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>
17struct task_struct;
18struct user_regset;
19
20struct membuf {
21	void *p;
22	size_t left;
23};
24
25static 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
37static 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
49static 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 */
94typedef int user_regset_active_fn(struct task_struct *target,
95				  const struct user_regset *regset);
96
97typedef 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 */
117typedef 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 */
143typedef 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 */
200struct 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 */
230struct 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 */
251const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
252
253static 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
278static 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
300extern int regset_get(struct task_struct *target,
301		      const struct user_regset *regset,
302		      unsigned int size, void *data);
303
304extern int regset_get_alloc(struct task_struct *target,
305			    const struct user_regset *regset,
306			    unsigned int size,
307			    void **data);
308
309extern 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 */
323static 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