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 #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(R10). 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 R10, 14 // this might as well result in another SIGSEGV. 15 // Note: both functions will clobber R0 and R11 and 16 // can be called from 5c ABI code. 17 18 // On android and darwin, runtime.tlsg is a normal variable. 19 // TLS offset is computed in x_cgo_inittls. 20 #ifdef GOOS_android 21 #define TLSG_IS_VARIABLE 22 #endif 23 #ifdef GOOS_darwin 24 #define TLSG_IS_VARIABLE 25 #endif 26 27 // save_g saves the g register into pthread-provided 28 // thread-local memory, so that we can call externally compiled 29 // ARM code that will overwrite those registers. 30 // NOTE: runtime.gogo assumes that R1 is preserved by this function. 31 // runtime.mcall assumes this function only clobbers R0 and R11. 32 // Returns with g in R0. 33 TEXT runtimesave_g(SB),NOSPLIT,$-4 34 #ifdef GOOS_nacl 35 // nothing to do as nacl/arm does not use TLS at all. 36 MOVW g, R0 // preserve R0 across call to setg<> 37 RET 38 #endif 39 // If the host does not support MRC the linker will replace it with 40 // a call to runtime.read_tls_fallback which jumps to __kuser_get_tls. 41 // The replacement function saves LR in R11 over the call to read_tls_fallback. 42 MRC 15, 0, R0, C13, C0, 3 // fetch TLS base pointer 43 BIC $3, R0 // Darwin/ARM might return unaligned pointer 44 // $runtime.tlsg(SB) is a special linker symbol. 45 // It is the offset from the TLS base pointer to our 46 // thread-local storage for g. 47 #ifdef TLSG_IS_VARIABLE 48 MOVW runtimetlsg(SB), R11 49 #else 50 MOVW $runtimetlsg(SB), R11 51 #endif 52 ADD R11, R0 53 MOVW g, 0(R0) 54 MOVW g, R0 // preserve R0 across call to setg<> 55 RET 56 57 // load_g loads the g register from pthread-provided 58 // thread-local memory, for use after calling externally compiled 59 // ARM code that overwrote those registers. 60 TEXT runtimeload_g(SB),NOSPLIT,$0 61 #ifdef GOOS_nacl 62 // nothing to do as nacl/arm does not use TLS at all. 63 RET 64 #endif 65 // See save_g 66 MRC 15, 0, R0, C13, C0, 3 // fetch TLS base pointer 67 BIC $3, R0 // Darwin/ARM might return unaligned pointer 68 // $runtime.tlsg(SB) is a special linker symbol. 69 // It is the offset from the TLS base pointer to our 70 // thread-local storage for g. 71 #ifdef TLSG_IS_VARIABLE 72 MOVW runtimetlsg(SB), R11 73 #else 74 MOVW $runtimetlsg(SB), R11 75 #endif 76 ADD R11, R0 77 MOVW 0(R0), g 78 RET 79 80 // This is called from rt0_go, which runs on the system stack 81 // using the initial stack allocated by the OS. 82 // It calls back into standard C using the BL (R4) below. 83 // To do that, the stack pointer must be 8-byte-aligned 84 // on some systems, notably FreeBSD. 85 // The ARM ABI says the stack pointer must be 8-byte-aligned 86 // on entry to any function, but only FreeBSD's C library seems to care. 87 // The caller was 8-byte aligned, but we push an LR. 88 // Declare a dummy word ($4, not $0) to make sure the 89 // frame is 8 bytes and stays 8-byte-aligned. 90 TEXT runtime_initcgo(SB),NOSPLIT,$4 91 #ifndef GOOS_nacl 92 // if there is an _cgo_init, call it. 93 MOVW _cgo_init(SB), R4 94 CMP $0, R4 95 B.EQ nocgo 96 MRC 15, 0, R0, C13, C0, 3 // load TLS base pointer 97 MOVW R0, R3 // arg 3: TLS base pointer 98 MOVW $runtimetlsg(SB), R2 // arg 2: tlsg 99 MOVW $setg_gcc<>(SB), R1 // arg 1: setg 100 MOVW g, R0 // arg 0: G 101 BL (R4) // will clobber R0-R3 102 #endif 103 nocgo: 104 RET 105 106 // void setg_gcc(G*); set g called from gcc. 107 TEXT setg_gcc<>(SB),NOSPLIT,$0 108 MOVW R0, g 109 B runtimesave_g(SB) 110 111 #ifdef TLSG_IS_VARIABLE 112 GLOBL runtimetlsg+0(SB), NOPTR, $4 113 #endif 114
