linux-kernel - Re: [PATCH v2 1/4] compiler.h: Make _

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Date:   Tue, 27 Nov 2018 09:49:09 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     "the arch/x86 maintainers" <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>, Jiri Kosina <jkosina@...e.cz>,
        David Laight <David.Laight@...lab.com>,
        Borislav Petkov <bp@...en8.de>, julia@...com,
        Jessica Yu <jeyu@...nel.org>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 1/4] compiler.h: Make __ADDRESSABLE() symbol truly unique

On Mon, 26 Nov 2018 at 14:55, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
>
> The __ADDRESSABLE() macro uses the __LINE__ macro to create a temporary
> symbol which has a unique name.  However, if the macro is used multiple
> times from within another macro, the line number will always be the
> same, resulting in duplicate symbols.
>
> Make the temporary symbols truly unique by using __UNIQUE_ID instead of
> __LINE__.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

> ---
>  include/linux/compiler.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 06396c1cf127..4bb73fd918b5 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -282,7 +282,7 @@ unsigned long read_word_at_a_time(const void *addr)
>   */
>  #define __ADDRESSABLE(sym) \
>         static void * __section(".discard.addressable") __used \
> -               __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
> +               __UNIQUE_ID(__addressable_##sym) = (void *)&sym;
>
>  /**
>   * offset_to_ptr - convert a relative memory offset to an absolute pointer
> --
> 2.17.2
>