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-rw-r--r--src/runtime/tls_s390x.s51
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diff --git a/src/runtime/tls_s390x.s b/src/runtime/tls_s390x.s
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+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "go_asm.h"
+#include "go_tls.h"
+#include "funcdata.h"
+#include "textflag.h"
+
+// We have to resort to TLS variable to save g (R13).
+// One reason is that external code might trigger
+// SIGSEGV, and our runtime.sigtramp don't even know we
+// are in external code, and will continue to use R13,
+// this might well result in another SIGSEGV.
+
+// save_g saves the g register into pthread-provided
+// thread-local memory, so that we can call externally compiled
+// s390x code that will overwrite this register.
+//
+// If !iscgo, this is a no-op.
+//
+// NOTE: setg_gcc<> assume this clobbers only R10 and R11.
+TEXT runtime·save_g(SB),NOSPLIT|NOFRAME,$0-0
+ MOVB runtime·iscgo(SB), R10
+ CMPBEQ R10, $0, nocgo
+ MOVW AR0, R11
+ SLD $32, R11
+ MOVW AR1, R11
+ MOVD runtime·tls_g(SB), R10
+ MOVD g, 0(R10)(R11*1)
+nocgo:
+ RET
+
+// load_g loads the g register from pthread-provided
+// thread-local memory, for use after calling externally compiled
+// s390x code that overwrote those registers.
+//
+// This is never called directly from C code (it doesn't have to
+// follow the C ABI), but it may be called from a C context, where the
+// usual Go registers aren't set up.
+//
+// NOTE: _cgo_topofstack assumes this only clobbers g (R13), R10 and R11.
+TEXT runtime·load_g(SB),NOSPLIT|NOFRAME,$0-0
+ MOVW AR0, R11
+ SLD $32, R11
+ MOVW AR1, R11
+ MOVD runtime·tls_g(SB), R10
+ MOVD 0(R10)(R11*1), g
+ RET
+
+GLOBL runtime·tls_g+0(SB),TLSBSS,$8