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 gc
6
7#include "textflag.h"
8
9TEXT ·RewindAndSetgid(SB),NOSPLIT|NOFRAME,$0-0
10 // Save link register
11 MOVD R30, R9
12
13 // Rewind stack pointer so anything that happens on the stack
14 // will clobber the test pattern created by the caller
15 ADD $(1024 * 8), RSP
16
17 // Ask signaller to setgid
18 MOVD $·Baton(SB), R0
19 MOVD $1, R1
20storeloop:
21 LDAXRW (R0), R2
22 STLXRW R1, (R0), R3
23 CBNZ R3, storeloop
24
25 // Wait for setgid completion
26 MOVW $0, R1
27 MOVW $0, R2
28loop:
29 LDAXRW (R0), R3
30 CMPW R1, R3
31 BNE loop
32 STLXRW R2, (R0), R3
33 CBNZ R3, loop
34
35 // Restore stack
36 SUB $(1024 * 8), RSP
37
38 MOVD R9, R30
39 RET
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