* @note this function passes bigcrush and practrand
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* @note this function takes at minimum 15 cycles
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* @asyncsignalsafe
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* @threadsafe
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* @vforksafe
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*/
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uint64_t rand64(void) {
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void *p;
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uint128_t s;
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cthread_spinlock(&rand64_lock);
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if (__pid == thepid) {
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s = thepool; // normal path
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} else {
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if (!thepid) {
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if (AT_RANDOM && (p = (void *)getauxval(AT_RANDOM))) {
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// linux / freebsd kernel supplied entropy
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memcpy(&s, p, 16);
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} else {
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// otherwise initialize w/ cheap timestamp
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s = kStartTsc;
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}
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} else {
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// blend another timestamp on fork contention
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s = thepool ^ rdtsc();
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}
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// blend the pid on startup and fork contention
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s ^= __pid;
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thepid = __pid;
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}
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thepool = (s *= 15750249268501108917ull); // lemur64
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cthread_spunlock(&rand64_lock);
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return s >> 64;
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}
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