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 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 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 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); 252 253 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 } 277 278 static inline int 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 0; 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 return 0; 299 } 300 301 extern int regset_get(struct task_struct *target, 302 const struct user_regset *regset, 303 unsigned int size, void *data); 304 305 extern int regset_get_alloc(struct task_struct *target, 306 const struct user_regset *regset, 307 unsigned int size, 308 void **data); 309 310 extern int copy_regset_to_user(struct task_struct *target, 311 const struct user_regset_view *view, 312 unsigned int setno, unsigned int offset, 313 unsigned int size, void __user *data); 314 315 /** 316 * copy_regset_from_user - store into thread's user_regset data from user memory 317 * @target: thread to be examined 318 * @view: &struct user_regset_view describing user thread machine state 319 * @setno: index in @view->regsets 320 * @offset: offset into the regset data, in bytes 321 * @size: amount of data to copy, in bytes 322 * @data: user-mode pointer to copy from 323 */ 324 static inline int copy_regset_from_user(struct task_struct *target, 325 const struct user_regset_view *view, 326 unsigned int setno, 327 unsigned int offset, unsigned int size, 328 const void __user *data) 329 { 330 const struct user_regset *regset = &view->regsets[setno]; 331 332 if (!regset->set) 333 return -EOPNOTSUPP; 334 335 if (!access_ok(data, size)) 336 return -EFAULT; 337 338 return regset->set(target, regset, offset, size, NULL, data); 339 } 340 341 #endif /* <linux/regset.h> */ 342