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| author | Arnd Bergmann <arnd@arndb.de> | 2016-02-29 13:20:28 +0100 |
|---|---|---|
| committer | Brian Norris <computersforpeace@gmail.com> | 2016-04-03 16:46:24 -0700 |
| commit | fddcca5107051adf9e4481d2a79ae0616577fd2c (patch) | |
| tree | 04c0d7b4c592fef44d0200344aa9090e09bf21cd /drivers/mtd/chips | |
| parent | 20c07a5bf094198ff2382aa5e7c930b3c9807792 (diff) | |
| download | linux-fddcca5107051adf9e4481d2a79ae0616577fd2c.tar.bz2 | |
mtd: avoid stack overflow in MTD CFI code
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>
Diffstat (limited to 'drivers/mtd/chips')
| -rw-r--r-- | drivers/mtd/chips/Kconfig | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/drivers/mtd/chips/Kconfig b/drivers/mtd/chips/Kconfig index 3b3dabce58de..bbfa1f129266 100644 --- a/drivers/mtd/chips/Kconfig +++ b/drivers/mtd/chips/Kconfig @@ -115,6 +115,7 @@ config MTD_MAP_BANK_WIDTH_16 config MTD_MAP_BANK_WIDTH_32 bool "Support 256-bit buswidth" if MTD_CFI_GEOMETRY + select MTD_COMPLEX_MAPPINGS if HAS_IOMEM default n help If you wish to support CFI devices on a physical bus which is |