| Message ID | 20240814100035.3100852-1-jani.nikula@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] string: add mem_is_zero() helper to check if memory area is all zeros | expand |
On Wed, Aug 14, 2024 at 1:00 PM Jani Nikula <jani.nikula@intel.com> wrote: > > Almost two thirds of the memchr_inv() usages check if the memory area is > all zeros, with no interest in where in the buffer the first non-zero > byte is located. Checking for !memchr_inv(s, 0, n) is also not very > intuitive or discoverable. Add an explicit mem_is_zero() helper for this > use case. > > Signed-off-by: Jani Nikula <jani.nikula@intel.com> ... > void *memchr_inv(const void *s, int c, size_t n); I would group them here, or move the above. > char *strreplace(char *str, char old, char new); > > +/** > + * mem_is_zero - Check if an area of memory is all 0's. > + * @s: The memory area > + * @n: The size of the area > + * > + * Return: True if the area of memory is all 0's. > + */ > +static inline bool mem_is_zero(const void *s, size_t n) > +{ > + return !memchr_inv(s, 0, n); > +} Reviewed-by: Andy Shevchenko <andy@kernel.org>
On Wed, Aug 14, 2024 at 01:00:34PM +0300, Jani Nikula wrote: > Almost two thirds of the memchr_inv() usages check if the memory area is > all zeros, with no interest in where in the buffer the first non-zero > byte is located. Checking for !memchr_inv(s, 0, n) is also not very > intuitive or discoverable. Add an explicit mem_is_zero() helper for this > use case. > > Signed-off-by: Jani Nikula <jani.nikula@intel.com> Reviewed-by: Kees Cook <kees@kernel.org>
diff --git a/include/linux/string.h b/include/linux/string.h index 9edace076ddb..5855c5626b4b 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -279,6 +279,18 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt) void *memchr_inv(const void *s, int c, size_t n); char *strreplace(char *str, char old, char new); +/** + * mem_is_zero - Check if an area of memory is all 0's. + * @s: The memory area + * @n: The size of the area + * + * Return: True if the area of memory is all 0's. + */ +static inline bool mem_is_zero(const void *s, size_t n) +{ + return !memchr_inv(s, 0, n); +} + extern void kfree_const(const void *x); extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
Almost two thirds of the memchr_inv() usages check if the memory area is all zeros, with no interest in where in the buffer the first non-zero byte is located. Checking for !memchr_inv(s, 0, n) is also not very intuitive or discoverable. Add an explicit mem_is_zero() helper for this use case. Signed-off-by: Jani Nikula <jani.nikula@intel.com> --- Cc: Kees Cook <keescook@chromium.org> Cc: Andy Shevchenko <andy@kernel.org> --- include/linux/string.h | 12 ++++++++++++ 1 file changed, 12 insertions(+)