linux-kernel - Re: [PATCH] initity: try to improve _

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Date:   Wed, 1 Feb 2017 22:05:15 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kees Cook <keescook@...omium.org>, pageexec@...email.hu,
        Emese Revfy <re.emese@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Josh Triplett <josh@...htriplett.org>,
        yamada.masahiro@...ionext.com, minipli@...linux.so,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        jlayton@...chiereds.net, Robert Moore <robert.moore@...el.com>,
        Lv Zheng <lv.zheng@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>, linux-arch@...r.kernel.org,
        kasan-dev@...glegroups.com,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH] initity: try to improve __nocapture annotations

On Wed, Feb 1, 2017 at 5:11 PM, Arnd Bergmann <arnd@...db.de> wrote:
> There are some additional declarations that got missed in the original patch,
> and some annotated functions that use the pointer is a correct but nonobvious
> way:
>
> mm/kasan/kasan.c: In function 'memmove':
> mm/kasan/kasan.c:346:7: error: 'memmove' captures its 2 ('src') parameter, please remove it from the nocapture attribute. [-Werror]
>  void *memmove(void *dest, const void *src, size_t len)
>        ^~~~~~~
> mm/kasan/kasan.c: In function 'memcpy':
> mm/kasan/kasan.c:355:7: error: 'memcpy' captures its 2 ('src') parameter, please remove it from the nocapture attribute. [-Werror]
>  void *memcpy(void *dest, const void *src, size_t len)
>        ^~~~~~
> drivers/acpi/acpica/utdebug.c: In function 'acpi_debug_print':
> drivers/acpi/acpica/utdebug.c:158:1: error: 'acpi_debug_print' captures its 3 ('function_name') parameter, please remove it from the nocapture attribute. [-Werror]
>
> lib/string.c:893:7: error: 'memchr_inv' captures its 1 ('start') parameter, please remove it from the nocapture attribute. [-Werror]
>  void *memchr_inv(const void *start, int c, size_t bytes)
> lib/string.c: In function 'strnstr':
> lib/string.c:832:7: error: 'strnstr' captures its 1 ('s1') parameter, please remove it from the nocapture attribute. [-Werror]
>  char *strnstr(const char *s1, const char *s2, size_t len)
>        ^~~~~~~
> lib/string.c:832:7: error: 'strnstr' captures its 2 ('s2') parameter, please remove it from the nocapture attribute. [-Werror]
>
> I'm not sure if these are all appropriate fixes, please have a careful look
>
> Fixes: c2bc07665495 ("initify: Mark functions with the __nocapture attribute")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/acpi/acpica/utdebug.c        | 2 +-
>  include/acpi/acpixf.h                | 2 +-
>  include/asm-generic/asm-prototypes.h | 8 ++++----
>  include/linux/string.h               | 2 +-
>  lib/string.c                         | 2 +-
>  mm/kasan/kasan.c                     | 4 ++--
>  6 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/acpi/acpica/utdebug.c b/drivers/acpi/acpica/utdebug.c
> index 044df9b0356e..de3c9cb305a2 100644
> --- a/drivers/acpi/acpica/utdebug.c
> +++ b/drivers/acpi/acpica/utdebug.c
> @@ -154,7 +154,7 @@ static const char *acpi_ut_trim_function_name(const char *function_name)
>   *
>   ******************************************************************************/
>
> -void ACPI_INTERNAL_VAR_XFACE
> +void __unverified_nocapture(3) ACPI_INTERNAL_VAR_XFACE

Generally speaking, there is a problem with adding annotations like
this to ACPICA code.

We get that code from an external project (upstream ACPICA) and the
more Linux-specific stuff is there in it, the more difficult to
maintain it becomes.

Thanks,
Rafael