From effc6710d97a71f1ffd419ad6e98f8b544b4f44f Mon Sep 17 00:00:00 2001
From: Achilleas Anagnostopoulos <achilleas.imap.mbox@gmail.com>
Date: Fri, 30 Jun 2017 08:04:10 +0100
Subject: [PATCH] Initialize Go memory allocator

---
 kernel/goruntime/bootstrap.go      | 30 ++++++++++++++++++++++++++++++
 kernel/goruntime/bootstrap_test.go | 11 +++++++++++
 kernel/kmain/kmain.go              |  3 +++
 3 files changed, 44 insertions(+)

diff --git a/kernel/goruntime/bootstrap.go b/kernel/goruntime/bootstrap.go
index 8e3b63f..e78cc35 100644
--- a/kernel/goruntime/bootstrap.go
+++ b/kernel/goruntime/bootstrap.go
@@ -5,6 +5,7 @@ package goruntime
 import (
 	"unsafe"
 
+	"github.com/achilleasa/gopher-os/kernel"
 	"github.com/achilleasa/gopher-os/kernel/mem"
 	"github.com/achilleasa/gopher-os/kernel/mem/pmm/allocator"
 	"github.com/achilleasa/gopher-os/kernel/mem/vmm"
@@ -14,8 +15,12 @@ var (
 	mapFn                = vmm.Map
 	earlyReserveRegionFn = vmm.EarlyReserveRegion
 	frameAllocFn         = allocator.AllocFrame
+	mallocInitFn         = mallocInit
 )
 
+//go:linkname mallocInit runtime.mallocinit
+func mallocInit()
+
 //go:linkname mSysStatInc runtime.mSysStatInc
 func mSysStatInc(*uint64, uintptr)
 
@@ -100,6 +105,30 @@ func sysAlloc(size uintptr, sysStat *uint64) unsafe.Pointer {
 	return unsafe.Pointer(regionStartAddr)
 }
 
+// nanotime returns a monotonically increasing clock value. This is a dummy
+// implementation and will be replaced when the timekeeper package is
+// implemented.
+//
+// This function replaces runtime.nanotime and is invoked by the Go allocator
+// when a span allocation is performed.
+//
+//go:redirect-from runtime.nanotime
+//go:nosplit
+func nanotime() uint64 {
+	// Use a dummy loop to prevent the compiler from inlining this function.
+	for i := 0; i < 100; i++ {
+	}
+	return 1
+}
+
+// Init enables support for various Go runtime features. After a call to init
+// the following runtime features become available for use:
+//  - heap memory allocation (new, make e.t.c)
+func Init() *kernel.Error {
+	mallocInitFn()
+	return nil
+}
+
 func init() {
 	// Dummy calls so the compiler does not optimize away the functions in
 	// this file.
@@ -112,4 +141,5 @@ func init() {
 	sysReserve(zeroPtr, 0, &reserved)
 	sysMap(zeroPtr, 0, reserved, &stat)
 	sysAlloc(0, &stat)
+	stat = nanotime()
 }
diff --git a/kernel/goruntime/bootstrap_test.go b/kernel/goruntime/bootstrap_test.go
index 603f123..0ab567f 100644
--- a/kernel/goruntime/bootstrap_test.go
+++ b/kernel/goruntime/bootstrap_test.go
@@ -235,3 +235,14 @@ func TestSysAlloc(t *testing.T) {
 		}
 	})
 }
+
+func TestInit(t *testing.T) {
+	defer func() {
+		mallocInitFn = mallocInit
+	}()
+	mallocInitFn = func() {}
+
+	if err := Init(); err != nil {
+		t.Fatal(t)
+	}
+}
diff --git a/kernel/kmain/kmain.go b/kernel/kmain/kmain.go
index 2c59342..631d67e 100644
--- a/kernel/kmain/kmain.go
+++ b/kernel/kmain/kmain.go
@@ -2,6 +2,7 @@ package kmain
 
 import (
 	"github.com/achilleasa/gopher-os/kernel"
+	"github.com/achilleasa/gopher-os/kernel/goruntime"
 	"github.com/achilleasa/gopher-os/kernel/hal"
 	"github.com/achilleasa/gopher-os/kernel/hal/multiboot"
 	"github.com/achilleasa/gopher-os/kernel/mem/pmm/allocator"
@@ -34,6 +35,8 @@ func Kmain(multibootInfoPtr, kernelStart, kernelEnd uintptr) {
 		panic(err)
 	} else if err = vmm.Init(); err != nil {
 		panic(err)
+	} else if err = goruntime.Init(); err != nil {
+		panic(err)
 	}
 
 	// Use kernel.Panic instead of panic to prevent the compiler from