On Tue, Aug 5, 2025 at 7:51 PM Zi Yan <[email protected]> wrote: > FORCE_READ() converts input value x to its pointer type then reads from > address x. This is wrong. If x is a non-pointer, it would be caught it > easily. But all FORCE_READ() callers are trying to read from a pointer and > FORCE_READ() basically reads a pointer to a pointer instead of the original > typed pointer. Almost no access violation was found, except the one from > split_huge_page_test. [...] > diff --git a/tools/testing/selftests/mm/vm_util.h > b/tools/testing/selftests/mm/vm_util.h > index c20298ae98ea..b55d1809debc 100644 > --- a/tools/testing/selftests/mm/vm_util.h > +++ b/tools/testing/selftests/mm/vm_util.h > @@ -23,7 +23,7 @@ > * anything with it in order to trigger a read page fault. We therefore must > use > * volatile to stop the compiler from optimising this away. > */ > -#define FORCE_READ(x) (*(volatile typeof(x) *)x) > +#define FORCE_READ(x) (*(const volatile typeof(x) *)&(x))
So is the problem with the old code basically that it should have been something like #define FORCE_READ(x) (*(volatile typeof(*(x)) *)(x)) to actually cast the normal pointer to a volatile pointer?
