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// +build !windows
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(R10).
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 R10,
16// this might as well result in another SIGSEGV.
17// Note: both functions will clobber R0 and R11 and
18// can be called from 5c ABI code.
19
20// On android and darwin, runtime.tls_g is a normal variable.
21// TLS offset is computed in x_cgo_inittls.
22#ifdef GOOS_android
23#define TLSG_IS_VARIABLE
24#endif
25#ifdef GOOS_darwin
26#define TLSG_IS_VARIABLE
27#endif
28
29// save_g saves the g register into pthread-provided
30// thread-local memory, so that we can call externally compiled
31// ARM code that will overwrite those registers.
32// NOTE: runtime.gogo assumes that R1 is preserved by this function.
33//       runtime.mcall assumes this function only clobbers R0 and R11.
34// Returns with g in R0.
35TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0
36	// If the host does not support MRC the linker will replace it with
37	// a call to runtime.read_tls_fallback which jumps to __kuser_get_tls.
38	// The replacement function saves LR in R11 over the call to read_tls_fallback.
39	MRC	15, 0, R0, C13, C0, 3 // fetch TLS base pointer
40	BIC $3, R0 // Darwin/ARM might return unaligned pointer
41	MOVW	runtime·tls_g(SB), R11
42	ADD	R11, R0
43	MOVW	g, 0(R0)
44	MOVW	g, R0 // preserve R0 across call to setg<>
45	RET
46
47// load_g loads the g register from pthread-provided
48// thread-local memory, for use after calling externally compiled
49// ARM code that overwrote those registers.
50TEXT runtime·load_g(SB),NOSPLIT,$0
51	// See save_g
52	MRC	15, 0, R0, C13, C0, 3 // fetch TLS base pointer
53	BIC $3, R0 // Darwin/ARM might return unaligned pointer
54	MOVW	runtime·tls_g(SB), R11
55	ADD	R11, R0
56	MOVW	0(R0), g
57	RET
58
59// This is called from rt0_go, which runs on the system stack
60// using the initial stack allocated by the OS.
61// It calls back into standard C using the BL (R4) below.
62// To do that, the stack pointer must be 8-byte-aligned
63// on some systems, notably FreeBSD.
64// The ARM ABI says the stack pointer must be 8-byte-aligned
65// on entry to any function, but only FreeBSD's C library seems to care.
66// The caller was 8-byte aligned, but we push an LR.
67// Declare a dummy word ($4, not $0) to make sure the
68// frame is 8 bytes and stays 8-byte-aligned.
69TEXT runtime·_initcgo(SB),NOSPLIT,$4
70	// if there is an _cgo_init, call it.
71	MOVW	_cgo_init(SB), R4
72	CMP	$0, R4
73	B.EQ	nocgo
74	MRC     15, 0, R0, C13, C0, 3 	// load TLS base pointer
75	MOVW 	R0, R3 			// arg 3: TLS base pointer
76#ifdef TLSG_IS_VARIABLE
77	MOVW 	$runtime·tls_g(SB), R2 	// arg 2: &tls_g
78#else
79	MOVW	$0, R2			// arg 2: not used when using platform tls
80#endif
81	MOVW	$setg_gcc<>(SB), R1 	// arg 1: setg
82	MOVW	g, R0 			// arg 0: G
83	BL	(R4) // will clobber R0-R3
84nocgo:
85	RET
86
87// void setg_gcc(G*); set g called from gcc.
88TEXT setg_gcc<>(SB),NOSPLIT,$0
89	MOVW	R0, g
90	B		runtime·save_g(SB)
91
92#ifdef TLSG_IS_VARIABLE
93#ifdef GOOS_android
94// Use the free TLS_SLOT_APP slot #2 on Android Q.
95// Earlier androids are set up in gcc_android.c.
96DATA runtime·tls_g+0(SB)/4, $8
97#endif
98GLOBL runtime·tls_g+0(SB), NOPTR, $4
99#else
100GLOBL runtime·tls_g+0(SB), TLSBSS, $4
101#endif
102