xref: /openbmc/linux/arch/x86/include/asm/uaccess.h (revision 1f012283)
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _ASM_X86_UACCESS_H
3 #define _ASM_X86_UACCESS_H
4 /*
5  * User space memory access functions
6  */
7 #include <linux/compiler.h>
8 #include <linux/kasan-checks.h>
9 #include <linux/string.h>
10 #include <asm/asm.h>
11 #include <asm/page.h>
12 #include <asm/smap.h>
13 #include <asm/extable.h>
14 
15 /*
16  * Test whether a block of memory is a valid user space address.
17  * Returns 0 if the range is valid, nonzero otherwise.
18  */
19 static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, unsigned long limit)
20 {
21 	/*
22 	 * If we have used "sizeof()" for the size,
23 	 * we know it won't overflow the limit (but
24 	 * it might overflow the 'addr', so it's
25 	 * important to subtract the size from the
26 	 * limit, not add it to the address).
27 	 */
28 	if (__builtin_constant_p(size))
29 		return unlikely(addr > limit - size);
30 
31 	/* Arbitrary sizes? Be careful about overflow */
32 	addr += size;
33 	if (unlikely(addr < size))
34 		return true;
35 	return unlikely(addr > limit);
36 }
37 
38 #define __range_not_ok(addr, size, limit)				\
39 ({									\
40 	__chk_user_ptr(addr);						\
41 	__chk_range_not_ok((unsigned long __force)(addr), size, limit); \
42 })
43 
44 #ifdef CONFIG_DEBUG_ATOMIC_SLEEP
45 static inline bool pagefault_disabled(void);
46 # define WARN_ON_IN_IRQ()	\
47 	WARN_ON_ONCE(!in_task() && !pagefault_disabled())
48 #else
49 # define WARN_ON_IN_IRQ()
50 #endif
51 
52 /**
53  * access_ok - Checks if a user space pointer is valid
54  * @addr: User space pointer to start of block to check
55  * @size: Size of block to check
56  *
57  * Context: User context only. This function may sleep if pagefaults are
58  *          enabled.
59  *
60  * Checks if a pointer to a block of memory in user space is valid.
61  *
62  * Note that, depending on architecture, this function probably just
63  * checks that the pointer is in the user space range - after calling
64  * this function, memory access functions may still return -EFAULT.
65  *
66  * Return: true (nonzero) if the memory block may be valid, false (zero)
67  * if it is definitely invalid.
68  */
69 #define access_ok(addr, size)					\
70 ({									\
71 	WARN_ON_IN_IRQ();						\
72 	likely(!__range_not_ok(addr, size, TASK_SIZE_MAX));		\
73 })
74 
75 extern int __get_user_1(void);
76 extern int __get_user_2(void);
77 extern int __get_user_4(void);
78 extern int __get_user_8(void);
79 extern int __get_user_nocheck_1(void);
80 extern int __get_user_nocheck_2(void);
81 extern int __get_user_nocheck_4(void);
82 extern int __get_user_nocheck_8(void);
83 extern int __get_user_bad(void);
84 
85 #define __uaccess_begin() stac()
86 #define __uaccess_end()   clac()
87 #define __uaccess_begin_nospec()	\
88 ({					\
89 	stac();				\
90 	barrier_nospec();		\
91 })
92 
93 /*
94  * This is the smallest unsigned integer type that can fit a value
95  * (up to 'long long')
96  */
97 #define __inttype(x) __typeof__(		\
98 	__typefits(x,char,			\
99 	  __typefits(x,short,			\
100 	    __typefits(x,int,			\
101 	      __typefits(x,long,0ULL)))))
102 
103 #define __typefits(x,type,not) \
104 	__builtin_choose_expr(sizeof(x)<=sizeof(type),(unsigned type)0,not)
105 
106 /*
107  * This is used for both get_user() and __get_user() to expand to
108  * the proper special function call that has odd calling conventions
109  * due to returning both a value and an error, and that depends on
110  * the size of the pointer passed in.
111  *
112  * Careful: we have to cast the result to the type of the pointer
113  * for sign reasons.
114  *
115  * The use of _ASM_DX as the register specifier is a bit of a
116  * simplification, as gcc only cares about it as the starting point
117  * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits
118  * (%ecx being the next register in gcc's x86 register sequence), and
119  * %rdx on 64 bits.
120  *
121  * Clang/LLVM cares about the size of the register, but still wants
122  * the base register for something that ends up being a pair.
