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 ppc64 ppc64le 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 (R30). 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 R30, 16 // this might well result in another SIGSEGV. 17 18 // save_g saves the g register into pthread-provided 19 // thread-local memory, so that we can call externally compiled 20 // ppc64 code that will overwrite this register. 21 // 22 // If !iscgo, this is a no-op. 23 // 24 // NOTE: setg_gcc<> assume this clobbers only R31. 25 TEXT runtimesave_g(SB),NOSPLIT,$-8-0 26 MOVB runtimeiscgo(SB), R31 27 CMP R31, $0 28 BEQ nocgo 29 30 // $runtime.tlsg(SB) is a special linker symbol. 31 // It is the offset from the start of TLS to our 32 // thread-local storage for g. 33 MOVD $runtimetlsg(SB), R31 34 ADD R13, R31 35 // The actual TLS base is 0x7000 below R13 36 SUB $0x7000, R31 37 38 // Store g in TLS 39 MOVD g, 0(R31) 40 41 nocgo: 42 RET 43 44 // load_g loads the g register from pthread-provided 45 // thread-local memory, for use after calling externally compiled 46 // ppc64 code that overwrote those registers. 47 // 48 // This is never called directly from C code (it doesn't have to 49 // follow the C ABI), but it may be called from a C context, where the 50 // usual Go registers aren't set up. 51 // 52 // NOTE: _cgo_topofstack assumes this only clobbers g (R30), and R31. 53 TEXT runtimeload_g(SB),NOSPLIT,$-8-0 54 MOVD $runtimetlsg(SB), R31 55 // R13 is the C ABI TLS base pointer + 0x7000 56 ADD R13, R31 57 SUB $0x7000, R31 58 59 MOVD 0(R31), g 60 RET 61
