[dev.cc] runtime: convert Plan 9 port to Go

Thanks to Aram H?v?rneanu, Nick Owens
and Russ Cox for the early reviews.

LGTM=aram, rsc
R=rsc, lucio.dere, aram, ality
CC=golang-codereviews, mischief
https://codereview.appspot.com/175370043

1 files changed, 70 insertions, 0 deletions

diff --git a/src/runtime/mem_plan9.go b/src/runtime/mem_plan9.go
new file mode 100644
index 000000000..a5d7c1a4c
--- /dev/null
+++ b/src/runtime/mem_plan9.go
@@ -0,0 +1,70 @@
+// Copyright 2010 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.
+
+package runtime
+
+import "unsafe"
+
+var bloc uintptr
+var memlock mutex
+
+const memRound = _PAGESIZE - 1
+
+func initBloc() {
+	bloc = uintptr(unsafe.Pointer(&end))
+}
+
+func sbrk(n uintptr) unsafe.Pointer {
+	lock(&memlock)
+	// Plan 9 sbrk from /sys/src/libc/9sys/sbrk.c
+	bl := (bloc + memRound) &^ memRound
+	if brk_(unsafe.Pointer(bl+n)) < 0 {
+		unlock(&memlock)
+		return nil
+	}
+	bloc = bl + n
+	unlock(&memlock)
+	return unsafe.Pointer(bl)
+}
+
+func sysAlloc(n uintptr, stat *uint64) unsafe.Pointer {
+	p := sbrk(n)
+	if p != nil {
+		xadd64(stat, int64(n))
+	}
+	return p
+}
+
+func sysFree(v unsafe.Pointer, n uintptr, stat *uint64) {
+	xadd64(stat, -int64(n))
+	lock(&memlock)
+	// from tiny/mem.c
+	// Push pointer back if this is a free
+	// of the most recent sysAlloc.
+	n += (n + memRound) &^ memRound
+	if bloc == uintptr(v)+n {
+		bloc -= n
+	}
+	unlock(&memlock)
+}
+
+func sysUnused(v unsafe.Pointer, n uintptr) {
+}
+
+func sysUsed(v unsafe.Pointer, n uintptr) {
+}
+
+func sysMap(v unsafe.Pointer, n uintptr, reserved bool, stat *uint64) {
+	// sysReserve has already allocated all heap memory,
+	// but has not adjusted stats.
+	xadd64(stat, int64(n))
+}
+
+func sysFault(v unsafe.Pointer, n uintptr) {
+}
+
+func sysReserve(v unsafe.Pointer, n uintptr, reserved *bool) unsafe.Pointer {
+	*reserved = true
+	return sbrk(n)
+}