On Wed, Nov 18, 2020 at 11:50 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > > On Wed, Nov 18, 2020 at 5:21 PM Willem de Bruijn > <willemdebruijn.kernel@xxxxxxxxx> wrote: > > > diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl > > > index 109e6681b8fa..9a4e8ec207fc 100644 > > > --- a/arch/x86/entry/syscalls/syscall_32.tbl > > > +++ b/arch/x86/entry/syscalls/syscall_32.tbl > > > @@ -447,3 +447,4 @@ > > > 440 i386 process_madvise sys_process_madvise > > > 441 i386 watch_mount sys_watch_mount > > > 442 i386 memfd_secret sys_memfd_secret > > > +443 i386 epoll_pwait2 sys_epoll_pwait2 compat_sys_epoll_pwait2 > > > > I should have caught this sooner, but this does not work as intended. > > > > x86 will still call epoll_pwait2 with old_timespec32. > > > > One approach is a separate epoll_pwait2_time64 syscall, similar to > > ppoll_time64. But that was added to work around legacy 32-bit ppoll. > > Not needed for a new API. > > > > In libc, ppoll_time64 is declared with type struct __timespec64. That > > type is not defined in Linux uapi. Will need to look at this some > > more. > > The libc __timespec64 corresponds to the __kernel_timespec64 > structure in uapi. It is defined to only have 'long' nanoseconds > member because that's what c99 and posix require, but the bits > are in the position that matches the lower 32 bits of the 64-bit > tv_nsec in the kernel, and get_timespec64() performs the > necessary conversion to either check or zero the upper bits. > > I think all you need in user space is to pass the timeout as a > __timespec64 structure and add a conversion in the exported > library interface. Indeed, that resolves it, thanks. I'll define that struct in the selftest and update the definition of sys_epoll_pwait2 there.
