Current File : //usr/local/go/src/runtime/time_linux_amd64.s
// Copyright 2021 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.
//go:build !faketime
// +build !faketime
#include "go_asm.h"
#include "go_tls.h"
#include "textflag.h"
#define SYS_clock_gettime 228
// func time.now() (sec int64, nsec int32, mono int64)
TEXT time·now(SB),NOSPLIT,$16-24
MOVQ SP, R12 // Save old SP; R12 unchanged by C code.
#ifdef GOEXPERIMENT_regabig
MOVQ g_m(R14), BX // BX unchanged by C code.
#else
get_tls(CX)
MOVQ g(CX), AX
MOVQ g_m(AX), BX // BX unchanged by C code.
#endif
// Store CLOCK_REALTIME results directly to return space.
LEAQ sec+0(FP), SI
// Set vdsoPC and vdsoSP for SIGPROF traceback.
// Save the old values on stack and restore them on exit,
// so this function is reentrant.
MOVQ m_vdsoPC(BX), CX
MOVQ m_vdsoSP(BX), DX
MOVQ CX, 0(SP)
MOVQ DX, 8(SP)
MOVQ -8(SI), CX // Sets CX to function return address.
MOVQ CX, m_vdsoPC(BX)
MOVQ SI, m_vdsoSP(BX)
#ifdef GOEXPERIMENT_regabig
CMPQ R14, m_curg(BX) // Only switch if on curg.
#else
CMPQ AX, m_curg(BX) // Only switch if on curg.
#endif
JNE noswitch
MOVQ m_g0(BX), DX
MOVQ (g_sched+gobuf_sp)(DX), SP // Set SP to g0 stack
noswitch:
SUBQ $16, SP // Space for monotonic time results
ANDQ $~15, SP // Align for C code
MOVL $0, DI // CLOCK_REALTIME
MOVQ runtime·vdsoClockgettimeSym(SB), AX
CMPQ AX, $0
JEQ fallback
CALL AX
MOVL $1, DI // CLOCK_MONOTONIC
LEAQ 0(SP), SI
MOVQ runtime·vdsoClockgettimeSym(SB), AX
CALL AX
ret:
MOVQ 0(SP), AX // sec
MOVQ 8(SP), DX // nsec
MOVQ R12, SP // Restore real SP
// Restore vdsoPC, vdsoSP
// We don't worry about being signaled between the two stores.
// If we are not in a signal handler, we'll restore vdsoSP to 0,
// and no one will care about vdsoPC. If we are in a signal handler,
// we cannot receive another signal.
MOVQ 8(SP), CX
MOVQ CX, m_vdsoSP(BX)
MOVQ 0(SP), CX
MOVQ CX, m_vdsoPC(BX)
// sec is in AX, nsec in DX
// return nsec in AX
IMULQ $1000000000, AX
ADDQ DX, AX
MOVQ AX, mono+16(FP)
RET
fallback:
MOVQ $SYS_clock_gettime, AX
SYSCALL
MOVL $1, DI // CLOCK_MONOTONIC
LEAQ 0(SP), SI
MOVQ $SYS_clock_gettime, AX
SYSCALL
JMP ret
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