From 8781c1301d55db0a95398eb24c11b99205706bae Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Thu, 14 Nov 2019 18:18:24 -0300 Subject: [PATCH] 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. --- misc/pselect.c | 46 ++---------------- sysdeps/unix/sysv/linux/microblaze/pselect.c | 73 ++++++++++++++++++++++++++++ sysdeps/unix/sysv/linux/pselect.c | 37 ++------------ 3 files changed, 80 insertions(+), 76 deletions(-) create mode 100644 sysdeps/unix/sysv/linux/microblaze/pselect.c diff --git a/misc/pselect.c b/misc/pselect.c index 76ded85..b53d9cd 100644 --- a/misc/pselect.c +++ b/misc/pselect.c @@ -17,12 +17,7 @@ . */ #include -#include -#include /* For NULL. */ -#include #include -#include - /* Check the first NFDS descriptors each in READFDS (if not NULL) for read readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS @@ -34,43 +29,8 @@ int __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) { - struct timeval tval; - int retval; - sigset_t savemask; - - /* Change nanosecond number to microseconds. This might mean losing - precision and therefore the `pselect` should be available. But - for now it is hardly found. */ - if (timeout != NULL) - { - /* Catch bugs which would be hidden by the TIMESPEC_TO_TIMEVAL - computations. The division by 1000 truncates values. */ - if (__glibc_unlikely (timeout->tv_nsec < 0)) - { - __set_errno (EINVAL); - return -1; - } - - TIMESPEC_TO_TIMEVAL (&tval, timeout); - } - - /* The setting and restoring of the signal mask and the select call - should be an atomic operation. This can't be done without kernel - help. */ - if (sigmask != NULL) - __sigprocmask (SIG_SETMASK, sigmask, &savemask); - - /* Note the pselect() is a cancellation point. But since we call - select() which itself is a cancellation point we do not have - to do anything here. */ - retval = __select (nfds, readfds, writefds, exceptfds, - timeout != NULL ? &tval : NULL); - - if (sigmask != NULL) - __sigprocmask (SIG_SETMASK, &savemask, NULL); - - return retval; + __set_errno (ENOSYS); + return -1; } -#ifndef __pselect weak_alias (__pselect, pselect) -#endif +stub_warning (pselect) diff --git a/sysdeps/unix/sysv/linux/microblaze/pselect.c b/sysdeps/unix/sysv/linux/microblaze/pselect.c new file mode 100644 index 0000000..19efce8 --- /dev/null +++ b/sysdeps/unix/sysv/linux/microblaze/pselect.c @@ -0,0 +1,73 @@ +/* Synchronous I/O multiplexing. Linux/microblaze version. + Copyright (C) 2019 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 + . */ + +#include +#include +#include +#include +#include + +#ifndef __ASSUME_PSELECT +# define __pselect __pselect_syscall +#endif + +/* If pselect is supported, just use the Linux generic implementation. */ +#include + +#ifndef __ASSUME_PSELECT +# undef __pselect +int +__pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, + const struct timespec *timeout, const sigset_t *sigmask) +{ + int ret = __pselect_syscall (nfds, readfds, writefds, exceptfds, timeout, + sigmask); + if (ret >= 0 || errno != ENOSYS) + return ret; + + /* The fallback uses 'select' which shows the race condition regarding + signal mask set/restore, requires two additional syscalls, and has + a worse timeout precision (microseconds instead of nanoseconds). */ + + struct timeval tval, *ptval = NULL; + if (timeout != NULL) + { + if (! valid_nanoseconds (timeout->tv_nsec)) + { + __set_errno (EINVAL); + return -1; + } + + TIMESPEC_TO_TIMEVAL (&tval, timeout); + ptval = &tval; + } + + sigset_t savemask; + if (sigmask != NULL) + __sigprocmask (SIG_SETMASK, sigmask, &savemask); + + /* select itself is a cancellation entrypoint. */ + ret = __select (nfds, readfds, writefds, exceptfds, ptval); + + if (sigmask != NULL) + __sigprocmask (SIG_SETMASK, &savemask, NULL); + + return ret; +} +weak_alias (__pselect, pselect) +#endif diff --git a/sysdeps/unix/sysv/linux/pselect.c b/sysdeps/unix/sysv/linux/pselect.c index acda3e0..7a3dc8c 100644 --- a/sysdeps/unix/sysv/linux/pselect.c +++ b/sysdeps/unix/sysv/linux/pselect.c @@ -16,23 +16,9 @@ License along with the GNU C Library; if not, see . */ -#include -#include -#include -#include -#include +#include #include - -#ifdef __NR_pselect6 -# ifndef __ASSUME_PSELECT -static int __generic_pselect (int nfds, fd_set *readfds, fd_set *writefds, - fd_set *exceptfds, - const struct timespec *timeout, - const sigset_t *sigmask); -# endif - - int __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, const struct timespec *timeout, const sigset_t *sigmask) @@ -59,24 +45,9 @@ __pselect (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, data.ss = (__syscall_ulong_t) (uintptr_t) sigmask; data.ss_len = _NSIG / 8; - int result = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, - timeout, &data); - -# ifndef __ASSUME_PSELECT - if (result == -1 && errno == ENOSYS) - result = __generic_pselect (nfds, readfds, writefds, exceptfds, timeout, - sigmask); -# endif - - return result; + return SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, + timeout, &data); } +#ifndef __pselect weak_alias (__pselect, pselect) - -# ifndef __ASSUME_PSELECT -# define __pselect static __generic_pselect -# endif -#endif - -#ifndef __ASSUME_PSELECT -# include #endif -- 2.7.4