struct user_regset — accessible thread CPU state
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;
}; Function to fetch values.
Function to store values.
Function to report if regset is active, or NULL.
Function to write data back to user memory, or NULL.
Number of slots (registers).
Size in bytes of a slot (register).
Required alignment, in bytes.
Bias from natural indexing.
ELF note n_type value used in core dumps.
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.