On Tue, Jan 5, 2021 at 7:28 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > Mention in the documentation that enabling CONFIG_KASAN_HW_TAGS > always results in in-kernel TBI (Top Byte Ignore) being enabled. > > Also do a few minor documentation cleanups. > > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > Link: https://linux-review.googlesource.com/id/Iba2a6697e3c6304cb53f89ec61dedc77fa29e3ae Reviewed-by: Alexander Potapenko <glider@xxxxxxxxxx> > --- > Documentation/dev-tools/kasan.rst | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst > index 0fc3fb1860c4..26c99852a852 100644 > --- a/Documentation/dev-tools/kasan.rst > +++ b/Documentation/dev-tools/kasan.rst > @@ -147,15 +147,14 @@ negative values to distinguish between different kinds of inaccessible memory > like redzones or freed memory (see mm/kasan/kasan.h). > > In the report above the arrows point to the shadow byte 03, which means that > -the accessed address is partially accessible. > - > -For tag-based KASAN this last report section shows the memory tags around the > -accessed address (see `Implementation details`_ section). > +the accessed address is partially accessible. For tag-based KASAN modes this > +last report section shows the memory tags around the accessed address > +(see the `Implementation details`_ section). > > Boot parameters > ~~~~~~~~~~~~~~~ > > -Hardware tag-based KASAN mode (see the section about different mode below) is > +Hardware tag-based KASAN mode (see the section about various modes below) is > intended for use in production as a security mitigation. Therefore it supports > boot parameters that allow to disable KASAN competely or otherwise control > particular KASAN features. > @@ -305,6 +304,13 @@ reserved to tag freed memory regions. > Hardware tag-based KASAN currently only supports tagging of > kmem_cache_alloc/kmalloc and page_alloc memory. > > +If the hardware doesn't support MTE (pre ARMv8.5), hardware tag-based KASAN > +won't be enabled. In this case all boot parameters are ignored. > + > +Note, that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being > +enabled. Even when kasan.mode=off is provided, or when the hardware doesn't > +support MTE (but supports TBI). > + > What memory accesses are sanitised by KASAN? > -------------------------------------------- > > -- > 2.29.2.729.g45daf8777d-goog > -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
