linux/include/linux/regset.h
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   1/*
   2 * User-mode machine state access
   3 *
   4 * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
   5 *
   6 * This copyrighted material is made available to anyone wishing to use,
   7 * modify, copy, or redistribute it subject to the terms and conditions
   8 * of the GNU General Public License v.2.
   9 *
  10 * Red Hat Author: Roland McGrath.
  11 */
  12
  13#ifndef _LINUX_REGSET_H
  14#define _LINUX_REGSET_H 1
  15
  16#include <linux/compiler.h>
  17#include <linux/types.h>
  18#include <linux/bug.h>
  19#include <linux/uaccess.h>
  20struct task_struct;
  21struct user_regset;
  22
  23
  24/**
  25 * user_regset_active_fn - type of @active function in &struct user_regset
  26 * @target:     thread being examined
  27 * @regset:     regset being examined
  28 *
  29 * Return -%ENODEV if not available on the hardware found.
  30 * Return %0 if no interesting state in this thread.
  31 * Return >%0 number of @size units of interesting state.
  32 * Any get call fetching state beyond that number will
  33 * see the default initialization state for this data,
  34 * so a caller that knows what the default state is need
  35 * not copy it all out.
  36 * This call is optional; the pointer is %NULL if there
  37 * is no inexpensive check to yield a value < @n.
  38 */
  39typedef int user_regset_active_fn(struct task_struct *target,
  40                                  const struct user_regset *regset);
  41
  42/**
  43 * user_regset_get_fn - type of @get function in &struct user_regset
  44 * @target:     thread being examined
  45 * @regset:     regset being examined
  46 * @pos:        offset into the regset data to access, in bytes
  47 * @count:      amount of data to copy, in bytes
  48 * @kbuf:       if not %NULL, a kernel-space pointer to copy into
  49 * @ubuf:       if @kbuf is %NULL, a user-space pointer to copy into
  50 *
  51 * Fetch register values.  Return %0 on success; -%EIO or -%ENODEV
  52 * are usual failure returns.  The @pos and @count values are in
  53 * bytes, but must be properly aligned.  If @kbuf is non-null, that
  54 * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
  55 * ubuf gives a userland pointer to access directly, and an -%EFAULT
  56 * return value is possible.
  57 */
  58typedef int user_regset_get_fn(struct task_struct *target,
  59                               const struct user_regset *regset,
  60                               unsigned int pos, unsigned int count,
  61                               void *kbuf, void __user *ubuf);
  62
  63/**
  64 * user_regset_set_fn - type of @set function in &struct user_regset
  65 * @target:     thread being examined
  66 * @regset:     regset being examined
  67 * @pos:        offset into the regset data to access, in bytes
  68 * @count:      amount of data to copy, in bytes
  69 * @kbuf:       if not %NULL, a kernel-space pointer to copy from
  70 * @ubuf:       if @kbuf is %NULL, a user-space pointer to copy from
  71 *
  72 * Store register values.  Return %0 on success; -%EIO or -%ENODEV
  73 * are usual failure returns.  The @pos and @count values are in
  74 * bytes, but must be properly aligned.  If @kbuf is non-null, that
  75 * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
  76 * ubuf gives a userland pointer to access directly, and an -%EFAULT
  77 * return value is possible.
  78 */
  79typedef int user_regset_set_fn(struct task_struct *target,
  80                               const struct user_regset *regset,
  81                               unsigned int pos, unsigned int count,
  82                               const void *kbuf, const void __user *ubuf);
  83
  84/**
  85 * user_regset_writeback_fn - type of @writeback function in &struct user_regset
  86 * @target:     thread being examined
  87 * @regset:     regset being examined
  88 * @immediate:  zero if writeback at completion of next context switch is OK
  89 *
  90 * This call is optional; usually the pointer is %NULL.  When
  91 * provided, there is some user memory associated with this regset's
  92 * hardware, such as memory backing cached register data on register
  93 * window machines; the regset's data controls what user memory is
  94 * used (e.g. via the stack pointer value).
  95 *
  96 * Write register data back to user memory.  If the @immediate flag
  97 * is nonzero, it must be written to the user memory so uaccess or
  98 * access_process_vm() can see it when this call returns; if zero,
  99 * then it must be written back by the time the task completes a
 100 * context switch (as synchronized with wait_task_inactive()).
 101 * Return %0 on success or if there was nothing to do, -%EFAULT for
 102 * a memory problem (bad stack pointer or whatever), or -%EIO for a
 103 * hardware problem.
 104 */
 105typedef int user_regset_writeback_fn(struct task_struct *target,
 106                                     const struct user_regset *regset,
 107                                     int immediate);
 108
 109/**
 110 * struct user_regset - accessible thread CPU state
 111 * @n:                  Number of slots (registers).
 112 * @size:               Size in bytes of a slot (register).
 113 * @align:              Required alignment, in bytes.
 114 * @bias:               Bias from natural indexing.
 115 * @core_note_type:     ELF note @n_type value used in core dumps.
 116 * @get:                Function to fetch values.
 117 * @set:                Function to store values.
 118 * @active:             Function to report if regset is active, or %NULL.
