/*
   * User-mode machine state access
   *
   * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions
   * of the GNU General Public License v.2.
   *
   * Red Hat Author: Roland McGrath.
   */
  
  #ifndef _LINUX_REGSET_H
  #define _LINUX_REGSET_H	1
  
  #include <linux/compiler.h>
  #include <linux/types.h>
  #include <linux/bug.h>
  #include <linux/uaccess.h>
  struct task_struct;
  struct user_regset;
  
  
  /**
   * user_regset_active_fn - type of @active function in &struct user_regset
   * @target:	thread being examined
   * @regset:	regset being examined
   *
   * Return -%ENODEV if not available on the hardware found.
   * Return %0 if no interesting state in this thread.
   * Return >%0 number of @size units of interesting state.
   * Any get call fetching state beyond that number will
   * see the default initialization state for this data,
   * so a caller that knows what the default state is need
   * not copy it all out.
   * This call is optional; the pointer is %NULL if there
   * is no inexpensive check to yield a value < @n.
   */
  typedef int user_regset_active_fn(struct task_struct *target,
  				  const struct user_regset *regset);
  
  /**
   * user_regset_get_fn - type of @get function in &struct user_regset
   * @target:	thread being examined
   * @regset:	regset being examined
   * @pos:	offset into the regset data to access, in bytes
   * @count:	amount of data to copy, in bytes
   * @kbuf:	if not %NULL, a kernel-space pointer to copy into
   * @ubuf:	if @kbuf is %NULL, a user-space pointer to copy into
   *
   * Fetch register values.  Return %0 on success; -%EIO or -%ENODEV
   * are usual failure returns.  The @pos and @count values are in
   * bytes, but must be properly aligned.  If @kbuf is non-null, that
   * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
   * ubuf gives a userland pointer to access directly, and an -%EFAULT
   * return value is possible.
   */
  typedef int user_regset_get_fn(struct task_struct *target,
  			       const struct user_regset *regset,
  			       unsigned int pos, unsigned int count,
  			       void *kbuf, void __user *ubuf);
  
  /**
   * user_regset_set_fn - type of @set function in &struct user_regset
   * @target:	thread being examined
   * @regset:	regset being examined
   * @pos:	offset into the regset data to access, in bytes
   * @count:	amount of data to copy, in bytes
   * @kbuf:	if not %NULL, a kernel-space pointer to copy from
   * @ubuf:	if @kbuf is %NULL, a user-space pointer to copy from
   *
   * Store register values.  Return %0 on success; -%EIO or -%ENODEV
   * are usual failure returns.  The @pos and @count values are in
   * bytes, but must be properly aligned.  If @kbuf is non-null, that
   * buffer is used and @ubuf is ignored.  If @kbuf is %NULL, then
   * ubuf gives a userland pointer to access directly, and an -%EFAULT
   * return value is possible.
   */
  typedef int user_regset_set_fn(struct task_struct *target,
  			       const struct user_regset *regset,
  			       unsigned int pos, unsigned int count,
  			       const void *kbuf, const void __user *ubuf);
  
  /**
   * user_regset_writeback_fn - type of @writeback function in &struct user_regset
   * @target:	thread being examined
   * @regset:	regset being examined
   * @immediate:	zero if writeback at completion of next context switch is OK
   *
   * This call is optional; usually the pointer is %NULL.  When
   * provided, there is some user memory associated with this regset's
   * hardware, such as memory backing cached register data on register
   * window machines; the regset's data controls what user memory is
   * used (e.g. via the stack pointer value).
   *
   * Write register data back to user memory.  If the @immediate flag
   * is nonzero, it must be written to the user memory so uaccess or
   * access_process_vm() can see it when this call returns; if zero,
   * then it must be written back by the time the task completes a
   * context switch (as synchronized with wait_task_inactive()).
   * Return %0 on success or if there was nothing to do, -%EFAULT for
   * a memory problem (bad stack pointer or whatever), or -%EIO for a
   * hardware problem.
   */
  typedef int user_regset_writeback_fn(struct task_struct *target,
  				     const struct user_regset *regset,
  				     int immediate);
  
