projects / GitHub / moto-9609 / android_kernel_motorola_exynos9610.git / blame
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|---|---|---|
| e45b082d MCC |
1 | =================================================== |
| 2 | Notes on the change from 16-bit UIDs to 32-bit UIDs | |
| 3 | =================================================== | |
| 4 | ||
| 5 | :Author: Chris Wing <wingc@umich.edu> | |
| 6 | :Last updated: January 11, 2000 | |
| 1da177e4 LT |
7 | |
| 8 | - kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t | |
| 9 | when communicating between user and kernel space in an ioctl or data | |
| 10 | structure. | |
| 11 | ||
| 12 | - kernel code should use uid_t and gid_t in kernel-private structures and | |
| 13 | code. | |
| 14 | ||
| 15 | What's left to be done for 32-bit UIDs on all Linux architectures: | |
| 16 | ||
| 17 | - Disk quotas have an interesting limitation that is not related to the | |
| 18 | maximum UID/GID. They are limited by the maximum file size on the | |
| 19 | underlying filesystem, because quota records are written at offsets | |
| 20 | corresponding to the UID in question. | |
| 21 | Further investigation is needed to see if the quota system can cope | |
| 22 | properly with huge UIDs. If it can deal with 64-bit file offsets on all | |
| 23 | architectures, this should not be a problem. | |
| 24 | ||
| 25 | - Decide whether or not to keep backwards compatibility with the system | |
| 26 | accounting file, or if we should break it as the comments suggest | |
| 27 | (currently, the old 16-bit UID and GID are still written to disk, and | |
| 28 | part of the former pad space is used to store separate 32-bit UID and | |
| 29 | GID) | |
| 30 | ||
| 31 | - Need to validate that OS emulation calls the 16-bit UID | |
| 32 | compatibility syscalls, if the OS being emulated used 16-bit UIDs, or | |
| 33 | uses the 32-bit UID system calls properly otherwise. | |
| 34 | ||
| 35 | This affects at least: | |
| 1da177e4 | 36 | |
| e45b082d MCC |
37 | - iBCS on Intel |
| 38 | ||
| 39 | - sparc32 emulation on sparc64 | |
| 40 | (need to support whatever new 32-bit UID system calls are added to | |
| 41 | sparc32) | |
| 1da177e4 LT |
42 | |
| 43 | - Validate that all filesystems behave properly. | |
| 44 | ||
| 45 | At present, 32-bit UIDs _should_ work for: | |
| e45b082d MCC |
46 | |
| 47 | - ext2 | |
| 48 | - ufs | |
| 49 | - isofs | |
| 50 | - nfs | |
| 51 | - coda | |
| 52 | - udf | |
| 1da177e4 LT |
53 | |
| 54 | Ioctl() fixups have been made for: | |
| e45b082d MCC |
55 | |
| 56 | - ncpfs | |
| 57 | - smbfs | |
| 1da177e4 LT |
58 | |
| 59 | Filesystems with simple fixups to prevent 16-bit UID wraparound: | |
| e45b082d MCC |
60 | |
| 61 | - minix | |
| 62 | - sysv | |
| 63 | - qnx4 | |
| 1da177e4 LT |
64 | |
| 65 | Other filesystems have not been checked yet. | |
| 66 | ||
| 84eb8d06 | 67 | - The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in |
| 1da177e4 LT |
68 | all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but |
| 69 | more are needed. (as well as new user<->kernel data structures) | |
| 70 | ||
| 71 | - The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k, | |
| 72 | sh, and sparc32. Fixing this is probably not that important, but would | |
| 73 | require adding a new ELF section. | |
| 74 | ||
| 75 | - The ioctl()s used to control the in-kernel NFS server only support | |
| 76 | 16-bit UIDs on arm, i386, m68k, sh, and sparc32. | |
| 77 | ||
| 78 | - make sure that the UID mapping feature of AX25 networking works properly | |
| 79 | (it should be safe because it's always used a 32-bit integer to | |
| 80 | communicate between user and kernel) |