 119 * @writeback:          Function to write data back to user memory, or %NULL.
 120 *
 121 * This data structure describes a machine resource we call a register set.
 122 * This is part of the state of an individual thread, not necessarily
 123 * actual CPU registers per se.  A register set consists of a number of
 124 * similar slots, given by @n.  Each slot is @size bytes, and aligned to
 125 * @align bytes (which is at least @size).
 126 *
 127 * These functions must be called only on the current thread or on a
 128 * thread that is in %TASK_STOPPED or %TASK_TRACED state, that we are
 129 * guaranteed will not be woken up and return to user mode, and that we
 130 * have called wait_task_inactive() on.  (The target thread always might
 131 * wake up for SIGKILL while these functions are working, in which case
 132 * that thread's user_regset state might be scrambled.)
 133 *
 134 * The @pos argument must be aligned according to @align; the @count
 135 * argument must be a multiple of @size.  These functions are not
 136 * responsible for checking for invalid arguments.
 137 *
 138 * When there is a natural value to use as an index, @bias gives the
 139 * difference between the natural index and the slot index for the
 140 * register set.  For example, x86 GDT segment descriptors form a regset;
 141 * the segment selector produces a natural index, but only a subset of
 142 * that index space is available as a regset (the TLS slots); subtracting
 143 * @bias from a segment selector index value computes the regset slot.
 144 *
 145 * If nonzero, @core_note_type gives the n_type field (NT_* value)
 146 * of the core file note in which this regset's data appears.
 147 * NT_PRSTATUS is a special case in that the regset data starts at
 148 * offsetof(struct elf_prstatus, pr_reg) into the note data; that is
 149 * part of the per-machine ELF formats userland knows about.  In
 150 * other cases, the core file note contains exactly the whole regset
 151 * (@n * @size) and nothing else.  The core file note is normally
 152 * omitted when there is an @active function and it returns zero.
 153 */
 154struct user_regset {
 155        user_regset_get_fn              *get;
 156        user_regset_set_fn              *set;
 157        user_regset_active_fn           *active;
 158        user_regset_writeback_fn        *writeback;
 159        unsigned int                    n;
 160        unsigned int                    size;
 161        unsigned int                    align;
 162        unsigned int                    bias;
 163        unsigned int                    core_note_type;
 164};
 165
 166/**
 167 * struct user_regset_view - available regsets
 168 * @name:       Identifier, e.g. UTS_MACHINE string.
 169 * @regsets:    Array of @n regsets available in this view.
 170 * @n:          Number of elements in @regsets.
 171 * @e_machine:  ELF header @e_machine %EM_* value written in core dumps.
 172 * @e_flags:    ELF header @e_flags value written in core dumps.
 173 * @ei_osabi:   ELF header @e_ident[%EI_OSABI] value written in core dumps.
 174 *
 175 * A regset view is a collection of regsets (&struct user_regset,
 176 * above).  This describes all the state of a thread that can be seen
 177 * from a given architecture/ABI environment.  More than one view might
 178 * refer to the same &struct user_regset, or more than one regset
 179 * might refer to the same machine-specific state in the thread.  For
 180 * example, a 32-bit thread's state could be examined from the 32-bit
 181 * view or from the 64-bit view.  Either method reaches the same thread
 182 * register state, doing appropriate widening or truncation.
 183 */
 184struct user_regset_view {
 185        const char *name;
 186        const struct user_regset *regsets;
 187        unsigned int n;
 188        u32 e_flags;
 189        u16 e_machine;
 190        u8 ei_osabi;
 191};
 192
 193/*
 194 * This is documented here rather than at the definition sites because its
 195 * implementation is machine-dependent but its interface is universal.
 196 */
 197/**
 198 * task_user_regset_view - Return the process's native regset view.
 199 * @tsk: a thread of the process in question
 200 *
 201 * Return the &struct user_regset_view that is native for the given process.
 202 * For example, what it would access when it called ptrace().
 203 * Throughout the life of the process, this only changes at exec.
 204 */
 205const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
 206
 207
 208/*
 209 * These are helpers for writing regset get/set functions in arch code.
 210 * Because @start_pos and @end_pos are always compile-time constants,
 211 * these are inlined into very little code though they look large.
 212 *
 213 * Use one or more calls sequentially for each chunk of regset data stored
 214 * contiguously in memory.  Call with constants for @start_pos and @end_pos,
 215 * giving the range of byte positions in the regset that data corresponds
 216 * to; @end_pos can be -1 if this chunk is at the end of the regset layout.
 217 * Each call updates the arguments to point past its chunk.
