1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * User-mode machine state access
4  *
5  * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
6  *
7  * Red Hat Author: Roland McGrath.
8  */
9 
10 #ifndef _LINUX_REGSET_H
11 #define _LINUX_REGSET_H	1
12 
13 #include <linux/compiler.h>
14 #include <linux/types.h>
15 #include <linux/bug.h>
16 #include <linux/uaccess.h>
17 struct task_struct;
18 struct user_regset;
19 
20 struct membuf {
21 	void *p;
22 	size_t left;
23 };
24 
membuf_zero(struct membuf * s,size_t size)25 static inline int membuf_zero(struct membuf *s, size_t size)
26 {
27 	if (s->left) {
28 		if (size > s->left)
29 			size = s->left;
30 		memset(s->p, 0, size);
31 		s->p += size;
32 		s->left -= size;
33 	}
34 	return s->left;
35 }
36 
membuf_write(struct membuf * s,const void * v,size_t size)37 static inline int membuf_write(struct membuf *s, const void *v, size_t size)
38 {
39 	if (s->left) {
40 		if (size > s->left)
41 			size = s->left;
42 		memcpy(s->p, v, size);
43 		s->p += size;
44 		s->left -= size;
45 	}
46 	return s->left;
47 }
48 
membuf_at(const struct membuf * s,size_t offs)49 static inline struct membuf membuf_at(const struct membuf *s, size_t offs)
50 {
51 	struct membuf n = *s;
52 
53 	if (offs > n.left)
54 		offs = n.left;
55 	n.p += offs;
56 	n.left -= offs;
57 
58 	return n;
59 }
60 
61 /* current s->p must be aligned for v; v must be a scalar */
62 #define membuf_store(s, v)				\
63 ({							\
64 	struct membuf *__s = (s);			\
65         if (__s->left) {				\
66 		typeof(v) __v = (v);			\
67 		size_t __size = sizeof(__v);		\
68 		if (unlikely(__size > __s->left)) {	\
69 			__size = __s->left;		\
70 			memcpy(__s->p, &__v, __size);	\
71 		} else {				\
72 			*(typeof(__v + 0) *)__s->p = __v;	\
73 		}					\
74 		__s->p += __size;			\
75 		__s->left -= __size;			\
76 	}						\
77 	__s->left;})
78 
79 /**
80  * user_regset_active_fn - type of @active function in &struct user_regset
81  * @target:	thread being examined
82  * @regset:	regset being examined
83  *
84  * Return -%ENODEV if not available on the hardware found.
85  * Return %0 if no interesting state in this thread.
86  * Return >%0 number of @size units of interesting state.
87  * Any get call fetching state beyond that number will
88  * see the default initialization state for this data,
89  * so a caller that knows what the default state is need
90  * not copy it all out.
91  * This call is optional; the pointer is %NULL if there
92  * is no inexpensive check to yield a value < @n.
93  */
94 typedef int user_regset_active_fn(struct task_struct *target,
95 				  const struct user_regset *regset);
96 
97 typedef int user_regset_get2_fn(struct task_struct *target,
98 			       const struct user_regset *regset,
99 			       struct membuf to);
100 
101 /**
102  * user_regset_set_fn - type of @set function in &struct user_regset
103  * @target:	thread being examined
104  * @regset:	regset being examined
105  * @pos:	offset into the regset data to access, in bytes
106  * @count:	amount of data to copy, in bytes
107  * @kbuf:	if not %NULL, a kernel-space pointer to copy from
108  * @ubuf:	if @kbuf is %NULL, a user-space pointer to copy from
109  *
110  * Store register values.  Return %0 on success; -%EIO or -%ENODEV
111  * are usual failure returns.  The @pos and @count values are in
112  * bytes, but must be properly aligned.  If @kbuf is non-null, that
113  * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
114  * ubuf gives a userland pointer to access directly, and an -%EFAULT
115  * return value is possible.
116  */
117 typedef int user_regset_set_fn(struct task_struct *target,
118 			       const struct user_regset *regset,
119 			       unsigned int pos, unsigned int count,
120 			       const void *kbuf, const void __user *ubuf);
121 
122 /**
123  * user_regset_writeback_fn - type of @writeback function in &struct user_regset
124  * @target:	thread being examined
125  * @regset:	regset being examined
126  * @immediate:	zero if writeback at completion of next context switch is OK
127  *
128  * This call is optional; usually the pointer is %NULL.  When
129  * provided, there is some user memory associated with this regset's
130  * hardware, such as memory backing cached register data on register
131  * window machines; the regset's data controls what user memory is
132  * used (e.g. via the stack pointer value).
