mirror of git://sourceware.org/git/glibc.git
misc: Set generic pselect as ENOSYS
The generic pselect implementation has the very specific race condition that motived the creation of the pselect syscall (no atomicity in signal mask set/reset). Using it as generic implementation is counterproductive Also currently only microblaze uses it as fallback when used on kernel prior 3.15. This patch moves the generic implementation to a microblaze specific one, sets the generic internal as a ENOSYS, and cleanups the Linux generic implementation. The microblaze implementation mimics the previous Linux generic one, where it either uses pselect6 directly if __ASSUME_PSELECT or a first try pselect6 then the fallback otherwise. Checked on x86_64-linux-gnu and microblaze-linux-gnu.
This commit is contained in:
Adhemerval Zanella
parent
102b5b0caf
commit
8781c1301d
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@ -17,12 +17,7 @@
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.h>
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#include <stddef.h> /* For NULL. */
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#include <sys/time.h>
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#include <sys/select.h>
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#include <sysdep-cancel.h>
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/* Check the first NFDS descriptors each in READFDS (if not NULL) for read
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readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
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@ -34,43 +29,8 @@ int
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__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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const struct timespec *timeout, const sigset_t *sigmask)
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{
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struct timeval tval;
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int retval;
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sigset_t savemask;
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/* Change nanosecond number to microseconds. This might mean losing
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precision and therefore the `pselect` should be available. But
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for now it is hardly found. */
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if (timeout != NULL)
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{
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/* Catch bugs which would be hidden by the TIMESPEC_TO_TIMEVAL
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computations. The division by 1000 truncates values. */
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if (__glibc_unlikely (timeout->tv_nsec < 0))
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{
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__set_errno (EINVAL);
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return -1;
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}
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TIMESPEC_TO_TIMEVAL (&tval, timeout);
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}
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/* The setting and restoring of the signal mask and the select call
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should be an atomic operation. This can't be done without kernel
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help. */
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if (sigmask != NULL)
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__sigprocmask (SIG_SETMASK, sigmask, &savemask);
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/* Note the pselect() is a cancellation point. But since we call
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select() which itself is a cancellation point we do not have
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to do anything here. */
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retval = __select (nfds, readfds, writefds, exceptfds,
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timeout != NULL ? &tval : NULL);
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if (sigmask != NULL)
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__sigprocmask (SIG_SETMASK, &savemask, NULL);
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return retval;
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__set_errno (ENOSYS);
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return -1;
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}
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#ifndef __pselect
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weak_alias (__pselect, pselect)
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#endif
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stub_warning (pselect)
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@ -0,0 +1,73 @@
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/* Synchronous I/O multiplexing. Linux/microblaze version.
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Copyright (C) 2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.h>
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#include <time.h>
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#include <sys/poll.h>
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#include <sysdep-cancel.h>
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#ifndef __ASSUME_PSELECT
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# define __pselect __pselect_syscall
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#endif
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/* If pselect is supported, just use the Linux generic implementation. */
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#include <sysdeps/unix/sysv/linux/pselect.c>
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#ifndef __ASSUME_PSELECT
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# undef __pselect
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int
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__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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const struct timespec *timeout, const sigset_t *sigmask)
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{
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int ret = __pselect_syscall (nfds, readfds, writefds, exceptfds, timeout,
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sigmask);
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if (ret >= 0 || errno != ENOSYS)
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return ret;
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/* The fallback uses 'select' which shows the race condition regarding
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signal mask set/restore, requires two additional syscalls, and has
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a worse timeout precision (microseconds instead of nanoseconds). */
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struct timeval tval, *ptval = NULL;
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if (timeout != NULL)
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{
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if (! valid_nanoseconds (timeout->tv_nsec))
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{
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__set_errno (EINVAL);
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return -1;
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}
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TIMESPEC_TO_TIMEVAL (&tval, timeout);
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ptval = &tval;
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}
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sigset_t savemask;
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if (sigmask != NULL)
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__sigprocmask (SIG_SETMASK, sigmask, &savemask);
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/* select itself is a cancellation entrypoint. */
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ret = __select (nfds, readfds, writefds, exceptfds, ptval);
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if (sigmask != NULL)
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__sigprocmask (SIG_SETMASK, &savemask, NULL);
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return ret;
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}
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weak_alias (__pselect, pselect)
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#endif
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@ -16,23 +16,9 @@
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <signal.h>
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#include <time.h>
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#include <sys/poll.h>
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#include <kernel-features.h>
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#include <sys/select.h>
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#include <sysdep-cancel.h>
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#ifdef __NR_pselect6
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# ifndef __ASSUME_PSELECT
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static int __generic_pselect (int nfds, fd_set *readfds, fd_set *writefds,
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fd_set *exceptfds,
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const struct timespec *timeout,
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const sigset_t *sigmask);
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# endif
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int
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__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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const struct timespec *timeout, const sigset_t *sigmask)
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@ -59,24 +45,9 @@ __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
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data.ss = (__syscall_ulong_t) (uintptr_t) sigmask;
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data.ss_len = _NSIG / 8;
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int result = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
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timeout, &data);
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# ifndef __ASSUME_PSELECT
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if (result == -1 && errno == ENOSYS)
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result = __generic_pselect (nfds, readfds, writefds, exceptfds, timeout,
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sigmask);
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# endif
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return result;
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return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds,
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timeout, &data);
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}
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#ifndef __pselect
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weak_alias (__pselect, pselect)
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# ifndef __ASSUME_PSELECT
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# define __pselect static __generic_pselect
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# endif
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#endif
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#ifndef __ASSUME_PSELECT
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# include <misc/pselect.c>
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#endif
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