MFC r306162:

  Make it possible to safely use TPIDRURW from userspace.

  On amd64, arm64 and i386, we have the possibility to switch between TLS
  areas in userspace. The nice thing about this is that it makes it easier
  to do light-weight threading, if we ever feel like doing that. On armv6,
  let's go into the same direction by making it possible to safely use the
  TPIDRURW register, which is intended for this purpose.

  Clean up the ARMv6 code to remove md_tp entirely. Simply add a dedicated
  field to the PCB to hold the value of TPIDRURW across context switches,
  like we do for any other register. As userspace currently uses the
  read-only TPIDRURO register, simply ensure that we keep both values in
  sync where possible. The system calls for modifying the read-only
  register will simply write the intended value into both registers, so
  that it lazily ends up in the PCB during the next context switch.

  Approved by:    andrew
  Reviewed by:    imp
  Differential Revision:  https://reviews.freebsd.org/D7951

0 files changed, 0 insertions, 0 deletions