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    SubjectRe: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen
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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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