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The openat2 syscall was added on Linux 5.6, as an extension of openat. Unlike other open-like functions, the kernel only provides the LFS variant (so files larger than 4GB always succeed, unlike other functions with an offset larger than off_t). Also, similar to other open functions, the new symbol is a cancellable entrypoint. The test case added only stress tests for some of the syscalls' provided functionality, and it is based on an existing kernel self-test. A fortify wrapper is added to verify the argument size if not larger than the current support open_how struct. Gnulib added an openat2 module, which uses read-only for the open_how argument [1]. There is no clear indication whether the kernel will indeed use the argument as in-out, how it would do so, or for which kind of functionality [2]. Also, adding a potentially different prototype than gnulib only would add extra unnecessary friction and extra wrappers to handle it. Checked on x86_64-linux-gnu and aarch64-linux-gnu. [1] https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=0b97ffdf32bdab909d02449043447237273df75e [2] https://sourceware.org/pipermail/libc-alpha/2025-September/169740.html Reviewed-by: Carlos O'Donell <carlos@redhat.com>
61 lines
2.0 KiB
C
61 lines
2.0 KiB
C
/* openat2 definition. Linux specific.
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Copyright (C) 2025 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 _FCNTL_H
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# error "Never use <bits/openat2.h> directly; include <fcntl.h> instead."
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#endif
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#ifndef __glibc_has_open_how
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/* Arguments for how openat2 should open the target path. */
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struct open_how
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{
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__uint64_t flags;
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__uint64_t mode;
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__uint64_t resolve;
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};
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#endif
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/* how->resolve flags for openat2. */
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#ifndef RESOLVE_NO_XDEV
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# define RESOLVE_NO_XDEV 0x01 /* Block mount-point crossings
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(includes bind-mounts). */
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#endif
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#ifndef RESOLVE_NO_MAGICLINKS
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# define RESOLVE_NO_MAGICLINKS 0x02 /* Block traversal through procfs-style
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"magic-links". */
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#endif
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#ifndef RESOLVE_NO_SYMLINKS
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# define RESOLVE_NO_SYMLINKS 0x04 /* Block traversal through all symlinks. */
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#endif
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#ifndef RESOLVE_BENEATH
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# define RESOLVE_BENEATH 0x08 /* Block "lexical" trickery like
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"..", symlinks, and absolute
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paths which escape the dirfd. */
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#endif
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#ifndef RESOLVE_IN_ROOT
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# define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
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be scoped inside the dirfd
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(similar to chroot). */
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#endif
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#ifndef RESOLVE_CACHED
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# define RESOLVE_CACHED 0x20 /* Only complete if resolution can be
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completed through cached lookup. May
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return -EAGAIN if that's not
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possible. */
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#endif
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