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