/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-â
âvi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :viâ
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â Copyright 2020 Justine Alexandra Roberts Tunney                              â
â                                                                              â
â Permission to use, copy, modify, and/or distribute this software for         â
â any purpose with or without fee is hereby granted, provided that the         â
â above copyright notice and this permission notice appear in all copies.      â
â                                                                              â
â THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                â
â WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                â
â WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             â
â AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         â
â DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        â
â PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               â
â TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             â
â PERFORMANCE OF THIS SOFTWARE.                                                â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ*/
#include "libc/calls/blockcancel.internal.h"
#include "libc/calls/blocksigs.internal.h"
#include "libc/calls/syscall_support-sysv.internal.h"
#include "libc/dce.h"
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/stdio/rand.h"
#include "libc/sysv/errfuns.h"

int sys_getentropy(void *, size_t) asm("sys_getrandom");

/**
 * Returns random seeding bytes, the XNU/OpenBSD way.
 *
 * @return 0 on success, or -1 w/ errno
 * @raise EFAULT if the `n` bytes at `p` aren't valid memory
 * @raise EIO is returned if more than 256 bytes are requested
 * @see getrandom()
 */
int getentropy(void *p, size_t n) {
  int rc;
  if (n > 256) {
    rc = eio();
  } else if ((!p && n) || (IsAsan() && !__asan_is_valid(p, n))) {
    rc = efault();
  } else if (IsXnu() || IsOpenbsd()) {
    if (sys_getentropy(p, n)) notpossible;
    rc = 0;
  } else {
    BLOCK_SIGNALS;
    BLOCK_CANCELLATIONS;
    if (__getrandom(p, n, 0) != n) notpossible;
    ALLOW_CANCELLATIONS;
    ALLOW_SIGNALS;
    rc = 0;
  }
  STRACE("getentropy(%p, %'zu) â %'ld% m", p, n, rc);
  return rc;
}
