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/* Hurdish implementation of getrandom
Copyright (C) 2016-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <hurd.h>
#include <sys/random.h>
#include <fcntl.h>
__libc_rwlock_define_initialized (static, lock);
static file_t random_server, random_server_nonblock,
urandom_server, urandom_server_nonblock;
extern char *__trivfs_server_name __attribute__((weak));
/* Write up to LENGTH bytes of randomness starting at BUFFER.
Return the number of bytes written, or -1 on error. */
ssize_t
__getrandom (void *buffer, size_t length, unsigned int flags)
{
const char *random_source = "/dev/urandom";
int open_flags = O_RDONLY;
file_t server, *cached_server;
error_t err;
char *data = buffer;
mach_msg_type_number_t nread = length;
switch (flags)
{
case 0:
cached_server = &urandom_server;
break;
case GRND_RANDOM:
cached_server = &random_server;
break;
case GRND_NONBLOCK:
cached_server = &urandom_server_nonblock;
break;
case GRND_RANDOM | GRND_NONBLOCK:
cached_server = &random_server_nonblock;
break;
default:
return __hurd_fail (EINVAL);
}
if (flags & GRND_RANDOM)
random_source = "/dev/random";
if (flags & GRND_NONBLOCK)
open_flags |= O_NONBLOCK;
/* No point in passing either O_NOCTTY, O_IGNORE_CTTY, or O_CLOEXEC
to file_name_lookup, since we're not making an fd. */
if (&__trivfs_server_name && __trivfs_server_name
&& __trivfs_server_name[0] == 'r'
&& __trivfs_server_name[1] == 'a'
&& __trivfs_server_name[2] == 'n'
&& __trivfs_server_name[3] == 'd'
&& __trivfs_server_name[4] == 'o'
&& __trivfs_server_name[5] == 'm'
&& __trivfs_server_name[6] == '\0')
/* We are random, don't try to read ourselves! */
return length;
again:
__libc_rwlock_rdlock (lock);
server = *cached_server;
if (MACH_PORT_VALID (server))
/* Attempt to read some random data using this port. */
err = __io_read (server, &data, &nread, -1, length);
else
err = MACH_SEND_INVALID_DEST;
__libc_rwlock_unlock (lock);
if (err == MACH_SEND_INVALID_DEST || err == MIG_SERVER_DIED)
{
file_t oldserver = server;
mach_port_urefs_t urefs;
/* Slow path: the cached port didn't work, or there was no
cached port in the first place. */
__libc_rwlock_wrlock (lock);
server = *cached_server;
if (server != oldserver)
{
/* Someone else must have refetched the port while we were
waiting for the lock. */
__libc_rwlock_unlock (lock);
goto again;
}
if (MACH_PORT_VALID (server))
{
/* It could be that someone else has refetched the port and
it got the very same name. So check whether it is a send
right (and not a dead name). */
err = __mach_port_get_refs (__mach_task_self (), server,
MACH_PORT_RIGHT_SEND, &urefs);
if (!err && urefs > 0)
{
__libc_rwlock_unlock (lock);
goto again;
}
/* Now we're sure that it's dead. */
__mach_port_deallocate (__mach_task_self (), server);
}
server = *cached_server = __file_name_lookup (random_source,
open_flags, 0);
__libc_rwlock_unlock (lock);
if (!MACH_PORT_VALID (server))
{
if (errno == ENOENT)
/* No translator set up, we won't have support for it. */
errno = ENOSYS;
/* No luck. */
return -1;
}
goto again;
}
if (err)
return __hurd_fail (err);
if (data != buffer)
{
if (nread > length)
{
__vm_deallocate (__mach_task_self (), (vm_address_t) data, nread);
return __hurd_fail (EGRATUITOUS);
}
memcpy (buffer, data, nread);
__vm_deallocate (__mach_task_self (), (vm_address_t) data, nread);
}
return nread;
}
libc_hidden_def (__getrandom)
weak_alias (__getrandom, getrandom)
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