UPSTREAM: x86/uaccess, kasan: Fix KASAN vs SMAP

(Upstream commit 57b78a62e7f23c4686fe54091cdc3d12e60d6513).

KASAN inserts extra code for every LOAD/STORE emitted by te compiler.
Much of this code is simple and safe to run with AC=1, however the
kasan_report() function, called on error, is most certainly not safe
to call with AC=1.

Therefore wrap kasan_report() in user_access_{save,restore}; which for
x86 SMAP, saves/restores EFLAGS and clears AC before calling the real
function.

Also ensure all the functions are without __fentry__ hook. The
function tracer is also not safe.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Bug: 128674696
Change-Id: I636890ae2e0dcb5a54f27942d1b00098bb1a43fe