  /**
   * struct user_regset - accessible thread CPU state
   * @n:			Number of slots (registers).
   * @size:		Size in bytes of a slot (register).
   * @align:		Required alignment, in bytes.
   * @bias:		Bias from natural indexing.
   * @core_note_type:	ELF note @n_type value used in core dumps.
   * @get:		Function to fetch values.
   * @set:		Function to store values.
   * @active:		Function to report if regset is active, or %NULL.
   * @writeback:		Function to write data back to user memory, or %NULL.
   *
   * This data structure describes a machine resource we call a register set.
   * This is part of the state of an individual thread, not necessarily
   * actual CPU registers per se.  A register set consists of a number of
   * similar slots, given by @n.  Each slot is @size bytes, and aligned to
   * @align bytes (which is at least @size).
   *
   * These functions must be called only on the current thread or on a
   * thread that is in %TASK_STOPPED or %TASK_TRACED state, that we are
   * guaranteed will not be woken up and return to user mode, and that we
   * have called wait_task_inactive() on.  (The target thread always might
   * wake up for SIGKILL while these functions are working, in which case
   * that thread's user_regset state might be scrambled.)
   *
   * The @pos argument must be aligned according to @align; the @count
   * argument must be a multiple of @size.  These functions are not
   * responsible for checking for invalid arguments.
   *
   * When there is a natural value to use as an index, @bias gives the
   * difference between the natural index and the slot index for the
   * register set.  For example, x86 GDT segment descriptors form a regset;
   * the segment selector produces a natural index, but only a subset of
   * that index space is available as a regset (the TLS slots); subtracting
   * @bias from a segment selector index value computes the regset slot.
   *
   * If nonzero, @core_note_type gives the n_type field (NT_* value)
   * of the core file note in which this regset's data appears.
   * NT_PRSTATUS is a special case in that the regset data starts at
   * offsetof(struct elf_prstatus, pr_reg) into the note data; that is
   * part of the per-machine ELF formats userland knows about.  In
   * other cases, the core file note contains exactly the whole regset
   * (@n * @size) and nothing else.  The core file note is normally
   * omitted when there is an @active function and it returns zero.
   */
  struct user_regset {
  	user_regset_get_fn		*get;
  	user_regset_set_fn		*set;
  	user_regset_active_fn		*active;
  	user_regset_writeback_fn	*writeback;
  	unsigned int			n;
  	unsigned int 			size;
  	unsigned int 			align;
  	unsigned int 			bias;
  	unsigned int 			core_note_type;
  };
  
  /**
   * struct user_regset_view - available regsets
   * @name:	Identifier, e.g. UTS_MACHINE string.
   * @regsets:	Array of @n regsets available in this view.
   * @n:		Number of elements in @regsets.
   * @e_machine:	ELF header @e_machine %EM_* value written in core dumps.
   * @e_flags:	ELF header @e_flags value written in core dumps.
   * @ei_osabi:	ELF header @e_ident[%EI_OSABI] value written in core dumps.
   *
   * A regset view is a collection of regsets (&struct user_regset,
   * above).  This describes all the state of a thread that can be seen
   * from a given architecture/ABI environment.  More than one view might
   * refer to the same &struct user_regset, or more than one regset
   * might refer to the same machine-specific state in the thread.  For
   * example, a 32-bit thread's state could be examined from the 32-bit
   * view or from the 64-bit view.  Either method reaches the same thread
   * register state, doing appropriate widening or truncation.
   */
  struct user_regset_view {
  	const char *name;
  	const struct user_regset *regsets;
  	unsigned int n;
  	u32 e_flags;
  	u16 e_machine;
  	u8 ei_osabi;
  };
  
  /*
   * This is documented here rather than at the definition sites because its
   * implementation is machine-dependent but its interface is universal.
   */
  /**
   * task_user_regset_view - Return the process's native regset view.
   * @tsk: a thread of the process in question
   *
   * Return the &struct user_regset_view that is native for the given process.
   * For example, what it would access when it called ptrace().
   * Throughout the life of the process, this only changes at exec.
   */
  const struct user_regset_view *task_user_regset_view(struct task_struct *tsk);
  
  
  /*
   * These are helpers for writing regset get/set functions in arch code.
   * Because @start_pos and @end_pos are always compile-time constants,
   * these are inlined into very little code though they look large.
   *
   * Use one or more calls sequentially for each chunk of regset data stored
   * contiguously in memory.  Call with constants for @start_pos and @end_pos,
   * giving the range of byte positions in the regset that data corresponds
   * to; @end_pos can be -1 if this chunk is at the end of the regset layout.
   * Each call updates the arguments to point past its chunk.
   */
  
  static inline int user_regset_copyout(unsigned int *pos, unsigned int *count,
  				      void **kbuf,
  				      void __user **ubuf, const void *data,
  				      const int start_pos, const int end_pos)
  {
  	if (*count == 0)
  		return 0;
  	BUG_ON(*pos < start_pos);
  	if (end_pos < 0 || *pos < end_pos) {
  		unsigned int copy = (end_pos < 0 ? *count
  				     : min(*count, end_pos - *pos));
  		data += *pos - start_pos;
  		if (*kbuf) {
  			memcpy(*kbuf, data, copy);
  			*kbuf += copy;
  		} else if (__copy_to_user(*ubuf, data, copy))
  			return -EFAULT;
  		else
  			*ubuf += copy;
  		*pos += copy;
  		*count -= copy;
  	}
  	return 0;
  }
  
