On Fri, 10 Feb 2023 at 20:25, Jakub Jelinek <jakub@xxxxxxxxxx> wrote: > > On Wed, Feb 08, 2023 at 07:42:03PM +0100, Marco Elver wrote: > > Clang 15 will provide an option to prefix calls to memcpy/memset/memmove > > with __asan_ in instrumented functions: https://reviews.llvm.org/D122724 > > > > GCC does not yet have similar support. > > GCC has support to rename memcpy/memset etc. for years, say on > following compiled with > -fsanitize=kernel-address -O2 -mstringop-strategy=libcall > (the last option just to make sure the compiler doesn't prefer to emit > rep mov*/stos* or loop or something similar, of course kernel can keep > whatever it uses) you'll get just __asan_memcpy/__asan_memset calls, > no memcpy/memset, while without -fsanitize=kernel-address you get > normally memcpy/memset. > Or do you need the __asan_* functions only in asan instrumented functions > and normal ones in non-instrumented functions in the same TU? Yes, exactly that: __asan_ in instrumented, and normal ones in no_sanitize functions; they can be mixed in the same TU. We can't rename normal mem*() functions everywhere. In no_sanitize functions (in particular noinstr), normal mem*() should be used. But in instrumented code, it should be __asan_mem*(). Another longer explanation I also just replied here: https://lore.kernel.org/all/CANpmjNNH-O+38U6zRWJUCU-eJTfMhUosy==GWEOn1vcu=J2dcw@xxxxxxxxxxxxxx/ At least clang has had this behaviour for user space ASan forever: https://godbolt.org/z/h5sWExzef - so it was easy to just add the flag to make it behave like in user space for mem*() in the kernel. It might also be worthwhile for GCC to emit __asan_ for user space, given that the runtimes are shared and the user space runtime definitely has __asan_. The kernel needs the param (asan-kernel-mem-intrinsic-prefix) though, to not break older kernels. Thanks, -- Marco
