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From:   Marco Elver <elver@google.com>
Date:   Fri, 12 May 2023 18:09:46 +0200
Message-ID: <CANpmjNMm-2Tdhp6rDzA7CYvotmmGmLUnZnA_35yLUvxHB=7s0g@mail.gmail.com>
Subject: Re: [PATCH 1/3] kcsan: Don't expect 64 bits atomic builtins from 32
 bits architectures
To:     Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Chris Zankel <chris@zankel.net>,
        Max Filippov <jcmvbkbc@gmail.com>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        kasan-dev@googlegroups.com, Rohan McLure <rmclure@linux.ibm.com>
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On Fri, 12 May 2023 at 17:31, Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> Activating KCSAN on a 32 bits architecture leads to the following
> link-time failure:
>
>     LD      .tmp_vmlinux.kallsyms1
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_load':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_load_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_store':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_store_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_exchange':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_exchange_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_add':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_add_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_sub':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_sub_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_and':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_and_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_or':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_or_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_xor':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_xor_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_fetch_nand':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_fetch_nand_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_compare_exchange_strong':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_compare_exchange_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_compare_exchange_weak':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_compare_exchange_8'
>   powerpc64-linux-ld: kernel/kcsan/core.o: in function `__tsan_atomic64_compare_exchange_val':
>   kernel/kcsan/core.c:1273: undefined reference to `__atomic_compare_exchange_8'
>
> 32 bits architectures don't have 64 bits atomic builtins. Only
> include DEFINE_TSAN_ATOMIC_OPS(64) on 64 bits architectures.
>
> Fixes: 0f8ad5f2e934 ("kcsan: Add support for atomic builtins")
> Suggested-by: Marco Elver <elver@google.com>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Reviewed-by: Marco Elver <elver@google.com>

Do you have your own tree to take this through with the other patches?

> ---
>  kernel/kcsan/core.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> index 5a60cc52adc0..8a7baf4e332e 100644
> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -1270,7 +1270,9 @@ static __always_inline void kcsan_atomic_builtin_memorder(int memorder)
>  DEFINE_TSAN_ATOMIC_OPS(8);
>  DEFINE_TSAN_ATOMIC_OPS(16);
>  DEFINE_TSAN_ATOMIC_OPS(32);
> +#ifdef CONFIG_64BIT
>  DEFINE_TSAN_ATOMIC_OPS(64);
> +#endif
>
>  void __tsan_atomic_thread_fence(int memorder);
>  void __tsan_atomic_thread_fence(int memorder)
> --
> 2.40.1
>