diff options
Diffstat (limited to 'sysdeps/nacl')
| -rw-r--r-- | sysdeps/nacl/createthread.c | 3 | ||||
| -rw-r--r-- | sysdeps/nacl/pthread-pids.h | 65 |
2 files changed, 68 insertions, 0 deletions
diff --git a/sysdeps/nacl/createthread.c b/sysdeps/nacl/createthread.c index 9df4eaee74..9d9284a7b5 100644 --- a/sysdeps/nacl/createthread.c +++ b/sysdeps/nacl/createthread.c @@ -17,6 +17,7 @@ <http://www.gnu.org/licenses/>. */ #include <nacl-interfaces.h> +#include <pthread-pids.h> /* See the comments in pthread_create.c for the requirements for these two macros and the create_thread function. */ @@ -33,6 +34,8 @@ static int create_thread (struct pthread *pd, const struct pthread_attr *attr, bool stopped_start, STACK_VARIABLES_PARMS, bool *thread_ran) { + pd->tid = __nacl_get_tid (pd); + pd->stopped_start = stopped_start; if (__glibc_unlikely (stopped_start)) /* We make sure the thread does not run far by forcing it to get a diff --git a/sysdeps/nacl/pthread-pids.h b/sysdeps/nacl/pthread-pids.h new file mode 100644 index 0000000000..ccb99d6b0c --- /dev/null +++ b/sysdeps/nacl/pthread-pids.h @@ -0,0 +1,65 @@ +/* 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); + 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; +} |