 218 */
 219
 220static inline int user_regset_copyout(unsigned int *pos, unsigned int *count,
 221                                      void **kbuf,
 222                                      void __user **ubuf, const void *data,
 223                                      const int start_pos, const int end_pos)
 224{
 225        if (*count == 0)
 226                return 0;
 227        BUG_ON(*pos < start_pos);
 228        if (end_pos < 0 || *pos < end_pos) {
 229                unsigned int copy = (end_pos < 0 ? *count
 230                                     : min(*count, end_pos - *pos));
 231                data += *pos - start_pos;
 232                if (*kbuf) {
 233                        memcpy(*kbuf, data, copy);
 234                        *kbuf += copy;
 235                } else if (__copy_to_user(*ubuf, data, copy))
 236                        return -EFAULT;
 237                else
 238                        *ubuf += copy;
 239                *pos += copy;
 240                *count -= copy;
 241        }
 242        return 0;
 243}
 244
 245static inline int user_regset_copyin(unsigned int *pos, unsigned int *count,
 246                                     const void **kbuf,
 247                                     const void __user **ubuf, void *data,
 248                                     const int start_pos, const int end_pos)
 249{
 250        if (*count == 0)
 251                return 0;
 252        BUG_ON(*pos < start_pos);
 253        if (end_pos < 0 || *pos < end_pos) {
 254                unsigned int copy = (end_pos < 0 ? *count
 255                                     : min(*count, end_pos - *pos));
 256                data += *pos - start_pos;
 257                if (*kbuf) {
 258                        memcpy(data, *kbuf, copy);
 259                        *kbuf += copy;
 260                } else if (__copy_from_user(data, *ubuf, copy))
 261                        return -EFAULT;
 262                else
 263                        *ubuf += copy;
 264                *pos += copy;
 265                *count -= copy;
 266        }
 267        return 0;
 268}
 269
 270/*
 271 * These two parallel the two above, but for portions of a regset layout
 272 * that always read as all-zero or for which writes are ignored.
 273 */
 274static inline int user_regset_copyout_zero(unsigned int *pos,
 275                                           unsigned int *count,
 276                                           void **kbuf, void __user **ubuf,
 277                                           const int start_pos,
 278                                           const int end_pos)
 279{
 280        if (*count == 0)
 281                return 0;
 282        BUG_ON(*pos < start_pos);
 283        if (end_pos < 0 || *pos < end_pos) {
 284                unsigned int copy = (end_pos < 0 ? *count
 285                                     : min(*count, end_pos - *pos));
 286                if (*kbuf) {
 287                        memset(*kbuf, 0, copy);
 288                        *kbuf += copy;
 289                } else if (__clear_user(*ubuf, copy))
 290                        return -EFAULT;
 291                else
 292                        *ubuf += copy;
 293                *pos += copy;
 294                *count -= copy;
 295        }
 296        return 0;
 297}
 298
 299static inline int user_regset_copyin_ignore(unsigned int *pos,
 300                                            unsigned int *count,
 301                                            const void **kbuf,
 302                                            const void __user **ubuf,
 303                                            const int start_pos,
 304                                            const int end_pos)
 305{
 306        if (*count == 0)
 307                return 0;
 308        BUG_ON(*pos < start_pos);
 309        if (end_pos < 0 || *pos < end_pos) {
 310                unsigned int copy = (end_pos < 0 ? *count
 311                                     : min(*count, end_pos - *pos));
 312                if (*kbuf)
 313                        *kbuf += copy;
 314                else
 315                        *ubuf += copy;
 316                *pos += copy;
 317                *count -= copy;
 318        }
 319        return 0;
 320}
 321
 322/**
 323 * copy_regset_to_user - fetch a thread's user_regset data into user memory
 324 * @target:     thread to be examined
 325 * @view:       &struct user_regset_view describing user thread machine state
 326 * @setno:      index in @view->regsets
 327 * @offset:     offset into the regset data, in bytes
 328 * @size:       amount of data to copy, in bytes
 329 * @data:       user-mode pointer to copy into
 330 */
 331static inline int copy_regset_to_user(struct task_struct *target,
 332                                      const struct user_regset_view *view,
 333                                      unsigned int setno,
 334                                      unsigned int offset, unsigned int size,
 335                                      void __user *data)
 336{
 337        const struct user_regset *regset = &view->regsets[setno];
 338
 339        if (!regset->get)
 340                return -EOPNOTSUPP;
 341
 342        if (!access_ok(VERIFY_WRITE, data, size))
 343                return -EFAULT;
 344
 345        return regset->get(target, regset, offset, size, NULL, data);
 346}
 347
 348/**
 349 * copy_regset_from_user - store into thread's user_regset data from user memory
 350 * @target:     thread to be examined
 351 * @view:       &struct user_regset_view describing user thread machine state
 352 * @setno:      index in @view->regsets
 353 * @offset:     offset into the regset data, in bytes
 354 * @size:       amount of data to copy, in bytes
 355 * @data:       user-mode pointer to copy from
 356 */
 357static inline int copy_regset_from_user(struct task_struct *target,
 358                                        const struct user_regset_view *view,
 359                                        unsigned int setno,
 360                                        unsigned int offset, unsigned int size,
 361                                        const void __user *data)
 362{
 363        const struct user_regset *regset = &view->regsets[setno];
 364
 365        if (!regset->set)
 366                return -EOPNOTSUPP;
 367
 368        if (!access_ok(VERIFY_READ, data, size))
 369                return -EFAULT;
 370
 371        return regset->set(target, regset, offset, size, NULL, data);
 372}
 373
 374
 375#endif  /* <linux/regset.h> */
 376
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