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