Hi, Le mercredi 16 mai 2018 à 15:20 +0100, Dave Martin a écrit : > There are constraints on defining AT_* auxvec tags that are not > obvious to the casual maintainer of either the global > <uapi/linux/auxvec.h> or the arch-specific headers. This is likely > to lead to mistakes. (I certainly fell foul of it...) > > For the benefit of future maintainers, this patch collects the > relevant information in one place, documenting how the namespace > needs to be managed, and noting all the values currently in use. > > Maintaining a global list may result in some merge conflicts, but > AT_* values are not added frequently. I'm open to suggestions on > the best approach. > > I also assume that values 38 and 39 may have been used for > historical purposes, such as an architecture that is no longer > supported. If they have definitely never been used for anything, > they could be removed from the "reserved" list. > Some of those AT_* values are described in getauxval(3) man-page: http://man7.org/linux/man-pages/man3/getauxval.3.html https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man3/g etauxval.3?id=4eae8eb731386d81797d5c30365426722410874e And glibc provides <elf.h> with definitions for almost all AT_*, regardless of the current target architecture: https://sourceware.org/git/?p=glibc.git;a=blob;f=elf/elf.h;h=954f3266f7 11ab83996670ea504a17dcf668e061;hb=23158b08a0908f381459f273a984c6fd32836 3cb#l1135 Also, despite not being listed as a reserved namespace by POSIX, one should try to avoid name collision with other AT_ constants, those used with *at() functions (openat(), etc.): - AT_EACCESS - AT_EMPTY_PATH - AT_FDCWD - AT_NO_AUTOMOUNT - AT_REMOVEDIR - AT_STATX_DONT_SYNC - AT_STATX_FORCE_SYNC - AT_STATX_SYNC_AS_STAT - AT_SYMLINK_FOLLOW - AT_SYMLINK_NOFOLLOW http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fcntl.h.html http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.htm l#tag_15_02_02 https://sourceware.org/git/?p=glibc.git;a=blob;f=io/fcntl.h;h=3d239e8f0 9f7ce0a3106621be327e1ea4cd1a3e7;hb=23158b08a0908f381459f273a984c6fd3283 63cb#l142 And there's also AT_ANYNET and AT_ANYNODE from ddp (aka. AppleTalk) http://man7.org/linux/man-pages/man7/ddp.7.html Regards. -- Yann Droneaud OPTEYA
