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Diffstat (limited to 'src/runtime/tls_arm.s')
| -rw-r--r-- | src/runtime/tls_arm.s | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/src/runtime/tls_arm.s b/src/runtime/tls_arm.s new file mode 100644 index 0000000..e42de8d --- /dev/null +++ b/src/runtime/tls_arm.s @@ -0,0 +1,98 @@ +// 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. + +// +build !windows + +#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.tls_g is a normal variable. +// TLS offset is computed in x_cgo_inittls. +#ifdef GOOS_android +#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|NOFRAME,$0 + // 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 + // 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 + // 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 +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 +#ifdef GOOS_android +// Use the free TLS_SLOT_APP slot #2 on Android Q. +// Earlier androids are set up in gcc_android.c. +DATA runtime·tls_g+0(SB)/4, $8 +#endif +GLOBL runtime·tls_g+0(SB), NOPTR, $4 +#else +GLOBL runtime·tls_g+0(SB), TLSBSS, $4 +#endif |