• Arnd Bergmann's avatar
    y2038: socket: Add compat_sys_recvmmsg_time64 · e11d4284
    Arnd Bergmann authored
    recvmmsg() takes two arguments to pointers of structures that differ
    between 32-bit and 64-bit architectures: mmsghdr and timespec.
    
    For y2038 compatbility, we are changing the native system call from
    timespec to __kernel_timespec with a 64-bit time_t (in another patch),
    and use the existing compat system call on both 32-bit and 64-bit
    architectures for compatibility with traditional 32-bit user space.
    
    As we now have two variants of recvmmsg() for 32-bit tasks that are both
    different from the variant that we use on 64-bit tasks, this means we
    also require two compat system calls!
    
    The solution I picked is to flip things around: The existing
    compat_sys_recvmmsg() call gets moved from net/compat.c into net/socket.c
    and now handles the case for old user space on all architectures that
    have set CONFIG_COMPAT_32BIT_TIME.  A new compat_sys_recvmmsg_time64()
    call gets added in the old place for 64-bit architectures only, this
    one handles the case of a compat mmsghdr structure combined with
    __kernel_timespec.
    
    In the indirect sys_socketcall(), we now need to call either
    do_sys_recvmmsg() or __compat_sys_recvmmsg(), depending on what kind of
    architecture we are on. For compat_sys_socketcall(), no such change is
    needed, we always call __compat_sys_recvmmsg().
    
    I decided to not add a new SYS_RECVMMSG_TIME64 socketcall: Any libc
    implementation for 64-bit time_t will need significant changes including
    an updated asm/unistd.h, and it seems better to consistently use the
    separate syscalls that configuration, leaving the socketcall only for
    backward compatibility with 32-bit time_t based libc.
    
    The naming is asymmetric for the moment, so both existing syscalls
    entry points keep their names, while the new ones are recvmmsg_time32
    and compat_recvmmsg_time64 respectively. I expect that we will rename
    the compat syscalls later as we start using generated syscall tables
    everywhere and add these entry points.
    Signed-off-by: 's avatarArnd Bergmann <arnd@arndb.de>
    e11d4284