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authorMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-06-27 14:56:51 -0300
committerMauro Carvalho Chehab <mchehab+samsung@kernel.org>2019-07-15 11:03:02 -0300
commit4f4cfa6c560c93ba180c30675cf845e1597de44c (patch)
tree0bbe2ec9e6ef62ed2a347504dda50c6bdbe43703 /Documentation/highuid.txt
parentda82c92f1150f66afabf78d2c85ef9ac18dc6d38 (diff)
docs: admin-guide: add a series of orphaned documents
There are lots of documents that belong to the admin-guide but are on random places (most under Documentation root dir). Move them to the admin guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
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-===================================================
-Notes on the change from 16-bit UIDs to 32-bit UIDs
-===================================================
-
-:Author: Chris Wing <wingc@umich.edu>
-:Last updated: January 11, 2000
-
-- kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t
- when communicating between user and kernel space in an ioctl or data
- structure.
-
-- kernel code should use uid_t and gid_t in kernel-private structures and
- code.
-
-What's left to be done for 32-bit UIDs on all Linux architectures:
-
-- Disk quotas have an interesting limitation that is not related to the
- maximum UID/GID. They are limited by the maximum file size on the
- underlying filesystem, because quota records are written at offsets
- corresponding to the UID in question.
- Further investigation is needed to see if the quota system can cope
- properly with huge UIDs. If it can deal with 64-bit file offsets on all
- architectures, this should not be a problem.
-
-- Decide whether or not to keep backwards compatibility with the system
- accounting file, or if we should break it as the comments suggest
- (currently, the old 16-bit UID and GID are still written to disk, and
- part of the former pad space is used to store separate 32-bit UID and
- GID)
-
-- Need to validate that OS emulation calls the 16-bit UID
- compatibility syscalls, if the OS being emulated used 16-bit UIDs, or
- uses the 32-bit UID system calls properly otherwise.
-
- This affects at least:
-
- - iBCS on Intel
-
- - sparc32 emulation on sparc64
- (need to support whatever new 32-bit UID system calls are added to
- sparc32)
-
-- Validate that all filesystems behave properly.
-
- At present, 32-bit UIDs _should_ work for:
-
- - ext2
- - ufs
- - isofs
- - nfs
- - coda
- - udf
-
- Ioctl() fixups have been made for:
-
- - ncpfs
- - smbfs
-
- Filesystems with simple fixups to prevent 16-bit UID wraparound:
-
- - minix
- - sysv
- - qnx4
-
- Other filesystems have not been checked yet.
-
-- The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in
- all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but
- more are needed. (as well as new user<->kernel data structures)
-
-- The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k,
- sh, and sparc32. Fixing this is probably not that important, but would
- require adding a new ELF section.
-
-- The ioctl()s used to control the in-kernel NFS server only support
- 16-bit UIDs on arm, i386, m68k, sh, and sparc32.
-
-- make sure that the UID mapping feature of AX25 networking works properly
- (it should be safe because it's always used a 32-bit integer to
- communicate between user and kernel)