From: T.J. Mercier
> Sent: 14 March 2022 23:45
>
> On Thu, Mar 10, 2022 at 11:33 AM Todd Kjos <tkjos@xxxxxxxxxx> wrote:
> >
> > On Wed, Mar 9, 2022 at 8:52 AM T.J. Mercier <tjmercier@xxxxxxxxxx> wrote:
> > >
> > > The kernel interface should use types that the kernel defines instead of
> > > pid_t and uid_t, whose definiton is owned by libc. This fixes the header
> > > so that it can be included without first including sys/types.h.
> > >
> > > Signed-off-by: T.J. Mercier <tjmercier@xxxxxxxxxx>
> > > ---
> > > include/uapi/linux/android/binder.h | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h
> > > index 169fd5069a1a..aa28454dbca3 100644
> > > --- a/include/uapi/linux/android/binder.h
> > > +++ b/include/uapi/linux/android/binder.h
> > > @@ -289,8 +289,8 @@ struct binder_transaction_data {
> > >
> > > /* General information about the transaction. */
> > > __u32 flags;
> > > - pid_t sender_pid;
> > > - uid_t sender_euid;
> > > + __kernel_pid_t sender_pid;
> > > + __kernel_uid_t sender_euid;
> >
> > Are we guaranteed that this does not affect the UAPI at all? Userspace
> > code using this definition will have to run with kernels using the old
> > definition and visa-versa.
>
> A standards compliant userspace should be expecting a signed integer
> type here. So the only way I can think userspace would be affected is
> if:
> 1) pid_t is a long AND
> 2) sizeof(long) > sizeof(int) AND
> 3) Consumers of the pid_t definition actually attempt to mutate the
> result to make use of extra bits in the variable (which are not there)
Or the userspace headers have a 16bit pid_t.
I can't help feeling that uapi headers should only use explicit
fixed sized types.
There is no point indirecting the type names - the sizes still
can't be changes.
David
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