1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_UACCESS_64_H 3 #define _ASM_X86_UACCESS_64_H 4 5 /* 6 * User space memory access functions 7 */ 8 #include <linux/compiler.h> 9 #include <linux/lockdep.h> 10 #include <linux/kasan-checks.h> 11 #include <asm/alternative.h> 12 #include <asm/cpufeatures.h> 13 #include <asm/page.h> 14 #include <asm/percpu.h> 15 16 #ifdef CONFIG_ADDRESS_MASKING 17 /* 18 * Mask out tag bits from the address. 19 */ 20 static inline unsigned long __untagged_addr(unsigned long addr) 21 { 22 asm (ALTERNATIVE("", 23 "and " __percpu_arg([mask]) ", %[addr]", X86_FEATURE_LAM) 24 : [addr] "+r" (addr) 25 : [mask] "m" (__my_cpu_var(tlbstate_untag_mask))); 26 27 return addr; 28 } 29 30 #define untagged_addr(addr) ({ \ 31 unsigned long __addr = (__force unsigned long)(addr); \ 32 (__force __typeof__(addr))__untagged_addr(__addr); \ 33 }) 34 35 static inline unsigned long __untagged_addr_remote(struct mm_struct *mm, 36 unsigned long addr) 37 { 38 mmap_assert_locked(mm); 39 return addr & (mm)->context.untag_mask; 40 } 41 42 #define untagged_addr_remote(mm, addr) ({ \ 43 unsigned long __addr = (__force unsigned long)(addr); \ 44 (__force __typeof__(addr))__untagged_addr_remote(mm, __addr); \ 45 }) 46 47 #endif 48 49 /* 50 * The virtual address space space is logically divided into a kernel 51 * half and a user half. When cast to a signed type, user pointers 52 * are positive and kernel pointers are negative. 53 */ 54 #define valid_user_address(x) ((__force long)(x) >= 0) 55 56 /* 57 * User pointers can have tag bits on x86-64. This scheme tolerates 58 * arbitrary values in those bits rather then masking them off. 59 * 60 * Enforce two rules: 61 * 1. 'ptr' must be in the user half of the address space 62 * 2. 'ptr+size' must not overflow into kernel addresses 63 * 64 * Note that addresses around the sign change are not valid addresses, 65 * and will GP-fault even with LAM enabled if the sign bit is set (see 66 * "CR3.LAM_SUP" that can narrow the canonicality check if we ever 67 * enable it, but not remove it entirely). 68 * 69 * So the "overflow into kernel addresses" does not imply some sudden 70 * exact boundary at the sign bit, and we can allow a lot of slop on the 71 * size check. 72 * 73 * In fact, we could probably remove the size check entirely, since 74 * any kernel accesses will be in increasing address order starting 75 * at 'ptr', and even if the end might be in kernel space, we'll 76 * hit the GP faults for non-canonical accesses before we ever get 77 * there. 78 * 79 * That's a separate optimization, for now just handle the small 80 * constant case. 81 */ 82 static inline bool __access_ok(const void __user *ptr, unsigned long size) 83 { 84 if (__builtin_constant_p(size <= PAGE_SIZE) && size <= PAGE_SIZE) { 85 return valid_user_address(ptr); 86 } else { 87 unsigned long sum = size + (__force unsigned long)ptr; 88 89 return valid_user_address(sum) && sum >= (__force unsigned long)ptr; 90 } 91 } 92 #define __access_ok __access_ok 93 94 /* 95 * Copy To/From Userspace 96 */ 97 98 /* Handles exceptions in both to and from, but doesn't do access_ok */ 99 __must_check unsigned long 100 rep_movs_alternative(void *to, const void *from, unsigned len); 101 102 static __always_inline __must_check unsigned long 103 copy_user_generic(void *to, const void *from, unsigned long len) 104 { 105 stac(); 106 /* 107 * If CPU has FSRM feature, use 'rep movs'. 108 * Otherwise, use rep_movs_alternative. 109 */ 110 asm volatile( 111 "1:\n\t" 112 ALTERNATIVE("rep movsb", 113 "call rep_movs_alternative", ALT_NOT(X86_FEATURE_FSRM)) 114 "2:\n" 115 _ASM_EXTABLE_UA(1b, 2b) 116 :"+c" (len), "+D" (to), "+S" (from), ASM_CALL_CONSTRAINT 117 : : "memory", "rax"); 118 clac(); 119 return len; 120 } 121 122 static __always_inline __must_check unsigned long 123 raw_copy_from_user(void *dst, const void __user *src, unsigned long size) 124 { 125 return copy_user_generic(dst, (__force void *)src, size); 126 } 127 128 static __always_inline __must_check unsigned long 129 raw_copy_to_user(void __user *dst, const void *src, unsigned long size) 130 { 131 return copy_user_generic((__force void *)dst, src, size); 132 } 133 134 extern long __copy_user_nocache(void *dst, const void __user *src, unsigned size); 135 extern long __copy_user_flushcache(void *dst, const void __user *src, unsigned size); 136 137 static inline int 138 __copy_from_user_inatomic_nocache(void *dst, const void __user *src, 139 unsigned size) 140 { 141 long ret; 142 kasan_check_write(dst, size); 143 stac(); 144 ret = __copy_user_nocache(dst, src, size); 145 clac(); 146 return ret; 147 } 148 149 static inline int 150 __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size) 151 { 152 kasan_check_write(dst, size); 153 return __copy_user_flushcache(dst, src, size); 154 } 155 156 /* 157 * Zero Userspace. 158 */ 159 160 __must_check unsigned long 161 rep_stos_alternative(void __user *addr, unsigned long len); 162 163 static __always_inline __must_check unsigned long __clear_user(void __user *addr, unsigned long size) 164 { 165 might_fault(); 166 stac(); 167 168 /* 169 * No memory constraint because it doesn't change any memory gcc 170 * knows about. 171 */ 172 asm volatile( 173 "1:\n\t" 174 ALTERNATIVE("rep stosb", 175 "call rep_stos_alternative", ALT_NOT(X86_FEATURE_FSRS)) 176 "2:\n" 177 _ASM_EXTABLE_UA(1b, 2b) 178 : "+c" (size), "+D" (addr), ASM_CALL_CONSTRAINT 179 : "a" (0)); 180 181 clac(); 182 183 return size; 184 } 185 186 static __always_inline unsigned long clear_user(void __user *to, unsigned long n) 187 { 188 if (__access_ok(to, n)) 189 return __clear_user(to, n); 190 return n; 191 } 192 #endif /* _ASM_X86_UACCESS_64_H */ 193