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  // +build !faketime
     7  
     8  #include "go_asm.h"
     9  #include "go_tls.h"
    10  #include "textflag.h"
    11  
    12  #define SYS_clock_gettime	228
    13  
    14  // func time.now() (sec int64, nsec int32, mono int64)
    15  TEXT time·now(SB),NOSPLIT,$16-24
    16  	MOVQ	SP, R12 // Save old SP; R12 unchanged by C code.
    17  
    18  #ifdef GOEXPERIMENT_regabig
    19  	MOVQ	g_m(R14), BX // BX unchanged by C code.
    20  #else
    21  	get_tls(CX)
    22  	MOVQ	g(CX), AX
    23  	MOVQ	g_m(AX), BX // BX unchanged by C code.
    24  #endif
    25  
    26  	// Store CLOCK_REALTIME results directly to return space.
    27  	LEAQ	sec+0(FP), SI
    28  
    29  	// Set vdsoPC and vdsoSP for SIGPROF traceback.
    30  	// Save the old values on stack and restore them on exit,
    31  	// so this function is reentrant.
    32  	MOVQ	m_vdsoPC(BX), CX
    33  	MOVQ	m_vdsoSP(BX), DX
    34  	MOVQ	CX, 0(SP)
    35  	MOVQ	DX, 8(SP)
    36  
    37  	MOVQ	-8(SI), CX	// Sets CX to function return address.
    38  	MOVQ	CX, m_vdsoPC(BX)
    39  	MOVQ	SI, m_vdsoSP(BX)
    40  
    41  #ifdef GOEXPERIMENT_regabig
    42  	CMPQ	R14, m_curg(BX)	// Only switch if on curg.
    43  #else
    44  	CMPQ	AX, m_curg(BX)	// Only switch if on curg.
    45  #endif
    46  	JNE	noswitch
    47  
    48  	MOVQ	m_g0(BX), DX
    49  	MOVQ	(g_sched+gobuf_sp)(DX), SP	// Set SP to g0 stack
    50  
    51  noswitch:
    52  	SUBQ	$16, SP		// Space for monotonic time results
    53  	ANDQ	$~15, SP	// Align for C code
    54  
    55  	MOVL	$0, DI // CLOCK_REALTIME
    56  	MOVQ	runtime·vdsoClockgettimeSym(SB), AX
    57  	CMPQ	AX, $0
    58  	JEQ	fallback
    59  	CALL	AX
    60  
    61  	MOVL	$1, DI // CLOCK_MONOTONIC
    62  	LEAQ	0(SP), SI
    63  	MOVQ	runtime·vdsoClockgettimeSym(SB), AX
    64  	CALL	AX
    65  
    66  ret:
    67  	MOVQ	0(SP), AX	// sec
    68  	MOVQ	8(SP), DX	// nsec
    69  
    70  	MOVQ	R12, SP		// Restore real SP
    71  	// Restore vdsoPC, vdsoSP
    72  	// We don't worry about being signaled between the two stores.
    73  	// If we are not in a signal handler, we'll restore vdsoSP to 0,
    74  	// and no one will care about vdsoPC. If we are in a signal handler,
    75  	// we cannot receive another signal.
    76  	MOVQ	8(SP), CX
    77  	MOVQ	CX, m_vdsoSP(BX)
    78  	MOVQ	0(SP), CX
    79  	MOVQ	CX, m_vdsoPC(BX)
    80  
    81  	// sec is in AX, nsec in DX
    82  	// return nsec in AX
    83  	IMULQ	$1000000000, AX
    84  	ADDQ	DX, AX
    85  	MOVQ	AX, mono+16(FP)
    86  	RET
    87  
    88  fallback:
    89  	MOVQ	$SYS_clock_gettime, AX
    90  	SYSCALL
    91  
    92  	MOVL	$1, DI // CLOCK_MONOTONIC
    93  	LEAQ	0(SP), SI
    94  	MOVQ	$SYS_clock_gettime, AX
    95  	SYSCALL
    96  
    97  	JMP	ret
    98
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