x86-urgent-2020-10-27

  - Drop lazy TLB mode before switching to the temporary address space for
    text patching. text_poke() switches to the temporary mm which clears
    the lazy mode and restores the original mm afterwards. Due to clearing
    lazy mode this might restore a already dead mm if exit_mmap() runs in
    parallel on another CPU.

  - Document the x32 syscall design fail vs. syscall numbers 512-547
    properly.

  - Fix the ORC unwinder to handle the inactive task frame correctly. This
    was unearthed due to the slightly different code generation of GCC10.

  - Use an up to date screen_info for the boot params of kexec instead of
    the possibly stale and invalid version which happened to be valid when
    the kexec kernel was loaded.