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c82bdf033f
In the context of a function definition, the size hints imply that the
size of an object pointed to by one parameter is another parameter.
This doesn't make sense for the fortified versions of the functions
since that's the bit it's trying to validate.
This is harmless with __builtin_object_size since it has fairly simple
semantics when it comes to objects passed as function parameters.
With __builtin_dynamic_object_size we could (as my patchset for gcc[1]
already does) use the access attribute to determine the object size in
the general case but it misleads the fortified functions.
Basically the problem occurs when access attributes are present on
regular functions that have inline fortified definitions to generate
_chk variants; the attributes get inherited by these definitions,
causing problems when analyzing them. For example with poll(fds, nfds,
timeout), nfds is hinted using the __attr_access as being the size of
fds.
Now, when analyzing the inline function definition in bits/poll2.h, the
compiler sees that nfds is the size of fds and tries to use that
information in the function body. In _FORTIFY_SOURCE=3 case, where the
object size could be a non-constant expression, this information results
in the conclusion that nfds is the size of fds, which defeats the
purpose of the implementation because we're trying to check here if nfds
does indeed represent the size of fds. Hence for this case, it is best
to not have the access attribute.
With the attributes gone, the expression evaluation should get delayed
until the function is actually inlined into its destinations.
Disable the access attribute for fortified function inline functions
when building at _FORTIFY_SOURCE=3 to make this work better. The
access attributes remain for the _chk variants since they can be used
by the compiler to warn when the caller is passing invalid arguments.
[1] https://gcc.gnu.org/pipermail/gcc-patches/2021-October/581125.html
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
(cherry picked from commit e938c02748)
91 lines
3.0 KiB
C
91 lines
3.0 KiB
C
/* Compatibility definitions for System V `poll' interface.
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Copyright (C) 1994-2021 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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#ifndef _SYS_POLL_H
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#define _SYS_POLL_H 1
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#include <features.h>
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/* Get the platform dependent bits of `poll'. */
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#include <bits/poll.h>
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#ifdef __USE_GNU
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# include <bits/types/__sigset_t.h>
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# include <bits/types/struct_timespec.h>
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#endif
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/* Type used for the number of file descriptors. */
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typedef unsigned long int nfds_t;
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/* Data structure describing a polling request. */
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struct pollfd
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{
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int fd; /* File descriptor to poll. */
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short int events; /* Types of events poller cares about. */
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short int revents; /* Types of events that actually occurred. */
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};
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__BEGIN_DECLS
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/* Poll the file descriptors described by the NFDS structures starting at
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FDS. If TIMEOUT is nonzero and not -1, allow TIMEOUT milliseconds for
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an event to occur; if TIMEOUT is -1, block until an event occurs.
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Returns the number of file descriptors with events, zero if timed out,
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or -1 for errors.
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This function is a cancellation point and therefore not marked with
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__THROW. */
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extern int poll (struct pollfd *__fds, nfds_t __nfds, int __timeout)
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__fortified_attr_access (__write_only__, 1, 2);
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#ifdef __USE_GNU
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/* Like poll, but before waiting the threads signal mask is replaced
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with that specified in the fourth parameter. For better usability,
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the timeout value is specified using a TIMESPEC object.
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This function is a cancellation point and therefore not marked with
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__THROW. */
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extern int ppoll (struct pollfd *__fds, nfds_t __nfds,
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const struct timespec *__timeout,
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const __sigset_t *__ss)
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__fortified_attr_access (__write_only__, 1, 2);
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# ifdef __USE_TIME_BITS64
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# ifdef __REDIRECT
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extern int __REDIRECT (ppoll, (struct pollfd *__fds, nfds_t __nfds,
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const struct timespec *__timeout,
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const __sigset_t *__ss),
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__ppoll64)
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__fortified_attr_access (__write_only__, 1, 2);
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# else
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# define ppoll __ppoll64
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# endif
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# endif
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#endif
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__END_DECLS
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/* Define some inlines helping to catch common problems. */
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#if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function
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# include <bits/poll2.h>
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#endif
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#endif /* sys/poll.h */
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