diff options
Diffstat (limited to 'arch/x86/include/asm/uaccess_64.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess_64.h | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index 04789f45ab2b..afce8ee5d7b7 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -54,6 +54,17 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, #define valid_user_address(x) ((__force long)(x) >= 0) /* + * Masking the user address is an alternative to a conditional + * user_access_begin that can avoid the fencing. This only works + * for dense accesses starting at the address. + */ +#define mask_user_address(x) ((typeof(x))((long)(x)|((long)(x)>>63))) +#define masked_user_access_begin(x) ({ \ + __auto_type __masked_ptr = (x); \ + __masked_ptr = mask_user_address(__masked_ptr); \ + __uaccess_begin(); __masked_ptr; }) + +/* * User pointers can have tag bits on x86-64. This scheme tolerates * arbitrary values in those bits rather then masking them off. * |