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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 void 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;
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;
}
}
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> */