diff options
| author | Arnd Bergmann <arnd@arndb.de> | 2016-02-29 13:20:28 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-05-08 07:46:01 +0200 |
| commit | fd79e436325841863d070f8e72246b437c0f5a15 (patch) | |
| tree | aaf860bc6b03c76937f5531ef5c4c00b63db7600 /include | |
| parent | ee6b88767e872fcc7af8e786a05d29d1ba229e75 (diff) | |
mtd: avoid stack overflow in MTD CFI code
commit fddcca5107051adf9e4481d2a79ae0616577fd2c upstream.
When map_word gets too large, we use a lot of kernel stack, and for
MTD_MAP_BANK_WIDTH_32, this means we use more than the recommended
1024 bytes in a number of functions:
drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_write_buffers':
drivers/mtd/chips/cfi_cmdset_0020.c:651:1: warning: the frame size of 1336 bytes is larger than 1024 bytes [-Wframe-larger-than=]
drivers/mtd/chips/cfi_cmdset_0020.c: In function 'cfi_staa_erase_varsize':
drivers/mtd/chips/cfi_cmdset_0020.c:972:1: warning: the frame size of 1208 bytes is larger than 1024 bytes [-Wframe-larger-than=]
drivers/mtd/chips/cfi_cmdset_0001.c: In function 'do_write_buffer':
drivers/mtd/chips/cfi_cmdset_0001.c:1835:1: warning: the frame size of 1240 bytes is larger than 1024 bytes [-Wframe-larger-than=]
This can be avoided if all operations on the map word are done
indirectly and the stack gets reused between the calls. We can
mostly achieve this by selecting MTD_COMPLEX_MAPPINGS whenever
MTD_MAP_BANK_WIDTH_32 is set, but for the case that no other
bank width is enabled, we also need to use a non-constant
map_bankwidth() to convince the compiler to use less stack.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[Brian: this patch mostly achieves its goal by forcing
MTD_COMPLEX_MAPPINGS (and the accompanying indirection) for 256-bit
mappings; the rest of the change is mostly a wash, though it helps
reduce stack size slightly. If we really care about supporting
256-bit mappings though, we should consider rewriting some of this
code to avoid keeping and assigning so many 256-bit objects on the
stack.]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/mtd/map.h | 19 |
1 files changed, 7 insertions, 12 deletions
diff --git a/include/linux/mtd/map.h b/include/linux/mtd/map.h index 366cf77953b5..806d0ab845e0 100644 --- a/include/linux/mtd/map.h +++ b/include/linux/mtd/map.h @@ -122,18 +122,13 @@ #endif #ifdef CONFIG_MTD_MAP_BANK_WIDTH_32 -# ifdef map_bankwidth -# undef map_bankwidth -# define map_bankwidth(map) ((map)->bankwidth) -# undef map_bankwidth_is_large -# define map_bankwidth_is_large(map) (map_bankwidth(map) > BITS_PER_LONG/8) -# undef map_words -# define map_words(map) map_calc_words(map) -# else -# define map_bankwidth(map) 32 -# define map_bankwidth_is_large(map) (1) -# define map_words(map) map_calc_words(map) -# endif +/* always use indirect access for 256-bit to preserve kernel stack */ +# undef map_bankwidth +# define map_bankwidth(map) ((map)->bankwidth) +# undef map_bankwidth_is_large +# define map_bankwidth_is_large(map) (map_bankwidth(map) > BITS_PER_LONG/8) +# undef map_words +# define map_words(map) map_calc_words(map) #define map_bankwidth_is_32(map) (map_bankwidth(map) == 32) #undef MAX_MAP_BANKWIDTH #define MAX_MAP_BANKWIDTH 32 |