linux-kernel - Re: [PATCH 2/2] objtool, kcsan: Add volatile read/write instrumentation to whitelist

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Message-ID: <YxjXwBXpejAP6zoy@boqun-archlinux>
Date:   Wed, 7 Sep 2022 10:41:20 -0700
From:   Boqun Feng <boqun.feng@...il.com>
To:     Marco Elver <elver@...gle.com>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH 2/2] objtool, kcsan: Add volatile read/write
 instrumentation to whitelist

On Wed, Sep 07, 2022 at 07:39:03PM +0200, Marco Elver wrote:
> Adds KCSAN's volatile barrier instrumentation to objtool's uaccess

Confused. Are things like "__tsan_volatile_read4" considered as
"barrier" for KCSAN?

Regards,
Boqun

> whitelist.
> 
> Recent kernel change have shown that this was missing from the uaccess
> whitelist (since the first upstreamed version of KCSAN):
> 
>   mm/gup.o: warning: objtool: fault_in_readable+0x101: call to __tsan_volatile_write1() with UACCESS enabled
> 
> Fixes: 75d75b7a4d54 ("kcsan: Support distinguishing volatile accesses")
> Signed-off-by: Marco Elver <elver@...gle.com>
> ---
>  tools/objtool/check.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index e55fdf952a3a..67afdce3421f 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -999,6 +999,16 @@ static const char *uaccess_safe_builtin[] = {
>  	"__tsan_read_write4",
>  	"__tsan_read_write8",
>  	"__tsan_read_write16",
> +	"__tsan_volatile_read1",
> +	"__tsan_volatile_read2",
> +	"__tsan_volatile_read4",
> +	"__tsan_volatile_read8",
> +	"__tsan_volatile_read16",
> +	"__tsan_volatile_write1",
> +	"__tsan_volatile_write2",
> +	"__tsan_volatile_write4",
> +	"__tsan_volatile_write8",
> +	"__tsan_volatile_write16",
>  	"__tsan_atomic8_load",
>  	"__tsan_atomic16_load",
>  	"__tsan_atomic32_load",
> -- 
> 2.37.2.789.g6183377224-goog
>