1// Copyright 2016 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#include "go_asm.h"
6#include "go_tls.h"
7#include "funcdata.h"
8#include "textflag.h"
9
10// We have to resort to TLS variable to save g (R13).
11// One reason is that external code might trigger
12// SIGSEGV, and our runtime.sigtramp don't even know we
13// are in external code, and will continue to use R13,
14// this might well result in another SIGSEGV.
15
16// save_g saves the g register into pthread-provided
17// thread-local memory, so that we can call externally compiled
18// s390x code that will overwrite this register.
19//
20// If !iscgo, this is a no-op.
21//
22// NOTE: setg_gcc<> assume this clobbers only R10 and R11.
23TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0-0
24	MOVB	runtime·iscgo(SB),  R10
25	CMPBEQ	R10, $0, nocgo
26	MOVW	AR0, R11
27	SLD	$32, R11
28	MOVW	AR1, R11
29	MOVD	runtime·tls_g(SB), R10
30	MOVD	g, 0(R10)(R11*1)
31nocgo:
32	RET
33
34// load_g loads the g register from pthread-provided
35// thread-local memory, for use after calling externally compiled
36// s390x code that overwrote those registers.
37//
38// This is never called directly from C code (it doesn't have to
39// follow the C ABI), but it may be called from a C context, where the
40// usual Go registers aren't set up.
41//
42// NOTE: _cgo_topofstack assumes this only clobbers g (R13), R10 and R11.
43TEXT runtime·load_g(SB),NOSPLIT|NOFRAME,$0-0
44	MOVW	AR0, R11
45	SLD	$32, R11
46	MOVW	AR1, R11
47	MOVD	runtime·tls_g(SB), R10
48	MOVD	0(R10)(R11*1), g
49	RET
50
51GLOBL runtime·tls_g+0(SB),TLSBSS,$8
52