133  *
134  * Write register data back to user memory.  If the @immediate flag
135  * is nonzero, it must be written to the user memory so uaccess or
136  * access_process_vm() can see it when this call returns; if zero,
137  * then it must be written back by the time the task completes a
138  * context switch (as synchronized with wait_task_inactive()).
139  * Return %0 on success or if there was nothing to do, -%EFAULT for
140  * a memory problem (bad stack pointer or whatever), or -%EIO for a
141  * hardware problem.
142  */
143 typedef int user_regset_writeback_fn(struct task_struct *target,
144 				     const struct user_regset *regset,
145 				     int immediate);
146 
147 /**
148  * struct user_regset - accessible thread CPU state
149  * @n:			Number of slots (registers).
150  * @size:		Size in bytes of a slot (register).
151  * @align:		Required alignment, in bytes.
152  * @bias:		Bias from natural indexing.
153  * @core_note_type:	ELF note @n_type value used in core dumps.
154  * @get:		Function to fetch values.
155  * @set:		Function to store values.
156  * @active:		Function to report if regset is active, or %NULL.
157  * @writeback:		Function to write data back to user memory, or %NULL.
158  *
159  * This data structure describes a machine resource we call a register set.
160  * This is part of the state of an individual thread, not necessarily
161  * actual CPU registers per se.  A register set consists of a number of
162  * similar slots, given by @n.  Each slot is @size bytes, and aligned to
163  * @align bytes (which is at least @size).  For dynamically-sized
164  * regsets, @n must contain the maximum possible number of slots for the
165  * regset.
166  *
167  * For backward compatibility, the @get and @set methods must pad to, or
168  * accept, @n * @size bytes, even if the current regset size is smaller.
169  * The precise semantics of these operations depend on the regset being
170  * accessed.
171  *
172  * The functions to which &struct user_regset members point must be
173  * called only on the current thread or on a thread that is in
174  * %TASK_STOPPED or %TASK_TRACED state, that we are guaranteed will not
175  * be woken up and return to user mode, and that we have called
176  * wait_task_inactive() on.  (The target thread always might wake up for
177  * SIGKILL while these functions are working, in which case that
178  * thread's user_regset state might be scrambled.)
179  *
180  * The @pos argument must be aligned according to @align; the @count
181  * argument must be a multiple of @size.  These functions are not
182  * responsible for checking for invalid arguments.
183  *
184  * When there is a natural value to use as an index, @bias gives the
185  * difference between the natural index and the slot index for the
186  * register set.  For example, x86 GDT segment descriptors form a regset;
187  * the segment selector produces a natural index, but only a subset of
188  * that index space is available as a regset (the TLS slots); subtracting
189  * @bias from a segment selector index value computes the regset slot.
190  *
191  * If nonzero, @core_note_type gives the n_type field (NT_* value)
192  * of the core file note in which this regset's data appears.
193  * NT_PRSTATUS is a special case in that the regset data starts at
194  * offsetof(struct elf_prstatus, pr_reg) into the note data; that is
195  * part of the per-machine ELF formats userland knows about.  In
196  * other cases, the core file note contains exactly the whole regset
197  * (@n * @size) and nothing else.  The core file note is normally
198  * omitted when there is an @active function and it returns zero.
199  */
200 struct user_regset {
201 	user_regset_get2_fn		*regset_get;
202 	user_regset_set_fn		*set;
203 	user_regset_active_fn		*active;
204 	user_regset_writeback_fn	*writeback;
205 	unsigned int			n;
206 	unsigned int 			size;
207 	unsigned int 			align;
208 	unsigned int 			bias;
209 	unsigned int 			core_note_type;
210 };
211 
212 /**
213  * struct user_regset_view - available regsets
214  * @name:	Identifier, e.g. UTS_MACHINE string.
215  * @regsets:	Array of @n regsets available in this view.
216  * @n:		Number of elements in @regsets.
217  * @e_machine:	ELF header @e_machine %EM_* value written in core dumps.
218  * @e_flags:	ELF header @e_flags value written in core dumps.
219  * @ei_osabi:	ELF header @e_ident[%EI_OSABI] value written in core dumps.