123  */
124 #define do_get_user_call(fn,x,ptr)					\
125 ({									\
126 	int __ret_gu;							\
127 	register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX);		\
128 	__chk_user_ptr(ptr);						\
129 	asm volatile("call __" #fn "_%P4"				\
130 		     : "=a" (__ret_gu), "=r" (__val_gu),		\
131 			ASM_CALL_CONSTRAINT				\
132 		     : "0" (ptr), "i" (sizeof(*(ptr))));		\
133 	(x) = (__force __typeof__(*(ptr))) __val_gu;			\
134 	__builtin_expect(__ret_gu, 0);					\
135 })
136 
137 /**
138  * get_user - Get a simple variable from user space.
139  * @x:   Variable to store result.
140  * @ptr: Source address, in user space.
141  *
142  * Context: User context only. This function may sleep if pagefaults are
143  *          enabled.
144  *
145  * This macro copies a single simple variable from user space to kernel
146  * space.  It supports simple types like char and int, but not larger
147  * data types like structures or arrays.
148  *
149  * @ptr must have pointer-to-simple-variable type, and the result of
150  * dereferencing @ptr must be assignable to @x without a cast.
151  *
152  * Return: zero on success, or -EFAULT on error.
153  * On error, the variable @x is set to zero.
154  */
155 #define get_user(x,ptr) ({ might_fault(); do_get_user_call(get_user,x,ptr); })
156 
157 /**
158  * __get_user - Get a simple variable from user space, with less checking.
159  * @x:   Variable to store result.
160  * @ptr: Source address, in user space.
161  *
162  * Context: User context only. This function may sleep if pagefaults are
163  *          enabled.
164  *
165  * This macro copies a single simple variable from user space to kernel
166  * space.  It supports simple types like char and int, but not larger
167  * data types like structures or arrays.
168  *
169  * @ptr must have pointer-to-simple-variable type, and the result of
170  * dereferencing @ptr must be assignable to @x without a cast.
171  *
172  * Caller must check the pointer with access_ok() before calling this
173  * function.
174  *
175  * Return: zero on success, or -EFAULT on error.
176  * On error, the variable @x is set to zero.
177  */
178 #define __get_user(x,ptr) do_get_user_call(get_user_nocheck,x,ptr)
179 
180 
181 #ifdef CONFIG_X86_32
182 #define __put_user_goto_u64(x, addr, label)			\
183 	asm_volatile_goto("\n"					\
184 		     "1:	movl %%eax,0(%1)\n"		\
185 		     "2:	movl %%edx,4(%1)\n"		\
186 		     _ASM_EXTABLE_UA(1b, %l2)			\
187 		     _ASM_EXTABLE_UA(2b, %l2)			\
188 		     : : "A" (x), "r" (addr)			\
189 		     : : label)
190 
191 #else
192 #define __put_user_goto_u64(x, ptr, label) \
193 	__put_user_goto(x, ptr, "q", "er", label)
194 #endif
195 
196 extern void __put_user_bad(void);
197 
198 /*
199  * Strange magic calling convention: pointer in %ecx,
200  * value in %eax(:%edx), return value in %ecx. clobbers %rbx
201  */
202 extern void __put_user_1(void);
203 extern void __put_user_2(void);
204 extern void __put_user_4(void);
205 extern void __put_user_8(void);
206 extern void __put_user_nocheck_1(void);
207 extern void __put_user_nocheck_2(void);
208 extern void __put_user_nocheck_4(void);
209 extern void __put_user_nocheck_8(void);
210 
211 /*
212  * ptr must be evaluated and assigned to the temporary __ptr_pu before
213  * the assignment of x to __val_pu, to avoid any function calls
214  * involved in the ptr expression (possibly implicitly generated due
215  * to KASAN) from clobbering %ax.
216  */
217 #define do_put_user_call(fn,x,ptr)					\
218 ({									\
219 	int __ret_pu;							\
220 	void __user *__ptr_pu;						\
221 	register __typeof__(*(ptr)) __val_pu asm("%"_ASM_AX);		\
222 	__chk_user_ptr(ptr);						\
223 	__ptr_pu = (ptr);						\
224 	__val_pu = (x);							\
225 	asm volatile("call __" #fn "_%P[size]"				\
226 		     : "=c" (__ret_pu),					\
227 			ASM_CALL_CONSTRAINT				\
228 		     : "0" (__ptr_pu),					\
229 		       "r" (__val_pu),					\
230 		       [size] "i" (sizeof(*(ptr)))			\
231 		     :"ebx");						\
232 	__builtin_expect(__ret_pu, 0);					\
233 })
234 
235 /**
236  * put_user - Write a simple value into user space.
