include/linux/regset.h

   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 struct task_struct;
  19 struct user_regset;
  20
  21
  22 /**
  23  * user_regset_active_fn - type of @active function in &struct user_regset
  24  * @target:     thread being examined
  25  * @regset:     regset being examined
  26  *
  27  * Return -%ENODEV if not available on the hardware found.
  28  * Return %0 if no interesting state in this thread.
  29  * Return >%0 number of @size units of interesting state.
  30  * Any get call fetching state beyond that number will
  31  * see the default initialization state for this data,
  32  * so a caller that knows what the default state is need
  33  * not copy it all out.
  34  * This call is optional; the pointer is %NULL if there
  35  * is no inexpensive check to yield a value < @n.
  36  */
  37 typedef int user_regset_active_fn(struct task_struct *target,
  38                                   const struct user_regset *regset);
  39
  40 /**
  41  * user_regset_get_fn - type of @get function in &struct user_regset
  42  * @target:     thread being examined
  43  * @regset:     regset being examined
  44  * @pos:        offset into the regset data to access, in bytes
  45  * @count:      amount of data to copy, in bytes
  46  * @kbuf:       if not %NULL, a kernel-space pointer to copy into
  47  * @ubuf:       if @kbuf is %NULL, a user-space pointer to copy into
  48  *
  49  * Fetch register values.  Return %0 on success; -%EIO or -%ENODEV
  50  * are usual failure returns.  The @pos and @count values are in
  51  * bytes, but must be properly aligned.  If @kbuf is non-null, that
  52  * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
  53  * ubuf gives a userland pointer to access directly, and an -%EFAULT
  54  * return value is possible.
  55  */
  56 typedef int user_regset_get_fn(struct task_struct *target,
  57                                const struct user_regset *regset,
  58                                unsigned int pos, unsigned int count,
  59                                void *kbuf, void __user *ubuf);
  60
  61 /**
  62  * user_regset_set_fn - type of @set function in &struct user_regset
  63  * @target:     thread being examined
  64  * @regset:     regset being examined
  65  * @pos:        offset into the regset data to access, in bytes
  66  * @count:      amount of data to copy, in bytes
  67  * @kbuf:       if not %NULL, a kernel-space pointer to copy from
  68  * @ubuf:       if @kbuf is %NULL, a user-space pointer to copy from
  69  *
  70  * Store register values.  Return %0 on success; -%EIO or -%ENODEV
  71  * are usual failure returns.  The @pos and @count values are in
  72  * bytes, but must be properly aligned.  If @kbuf is non-null, that
  73  * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
  74  * ubuf gives a userland pointer to access directly, and an -%EFAULT
  75  * return value is possible.
  76  */
  77 typedef int user_regset_set_fn(struct task_struct *target,
  78                                const struct user_regset *regset,
  79                                unsigned int pos, unsigned int count,
  80                                const void *kbuf, const void __user *ubuf);
  81
  82 /**
  83  * user_regset_writeback_fn - type of @writeback function in &struct user_regset
  84  * @target:     thread being examined
  85  * @regset:     regset being examined
  86  * @immediate:  zero if writeback at completion of next context switch is OK
  87  *
  88  * This call is optional; usually the pointer is %NULL.  When
  89  * provided, there is some user memory associated with this regset's
  90  * hardware, such as memory backing cached register data on register
  91  * window machines; the regset's data controls what user memory is
  92  * used (e.g. via the stack pointer value).
  93  *
  94  * Write register data back to user memory.  If the @immediate flag
  95  * is nonzero, it must be written to the user memory so uaccess or
  96  * access_process_vm() can see it when this call returns; if zero,
  97  * then it must be written back by the time the task completes a
  98  * context switch (as synchronized with wait_task_inactive()).
  99  * Return %0 on success or if there was nothing to do, -%EFAULT for
 100  * a memory problem (bad stack pointer or whatever), or -%EIO for a
 101  * hardware problem.
 102  */
 103 typedef int user_regset_writeback_fn(struct task_struct *target,
 104                                      const struct user_regset *regset,
 105                                      int immediate);
 106
 107 /**
 108  * struct user_regset - accessible thread CPU state
 109  * @n:                  Number of slots (registers).
 110  * @size:               Size in bytes of a slot (register).
 111  * @align:              Required alignment, in bytes.
 112  * @bias:               Bias from natural indexing.
