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: s->p, c: 0, n: 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(to: s->p, from: v, len: 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 * @core_note_name: ELF note name to qualify the note type.
155 * @regset_get: Function to fetch values.
156 * @set: Function to store values.
157 * @active: Function to report if regset is active, or %NULL.
158 * @writeback: Function to write data back to user memory, or %NULL.
159 *
160 * This data structure describes a machine resource we call a register set.
161 * This is part of the state of an individual thread, not necessarily
162 * actual CPU registers per se. A register set consists of a number of
163 * similar slots, given by @n. Each slot is @size bytes, and aligned to
164 * @align bytes (which is at least @size). For dynamically-sized
165 * regsets, @n must contain the maximum possible number of slots for the
166 * regset.
167 *
168 * For backward compatibility, the @get and @set methods must pad to, or
169 * accept, @n * @size bytes, even if the current regset size is smaller.
170 * The precise semantics of these operations depend on the regset being
171 * accessed.
172 *
173 * The functions to which &struct user_regset members point must be
174 * called only on the current thread or on a thread that is in
175 * %TASK_STOPPED or %TASK_TRACED state, that we are guaranteed will not
176 * be woken up and return to user mode, and that we have called
177 * wait_task_inactive() on. (The target thread always might wake up for
178 * SIGKILL while these functions are working, in which case that
179 * thread's user_regset state might be scrambled.)
180 *
181 * The @pos argument must be aligned according to @align; the @count
182 * argument must be a multiple of @size. These functions are not
183 * responsible for checking for invalid arguments.
184 *
185 * When there is a natural value to use as an index, @bias gives the
186 * difference between the natural index and the slot index for the
187 * register set. For example, x86 GDT segment descriptors form a regset;
188 * the segment selector produces a natural index, but only a subset of
189 * that index space is available as a regset (the TLS slots); subtracting
190 * @bias from a segment selector index value computes the regset slot.
191 *
192 * If nonzero, @core_note_type gives the n_type field (NT_* value)
193 * of the core file note in which this regset's data appears.
194 * @core_note_name specifies the note name. The preferred way to
195 * specify these two fields is to use the @USER_REGSET_NOTE_TYPE()
196 * macro.
197 *
198 * NT_PRSTATUS is a special case in that the regset data starts at
199 * offsetof(struct elf_prstatus, pr_reg) into the note data; that is
200 * part of the per-machine ELF formats userland knows about. In
201 * other cases, the core file note contains exactly the whole regset
202 * (@n * @size) and nothing else. The core file note is normally
203 * omitted when there is an @active function and it returns zero.
204 */
205struct user_regset {
206 user_regset_get2_fn *regset_get;
207 user_regset_set_fn *set;
208 user_regset_active_fn *active;
209 user_regset_writeback_fn *writeback;
210 unsigned int n;
211 unsigned int size;
212 unsigned int align;
213 unsigned int bias;
214 unsigned int core_note_type;
215 const char *core_note_name;
216};
217
218#define USER_REGSET_NOTE_TYPE(type) \
219 .core_note_type = (NT_ ## type), \
220 .core_note_name = (NN_ ## type)
221
222/**
223 * struct user_regset_view - available regsets
224 * @name: Identifier, e.g. UTS_MACHINE string.
225 * @regsets: Array of @n regsets available in this view.
226 * @n: Number of elements in @regsets.
227 * @e_machine: ELF header @e_machine %EM_* value written in core dumps.
228 * @e_flags: ELF header @e_flags value written in core dumps.
229 * @ei_osabi: ELF header @e_ident[%EI_OSABI] value written in core dumps.
230 *
231 * A regset view is a collection of regsets (&struct user_regset,
232 * above). This describes all the state of a thread that can be seen
233 * from a given architecture/ABI environment. More than one view might
234 * refer to the same &struct user_regset, or more than one regset
235 * might refer to the same machine-specific state in the thread. For
236 * example, a 32-bit thread's state could be examined from the 32-bit
237 * view or from the 64-bit view. Either method reaches the same thread
238 * register state, doing appropriate widening or truncation.
239 */
240struct user_regset_view {
241 const char *name;
242 const struct user_regset *regsets;
243 unsigned int n;
244 u32 e_flags;
245 u16 e_machine;
246 u8 ei_osabi;
247};
248
249/*
250 * This is documented here rather than at the definition sites because its
251 * implementation is machine-dependent but its interface is universal.
252 */
253/**
254 * task_user_regset_view - Return the process's native regset view.
255 * @tsk: a thread of the process in question
256 *
257 * Return the &struct user_regset_view that is native for the given process.
258 * For example, what it would access when it called ptrace().
259 * Throughout the life of the process, this only changes at exec.
260 */
261const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
262
263static inline int user_regset_copyin(unsigned int *pos, unsigned int *count,
264 const void **kbuf,
265 const void __user **ubuf, void *data,
266 const int start_pos, const int end_pos)
267{
268 if (*count == 0)
269 return 0;
270 BUG_ON(*pos < start_pos);
271 if (end_pos < 0 || *pos < end_pos) {
272 unsigned int copy = (end_pos < 0 ? *count
273 : min(*count, end_pos - *pos));
274 data += *pos - start_pos;
275 if (*kbuf) {
276 memcpy(to: data, from: *kbuf, len: copy);
277 *kbuf += copy;
278 } else if (__copy_from_user(to: data, from: *ubuf, n: copy))
279 return -EFAULT;
280 else
281 *ubuf += copy;
282 *pos += copy;
283 *count -= copy;
284 }
285 return 0;
286}
287
288static inline void user_regset_copyin_ignore(unsigned int *pos,
289 unsigned int *count,
290 const void **kbuf,
291 const void __user **ubuf,
292 const int start_pos,
293 const int end_pos)
294{
295 if (*count == 0)
296 return;
297 BUG_ON(*pos < start_pos);
298 if (end_pos < 0 || *pos < end_pos) {
299 unsigned int copy = (end_pos < 0 ? *count
300 : min(*count, end_pos - *pos));
301 if (*kbuf)
302 *kbuf += copy;
303 else
304 *ubuf += copy;
305 *pos += copy;
306 *count -= copy;
307 }
308}
309
310extern int regset_get(struct task_struct *target,
311 const struct user_regset *regset,
312 unsigned int size, void *data);
313
314extern int regset_get_alloc(struct task_struct *target,
315 const struct user_regset *regset,
316 unsigned int size,
317 void **data);
318
319extern int copy_regset_to_user(struct task_struct *target,
320 const struct user_regset_view *view,
321 unsigned int setno, unsigned int offset,
322 unsigned int size, void __user *data);
323
324/**
325 * copy_regset_from_user - store into thread's user_regset data from user memory
326 * @target: thread to be examined
327 * @view: &struct user_regset_view describing user thread machine state
328 * @setno: index in @view->regsets
329 * @offset: offset into the regset data, in bytes
330 * @size: amount of data to copy, in bytes
331 * @data: user-mode pointer to copy from
332 */
333static inline int copy_regset_from_user(struct task_struct *target,
334 const struct user_regset_view *view,
335 unsigned int setno,
336 unsigned int offset, unsigned int size,
337 const void __user *data)
338{
339 const struct user_regset *regset = &view->regsets[setno];
340
341 if (!regset->set)
342 return -EOPNOTSUPP;
343
344 if (!access_ok(data, size))
345 return -EFAULT;
346
347 return regset->set(target, regset, offset, size, NULL, data);
348}
349
350#endif /* <linux/regset.h> */
351