// 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 and darwin, runtime.tls_g is a normal variable. // TLS offset is computed in x_cgo_inittls. #ifdef GOOS_android #define TLSG_IS_VARIABLE #endif #ifdef GOOS_darwin #define TLSG_IS_VARIABLE #endif // 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 BIC $3, R0 // Darwin/ARM might return unaligned pointer MOVW runtime·tls_g(SB), R11 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 BIC $3, R0 // Darwin/ARM might return unaligned pointer MOVW runtime·tls_g(SB), R11 ADD R11, R0 MOVW 0(R0), g RET // This is called from rt0_go, which runs on the system stack // using the initial stack allocated by the OS. // It calls back into standard C using the BL (R4) below. // To do that, the stack pointer must be 8-byte-aligned // on some systems, notably FreeBSD. // The ARM ABI says the stack pointer must be 8-byte-aligned // on entry to any function, but only FreeBSD's C library seems to care. // The caller was 8-byte aligned, but we push an LR. // Declare a dummy word ($4, not $0) to make sure the // frame is 8 bytes and stays 8-byte-aligned. TEXT runtime·_initcgo(SB),NOSPLIT,$4 #ifndef GOOS_nacl // if there is an _cgo_init, call it. MOVW _cgo_init(SB), R4 CMP $0, R4 B.EQ nocgo MRC 15, 0, R0, C13, C0, 3 // load TLS base pointer MOVW R0, R3 // arg 3: TLS base pointer #ifdef TLSG_IS_VARIABLE MOVW $runtime·tls_g(SB), R2 // arg 2: &tls_g #else MOVW $0, R2 // arg 2: not used when using platform tls #endif MOVW $setg_gcc<>(SB), R1 // arg 1: setg MOVW g, R0 // arg 0: G BL (R4) // will clobber R0-R3 #endif nocgo: RET // void setg_gcc(G*); set g called from gcc. TEXT setg_gcc<>(SB),NOSPLIT,$0 MOVW R0, g B runtime·save_g(SB) #ifdef TLSG_IS_VARIABLE GLOBL runtime·tls_g+0(SB), NOPTR, $4 #else GLOBL runtime·tls_g+0(SB), TLSBSS, $4 #endif