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6e88abb862
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
71 lines
2.7 KiB
C
71 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
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/*
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* FS_IOC_FIEMAP ioctl infrastructure.
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*
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* Some portions copyright (C) 2007 Cluster File Systems, Inc
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*
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* Authors: Mark Fasheh <mfasheh@suse.com>
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* Kalpak Shah <kalpak.shah@sun.com>
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* Andreas Dilger <adilger@sun.com>
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*/
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#ifndef _LINUX_FIEMAP_H
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#define _LINUX_FIEMAP_H
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#include <linux/types.h>
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struct fiemap_extent {
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__u64 fe_logical; /* logical offset in bytes for the start of
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* the extent from the beginning of the file */
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__u64 fe_physical; /* physical offset in bytes for the start
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* of the extent from the beginning of the disk */
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__u64 fe_length; /* length in bytes for this extent */
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__u64 fe_reserved64[2];
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__u32 fe_flags; /* FIEMAP_EXTENT_* flags for this extent */
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__u32 fe_reserved[3];
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};
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struct fiemap {
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__u64 fm_start; /* logical offset (inclusive) at
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* which to start mapping (in) */
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__u64 fm_length; /* logical length of mapping which
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* userspace wants (in) */
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__u32 fm_flags; /* FIEMAP_FLAG_* flags for request (in/out) */
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__u32 fm_mapped_extents;/* number of extents that were mapped (out) */
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__u32 fm_extent_count; /* size of fm_extents array (in) */
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__u32 fm_reserved;
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struct fiemap_extent fm_extents[]; /* array of mapped extents (out) */
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};
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#define FIEMAP_MAX_OFFSET (~0ULL)
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#define FIEMAP_FLAG_SYNC 0x00000001 /* sync file data before map */
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#define FIEMAP_FLAG_XATTR 0x00000002 /* map extended attribute tree */
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#define FIEMAP_FLAG_CACHE 0x00000004 /* request caching of the extents */
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#define FIEMAP_FLAGS_COMPAT (FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR)
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#define FIEMAP_EXTENT_LAST 0x00000001 /* Last extent in file. */
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#define FIEMAP_EXTENT_UNKNOWN 0x00000002 /* Data location unknown. */
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#define FIEMAP_EXTENT_DELALLOC 0x00000004 /* Location still pending.
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* Sets EXTENT_UNKNOWN. */
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#define FIEMAP_EXTENT_ENCODED 0x00000008 /* Data can not be read
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* while fs is unmounted */
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#define FIEMAP_EXTENT_DATA_ENCRYPTED 0x00000080 /* Data is encrypted by fs.
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* Sets EXTENT_NO_BYPASS. */
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#define FIEMAP_EXTENT_NOT_ALIGNED 0x00000100 /* Extent offsets may not be
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* block aligned. */
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#define FIEMAP_EXTENT_DATA_INLINE 0x00000200 /* Data mixed with metadata.
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* Sets EXTENT_NOT_ALIGNED.*/
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#define FIEMAP_EXTENT_DATA_TAIL 0x00000400 /* Multiple files in block.
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* Sets EXTENT_NOT_ALIGNED.*/
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#define FIEMAP_EXTENT_UNWRITTEN 0x00000800 /* Space allocated, but
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* no data (i.e. zero). */
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#define FIEMAP_EXTENT_MERGED 0x00001000 /* File does not natively
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* support extents. Result
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* merged for efficiency. */
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#define FIEMAP_EXTENT_SHARED 0x00002000 /* Space shared with other
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* files. */
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#endif /* _LINUX_FIEMAP_H */
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