220  *
221  * A regset view is a collection of regsets (&struct user_regset,
222  * above).  This describes all the state of a thread that can be seen
223  * from a given architecture/ABI environment.  More than one view might
224  * refer to the same &struct user_regset, or more than one regset
225  * might refer to the same machine-specific state in the thread.  For
226  * example, a 32-bit thread's state could be examined from the 32-bit
227  * view or from the 64-bit view.  Either method reaches the same thread
228  * register state, doing appropriate widening or truncation.
229  */
230 struct user_regset_view {
231 	const char *name;
232 	const struct user_regset *regsets;
233 	unsigned int n;
234 	u32 e_flags;
235 	u16 e_machine;
236 	u8 ei_osabi;
237 };
238 
239 /*
240  * This is documented here rather than at the definition sites because its
241  * implementation is machine-dependent but its interface is universal.
242  */
243 /**
244  * task_user_regset_view - Return the process's native regset view.
245  * @tsk: a thread of the process in question
246  *
247  * Return the &struct user_regset_view that is native for the given process.
248  * For example, what it would access when it called ptrace().
249  * Throughout the life of the process, this only changes at exec.
250  */
251 const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
252 
user_regset_copyin(unsigned int * pos,unsigned int * count,const void ** kbuf,const void __user ** ubuf,void * data,const int start_pos,const int end_pos)253 static inline int user_regset_copyin(unsigned int *pos, unsigned int *count,
254 				     const void **kbuf,
255 				     const void __user **ubuf, void *data,
256 				     const int start_pos, const int end_pos)
257 {
258 	if (*count == 0)
259 		return 0;
260 	BUG_ON(*pos < start_pos);
261 	if (end_pos < 0 || *pos < end_pos) {
262 		unsigned int copy = (end_pos < 0 ? *count
263 				     : min(*count, end_pos - *pos));
264 		data += *pos - start_pos;
265 		if (*kbuf) {
266 			memcpy(data, *kbuf, copy);
267 			*kbuf += copy;
268 		} else if (__copy_from_user(data, *ubuf, copy))
269 			return -EFAULT;
270 		else
271 			*ubuf += copy;
272 		*pos += copy;
273 		*count -= copy;
274 	}
275 	return 0;
276 }
277 
user_regset_copyin_ignore(unsigned int * pos,unsigned int * count,const void ** kbuf,const void __user ** ubuf,const int start_pos,const int end_pos)278 static inline void user_regset_copyin_ignore(unsigned int *pos,
279 					     unsigned int *count,
280 					     const void **kbuf,
281 					     const void __user **ubuf,
282 					     const int start_pos,
283 					     const int end_pos)
284 {
285 	if (*count == 0)
286 		return;
287 	BUG_ON(*pos < start_pos);
288 	if (end_pos < 0 || *pos < end_pos) {
289 		unsigned int copy = (end_pos < 0 ? *count
290 				     : min(*count, end_pos - *pos));
291 		if (*kbuf)
292 			*kbuf += copy;
293 		else
294 			*ubuf += copy;
295 		*pos += copy;
296 		*count -= copy;
297 	}
298 }
299 
300 extern int regset_get(struct task_struct *target,
301 		      const struct user_regset *regset,
302 		      unsigned int size, void *data);
303 
304 extern int regset_get_alloc(struct task_struct *target,
305 			    const struct user_regset *regset,
306 			    unsigned int size,
307 			    void **data);
308 
309 extern int copy_regset_to_user(struct task_struct *target,
310 			       const struct user_regset_view *view,
311 			       unsigned int setno, unsigned int offset,
312 			       unsigned int size, void __user *data);
313 
314 /**
315  * copy_regset_from_user - store into thread's user_regset data from user memory
316  * @target:	thread to be examined
317  * @view:	&struct user_regset_view describing user thread machine state
318  * @setno:	index in @view->regsets
319  * @offset:	offset into the regset data, in bytes
320  * @size:	amount of data to copy, in bytes
321  * @data:	user-mode pointer to copy from
322  */
copy_regset_from_user(struct task_struct * target,const struct user_regset_view * view,unsigned int setno,unsigned int offset,unsigned int size,const void __user * data)323 static inline int copy_regset_from_user(struct task_struct *target,
324 					const struct user_regset_view *view,
325 					unsigned int setno,
326 					unsigned int offset, unsigned int size,
327 					const void __user *data)
328 {
329 	const struct user_regset *regset = &view->regsets[setno];
330 
331 	if (!regset->set)
332 		return -EOPNOTSUPP;
333 
334 	if (!access_ok(data, size))
335 		return -EFAULT;
336 
337 	return regset->set(target, regset, offset, size, NULL, data);
338 }
339 
340 #endif	/* <linux/regset.h> */
341