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SubjectRe: [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN
On Wed, 14 Jun 2017 23:15:40 +0200
Arnd Bergmann <arnd@arndb.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@arndb.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;

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