1 files changed, 87 insertions, 0 deletions
diff --git a/src/runtime/time_linux_amd64.s b/src/runtime/time_linux_amd64.s
new file mode 100644
index 0000000..1416d23
--- /dev/null
+++ b/src/runtime/time_linux_amd64.s
@@ -0,0 +1,87 @@
+// 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
+
+#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<ABIInternal>(SB),NOSPLIT,$16-24
+	MOVQ	SP, R12 // Save old SP; R12 unchanged by C code.
+
+	MOVQ	g_m(R14), BX // BX unchanged by C code.
+
+	// 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)
+
+	LEAQ	sec+0(FP), DX
+	MOVQ	-8(DX), CX	// Sets CX to function return address.
+	MOVQ	CX, m_vdsoPC(BX)
+	MOVQ	DX, m_vdsoSP(BX)
+
+	CMPQ	R14, m_curg(BX)	// Only switch if on curg.
+	JNE	noswitch
+
+	MOVQ	m_g0(BX), DX
+	MOVQ	(g_sched+gobuf_sp)(DX), SP	// Set SP to g0 stack
+
+noswitch:
+	SUBQ	$32, SP		// Space for two time results
+	ANDQ	$~15, SP	// Align for C code
+
+	MOVL	$0, DI // CLOCK_REALTIME
+	LEAQ	16(SP), SI
+	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	16(SP), AX	// realtime sec
+	MOVQ	24(SP), DI	// realtime nsec (moved to BX below)
+	MOVQ	0(SP), CX	// monotonic sec
+	IMULQ	$1000000000, CX
+	MOVQ	8(SP), DX	// monotonic 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), SI
+	MOVQ	SI, m_vdsoSP(BX)
+	MOVQ	0(SP), SI
+	MOVQ	SI, m_vdsoPC(BX)
+
+	// set result registers; AX is already correct
+	MOVQ	DI, BX
+	ADDQ	DX, CX
+	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