On Mon, 13 Feb 2023 at 13:36, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Mon, Feb 13, 2023 at 12:01:40PM +0100, Jakub Jelinek wrote: > > > The current gcc behavior is that operations like aggregate copies, or > > clearing which might or might not need memcpy/memset/memmove under the hood > > later are asan instrumented before the operation (in order not to limit the > > choices on how it will be expanded), uses of builtins (__builtin_ prefixed > > or not) are also instrumented before the calls unless they are one of the > > calls that is recognized as always instrumented. None for hwasan, > > for asan: > > index, memchr, memcmp, memcpy, memmove, memset, strcasecmp, strcat, strchr, > > strcmp, strcpy, strdup, strlen, strncasecmp, strncat, strncmp, strcspn, > > strpbrk, strspn, strstr, strncpy > > and for those builtins gcc disables inline expansion and enforces a library > > call (but until the expansion they are treated in optimizations like normal > > builtins and so could be say DCEd, or their aliasing behavior is considered > > etc.). kasan behaves the same I think. > > > > Now, I think libasan only has __asan_ prefixed > > __asan_memmove, __asan_memset and __asan_memcpy, nothing else, so most of > > the calls from the above list even can't be prefixed. Correct, right now libasan only does memmove, memset, and memcpy. I don't think it'll ever do more, at least not in the near future. > > So, do you want for --param asan-kernel-mem-intrinsic-prefix=1 to __asan_ > > prefix just memcpy/memmove/memset and nothing else? Yes. > > Is it ok to emit > > memcpy/memset/memmove from aggregate operations which are instrumented > > already at the caller (and similarly is it ok to handle those operations > > inline)? Yes, I think that's fair. > I'm thinking it is trivial to add more __asan prefixed functions as > needed, while trying to untangle the trainwreck created by assuming the > normal functions are instrumented is much more work. For the kernel param, I'd only do memcpy/memmove/memset, as those are the most brittle ones. The string functions are instrumented on most architectures through lib/string.c being instrumented. Thanks, -- Marco
