Re: [PATCH v3 1/2] arm64: refactor the rodata=xxx

[Shijie Huang]

On 2024/12/10 16:38, Anshuman Khandual wrote:
> On 12/10/24 12:51, Ard Biesheuvel wrote:
> > On Tue, 10 Dec 2024 at 08:17, Anshuman Khandual
> > <anshuman.khandual@xxxxxxx> wrote:
> > ...
> > > Reformatted and cleaned up the above comment a bit but feel free to
> > > improve it further.
> > >
> > > /*
> > >   * rodata=on (default)
> > >   *
> > >   *    This applies read-only attributes to VM areas and to the linear
> > >   *    alias of the backing pages as well. This prevents code or read-
> > >   *    only data from being modified (inadvertently or intentionally),
> > >   *    via another mapping for the same memory page.
> > >   *
> > >   *    But this might cause linear map region to be mapped down to base
> > >   *    pages, which may adversely affect performance in some cases.
> > >   *
> > >   * rodata=off
> > >   *
> > >   *    This provides more block mappings and contiguous hints for linear
> > >   *    map region which would minimize TLB footprint. This also leaves
> > >   *    read-only kernel memory writable for debugging.
> > >   *
> > >   * rodata=noalias
> > >   *
> > >   *    This provides more block mappings and contiguous hints for linear
> > >   *    map region which would minimize TLB footprint. Linear aliases of
> > >   *    pages belonging to read-only mappings in vmalloc region are also
> > >   *    marked as read-only.
> > If linear aliases are marked as read-only, how does 'noalias' differ from 'on'?
> Right, the last sentence can be can dropped.

Okay, no problem.


Thanks

Huang Shijie