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52193857e2
Android uses ashmem for sharing memory regions. We are looking forward to migrating all usecases of ashmem to memfd so that we can possibly remove the ashmem driver in the future from staging while also benefiting from using memfd and contributing to it. Note staging drivers are also not ABI and generally can be removed at anytime. One of the main usecases Android has is the ability to create a region and mmap it as writeable, then add protection against making any "future" writes while keeping the existing already mmap'ed writeable-region active. This allows us to implement a usecase where receivers of the shared memory buffer can get a read-only view, while the sender continues to write to the buffer. See CursorWindow documentation in Android for more details: https://developer.android.com/reference/android/database/CursorWindow This usecase cannot be implemented with the existing F_SEAL_WRITE seal. To support the usecase, this patch adds a new F_SEAL_FUTURE_WRITE seal which prevents any future mmap and write syscalls from succeeding while keeping the existing mmap active. Verified with test program at: https://lore.kernel.org/patchwork/patch/1008117/ Backport link: https://lore.kernel.org/patchwork/patch/1014892/ Bug: 113362644 Change-Id: If7424db3b64372932d455f0219cd9df613fec1d4 Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Joel Fernandes <joelaf@google.com>
95 lines
3 KiB
C
95 lines
3 KiB
C
#ifndef _LINUX_FCNTL_H
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#define _LINUX_FCNTL_H
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#include <asm/fcntl.h>
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#define F_SETLEASE (F_LINUX_SPECIFIC_BASE + 0)
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#define F_GETLEASE (F_LINUX_SPECIFIC_BASE + 1)
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/*
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* Cancel a blocking posix lock; internal use only until we expose an
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* asynchronous lock api to userspace:
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*/
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#define F_CANCELLK (F_LINUX_SPECIFIC_BASE + 5)
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/* Create a file descriptor with FD_CLOEXEC set. */
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#define F_DUPFD_CLOEXEC (F_LINUX_SPECIFIC_BASE + 6)
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/*
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* Request nofications on a directory.
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* See below for events that may be notified.
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*/
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#define F_NOTIFY (F_LINUX_SPECIFIC_BASE+2)
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/*
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* Set and get of pipe page size array
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*/
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#define F_SETPIPE_SZ (F_LINUX_SPECIFIC_BASE + 7)
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#define F_GETPIPE_SZ (F_LINUX_SPECIFIC_BASE + 8)
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/*
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* Set/Get seals
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*/
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#define F_ADD_SEALS (F_LINUX_SPECIFIC_BASE + 9)
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#define F_GET_SEALS (F_LINUX_SPECIFIC_BASE + 10)
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/*
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* Types of seals
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*/
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#define F_SEAL_SEAL 0x0001 /* prevent further seals from being set */
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#define F_SEAL_SHRINK 0x0002 /* prevent file from shrinking */
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#define F_SEAL_GROW 0x0004 /* prevent file from growing */
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#define F_SEAL_WRITE 0x0008 /* prevent writes */
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#define F_SEAL_FUTURE_WRITE 0x0010 /* prevent writes */
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/* (1U << 31) is reserved for signed error codes */
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/*
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* Types of directory notifications that may be requested.
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*/
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#define DN_ACCESS 0x00000001 /* File accessed */
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#define DN_MODIFY 0x00000002 /* File modified */
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#define DN_CREATE 0x00000004 /* File created */
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#define DN_DELETE 0x00000008 /* File removed */
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#define DN_RENAME 0x00000010 /* File renamed */
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#define DN_ATTRIB 0x00000020 /* File changed attibutes */
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#define DN_MULTISHOT 0x80000000 /* Don't remove notifier */
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#define AT_FDCWD -100 /* Special value used to indicate
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openat should use the current
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working directory. */
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#define AT_SYMLINK_NOFOLLOW 0x100 /* Do not follow symbolic links. */
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#define AT_REMOVEDIR 0x200 /* Remove directory instead of
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unlinking file. */
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#define AT_SYMLINK_FOLLOW 0x400 /* Follow symbolic links. */
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#define AT_NO_AUTOMOUNT 0x800 /* Suppress terminal automount traversal */
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#define AT_EMPTY_PATH 0x1000 /* Allow empty relative pathname */
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#ifdef __KERNEL__
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#ifndef force_o_largefile
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#define force_o_largefile() (BITS_PER_LONG != 32)
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#endif
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#if BITS_PER_LONG == 32
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#define IS_GETLK32(cmd) ((cmd) == F_GETLK)
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#define IS_SETLK32(cmd) ((cmd) == F_SETLK)
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#define IS_SETLKW32(cmd) ((cmd) == F_SETLKW)
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#define IS_GETLK64(cmd) ((cmd) == F_GETLK64)
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#define IS_SETLK64(cmd) ((cmd) == F_SETLK64)
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#define IS_SETLKW64(cmd) ((cmd) == F_SETLKW64)
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#else
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#define IS_GETLK32(cmd) (0)
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#define IS_SETLK32(cmd) (0)
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#define IS_SETLKW32(cmd) (0)
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#define IS_GETLK64(cmd) ((cmd) == F_GETLK)
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#define IS_SETLK64(cmd) ((cmd) == F_SETLK)
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#define IS_SETLKW64(cmd) ((cmd) == F_SETLKW)
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#endif /* BITS_PER_LONG == 32 */
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#define IS_GETLK(cmd) (IS_GETLK32(cmd) || IS_GETLK64(cmd))
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#define IS_SETLK(cmd) (IS_SETLK32(cmd) || IS_SETLK64(cmd))
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#define IS_SETLKW(cmd) (IS_SETLKW32(cmd) || IS_SETLKW64(cmd))
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#endif /* __KERNEL__ */
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#endif
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