• Brian Norris's avatar
    mtd: provide proper 32/64-bit compat_ioctl() support for BLKPG · 53bb724f
    Brian Norris authored
    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: default avatarBrian Norris <computersforpeace@gmail.com>
    53bb724f
blkpg.h 397 Bytes