1 ==============================================
2 Notes on the change from 16-bit UIDs to 32-bit
3 ==============================================
4
5 :Author: Chris Wing <wingc@umich.edu>
6 :Last updated: January 11, 2000
7
8 - kernel code MUST take into account __kernel_
9 when communicating between user and kernel s
10 structure.
11
12 - kernel code should use uid_t and gid_t in ke
13 code.
14
15 What's left to be done for 32-bit UIDs on all
16
17 - Disk quotas have an interesting limitation t
18 maximum UID/GID. They are limited by the max
19 underlying filesystem, because quota records
20 corresponding to the UID in question.
21 Further investigation is needed to see if th
22 properly with huge UIDs. If it can deal with
23 architectures, this should not be a problem.
24
25 - Decide whether or not to keep backwards comp
26 accounting file, or if we should break it as
27 (currently, the old 16-bit UID and GID are s
28 part of the former pad space is used to stor
29 GID)
30
31 - Need to validate that OS emulation calls the
32 compatibility syscalls, if the OS being emul
33 uses the 32-bit UID system calls properly ot
34
35 This affects at least:
36
37 - iBCS on Intel
38
39 - sparc32 emulation on sparc64
40 (need to support whatever new 32-bit
41 sparc32)
42
43 - Validate that all filesystems behave properl
44
45 At present, 32-bit UIDs _should_ work for:
46
47 - ext2
48 - ufs
49 - isofs
50 - nfs
51 - coda
52 - udf
53
54 Ioctl() fixups have been made for:
55
56 - ncpfs
57 - smbfs
58
59 Filesystems with simple fixups to prevent 16
60
61 - minix
62 - sysv
63 - qnx4
64
65 Other filesystems have not been checked yet.
66
67 - The ncpfs and smpfs filesystems cannot prese
68 all ioctl()s. Some new ioctl()s have been ad
69 more are needed. (as well as new user<->kern
70
71 - The ELF core dump format only supports 16-bi
72 sh, and sparc32. Fixing this is probably not
73 require adding a new ELF section.
74
75 - The ioctl()s used to control the in-kernel N
76 16-bit UIDs on arm, i386, m68k, sh, and spar
77
78 - make sure that the UID mapping feature of AX
79 (it should be safe because it's always used
80 communicate between user and kernel)
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.