kasan: allow an architecture to disable inline instrumentation

Patch series "KASAN core changes for ppc64 radix KASAN", v16.

Building on the work of Christophe, Aneesh and Balbir, I've ported KASAN
to 64-bit Book3S kernels running on the Radix MMU.  I've been trying this
for a while, but we keep having collisions between the kasan code in the
mm tree and the code I want to put in to the ppc tree.

This series just contains the kasan core changes that we need.  There
should be no noticeable changes to other platforms.

This patch (of 4):

For annoying architectural reasons, it's very difficult to support inline
instrumentation on powerpc64.*

Add a Kconfig flag to allow an arch to disable inline.  (It's a bit
annoying to be 'backwards', but I'm not aware of any way to have an arch
force a symbol to be 'n', rather than 'y'.)

We also disable stack instrumentation in this case as it does things that
are functionally equivalent to inline instrumentation, namely adding code
that touches the shadow directly without going through a C helper.

* on ppc64 atm, the shadow lives in virtual memory and isn't accessible in
real mode.  However, before we turn on virtual memory, we parse the device
tree to determine which platform and MMU we're running under.  That calls
generic DT code, which is instrumented.  Inline instrumentation in DT
would unconditionally attempt to touch the shadow region, which we won't
have set up yet, and would crash.  We can make outline mode wait for the
arch to be ready, but we can't change what the compiler inserts for inline
mode.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Daniel Axtens <[email protected]>
Reviewed-by: Marco Elver <[email protected]>
Reviewed-by: Andrey Konovalov <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Aneesh Kumar K.V <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions