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
88