Messages in this thread | | | Subject | Re: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen | From | Martin Liška <> | Date | Mon, 8 Jun 2020 19:32:37 +0200 |
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On 6/3/20 9:23 PM, Marco Elver wrote: > > > On Wed, 03 Jun 2020, Borislav Petkov wrote: > >> On Thu, May 14, 2020 at 12:05:38PM +0100, Will Deacon wrote: >>> Talking off-list, Clang >= 7 is pretty reasonable wrt inlining decisions >>> and the behaviour for __always_inline is: >>> >>> * An __always_inline function inlined into a __no_sanitize function is >>> not instrumented >>> * An __always_inline function inlined into an instrumented function is >>> instrumented >>> * You can't mark a function as both __always_inline __no_sanitize, because >>> __no_sanitize functions are never inlined >>> >>> GCC, on the other hand, may still inline __no_sanitize functions and then >>> subsequently instrument them. >> >> Yeah, about that: I've been looking for a way to trigger this so that >> I can show preprocessed source to gcc people. So do you guys have a >> .config or somesuch I can try? > > For example take this: > > int x; > > static inline __attribute__((no_sanitize_thread)) void do_not_sanitize(void) { > x++; > } > > void sanitize_this(void) { > do_not_sanitize(); > } > > Then > > gcc-10 -O3 -fsanitize=thread -o example.o -c example.c > objdump -D example.o
Hello.
Thank you for the example. It seems to me that Clang does not inline a no_sanitize_* function into one which is instrumented. Is it a documented behavior ([1] doesn't mention that)? If so, we can do the same in GCC.
Thanks, Martin
[1] https://clang.llvm.org/docs/AttributeReference.html#no-sanitize
> > will show that do_not_sanitize() was inlined into sanitize_this() and is > instrumented. (With Clang this doesn't happen.) > > Hope this is enough. > > Thanks, > -- Marco >
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