237  * @x:   Value to copy to user space.
238  * @ptr: Destination address, in user space.
239  *
240  * Context: User context only. This function may sleep if pagefaults are
241  *          enabled.
242  *
243  * This macro copies a single simple value from kernel space to user
244  * space.  It supports simple types like char and int, but not larger
245  * data types like structures or arrays.
246  *
247  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
248  * to the result of dereferencing @ptr.
249  *
250  * Return: zero on success, or -EFAULT on error.
251  */
252 #define put_user(x, ptr) ({ might_fault(); do_put_user_call(put_user,x,ptr); })
253 
254 /**
255  * __put_user - Write a simple value into user space, with less checking.
256  * @x:   Value to copy to user space.
257  * @ptr: Destination address, in user space.
258  *
259  * Context: User context only. This function may sleep if pagefaults are
260  *          enabled.
261  *
262  * This macro copies a single simple value from kernel space to user
263  * space.  It supports simple types like char and int, but not larger
264  * data types like structures or arrays.
265  *
266  * @ptr must have pointer-to-simple-variable type, and @x must be assignable
267  * to the result of dereferencing @ptr.
268  *
269  * Caller must check the pointer with access_ok() before calling this
270  * function.
271  *
272  * Return: zero on success, or -EFAULT on error.
273  */
274 #define __put_user(x, ptr) do_put_user_call(put_user_nocheck,x,ptr)
275 
276 #define __put_user_size(x, ptr, size, label)				\
277 do {									\
278 	__chk_user_ptr(ptr);						\
279 	switch (size) {							\
280 	case 1:								\
281 		__put_user_goto(x, ptr, "b", "iq", label);		\
282 		break;							\
283 	case 2:								\
284 		__put_user_goto(x, ptr, "w", "ir", label);		\
285 		break;							\
286 	case 4:								\
287 		__put_user_goto(x, ptr, "l", "ir", label);		\
288 		break;							\
289 	case 8:								\
290 		__put_user_goto_u64(x, ptr, label);			\
291 		break;							\
292 	default:							\
293 		__put_user_bad();					\
294 	}								\
295 } while (0)
296 
297 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
298 
299 #ifdef CONFIG_X86_32
300 #define __get_user_asm_u64(x, ptr, label) do {				\
301 	unsigned int __gu_low, __gu_high;				\
302 	const unsigned int __user *__gu_ptr;				\
303 	__gu_ptr = (const void __user *)(ptr);				\
304 	__get_user_asm(__gu_low, __gu_ptr, "l", "=r", label);		\
305 	__get_user_asm(__gu_high, __gu_ptr+1, "l", "=r", label);	\
306 	(x) = ((unsigned long long)__gu_high << 32) | __gu_low;		\
307 } while (0)
308 #else
309 #define __get_user_asm_u64(x, ptr, label)				\
310 	__get_user_asm(x, ptr, "q", "=r", label)
311 #endif
312 
313 #define __get_user_size(x, ptr, size, label)				\
314 do {									\
315 	__chk_user_ptr(ptr);						\
316 	switch (size) {							\
317 	unsigned char x_u8__;						\
318 	case 1:								\
319 		__get_user_asm(x_u8__, ptr, "b", "=q", label);		\
320 		(x) = x_u8__;						\
321 		break;							\
322 	case 2:								\
323 		__get_user_asm(x, ptr, "w", "=r", label);		\
324 		break;							\
325 	case 4:								\
326 		__get_user_asm(x, ptr, "l", "=r", label);		\
327 		break;							\
328 	case 8:								\
329 		__get_user_asm_u64(x, ptr, label);			\
330 		break;							\
331 	default:							\
332 		(x) = __get_user_bad();					\
333 	}								\
334 } while (0)
335 
336 #define __get_user_asm(x, addr, itype, ltype, label)			\
337 	asm_volatile_goto("\n"						\
338 		     "1:	mov"itype" %[umem],%[output]\n"		\
339 		     _ASM_EXTABLE_UA(1b, %l2)				\
340 		     : [output] ltype(x)				\
341 		     : [umem] "m" (__m(addr))				\
342 		     : : label)
343 
344 #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
345 
346 #ifdef CONFIG_X86_32
347 #define __get_user_asm_u64(x, ptr, retval)				\
348 ({									\
349 	__typeof__(ptr) __ptr = (ptr);					\
350 	asm volatile("\n"						\
351 		     "1:	movl %[lowbits],%%eax\n"		\
352 		     "2:	movl %[highbits],%%edx\n"		\
