2023-01-30 12:52:16 +00:00
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/* System-specific extensions of <sys/mman.h>, Hurd version.
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2024-01-01 18:12:26 +00:00
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Copyright (C) 2022-2024 Free Software Foundation, Inc.
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2023-01-30 12:52:16 +00:00
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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_MMAN_H
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# error "Never include <bits/mman_ext.h> directly; use <sys/mman.h> instead."
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#endif
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#ifdef __USE_GNU
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# define SHM_ANON ((const char *) 1)
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hurd: Implement MAP_EXCL
MAP_FIXED is defined to silently replace any existing mappings at the
address range being mapped over. This, however, is a dangerous, and only
rarely desired behavior.
Various Unix systems provide replacements or additions to MAP_FIXED:
* SerenityOS and Linux provide MAP_FIXED_NOREPLACE. If the address space
already contains a mapping in the requested range, Linux returns
EEXIST. SerenityOS returns ENOMEM, however that is a bug, as the
MAP_FIXED_NOREPLACE implementation is intended to be compatible with
Linux.
* FreeBSD provides the MAP_EXCL flag that has to be used in combination
with MAP_FIXED. It returns EINVAL if the requested range already
contains existing mappings. This is directly analogous to the O_EXCL
flag in the open () call.
* DragonFly BSD, NetBSD, and OpenBSD provide MAP_TRYFIXED, but with
different semantics. DragonFly BSD returns ENOMEM if the requested
range already contains existing mappings. NetBSD does not return an
error, but instead creates the mapping at a different address if the
requested range contains mappings. OpenBSD behaves the same, but also
notes that this is the default behavior even without MAP_TRYFIXED
(which is the case on the Hurd too).
Since the Hurd leans closer to the BSD side, add MAP_EXCL as the primary
API to request the behavior of not replacing existing mappings. Declare
MAP_FIXED_NOREPLACE and MAP_TRYFIXED as aliases of (MAP_FIXED|MAP_EXCL),
so any existing software that checks for either of those macros will
pick them up automatically. For compatibility with Linux, return EEXIST
if a mapping already exists.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230625231751.404120-5-bugaevc@gmail.com>
2023-06-25 23:17:51 +00:00
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# define MAP_32BIT 0x1000 /* Map in the lower 2 GB. */
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# define MAP_EXCL 0x4000 /* With MAP_FIXED, don't replace existing mappings. */
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# define MAP_TRYFIXED (MAP_FIXED | MAP_EXCL) /* BSD name. */
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# define MAP_FIXED_NOREPLACE (MAP_FIXED | MAP_EXCL) /* Linux name. */
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2023-01-30 12:52:16 +00:00
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#endif /* __USE_GNU */
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