mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-27 13:10:29 +00:00
69 lines
2.9 KiB
C
69 lines
2.9 KiB
C
/* Initialize pid and tid fields of struct pthread. NaCl version.
|
|
Copyright (C) 2015 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
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <pthreadP.h>
|
|
|
|
|
|
/* NaCl has no concept of PID or TID, nor even any notion of an
|
|
identifier for a thread within the process. But various places in
|
|
the NPTL implementation rely on using the 'tid' field of the TCB
|
|
(struct pthread) as an identifier that is unique at least among all
|
|
live threads in the process. So we must synthesize some number to
|
|
use. Conveniently, the 'pthread_t' value itself is already unique
|
|
in exactly this way (because it's the 'struct pthread' pointer).
|
|
|
|
The only wrinkle is that 'tid' is a (32-bit) 'int' and its high
|
|
(sign) bit is used for special purposes, so we must be absolutely
|
|
sure that we never use a pointer value with the high bit set. (It
|
|
also cannot be zero, but zero is never a valid pointer anyway.)
|
|
The NaCl sandbox models for 32-bit machines limit the address space
|
|
to less than 3GB (in fact, to 1GB), so it's already impossible that
|
|
a valid pointer will have its high bit set. But the NaCl x86-64
|
|
sandbox model allows a full 4GB of address space, so we cannot
|
|
assume that an arbitrary pointer value will not have the high bit
|
|
set. Conveniently, there are always unused bits in the pointer
|
|
value for a 'struct pthread', because it is always aligned to at
|
|
least 32 bits and so the low bits are always zero. Hence, we can
|
|
safely avoid the danger of a nonzero high bit just by shifting the
|
|
pointer value right. */
|
|
|
|
static inline int
|
|
__nacl_get_tid (struct pthread *pd)
|
|
{
|
|
uintptr_t id = (uintptr_t) pd;
|
|
int tid = id >> 1;
|
|
assert ((id & 1) == 0);
|
|
assert (sizeof id == sizeof tid);
|
|
assert (tid > 0);
|
|
/* This ensures that NACL_EXITING_TID (lowlevellock.h) can never
|
|
be a valid TID value. */
|
|
assert ((tid & 1) == 0);
|
|
return tid;
|
|
}
|
|
|
|
|
|
/* Initialize PD->pid and PD->tid for the initial thread. If there is
|
|
setup required to arrange that __exit_thread causes PD->tid to be
|
|
cleared and futex-woken, then this function should do that as well. */
|
|
static inline void
|
|
__pthread_initialize_pids (struct pthread *pd)
|
|
{
|
|
pd->tid = __nacl_get_tid (pd);
|
|
pd->pid = -1;
|
|
}
|