1// Copyright 2019 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// +build 386 arm mips mipsle wasm darwin,arm64 amd64p32 armbe m68k mips64p32 mips64p32le nios2 ppc s390 sh shbe sparc
6
7// wasm is a treated as a 32-bit architecture for the purposes of the page
8// allocator, even though it has 64-bit pointers. This is because any wasm
9// pointer always has its top 32 bits as zero, so the effective heap address
10// space is only 2^32 bytes in size (see heapAddrBits).
11
12// darwin/arm64 is treated as a 32-bit architecture for the purposes of the
13// page allocator, even though it has 64-bit pointers and a 33-bit address
14// space (see heapAddrBits). The 33 bit address space cannot be rounded up
15// to 64 bits because there are too many summary levels to fit in just 33
16// bits.
17
18package runtime
19
20import "unsafe"
21
22const (
23	// The number of levels in the radix tree.
24	summaryLevels = 4
25
26	// Constants for testing.
27	pageAlloc32Bit = 1
28	pageAlloc64Bit = 0
29
30	// Number of bits needed to represent all indices into the L1 of the
31	// chunks map.
32	//
33	// See (*pageAlloc).chunks for more details. Update the documentation
34	// there should this number change.
35	pallocChunksL1Bits = 0
36)
37
38// See comment in mpagealloc_64bit.go.
39var levelBits = [summaryLevels]uint{
40	summaryL0Bits,
41	summaryLevelBits,
42	summaryLevelBits,
43	summaryLevelBits,
44}
45
46// See comment in mpagealloc_64bit.go.
47var levelShift = [summaryLevels]uint{
48	heapAddrBits - summaryL0Bits,
49	heapAddrBits - summaryL0Bits - 1*summaryLevelBits,
50	heapAddrBits - summaryL0Bits - 2*summaryLevelBits,
51	heapAddrBits - summaryL0Bits - 3*summaryLevelBits,
52}
53
54// See comment in mpagealloc_64bit.go.
55var levelLogPages = [summaryLevels]uint{
56	logPallocChunkPages + 3*summaryLevelBits,
57	logPallocChunkPages + 2*summaryLevelBits,
58	logPallocChunkPages + 1*summaryLevelBits,
59	logPallocChunkPages,
60}
61
62// See mpagealloc_64bit.go for details.
63func (s *pageAlloc) sysInit() {
64	// Calculate how much memory all our entries will take up.
65	//
66	// This should be around 12 KiB or less.
67	totalSize := uintptr(0)
68	for l := 0; l < summaryLevels; l++ {
69		totalSize += (uintptr(1) << (heapAddrBits - levelShift[l])) * pallocSumBytes
70	}
71	totalSize = alignUp(totalSize, physPageSize)
72
73	// Reserve memory for all levels in one go. There shouldn't be much for 32-bit.
74	reservation := sysReserve(nil, totalSize)
75	if reservation == nil {
76		throw("failed to reserve page summary memory")
77	}
78	// There isn't much. Just map it and mark it as used immediately.
79	sysMap(reservation, totalSize, s.sysStat)
80	sysUsed(reservation, totalSize)
81
82	// Iterate over the reservation and cut it up into slices.
83	//
84	// Maintain i as the byte offset from reservation where
85	// the new slice should start.
86	for l, shift := range levelShift {
87		entries := 1 << (heapAddrBits - shift)
88
89		// Put this reservation into a slice.
90		sl := notInHeapSlice{(*notInHeap)(reservation), 0, entries}
91		s.summary[l] = *(*[]pallocSum)(unsafe.Pointer(&sl))
92
93		reservation = add(reservation, uintptr(entries)*pallocSumBytes)
94	}
95}
96
97// See mpagealloc_64bit.go for details.
98func (s *pageAlloc) sysGrow(base, limit uintptr) {
99	if base%pallocChunkBytes != 0 || limit%pallocChunkBytes != 0 {
100		print("runtime: base = ", hex(base), ", limit = ", hex(limit), "\n")
101		throw("sysGrow bounds not aligned to pallocChunkBytes")
102	}
103
104	// Walk up the tree and update the summary slices.
105	for l := len(s.summary) - 1; l >= 0; l-- {
106		// Figure out what part of the summary array this new address space needs.
107		// Note that we need to align the ranges to the block width (1<<levelBits[l])
108		// at this level because the full block is needed to compute the summary for
109		// the next level.
110		lo, hi := addrsToSummaryRange(l, base, limit)
111		_, hi = blockAlignSummaryRange(l, lo, hi)
112		if hi > len(s.summary[l]) {
113			s.summary[l] = s.summary[l][:hi]
114		}
115	}
116}
117