1STRUCT USER_REGSET(9) Machine State STRUCT USER_REGSET(9)
2
6 struct_user_regset - accessible thread CPU state
7
9 struct user_regset {
10 user_regset_get_fn * get;
11 user_regset_set_fn * set;
12 user_regset_active_fn * active;
13 user_regset_writeback_fn * writeback;
14 unsigned int n;
15 unsigned int size;
16 unsigned int align;
17 unsigned int bias;
18 unsigned int core_note_type;
19 };
20
22 get
23 Function to fetch values.
24 set
26 Function to store values.
27 active
29 Function to report if regset is active, or NULL.
30 writeback
32 Function to write data back to user memory, or NULL.
33 n
35 Number of slots (registers).
36 size
38 Size in bytes of a slot (register).
39 align
41 Required alignment, in bytes.
42 bias
44 Bias from natural indexing.
45 core_note_type
47 ELF note n_type value used in core dumps.
48
50 This data structure describes a machine resource we call a register
51 set. This is part of the state of an individual thread, not necessarily
52 actual CPU registers per se. A register set consists of a number of
53 similar slots, given by n. Each slot is size bytes, and aligned to
54 align bytes (which is at least size).
55 These functions must be called only on the current thread or on a
57 thread that is in TASK_STOPPED or TASK_TRACED state, that we are
58 guaranteed will not be woken up and return to user mode, and that we
59 have called wait_task_inactive on. (The target thread always might wake
60 up for SIGKILL while these functions are working, in which case that
61 thread´s user_regset state might be scrambled.)
62 The pos argument must be aligned according to align; the count argument
64 must be a multiple of size. These functions are not responsible for
65 checking for invalid arguments.
66 When there is a natural value to use as an index, bias gives the
68 difference between the natural index and the slot index for the
69 register set. For example, x86 GDT segment descriptors form a regset;
70 the segment selector produces a natural index, but only a subset of
71 that index space is available as a regset (the TLS slots); subtracting
72 bias from a segment selector index value computes the regset slot.
73 If nonzero, core_note_type gives the n_type field (NT_* value) of the
75 core file note in which this regset´s data appears. NT_PRSTATUS is a
76 special case in that the regset data starts at offsetof(struct
77 elf_prstatus, pr_reg) into the note data; that is part of the
78 per-machine ELF formats userland knows about. In other cases, the core
79 file note contains exactly the whole regset (n * size) and nothing
80 else. The core file note is normally omitted when there is an active
81 function and it returns zero.
82Kernel Hackers Manual 2.6. June 2019 STRUCT USER_REGSET(9)