1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build ppc64 || ppc64le
6
7#include "go_asm.h"
8#include "go_tls.h"
9#include "funcdata.h"
10#include "textflag.h"
11
12// We have to resort to TLS variable to save g (R30).
13// One reason is that external code might trigger
14// SIGSEGV, and our runtime.sigtramp don't even know we
15// are in external code, and will continue to use R30,
16// this might well result in another SIGSEGV.
17
18// save_g saves the g register into pthread-provided
19// thread-local memory, so that we can call externally compiled
20// ppc64 code that will overwrite this register.
21//
22// If !iscgo, this is a no-op.
23//
24// NOTE: setg_gcc<> assume this clobbers only R31.
25TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0-0
26#ifndef GOOS_aix
27#ifndef GOOS_openbsd
28	MOVBZ	runtime·iscgo(SB), R31
29	CMP	R31, $0
30	BEQ	nocgo
31#endif
32#endif
33	MOVD	runtime·tls_g(SB), R31
34	MOVD	g, 0(R31)
35
36nocgo:
37	RET
38
39// load_g loads the g register from pthread-provided
40// thread-local memory, for use after calling externally compiled
41// ppc64 code that overwrote those registers.
42//
43// This is never called directly from C code (it doesn't have to
44// follow the C ABI), but it may be called from a C context, where the
45// usual Go registers aren't set up.
46//
47// NOTE: _cgo_topofstack assumes this only clobbers g (R30), and R31.
48TEXT runtime·load_g(SB),NOSPLIT|NOFRAME,$0-0
49	MOVD	runtime·tls_g(SB), R31
50	MOVD	0(R31), g
51	RET
52
53GLOBL runtime·tls_g+0(SB), TLSBSS+DUPOK, $8
54