On 2/12/19 2:38 PM, Christophe Leroy wrote: > > > Le 12/02/2019 à 02:08, Daniel Axtens a écrit : >> Andrey Ryabinin <aryabi...@virtuozzo.com> writes: >> >>> >>> Christophe, you can specify KASAN_SHADOW_OFFSET either in Kconfig (e.g. >>> x86_64) or >>> in Makefile (e.g. arm64). And make early mapping writable, because compiler >>> generated code will write >>> to shadow memory in function prologue/epilogue. >> >> Hmm. Is this limitation just that compilers have not implemented >> out-of-line support for stack instrumentation, or is there a deeper >> reason that stack/global instrumentation relies upon inline >> instrumentation? > > No, it looks like as soon as we define KASAN_SHADOW_OFFSET in Makefile in > addition to asm/kasan.h, stack instrumentation works with out-of-line. >
I think you confusing two different things. CONFIG_KASAN_INLINE/CONFIG_KASAN_OUTLINE affects only generation of code that checks memory accesses, whether we call __asan_loadx()/__asan_storex() or directly insert code, checking shadow memory. But with stack instrumentation we also need to poison redzones around stack variables and unpoison them when we leave the function. That poisoning/unpoisoning thing is always inlined. Currently there is no option to make it out-of-line. So you can have stack instrumentation with KASAN_OUTLINE, but it just means that checking shadow memory on memory access will be outlined, poisoning/unpoisoing stack redzones will remain inlined.
