linux-kernel - Re: [PATCH v1 1/4] lib/vsprintf: Declare no_hash

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Date:   Fri, 4 Aug 2023 10:38:22 +0200
From:   Marco Elver <elver@...gle.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v1 1/4] lib/vsprintf: Declare no_hash_pointers in a local header

On Fri, 4 Aug 2023 at 10:26, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> Sparse is not happy to see non-static variable without declaration:
> lib/vsprintf.c:61:6: warning: symbol 'no_hash_pointers' was not declared. Should it be static?
>
> Declare respective variable in the local header.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  lib/test_printf.c  | 4 ++--
>  lib/vsprintf.c     | 1 +
>  lib/vsprintf.h     | 7 +++++++
>  mm/kfence/report.c | 3 +--
>  4 files changed, 11 insertions(+), 4 deletions(-)
>  create mode 100644 lib/vsprintf.h
>
> diff --git a/lib/test_printf.c b/lib/test_printf.c
> index 7677ebccf3c3..9e04b5f7244a 100644
> --- a/lib/test_printf.c
> +++ b/lib/test_printf.c
> @@ -24,6 +24,8 @@
>
>  #include <linux/property.h>
>
> +#include "vsprintf.h"
> +
>  #include "../tools/testing/selftests/kselftest_module.h"
>
>  #define BUF_SIZE 256
> @@ -41,8 +43,6 @@ KSTM_MODULE_GLOBALS();
>  static char *test_buffer __initdata;
>  static char *alloced_buffer __initdata;
>
> -extern bool no_hash_pointers;
> -
>  static int __printf(4, 0) __init
>  do_test(int bufsize, const char *expect, int elen,
>         const char *fmt, va_list ap)
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 40f560959b16..6774cf84e623 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -54,6 +54,7 @@
>
>  #include <linux/string_helpers.h>
>  #include "kstrtox.h"
> +#include "vsprintf.h"
>
>  /* Disable pointer hashing if requested */
>  bool no_hash_pointers __ro_after_init;
> diff --git a/lib/vsprintf.h b/lib/vsprintf.h
> new file mode 100644
> index 000000000000..ddffde905824
> --- /dev/null
> +++ b/lib/vsprintf.h
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LIB_VSPRINTF_H
> +#define _LIB_VSPRINTF_H
> +
> +extern bool no_hash_pointers;
> +
> +#endif

It seems odd to create such a local header and then refer to it from
other subsystems.

What's the downside of just putting this into the new
include/linux/sprintf.h? If someone wants to access this variable,
they will one way or another.