353 		     "3:\n"						\
354 		     ".section .fixup,\"ax\"\n"				\
355 		     "4:	mov %[efault],%[errout]\n"		\
356 		     "	xorl %%eax,%%eax\n"				\
357 		     "	xorl %%edx,%%edx\n"				\
358 		     "	jmp 3b\n"					\
359 		     ".previous\n"					\
360 		     _ASM_EXTABLE_UA(1b, 4b)				\
361 		     _ASM_EXTABLE_UA(2b, 4b)				\
362 		     : [errout] "=r" (retval),				\
363 		       [output] "=&A"(x)				\
364 		     : [lowbits] "m" (__m(__ptr)),			\
365 		       [highbits] "m" __m(((u32 __user *)(__ptr)) + 1),	\
366 		       [efault] "i" (-EFAULT), "0" (retval));		\
367 })
368 
369 #else
370 #define __get_user_asm_u64(x, ptr, retval) \
371 	 __get_user_asm(x, ptr, retval, "q", "=r")
372 #endif
373 
374 #define __get_user_size(x, ptr, size, retval)				\
375 do {									\
376 	unsigned char x_u8__;						\
377 									\
378 	retval = 0;							\
379 	__chk_user_ptr(ptr);						\
380 	switch (size) {							\
381 	case 1:								\
382 		__get_user_asm(x_u8__, ptr, retval, "b", "=q");		\
383 		(x) = x_u8__;						\
384 		break;							\
385 	case 2:								\
386 		__get_user_asm(x, ptr, retval, "w", "=r");		\
387 		break;							\
388 	case 4:								\
389 		__get_user_asm(x, ptr, retval, "l", "=r");		\
390 		break;							\
391 	case 8:								\
392 		__get_user_asm_u64(x, ptr, retval);			\
393 		break;							\
394 	default:							\
395 		(x) = __get_user_bad();					\
396 	}								\
397 } while (0)
398 
399 #define __get_user_asm(x, addr, err, itype, ltype)			\
400 	asm volatile("\n"						\
401 		     "1:	mov"itype" %[umem],%[output]\n"		\
402 		     "2:\n"						\
403 		     ".section .fixup,\"ax\"\n"				\
404 		     "3:	mov %[efault],%[errout]\n"		\
405 		     "	xorl %k[output],%k[output]\n"			\
406 		     "	jmp 2b\n"					\
407 		     ".previous\n"					\
408 		     _ASM_EXTABLE_UA(1b, 3b)				\
409 		     : [errout] "=r" (err),				\
410 		       [output] ltype(x)				\
411 		     : [umem] "m" (__m(addr)),				\
412 		       [efault] "i" (-EFAULT), "0" (err))
413 
414 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
415 
416 /* FIXME: this hack is definitely wrong -AK */
417 struct __large_struct { unsigned long buf[100]; };
418 #define __m(x) (*(struct __large_struct __user *)(x))
419 
420 /*
421  * Tell gcc we read from memory instead of writing: this is because
422  * we do not write to any memory gcc knows about, so there are no
423  * aliasing issues.
424  */
425 #define __put_user_goto(x, addr, itype, ltype, label)			\
426 	asm_volatile_goto("\n"						\
427 		"1:	mov"itype" %0,%1\n"				\
428 		_ASM_EXTABLE_UA(1b, %l2)				\
429 		: : ltype(x), "m" (__m(addr))				\
430 		: : label)
431 
432 extern unsigned long
433 copy_from_user_nmi(void *to, const void __user *from, unsigned long n);
434 extern __must_check long
435 strncpy_from_user(char *dst, const char __user *src, long count);
436 
437 extern __must_check long strnlen_user(const char __user *str, long n);
438 
439 unsigned long __must_check clear_user(void __user *mem, unsigned long len);
440 unsigned long __must_check __clear_user(void __user *mem, unsigned long len);
441 
442 #ifdef CONFIG_ARCH_HAS_COPY_MC
443 unsigned long __must_check
444 copy_mc_to_kernel(void *to, const void *from, unsigned len);
445 #define copy_mc_to_kernel copy_mc_to_kernel
446 
447 unsigned long __must_check
448 copy_mc_to_user(void *to, const void *from, unsigned len);
449 #endif
450 
451 /*
452  * movsl can be slow when source and dest are not both 8-byte aligned
453  */
454 #ifdef CONFIG_X86_INTEL_USERCOPY
455 extern struct movsl_mask {
456 	int mask;
457 } ____cacheline_aligned_in_smp movsl_mask;
458 #endif
459 
460 #define ARCH_HAS_NOCACHE_UACCESS 1
461 
462 #ifdef CONFIG_X86_32
463 # include <asm/uaccess_32.h>
464 #else
465 # include <asm/uaccess_64.h>
466 #endif
467 
468 /*
469  * The "unsafe" user accesses aren't really "unsafe", but the naming
470  * is a big fat warning: you have to not only do the access_ok()
471  * checking before using them, but you have to surround them with the
472  * user_access_begin/end() pair.
