Messages in this thread | | | Date | Tue, 18 Feb 2014 12:32:39 -0800 | From | Greg KH <> | Subject | Re: [PATCH 12/14] staging: binder: Fix ABI for 64bit Android |
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On Tue, Feb 18, 2014 at 12:02:07PM -0800, John Stultz wrote: > On Tue, Feb 18, 2014 at 11:49 AM, Greg KH <gregkh@linuxfoundation.org> wrote: > > On Tue, Feb 18, 2014 at 11:30:26AM -0800, John Stultz wrote: > >> On Tue, Feb 18, 2014 at 11:08 AM, Greg KH <gregkh@linuxfoundation.org> wrote: > >> > On Mon, Feb 17, 2014 at 01:58:40PM -0800, John Stultz wrote: > >> >> From: Serban Constantinescu <serban.constantinescu@arm.com> > >> >> > >> >> This patch fixes the ABI for 64bit Android userspace. > >> >> BC_REQUEST_DEATH_NOTIFICATION and BC_CLEAR_DEATH_NOTIFICATION claim > >> >> to be using struct binder_ptr_cookie, but they are using a 32bit handle > >> >> and a pointer. > >> >> > >> >> On 32bit systems the payload size is the same as the size of struct > >> >> binder_ptr_cookie, however for 64bit systems this will differ. This > >> >> patch adds struct binder_handle_cookie that fixes this issue for 64bit > >> >> Android. > >> >> > >> >> Since there are no 64bit users of this interface that we know of this > >> >> change should not affect any existing systems. > >> > > >> > But you are changing the ioctl structures here, what is that going to > >> > cause with old programs? > >> > >> So I'd be glad for Serban or Arve to clarify, but my understanding > >> (and as is described in the commit message) is that the assumption is > >> there are no 64bit binder users at this point, and the ioctl structure > >> changes are made such that existing 32bit applications are unaffected. > > > > How does changing the structure size, and contents, not affect any > > applications or the kernel code? What am I missing here? > > On 32bit pointers and ints are the same size? (Years ago I sat through > your presentation on this, so I'm worried I'm missing something here > :) > > struct binder_ptr_cookie { > void *ptr; > void *cookie; > }; > > struct binder_handle_cookie { > __u32 handle; > void *cookie; > } __attribute__((packed)); > > > On 32bit systems these are the same size. Now on 64bit systems, this > changes things, and would break users, but the assumption here is > there are no pre-existing 64bit binder users.
But you added a field to the existing structure, right? I don't really remember the patch, it was a few hundred back in my review of stuff today, sorry...
greg k-h
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