Messages in this thread | | | Date | Wed, 30 Mar 2022 10:58:26 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 13/48] kmsan: add KMSAN runtime core |
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On Tue, Mar 29, 2022 at 02:39:42PM +0200, Alexander Potapenko wrote: > +/* Handle llvm.memmove intrinsic. */ > +void *__msan_memmove(void *dst, const void *src, uintptr_t n) > +{ > + void *result; > + > + result = __memmove(dst, src, n); > + if (!n) > + /* Some people call memmove() with zero length. */ > + return result; > + if (!kmsan_enabled || kmsan_in_runtime()) > + return result; > + > + kmsan_internal_memmove_metadata(dst, (void *)src, n); > + > + return result; > +} > +EXPORT_SYMBOL(__msan_memmove); > + > +/* Handle llvm.memcpy intrinsic. */ > +void *__msan_memcpy(void *dst, const void *src, uintptr_t n) > +{ > + void *result; > + > + result = __memcpy(dst, src, n); > + if (!n) > + /* Some people call memcpy() with zero length. */ > + return result; > + > + if (!kmsan_enabled || kmsan_in_runtime()) > + return result; > + > + /* Using memmove instead of memcpy doesn't affect correctness. */ > + kmsan_internal_memmove_metadata(dst, (void *)src, n); > + > + return result; > +} > +EXPORT_SYMBOL(__msan_memcpy); > + > +/* Handle llvm.memset intrinsic. */ > +void *__msan_memset(void *dst, int c, uintptr_t n) > +{ > + void *result; > + > + result = __memset(dst, c, n); > + if (!kmsan_enabled || kmsan_in_runtime()) > + return result; > + > + kmsan_enter_runtime(); > + /* > + * Clang doesn't pass parameter metadata here, so it is impossible to > + * use shadow of @c to set up the shadow for @dst. > + */ > + kmsan_internal_unpoison_memory(dst, n, /*checked*/ false); > + kmsan_leave_runtime(); > + > + return result; > +} > +EXPORT_SYMBOL(__msan_memset);
This, we need this same for KASAN. KASAN must be changed to have the mem*() intrinsics emit __asan_mem*(), such that we can have uninstrumented base functions.
Currently we seem to have the problem that when a noinstr function trips one of those instrinsics it'll emit a call to an instrumented function, which is a complete no-no.
Also see:
https://lore.kernel.org/all/YjxTt3pFIcV3lt8I@zn.tnic/T/#m2049a14be400d4ae2b54a1f7da3ede28b7fd7564
Given the helpful feedback there, Mark and me are going to unilaterally break Kasan by deleting the existing wrappers.
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