Commit | Line | Data |
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1da177e4 LT |
1 | Notes on the change from 16-bit UIDs to 32-bit UIDs: |
2 | ||
3 | - kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t | |
4 | when communicating between user and kernel space in an ioctl or data | |
5 | structure. | |
6 | ||
7 | - kernel code should use uid_t and gid_t in kernel-private structures and | |
8 | code. | |
9 | ||
10 | What's left to be done for 32-bit UIDs on all Linux architectures: | |
11 | ||
12 | - Disk quotas have an interesting limitation that is not related to the | |
13 | maximum UID/GID. They are limited by the maximum file size on the | |
14 | underlying filesystem, because quota records are written at offsets | |
15 | corresponding to the UID in question. | |
16 | Further investigation is needed to see if the quota system can cope | |
17 | properly with huge UIDs. If it can deal with 64-bit file offsets on all | |
18 | architectures, this should not be a problem. | |
19 | ||
20 | - Decide whether or not to keep backwards compatibility with the system | |
21 | accounting file, or if we should break it as the comments suggest | |
22 | (currently, the old 16-bit UID and GID are still written to disk, and | |
23 | part of the former pad space is used to store separate 32-bit UID and | |
24 | GID) | |
25 | ||
26 | - Need to validate that OS emulation calls the 16-bit UID | |
27 | compatibility syscalls, if the OS being emulated used 16-bit UIDs, or | |
28 | uses the 32-bit UID system calls properly otherwise. | |
29 | ||
30 | This affects at least: | |
1da177e4 LT |
31 | iBCS on Intel |
32 | ||
33 | sparc32 emulation on sparc64 | |
34 | (need to support whatever new 32-bit UID system calls are added to | |
35 | sparc32) | |
36 | ||
37 | - Validate that all filesystems behave properly. | |
38 | ||
39 | At present, 32-bit UIDs _should_ work for: | |
40 | ext2 | |
41 | ufs | |
42 | isofs | |
43 | nfs | |
44 | coda | |
45 | udf | |
46 | ||
47 | Ioctl() fixups have been made for: | |
48 | ncpfs | |
49 | smbfs | |
50 | ||
51 | Filesystems with simple fixups to prevent 16-bit UID wraparound: | |
52 | minix | |
53 | sysv | |
54 | qnx4 | |
55 | ||
56 | Other filesystems have not been checked yet. | |
57 | ||
84eb8d06 | 58 | - The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in |
1da177e4 LT |
59 | all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but |
60 | more are needed. (as well as new user<->kernel data structures) | |
61 | ||
62 | - The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k, | |
63 | sh, and sparc32. Fixing this is probably not that important, but would | |
64 | require adding a new ELF section. | |
65 | ||
66 | - The ioctl()s used to control the in-kernel NFS server only support | |
67 | 16-bit UIDs on arm, i386, m68k, sh, and sparc32. | |
68 | ||
69 | - make sure that the UID mapping feature of AX25 networking works properly | |
70 | (it should be safe because it's always used a 32-bit integer to | |
71 | communicate between user and kernel) | |
72 | ||
73 | ||
74 | Chris Wing | |
75 | wingc@umich.edu | |
76 | ||
77 | last updated: January 11, 2000 |