netdev - Re: [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN

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Date:   Fri, 4 Aug 2017 09:42:54 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Arend van Spriel <arend.vanspriel@...adcom.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN

On Wed, 14 Jun 2017 23:15:40 +0200
Arnd Bergmann <arnd@...db.de> wrote:

> When CONFIG_KASAN is used, we consume a lot of extra stack space:
> 
> drivers/mtd/chips/cfi_cmdset_0020.c: In function 'do_write_buffer':
> drivers/mtd/chips/cfi_cmdset_0020.c:603:1: error: the frame size of 2184 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
> drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_erase_varsize':
> drivers/mtd/chips/cfi_cmdset_0020.c:972:1: error: the frame size of 1936 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
> drivers/mtd/chips/cfi_cmdset_0001.c: In function 'do_write_buffer':
> drivers/mtd/chips/cfi_cmdset_0001.c:1841:1: error: the frame size of 1776 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
> 
> This marks some functions as noinline_if_stackbloat to keep reduce the
> overall stack size.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/mtd/chips/cfi_cmdset_0020.c | 8 ++++----
>  include/linux/mtd/map.h             | 8 ++++----
>  2 files changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mtd/chips/cfi_cmdset_0020.c b/drivers/mtd/chips/cfi_cmdset_0020.c
> index 7d342965f392..5eee5e883f55 100644
> --- a/drivers/mtd/chips/cfi_cmdset_0020.c
> +++ b/drivers/mtd/chips/cfi_cmdset_0020.c
> @@ -244,7 +244,7 @@ static struct mtd_info *cfi_staa_setup(struct map_info *map)
>  }
>  
>  
> -static inline int do_read_onechip(struct map_info *map, struct flchip *chip, loff_t adr, size_t len, u_char *buf)
> +static noinline_if_stackbloat int do_read_onechip(struct map_info *map, struct flchip *chip, loff_t adr, size_t len, u_char *buf)

Why do we even need to mark those functions inline in the first place?
Isn't the compiler smart enough to decide when it should inline things?

>  {
>  	map_word status, status_OK;
>  	unsigned long timeo;
> @@ -728,7 +728,7 @@ cfi_staa_writev(struct mtd_info *mtd, const struct kvec *vecs,
>  }
>  
>  
> -static inline int do_erase_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
> +static noinline_if_stackbloat int do_erase_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
>  {
>  	struct cfi_private *cfi = map->fldrv_priv;
>  	map_word status, status_OK;
> @@ -1029,7 +1029,7 @@ static void cfi_staa_sync (struct mtd_info *mtd)
>  	}
>  }
>  
> -static inline int do_lock_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
> +static noinline_if_stackbloat int do_lock_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
>  {
>  	struct cfi_private *cfi = map->fldrv_priv;
>  	map_word status, status_OK;
> @@ -1175,7 +1175,7 @@ static int cfi_staa_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
>  	}
>  	return 0;
>  }
> -static inline int do_unlock_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
> +static noinline_if_stackbloat int do_unlock_oneblock(struct map_info *map, struct flchip *chip, unsigned long adr)
>  {
>  	struct cfi_private *cfi = map->fldrv_priv;
>  	map_word status, status_OK;
> diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h
> index 3aa56e3104bb..29db74314db8 100644
> --- a/include/linux/mtd/map.h
> +++ b/include/linux/mtd/map.h
> @@ -316,7 +316,7 @@ static inline map_word map_word_or(struct map_info *map, map_word val1, map_word
>  	return r;
>  }
>  
> -static inline int map_word_andequal(struct map_info *map, map_word val1, map_word val2, map_word val3)
> +static noinline_if_stackbloat int map_word_andequal(struct map_info *map, map_word val1, map_word val2, map_word val3)

It's indeed needed for those defined in a header.

>  {
>  	int i;
>  
> @@ -328,7 +328,7 @@ static inline int map_word_andequal(struct map_info *map, map_word val1, map_wor
>  	return 1;
>  }
>  
> -static inline int map_word_bitsset(struct map_info *map, map_word val1, map_word val2)
> +static noinline_if_stackbloat int map_word_bitsset(struct map_info *map, map_word val1, map_word val2)
>  {
>  	int i;
>  
> @@ -362,7 +362,7 @@ static inline map_word map_word_load(struct map_info *map, const void *ptr)
>  	return r;
>  }
>  
> -static inline map_word map_word_load_partial(struct map_info *map, map_word orig, const unsigned char *buf, int start, int len)
> +static noinline_if_stackbloat map_word map_word_load_partial(struct map_info *map, map_word orig, const unsigned char *buf, int start, int len)
>  {
>  	int i;
>  
> @@ -392,7 +392,7 @@ static inline map_word map_word_load_partial(struct map_info *map, map_word orig
>  #define MAP_FF_LIMIT 8
>  #endif
>  
> -static inline map_word map_word_ff(struct map_info *map)
> +static noinline_if_stackbloat map_word map_word_ff(struct map_info *map)
>  {
>  	map_word r;
>  	int i;