Re: [PATCH v2 05/11] mtd: cfi: reduce stack size with KASAN
From: Boris Brezillon <hidden>
Date: 2017-08-04 10:57:08
Also in:
lkml
On Fri, 4 Aug 2017 11:09:53 +0200 Arnd Bergmann [off-list ref] wrote:
On Fri, Aug 4, 2017 at 9:42 AM, Boris Brezillon [off-list ref] wrote:quoted
On Wed, 14 Jun 2017 23:15:40 +0200 Arnd Bergmann [off-list ref] wrote:quoted
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?I'm pretty sure it doesn't need the 'inline' keywork. I see that the code was addedlike this in linux-2.4.0-test3pre3 along with the rest of the mtd layer, so it has always been 'inline' and nobody ever bothered to remove that during later cleanups. We could probably just mark this function as 'noinline' here and never inline it, but I would rather not add more than one variant of noinline_if_stackbloat: almost all other users of noinline_if_stackbloat are for functions that have to be inline in normal builds, so it is defined as being either 'inline' or 'noinline' depending on whether KASAN is active.
Okay. Let's keep it like that then.