 113  * @core_note_type:     ELF note @n_type value used in core dumps.
 114  * @get:                Function to fetch values.
 115  * @set:                Function to store values.
 116  * @active:             Function to report if regset is active, or %NULL.
 117  * @writeback:          Function to write data back to user memory, or %NULL.
 118  *
 119  * This data structure describes a machine resource we call a register set.
 120  * This is part of the state of an individual thread, not necessarily
 121  * actual CPU registers per se.  A register set consists of a number of
 122  * similar slots, given by @n.  Each slot is @size bytes, and aligned to
 123  * @align bytes (which is at least @size).
 124  *
 125  * These functions must be called only on the current thread or on a
 126  * thread that is in %TASK_STOPPED or %TASK_TRACED state, that we are
 127  * guaranteed will not be woken up and return to user mode, and that we
 128  * have called wait_task_inactive() on.  (The target thread always might
 129  * wake up for SIGKILL while these functions are working, in which case
 130  * that thread's user_regset state might be scrambled.)
 131  *
 132  * The @pos argument must be aligned according to @align; the @count
 133  * argument must be a multiple of @size.  These functions are not
 134  * responsible for checking for invalid arguments.
 135  *
 136  * When there is a natural value to use as an index, @bias gives the
 137  * difference between the natural index and the slot index for the
 138  * register set.  For example, x86 GDT segment descriptors form a regset;
 139  * the segment selector produces a natural index, but only a subset of
 140  * that index space is available as a regset (the TLS slots); subtracting
 141  * @bias from a segment selector index value computes the regset slot.
 142  *
 143  * If nonzero, @core_note_type gives the n_type field (NT_* value)
 144  * of the core file note in which this regset's data appears.
 145  * NT_PRSTATUS is a special case in that the regset data starts at
 146  * offsetof(struct elf_prstatus, pr_reg) into the note data; that is
 147  * part of the per-machine ELF formats userland knows about.  In
 148  * other cases, the core file note contains exactly the whole regset
 149  * (@n * @size) and nothing else.  The core file note is normally
 150  * omitted when there is an @active function and it returns zero.
 151  */
 152 struct user_regset {
 153         user_regset_get_fn              *get;
 154         user_regset_set_fn              *set;
 155         user_regset_active_fn           *active;
 156         user_regset_writeback_fn        *writeback;
 157         unsigned int                    n;
 158         unsigned int                    size;
 159         unsigned int                    align;
 160         unsigned int                    bias;
 161         unsigned int                    core_note_type;
 162 };
 163
 164 /**
 165  * struct user_regset_view - available regsets
 166  * @name:       Identifier, e.g. UTS_MACHINE string.
 167  * @regsets:    Array of @n regsets available in this view.
 168  * @n:          Number of elements in @regsets.
 169  * @e_machine:  ELF header @e_machine %EM_* value written in core dumps.
 170  * @e_flags:    ELF header @e_flags value written in core dumps.
 171  * @ei_osabi:   ELF header @e_ident[%EI_OSABI] value written in core dumps.
 172  *
 173  * A regset view is a collection of regsets (&struct user_regset,
 174  * above).  This describes all the state of a thread that can be seen
 175  * from a given architecture/ABI environment.  More than one view might
 176  * refer to the same &struct user_regset, or more than one regset
 177  * might refer to the same machine-specific state in the thread.  For
 178  * example, a 32-bit thread's state could be examined from the 32-bit
 179  * view or from the 64-bit view.  Either method reaches the same thread
 180  * register state, doing appropriate widening or truncation.
 181  */
 182 struct user_regset_view {
 183         const char *name;
 184         const struct user_regset *regsets;
 185         unsigned int n;
 186         u32 e_flags;
 187         u16 e_machine;
 188         u8 ei_osabi;
 189 };
 190
 191 /*
 192  * This is documented here rather than at the definition sites because its
 193  * implementation is machine-dependent but its interface is universal.
 194  */
 195 /**
 196  * task_user_regset_view - Return the process's native regset view.
 197  * @tsk: a thread of the process in question
 198  *
 199  * Return the &struct user_regset_view that is native for the given process.
 200  * For example, what it would access when it called ptrace().
 201  * Throughout the life of the process, this only changes at exec.
 202  */
 203 const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
 204
 205
 206 #endif  /* <linux/regset.h> */