time_linux_amd64.s

Documentation: runtime

     1// Copyright 2021 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//go:build !faketime
     6
     7#include "go_asm.h"
     8#include "go_tls.h"
     9#include "textflag.h"
    10
    11#define SYS_clock_gettime	228
    12
    13// func time.now() (sec int64, nsec int32, mono int64)
    14TEXT time·now<ABIInternal>(SB),NOSPLIT,$16-24
    15	MOVQ	SP, R12 // Save old SP; R12 unchanged by C code.
    16
    17	MOVQ	g_m(R14), BX // BX unchanged by C code.
    18
    19	// Set vdsoPC and vdsoSP for SIGPROF traceback.
    20	// Save the old values on stack and restore them on exit,
    21	// so this function is reentrant.
    22	MOVQ	m_vdsoPC(BX), CX
    23	MOVQ	m_vdsoSP(BX), DX
    24	MOVQ	CX, 0(SP)
    25	MOVQ	DX, 8(SP)
    26
    27	LEAQ	sec+0(FP), DX
    28	MOVQ	-8(DX), CX	// Sets CX to function return address.
    29	MOVQ	CX, m_vdsoPC(BX)
    30	MOVQ	DX, m_vdsoSP(BX)
    31
    32	CMPQ	R14, m_curg(BX)	// Only switch if on curg.
    33	JNE	noswitch
    34
    35	MOVQ	m_g0(BX), DX
    36	MOVQ	(g_sched+gobuf_sp)(DX), SP	// Set SP to g0 stack
    37
    38noswitch:
    39	SUBQ	$32, SP		// Space for two time results
    40	ANDQ	$~15, SP	// Align for C code
    41
    42	MOVL	$0, DI // CLOCK_REALTIME
    43	LEAQ	16(SP), SI
    44	MOVQ	runtime·vdsoClockgettimeSym(SB), AX
    45	CMPQ	AX, $0
    46	JEQ	fallback
    47	CALL	AX
    48
    49	MOVL	$1, DI // CLOCK_MONOTONIC
    50	LEAQ	0(SP), SI
    51	MOVQ	runtime·vdsoClockgettimeSym(SB), AX
    52	CALL	AX
    53
    54ret:
    55	MOVQ	16(SP), AX	// realtime sec
    56	MOVQ	24(SP), DI	// realtime nsec (moved to BX below)
    57	MOVQ	0(SP), CX	// monotonic sec
    58	IMULQ	$1000000000, CX
    59	MOVQ	8(SP), DX	// monotonic nsec
    60
    61	MOVQ	R12, SP		// Restore real SP
    62
    63	// Restore vdsoPC, vdsoSP
    64	// We don't worry about being signaled between the two stores.
    65	// If we are not in a signal handler, we'll restore vdsoSP to 0,
    66	// and no one will care about vdsoPC. If we are in a signal handler,
    67	// we cannot receive another signal.
    68	MOVQ	8(SP), SI
    69	MOVQ	SI, m_vdsoSP(BX)
    70	MOVQ	0(SP), SI
    71	MOVQ	SI, m_vdsoPC(BX)
    72
    73	// set result registers; AX is already correct
    74	MOVQ	DI, BX
    75	ADDQ	DX, CX
    76	RET
    77
    78fallback:
    79	MOVQ	$SYS_clock_gettime, AX
    80	SYSCALL
    81
    82	MOVL	$1, DI // CLOCK_MONOTONIC
    83	LEAQ	0(SP), SI
    84	MOVQ	$SYS_clock_gettime, AX
    85	SYSCALL
    86
    87	JMP	ret
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