On Sun, Nov 11, 2018 at 11:14 PM Palmer Dabbelt <pal...@sifive.com> wrote: > > On Sat, 10 Nov 2018 00:35:15 PST (-0800), m...@packi.ch wrote: > > On 10.11.18 07:45, David Abdurachmanov wrote: > >> > >> The patch adds the missing S and U modes. > > > > This is the same patch I submitted earlier (see v2 here [1], based on > > Palmer's feedback). Palmer stated that the "S" extension should not be > > exposed to usermode. > > > > Since two people arrived at the same solution, I wonder if the > > supervisor mode should really be hidden from userspace, as it's about > > the CPU information, not about the environment the calling code is > > running as. > > > > [1] https://lkml.org/lkml/2018/11/10/96 > > I still think S should be hidden from applications. This patch was fairly > mechanical, so it probably just wasn't though about twice -- that's the > problem > with user ABI stuff, lots of times the obvious answer isn't the correct one > :). > True. It was mechanical based on warnings I noticed while booting Fedora with latest kernel and BBL.
Also true, that /proc/cpuinfo doesn't need to reveal all things to user space (especially if you don't want various programs to depend on it as some tend to parse /proc/cpuinfo). Note, that on server systems which probably would implement SMBIOS (based on the current proposal for RISC-V) the administrator could check for S mode.