  static inline int user_regset_copyin(unsigned int *pos, unsigned int *count,
  				     const void **kbuf,
  				     const void __user **ubuf, void *data,
  				     const int start_pos, const int end_pos)
  {
  	if (*count == 0)
  		return 0;
  	BUG_ON(*pos < start_pos);
  	if (end_pos < 0 || *pos < end_pos) {
  		unsigned int copy = (end_pos < 0 ? *count
  				     : min(*count, end_pos - *pos));
  		data += *pos - start_pos;
  		if (*kbuf) {
  			memcpy(data, *kbuf, copy);
  			*kbuf += copy;
  		} else if (__copy_from_user(data, *ubuf, copy))
  			return -EFAULT;
  		else
  			*ubuf += copy;
  		*pos += copy;
  		*count -= copy;
  	}
  	return 0;
  }
  
  /*
   * These two parallel the two above, but for portions of a regset layout
   * that always read as all-zero or for which writes are ignored.
   */
  static inline int user_regset_copyout_zero(unsigned int *pos,
  					   unsigned int *count,
  					   void **kbuf, void __user **ubuf,
  					   const int start_pos,
  					   const int end_pos)
  {
  	if (*count == 0)
  		return 0;
  	BUG_ON(*pos < start_pos);
  	if (end_pos < 0 || *pos < end_pos) {
  		unsigned int copy = (end_pos < 0 ? *count
  				     : min(*count, end_pos - *pos));
  		if (*kbuf) {
  			memset(*kbuf, 0, copy);
  			*kbuf += copy;
  		} else if (__clear_user(*ubuf, copy))
  			return -EFAULT;
  		else
  			*ubuf += copy;
  		*pos += copy;
  		*count -= copy;
  	}
  	return 0;
  }
  
  static inline int user_regset_copyin_ignore(unsigned int *pos,
  					    unsigned int *count,
  					    const void **kbuf,
  					    const void __user **ubuf,
  					    const int start_pos,
  					    const int end_pos)
  {
  	if (*count == 0)
  		return 0;
  	BUG_ON(*pos < start_pos);
  	if (end_pos < 0 || *pos < end_pos) {
  		unsigned int copy = (end_pos < 0 ? *count
  				     : min(*count, end_pos - *pos));
  		if (*kbuf)
  			*kbuf += copy;
  		else
  			*ubuf += copy;
  		*pos += copy;
  		*count -= copy;
  	}
  	return 0;
  }
  
  /**
   * copy_regset_to_user - fetch a thread's user_regset data into user memory
   * @target:	thread to be examined
   * @view:	&struct user_regset_view describing user thread machine state
   * @setno:	index in @view->regsets
   * @offset:	offset into the regset data, in bytes
   * @size:	amount of data to copy, in bytes
   * @data:	user-mode pointer to copy into
   */
  static inline int copy_regset_to_user(struct task_struct *target,
  				      const struct user_regset_view *view,
  				      unsigned int setno,
  				      unsigned int offset, unsigned int size,
  				      void __user *data)
  {
  	const struct user_regset *regset = &view->regsets[setno];
  
  	if (!regset->get)
  		return -EOPNOTSUPP;
  
  	if (!access_ok(VERIFY_WRITE, data, size))
  		return -EFAULT;
  
  	return regset->get(target, regset, offset, size, NULL, data);
  }
  
  /**
   * copy_regset_from_user - store into thread's user_regset data from user memory
   * @target:	thread to be examined
   * @view:	&struct user_regset_view describing user thread machine state
   * @setno:	index in @view->regsets
   * @offset:	offset into the regset data, in bytes
   * @size:	amount of data to copy, in bytes
   * @data:	user-mode pointer to copy from
   */
  static inline int copy_regset_from_user(struct task_struct *target,
  					const struct user_regset_view *view,
  					unsigned int setno,
  					unsigned int offset, unsigned int size,
  					const void __user *data)
  {
  	const struct user_regset *regset = &view->regsets[setno];
  
  	if (!regset->set)
  		return -EOPNOTSUPP;
  
  	if (!access_ok(VERIFY_READ, data, size))
  		return -EFAULT;
  
  	return regset->set(target, regset, offset, size, NULL, data);
  }
  
  
  #endif	/* <linux/regset.h> */