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-rw-r--r--include/uapi/linux/cramfs_fs.h113
1 files changed, 113 insertions, 0 deletions
diff --git a/include/uapi/linux/cramfs_fs.h b/include/uapi/linux/cramfs_fs.h
new file mode 100644
index 000000000..6713669aa
--- /dev/null
+++ b/include/uapi/linux/cramfs_fs.h
@@ -0,0 +1,113 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI__CRAMFS_H
+#define _UAPI__CRAMFS_H
+
+#include <linux/types.h>
+#include <linux/magic.h>
+
+#define CRAMFS_SIGNATURE "Compressed ROMFS"
+
+/*
+ * Width of various bitfields in struct cramfs_inode.
+ * Primarily used to generate warnings in mkcramfs.
+ */
+#define CRAMFS_MODE_WIDTH 16
+#define CRAMFS_UID_WIDTH 16
+#define CRAMFS_SIZE_WIDTH 24
+#define CRAMFS_GID_WIDTH 8
+#define CRAMFS_NAMELEN_WIDTH 6
+#define CRAMFS_OFFSET_WIDTH 26
+
+/*
+ * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs
+ * path length is 63 << 2 = 252.
+ */
+#define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)
+
+/*
+ * Reasonably terse representation of the inode data.
+ */
+struct cramfs_inode {
+ __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
+ /* SIZE for device files is i_rdev */
+ __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
+ /* NAMELEN is the length of the file name, divided by 4 and
+ rounded up. (cramfs doesn't support hard links.) */
+ /* OFFSET: For symlinks and non-empty regular files, this
+ contains the offset (divided by 4) of the file data in
+ compressed form (starting with an array of block pointers;
+ see README). For non-empty directories it is the offset
+ (divided by 4) of the inode of the first file in that
+ directory. For anything else, offset is zero. */
+ __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
+};
+
+struct cramfs_info {
+ __u32 crc;
+ __u32 edition;
+ __u32 blocks;
+ __u32 files;
+};
+
+/*
+ * Superblock information at the beginning of the FS.
+ */
+struct cramfs_super {
+ __u32 magic; /* 0x28cd3d45 - random number */
+ __u32 size; /* length in bytes */
+ __u32 flags; /* feature flags */
+ __u32 future; /* reserved for future use */
+ __u8 signature[16]; /* "Compressed ROMFS" */
+ struct cramfs_info fsid; /* unique filesystem info */
+ __u8 name[16]; /* user-defined name */
+ struct cramfs_inode root; /* root inode data */
+};
+
+/*
+ * Feature flags
+ *
+ * 0x00000000 - 0x000000ff: features that work for all past kernels
+ * 0x00000100 - 0xffffffff: features that don't work for past kernels
+ */
+#define CRAMFS_FLAG_FSID_VERSION_2 0x00000001 /* fsid version #2 */
+#define CRAMFS_FLAG_SORTED_DIRS 0x00000002 /* sorted dirs */
+#define CRAMFS_FLAG_HOLES 0x00000100 /* support for holes */
+#define CRAMFS_FLAG_WRONG_SIGNATURE 0x00000200 /* reserved */
+#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400 /* shifted root fs */
+#define CRAMFS_FLAG_EXT_BLOCK_POINTERS 0x00000800 /* block pointer extensions */
+
+/*
+ * Valid values in super.flags. Currently we refuse to mount
+ * if (flags & ~CRAMFS_SUPPORTED_FLAGS). Maybe that should be
+ * changed to test super.future instead.
+ */
+#define CRAMFS_SUPPORTED_FLAGS ( 0x000000ff \
+ | CRAMFS_FLAG_HOLES \
+ | CRAMFS_FLAG_WRONG_SIGNATURE \
+ | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \
+ | CRAMFS_FLAG_EXT_BLOCK_POINTERS )
+
+/*
+ * Block pointer flags
+ *
+ * The maximum block offset that needs to be represented is roughly:
+ *
+ * (1 << CRAMFS_OFFSET_WIDTH) * 4 +
+ * (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE)
+ * = 0x11004000
+ *
+ * That leaves room for 3 flag bits in the block pointer table.
+ */
+#define CRAMFS_BLK_FLAG_UNCOMPRESSED (1 << 31)
+#define CRAMFS_BLK_FLAG_DIRECT_PTR (1 << 30)
+
+#define CRAMFS_BLK_FLAGS ( CRAMFS_BLK_FLAG_UNCOMPRESSED \
+ | CRAMFS_BLK_FLAG_DIRECT_PTR )
+
+/*
+ * Direct blocks are at least 4-byte aligned.
+ * Pointers to direct blocks are shifted down by 2 bits.
+ */
+#define CRAMFS_BLK_DIRECT_PTR_SHIFT 2
+
+#endif /* _UAPI__CRAMFS_H */