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// Copyright 2014 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(R10).
// 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 R10,
// this might as well result in another SIGSEGV.
// Note: both functions will clobber R0 and R11 and
// can be called from 5c ABI code.
// On android, runtime.tlsg is a normal variable.
// TLS offset is computed in x_cgo_inittls.
// save_g saves the g register into pthread-provided
// thread-local memory, so that we can call externally compiled
// ARM code that will overwrite those registers.
// NOTE: runtime.gogo assumes that R1 is preserved by this function.
// runtime.mcall assumes this function only clobbers R0 and R11.
// Returns with g in R0.
TEXT runtime·save_g(SB),NOSPLIT,$-4
#ifdef GOOS_nacl
// nothing to do as nacl/arm does not use TLS at all.
MOVW g, R0 // preserve R0 across call to setg<>
RET
#endif
// If the host does not support MRC the linker will replace it with
// a call to runtime.read_tls_fallback which jumps to __kuser_get_tls.
// The replacement function saves LR in R11 over the call to read_tls_fallback.
MRC 15, 0, R0, C13, C0, 3 // fetch TLS base pointer
// $runtime.tlsg(SB) is a special linker symbol.
// It is the offset from the TLS base pointer to our
// thread-local storage for g.
#ifdef GOOS_android
MOVW runtime·tlsg(SB), R11
#else
MOVW $runtime·tlsg(SB), R11
#endif
ADD R11, R0
MOVW g, 0(R0)
MOVW g, R0 // preserve R0 across call to setg<>
RET
// load_g loads the g register from pthread-provided
// thread-local memory, for use after calling externally compiled
// ARM code that overwrote those registers.
TEXT runtime·load_g(SB),NOSPLIT,$0
#ifdef GOOS_nacl
// nothing to do as nacl/arm does not use TLS at all.
RET
#endif
// See save_g
MRC 15, 0, R0, C13, C0, 3 // fetch TLS base pointer
// $runtime.tlsg(SB) is a special linker symbol.
// It is the offset from the TLS base pointer to our
// thread-local storage for g.
#ifdef GOOS_android
MOVW runtime·tlsg(SB), R11
#else
MOVW $runtime·tlsg(SB), R11
#endif
ADD R11, R0
MOVW 0(R0), g
RET
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