[dev.cc] runtime: convert memory allocator and garbage collector to Go

The conversion was done with an automated tool and then
modified only as necessary to make it compile and run.

[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]

LGTM=r
R=r
CC=austin, dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/167540043

1 files changed, 135 insertions, 0 deletions

diff --git a/src/runtime/mem_linux.go b/src/runtime/mem_linux.go
new file mode 100644
index 0000000000..0ef6eeac18
--- /dev/null
+++ b/src/runtime/mem_linux.go
@@ -0,0 +1,135 @@
+// 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"
+
+const (
+	_PAGE_SIZE = 4096
+	_EACCES    = 13
+)
+
+// NOTE: vec must be just 1 byte long here.
+// Mincore returns ENOMEM if any of the pages are unmapped,
+// but we want to know that all of the pages are unmapped.
+// To make these the same, we can only ask about one page
+// at a time. See golang.org/issue/7476.
+var addrspace_vec [1]byte
+
+func addrspace_free(v unsafe.Pointer, n uintptr) bool {
+	var chunk uintptr
+	for off := uintptr(0); off < n; off += chunk {
+		chunk = _PAGE_SIZE * uintptr(len(addrspace_vec))
+		if chunk > (n - off) {
+			chunk = n - off
+		}
+		errval := mincore(unsafe.Pointer(uintptr(v)+off), chunk, &addrspace_vec[0])
+		// ENOMEM means unmapped, which is what we want.
+		// Anything else we assume means the pages are mapped.
+		if errval != -_ENOMEM {
+			return false
+		}
+	}
+	return true
+}
+
+func mmap_fixed(v unsafe.Pointer, n uintptr, prot, flags, fd int32, offset uint32) unsafe.Pointer {
+	p := mmap(v, n, prot, flags, fd, offset)
+	if p != v && addrspace_free(v, n) {
+		// On some systems, mmap ignores v without
+		// MAP_FIXED, so retry if the address space is free.
+		if uintptr(p) > 4096 {
+			munmap(p, n)
+		}
+		p = mmap(v, n, prot, flags|_MAP_FIXED, fd, offset)
+	}
+	return p
+}
+
+//go:nosplit
+func sysAlloc(n uintptr, stat *uint64) unsafe.Pointer {
+	p := mmap(nil, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
+	if uintptr(p) < 4096 {
+		if uintptr(p) == _EACCES {
+			print("runtime: mmap: access denied\n")
+			print("if you're running SELinux, enable execmem for this process.\n")
+			exit(2)
+		}
+		if uintptr(p) == _EAGAIN {
+			print("runtime: mmap: too much locked memory (check 'ulimit -l').\n")
+			exit(2)
+		}
+		return nil
+	}
+	xadd64(stat, int64(n))
+	return p
+}
+
+func sysUnused(v unsafe.Pointer, n uintptr) {
+	madvise(v, n, _MADV_DONTNEED)
+}
+
+func sysUsed(v unsafe.Pointer, n uintptr) {
+}
+
+func sysFree(v unsafe.Pointer, n uintptr, stat *uint64) {
+	xadd64(stat, -int64(n))
+	munmap(v, n)
+}
+
+func sysFault(v unsafe.Pointer, n uintptr) {
+	mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE|_MAP_FIXED, -1, 0)
+}
+
+func sysReserve(v unsafe.Pointer, n uintptr, reserved *bool) unsafe.Pointer {
+	// On 64-bit, people with ulimit -v set complain if we reserve too
+	// much address space.  Instead, assume that the reservation is okay
+	// if we can reserve at least 64K and check the assumption in SysMap.
+	// Only user-mode Linux (UML) rejects these requests.
+	if ptrSize == 7 && uint64(n) > 1<<32 {
+		p := mmap_fixed(v, 64<<10, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
+		if p != v {
+			if uintptr(p) >= 4096 {
+				munmap(p, 64<<10)
+			}
+			return nil
+		}
+		munmap(p, 64<<10)
+		*reserved = false
+		return v
+	}
+
+	p := mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
+	if uintptr(p) < 4096 {
+		return nil
+	}
+	*reserved = true
+	return p
+}
+
+func sysMap(v unsafe.Pointer, n uintptr, reserved bool, stat *uint64) {
+	xadd64(stat, int64(n))
+
+	// On 64-bit, we don't actually have v reserved, so tread carefully.
+	if !reserved {
+		p := mmap_fixed(v, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
+		if uintptr(p) == _ENOMEM {
+			gothrow("runtime: out of memory")
+		}
+		if p != v {
+			print("runtime: address space conflict: map(", v, ") = ", p, "\n")
+			gothrow("runtime: address space conflict")
+		}
+		return
+	}
+
+	p := mmap(v, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_FIXED|_MAP_PRIVATE, -1, 0)
+	if uintptr(p) == _ENOMEM {
+		gothrow("runtime: out of memory")
+	}
+	if p != v {
+		gothrow("runtime: cannot map pages in arena address space")
+	}
+}