diff options
Diffstat (limited to 'arch/x86/include/asm/uaccess_64.h')
| -rw-r--r-- | arch/x86/include/asm/uaccess_64.h | 43 |
1 files changed, 24 insertions, 19 deletions
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h index afce8ee5d7b7..b0a887209400 100644 --- a/arch/x86/include/asm/uaccess_64.h +++ b/arch/x86/include/asm/uaccess_64.h @@ -12,6 +12,13 @@ #include <asm/cpufeatures.h> #include <asm/page.h> #include <asm/percpu.h> +#include <asm/runtime-const.h> + +/* + * Virtual variable: there's no actual backing store for this, + * it can purely be used as 'runtime_const_ptr(USER_PTR_MAX)' + */ +extern unsigned long USER_PTR_MAX; #ifdef CONFIG_ADDRESS_MASKING /* @@ -46,19 +53,24 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, #endif -/* - * The virtual address space space is logically divided into a kernel - * half and a user half. When cast to a signed type, user pointers - * are positive and kernel pointers are negative. - */ -#define valid_user_address(x) ((__force long)(x) >= 0) +#define valid_user_address(x) \ + ((__force unsigned long)(x) <= runtime_const_ptr(USER_PTR_MAX)) /* * 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))) +static inline void __user *mask_user_address(const void __user *ptr) +{ + unsigned long mask; + asm("cmp %1,%0\n\t" + "sbb %0,%0" + :"=r" (mask) + :"r" (ptr), + "0" (runtime_const_ptr(USER_PTR_MAX))); + return (__force void __user *)(mask | (__force unsigned long)ptr); +} #define masked_user_access_begin(x) ({ \ __auto_type __masked_ptr = (x); \ __masked_ptr = mask_user_address(__masked_ptr); \ @@ -69,23 +81,16 @@ static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, * arbitrary values in those bits rather then masking them off. * * Enforce two rules: - * 1. 'ptr' must be in the user half of the address space + * 1. 'ptr' must be in the user part of the address space * 2. 'ptr+size' must not overflow into kernel addresses * - * Note that addresses around the sign change are not valid addresses, - * and will GP-fault even with LAM enabled if the sign bit is set (see - * "CR3.LAM_SUP" that can narrow the canonicality check if we ever - * enable it, but not remove it entirely). - * - * So the "overflow into kernel addresses" does not imply some sudden - * exact boundary at the sign bit, and we can allow a lot of slop on the - * size check. + * Note that we always have at least one guard page between the + * max user address and the non-canonical gap, allowing us to + * ignore small sizes entirely. * * In fact, we could probably remove the size check entirely, since * any kernel accesses will be in increasing address order starting - * at 'ptr', and even if the end might be in kernel space, we'll - * hit the GP faults for non-canonical accesses before we ever get - * there. + * at 'ptr'. * * That's a separate optimization, for now just handle the small * constant case. |