Messages in this thread Patch in this message | | | From | Yury Norov <> | Subject | [PATCH 1/2] bitmap: add sanity check function for find_bit() | Date | Wed, 19 Oct 2022 20:20:23 -0700 |
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find_bit() requires a pointer aligned to it's size. However some subsystems (fs, for example) cast char* variables to unsigned long* before passing them to find_bit(). Many architectures allow unaligned pointers with the cost of performance degradation.
This patch adds runtime check for the pointers to be aligned.
Signed-off-by: Yury Norov <yury.norov@gmail.com> --- include/linux/find.h | 35 +++++++++++++++++++++++++++++++++++ lib/Kconfig.debug | 7 +++++++ 2 files changed, 42 insertions(+)
diff --git a/include/linux/find.h b/include/linux/find.h index ccaf61a0f5fd..2d8f5419d787 100644 --- a/include/linux/find.h +++ b/include/linux/find.h @@ -7,6 +7,7 @@ #endif #include <linux/bitops.h> +#include <linux/bug.h> unsigned long _find_next_bit(const unsigned long *addr1, unsigned long nbits, unsigned long start); @@ -35,6 +36,14 @@ unsigned long _find_next_bit_le(const unsigned long *addr, unsigned long size, unsigned long offset); #endif +static __always_inline +void check_find_bit(const unsigned long *addr) +{ +#ifdef CONFIG_DEBUG_BITMAP + WARN_ON_ONCE(!IS_ALIGNED((unsigned long)addr, sizeof(unsigned long))); +#endif +} + #ifndef find_next_bit /** * find_next_bit - find the next set bit in a memory region @@ -49,6 +58,8 @@ static inline unsigned long find_next_bit(const unsigned long *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val; @@ -79,6 +90,9 @@ unsigned long find_next_and_bit(const unsigned long *addr1, const unsigned long *addr2, unsigned long size, unsigned long offset) { + check_find_bit(addr1); + check_find_bit(addr2); + if (small_const_nbits(size)) { unsigned long val; @@ -138,6 +152,8 @@ static inline unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val; @@ -164,6 +180,8 @@ unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, static inline unsigned long find_first_bit(const unsigned long *addr, unsigned long size) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val = *addr & GENMASK(size - 1, 0); @@ -270,6 +288,9 @@ unsigned long find_first_and_bit(const unsigned long *addr1, const unsigned long *addr2, unsigned long size) { + check_find_bit(addr1); + check_find_bit(addr2); + if (small_const_nbits(size)) { unsigned long val = *addr1 & *addr2 & GENMASK(size - 1, 0); @@ -292,6 +313,8 @@ unsigned long find_first_and_bit(const unsigned long *addr1, static inline unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val = *addr | ~GENMASK(size - 1, 0); @@ -313,6 +336,8 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size) static inline unsigned long find_last_bit(const unsigned long *addr, unsigned long size) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val = *addr & GENMASK(size - 1, 0); @@ -417,18 +442,24 @@ extern unsigned long find_next_clump8(unsigned long *clump, static inline unsigned long find_next_zero_bit_le(const void *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + return find_next_zero_bit(addr, size, offset); } static inline unsigned long find_next_bit_le(const void *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + return find_next_bit(addr, size, offset); } static inline unsigned long find_first_zero_bit_le(const void *addr, unsigned long size) { + check_find_bit(addr); + return find_first_zero_bit(addr, size); } @@ -439,6 +470,8 @@ static inline unsigned long find_next_zero_bit_le(const void *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val = *(const unsigned long *)addr; @@ -472,6 +505,8 @@ static inline unsigned long find_next_bit_le(const void *addr, unsigned long size, unsigned long offset) { + check_find_bit(addr); + if (small_const_nbits(size)) { unsigned long val = *(const unsigned long *)addr; diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 3fc7abffc7aa..1c7dcd33fc2a 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -543,6 +543,13 @@ endmenu # "Compiler options" menu "Generic Kernel Debugging Instruments" +config DEBUG_BITMAP + bool "Debug bitmaps" + help + Say Y here if you want to check bitmap functions parameters at + the runtime. Enable CONFIG_DEBUG_BITMAP only for debugging because + it may affect performance. + config MAGIC_SYSRQ bool "Magic SysRq key" depends on !UML -- 2.34.1
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