473  */
474 static __must_check __always_inline bool user_access_begin(const void __user *ptr, size_t len)
475 {
476 	if (unlikely(!access_ok(ptr,len)))
477 		return 0;
478 	__uaccess_begin_nospec();
479 	return 1;
480 }
481 #define user_access_begin(a,b)	user_access_begin(a,b)
482 #define user_access_end()	__uaccess_end()
483 
484 #define user_access_save()	smap_save()
485 #define user_access_restore(x)	smap_restore(x)
486 
487 #define unsafe_put_user(x, ptr, label)	\
488 	__put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)
489 
490 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
491 #define unsafe_get_user(x, ptr, err_label)					\
492 do {										\
493 	__inttype(*(ptr)) __gu_val;						\
494 	__get_user_size(__gu_val, (ptr), sizeof(*(ptr)), err_label);		\
495 	(x) = (__force __typeof__(*(ptr)))__gu_val;				\
496 } while (0)
497 #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
498 #define unsafe_get_user(x, ptr, err_label)					\
499 do {										\
500 	int __gu_err;								\
501 	__inttype(*(ptr)) __gu_val;						\
502 	__get_user_size(__gu_val, (ptr), sizeof(*(ptr)), __gu_err);		\
503 	(x) = (__force __typeof__(*(ptr)))__gu_val;				\
504 	if (unlikely(__gu_err)) goto err_label;					\
505 } while (0)
506 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
507 
508 /*
509  * We want the unsafe accessors to always be inlined and use
510  * the error labels - thus the macro games.
511  */
512 #define unsafe_copy_loop(dst, src, len, type, label)				\
513 	while (len >= sizeof(type)) {						\
514 		unsafe_put_user(*(type *)(src),(type __user *)(dst),label);	\
515 		dst += sizeof(type);						\
516 		src += sizeof(type);						\
517 		len -= sizeof(type);						\
518 	}
519 
520 #define unsafe_copy_to_user(_dst,_src,_len,label)			\
521 do {									\
522 	char __user *__ucu_dst = (_dst);				\
523 	const char *__ucu_src = (_src);					\
524 	size_t __ucu_len = (_len);					\
525 	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u64, label);	\
526 	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u32, label);	\
527 	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u16, label);	\
528 	unsafe_copy_loop(__ucu_dst, __ucu_src, __ucu_len, u8, label);	\
529 } while (0)
530 
531 #define HAVE_GET_KERNEL_NOFAULT
532 
533 #ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
534 #define __get_kernel_nofault(dst, src, type, err_label)			\
535 	__get_user_size(*((type *)(dst)), (__force type __user *)(src),	\
536 			sizeof(type), err_label)
537 #else // !CONFIG_CC_HAS_ASM_GOTO_OUTPUT
538 #define __get_kernel_nofault(dst, src, type, err_label)			\
539 do {									\
540 	int __kr_err;							\
541 									\
542 	__get_user_size(*((type *)(dst)), (__force type __user *)(src),	\
543 			sizeof(type), __kr_err);			\
544 	if (unlikely(__kr_err))						\
545 		goto err_label;						\
546 } while (0)
547 #endif // CONFIG_CC_HAS_ASM_GOTO_OUTPUT
548 
549 #define __put_kernel_nofault(dst, src, type, err_label)			\
550 	__put_user_size(*((type *)(src)), (__force type __user *)(dst),	\
551 			sizeof(type), err_label)
552 
553 #endif /* _ASM_X86_UACCESS_H */
554 
555