1/* Restartable Sequences Linux riscv architecture header.
2 Copyright (C) 2021-2026 Free Software Foundation, Inc.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <bits/endian.h>
19
20#ifndef _SYS_RSEQ_H
21# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
22#endif
23
24/* RSEQ_SIG is a signature required before each abort handler code.
25
26 It is a 32-bit value that maps to actual architecture code compiled
27 into applications and libraries. It needs to be defined for each
28 architecture. When choosing this value, it needs to be taken into
29 account that generating invalid instructions may have ill effects on
30 tools like objdump, and may also have impact on the CPU speculative
31 execution efficiency in some cases.
32
33 Select the instruction "csrw mhartid, x0" as the RSEQ_SIG. Unlike
34 other architectures, the ebreak instruction has no immediate field for
35 distinguishing purposes. Hence, ebreak is not suitable as RSEQ_SIG.
36 "csrw mhartid, x0" can also satisfy the RSEQ requirement because it
37 is an uncommon instruction and will raise an illegal instruction
38 exception when executed in all modes. */
39
40#if __BYTE_ORDER == __LITTLE_ENDIAN
41#define RSEQ_SIG 0xf1401073
42#else
43/* RSEQ is currently only supported on Little-Endian. */
44#endif