Ping? On Fri, Apr 09, 2021 at 01:43:04PM -0700, Yury Norov wrote: > Recently added memfd_secret() syscall had a flags parameter passed > as unsigned long, which requires creation of compat entry for it. > It was possible to change the type of flags to unsigned int and so > avoid bothering with compat layer. > > https://www.spinics.net/lists/linux-mm/msg251550.html > > Documentation/process/adding-syscalls.rst doesn't point clearly about > preference of ABI-agnostic types. This patch adds such notification. > > Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx> > --- > Documentation/process/adding-syscalls.rst | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/Documentation/process/adding-syscalls.rst b/Documentation/process/adding-syscalls.rst > index 9af35f4ec728..46add16edf14 100644 > --- a/Documentation/process/adding-syscalls.rst > +++ b/Documentation/process/adding-syscalls.rst > @@ -172,6 +172,13 @@ arguments (i.e. parameter 1, 3, 5), to allow use of contiguous pairs of 32-bit > registers. (This concern does not apply if the arguments are part of a > structure that's passed in by pointer.) > > +Whenever possible, try to use ABI-agnostic types for passing parameters to > +a syscall in order to avoid creating compat entry for it. Linux supports two > +ABI models - ILP32 and LP64. The types like ``void *``, ``long``, ``size_t``, > +``off_t`` have different size in those ABIs; types like ``char`` and ``int`` > +have the same size and don't require a compat layer support. For flags, it's > +always better to use ``unsigned int``. > + > > Proposing the API > ----------------- > -- > 2.25.1
