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 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * User-mode machine state access
  *
  * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.
  *
  * 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;
 
 struct membuf {
     void *p;
     size_t left;
 };
 
 static inline int membuf_zero(struct membuf *s, size_t size)
 {
     if (s->left) {
         if (size > s->left)
             size = s->left;
         memset(s->p, 0, size);
         s->p += size;
         s->left -= size;
     }
     return s->left;
 }
 
 static inline int membuf_write(struct membuf *s, const void *v, size_t size)
 {
     if (s->left) {
         if (size > s->left)
             size = s->left;
         memcpy(s->p, v, size);
         s->p += size;
         s->left -= size;
     }
     return s->left;
 }
 
 static inline struct membuf membuf_at(const struct membuf *s, size_t offs)
 {
     struct membuf n = *s;
 
     if (offs > n.left)
         offs = n.left;
     n.p += offs;
     n.left -= offs;
 
     return n;
 }
 
 /* current s->p must be aligned for v; v must be a scalar */
 #define membuf_store(s, v)              \
 ({                          \
     struct membuf *__s = (s);           \
         if (__s->left) {                \
         typeof(v) __v = (v);            \
         size_t __size = sizeof(__v);        \
         if (unlikely(__size > __s->left)) { \
             __size = __s->left;     \
             memcpy(__s->p, &__v, __size);   \
         } else {                \
             *(typeof(__v + 0) *)__s->p = __v;   \
         }                   \
         __s->p += __size;           \
         __s->left -= __size;            \
     }                       \
     __s->left;})
 
 /**
  * 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);
 
 typedef int user_regset_get2_fn(struct task_struct *target,
                    const struct user_regset *regset,
                    struct membuf to);
 
 /**
  * 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).  For dynamically-sized
  * regsets, @n must contain the maximum possible number of slots for the
  * regset.
  *
  * For backward compatibility, the @get and @set methods must pad to, or
  * accept, @n * @size bytes, even if the current regset size is smaller.
  * The precise semantics of these operations depend on the regset being
  * accessed.
  *
  * The functions to which &struct user_regset members point 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_get2_fn     *regset_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);
 
 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;
 }
 
 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;
 }
 
 extern int regset_get(struct task_struct *target,
               const struct user_regset *regset,
               unsigned int size, void *data);
 
 extern int regset_get_alloc(struct task_struct *target,
                 const struct user_regset *regset,
                 unsigned int size,
                 void **data);
 
 extern 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);
 
 /**
  * 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(data, size))
         return -EFAULT;
 
     return regset->set(target, regset, offset, size, NULL, data);
 }
 
 #endif  /* <linux/regset.h> */

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