On Mon, Sep 21, 2015 at 01:26:59PM -0700, Brian Norris wrote: > After a bit of poking around wondering why my 32-bit user-space can't > seem to send a proper ioctl(BLKPG) to an MTD on my 64-bit kernel > (ARM64), I noticed that struct blkpg_ioctl_arg is actually pretty > unsuitable for use in the ioctl() ABI, due to its use of raw pointers, > and its lack of alignment/packing restrictions (32-bit arch'es tend to > pack the 4 fields into 4 32-bit words, whereas 64-bit arch'es would add > padding after the third int, and make this 6 32-bit words). > > Anyway, this means BLKPG deserves some special compat_ioctl handling. Do > the conversion in a small shim for MTD. > > block/compat_ioctl.c already has compat support for the block subsystem, > but it does so by a re-marshalling data to/from user-space (see > compat_blkpg_ioctl()). Personally, I think this approach is cleaner. > > Tested only on MTD, with an ARM32 user space on an ARM64 kernel. > > Signed-off-by: Brian Norris <computersforpe...@gmail.com> > --- > You can find the initial bug report / patch here: > > http://article.gmane.org/gmane.linux.kernel/2028927 > https://lkml.org/lkml/2015/8/28/594 > > Changes since RFC: > * create new non-UAPI header, instead of cluttering the UAPI header with > compat stuff > * remove mention of "same bug in block/", since block/ solves this problem > already, just in a slightly different way
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