mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-26 06:04:14 +08:00
4f4cfa6c56
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>
81 lines
2.6 KiB
ReStructuredText
81 lines
2.6 KiB
ReStructuredText
===================================================
|
|
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)
|