Le 15/01/2020 à 14:55, Al Viro a écrit : > On Wed, Jan 15, 2020 at 01:19:16PM +0100, Laurent Vivier wrote: >> Le 07/01/2020 à 15:50, Laurent Vivier a écrit : >>> Hi, >>> >>> this change is simple, easy to read and understand but it is really >>> needed by user space application interpreter to know the status of the >>> system configuration. >>> >>> Could we have a comment saying if there is a problem or if it is good to >>> be merged? >> >> Anyone? > > FWIW, one thing that looks worrying here is that these bits become > userland ABI after this patch - specific values passed in that thing > can't be changed. And no a single mention of that in fs/binfmt_misc.c, > leaving a nasty trap. As far as one can tell, their values are fair game > for reordering, etc. - not even visible outside of fs/binfmt_misc.c; > purely internal constants. And the effect of such modifications after > your patch will not be "everything breaks, patch gets caught by somebody's > tests" - it will be a quiet breakage for some users. > >>>> #define MISC_FMT_OPEN_BINARY (1 << 30) >>>> #define MISC_FMT_CREDENTIALS (1 << 29) >>>> #define MISC_FMT_OPEN_FILE (1 << 28) >>>> +#define MISC_FMT_FLAGS_MASK (MISC_FMT_PRESERVE_ARGV0 | MISC_FMT_OPEN_BINARY | \ >>>> + MISC_FMT_CREDENTIALS | MISC_FMT_OPEN_FILE) > > IOW, you are making those parts of userland ABI cast in stone forever. > Whether this bit assignment does make sense or not, such things really > should not be hidden. > Thank you for your answer. So I think the patch from YunQiang Su is a better approach than mine, much cleaner, see: binfmt_misc: pass info about P flag by AT_FLAGS https://patchwork.kernel.org/patch/10902935/ It does the same thing as my patch but uses a dedicated value for AT_FLAGS. Perhaps YunQiang can send a new version (without the kdebug() part)? Thanks, Laurent
