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 //go:build amd64 || arm64 || mips64 || mips64le || ppc64 || ppc64le || riscv64 || s390x 6 // +build amd64 arm64 mips64 mips64le ppc64 ppc64le riscv64 s390x 7 8 package runtime 9 10 import "unsafe" 11 12 const ( 13 // The number of levels in the radix tree. 14 summaryLevels = 5 15 16 // Constants for testing. 17 pageAlloc32Bit = 0 18 pageAlloc64Bit = 1 19 20 // Number of bits needed to represent all indices into the L1 of the 21 // chunks map. 22 // 23 // See (*pageAlloc).chunks for more details. Update the documentation 24 // there should this number change. 25 pallocChunksL1Bits = 13 26 ) 27 28 // levelBits is the number of bits in the radix for a given level in the super summary 29 // structure. 30 // 31 // The sum of all the entries of levelBits should equal heapAddrBits. 32 var levelBits = [summaryLevels]uint{ 33 summaryL0Bits, 34 summaryLevelBits, 35 summaryLevelBits, 36 summaryLevelBits, 37 summaryLevelBits, 38 } 39 40 // levelShift is the number of bits to shift to acquire the radix for a given level 41 // in the super summary structure. 42 // 43 // With levelShift, one can compute the index of the summary at level l related to a 44 // pointer p by doing: 45 // p >> levelShift[l] 46 var levelShift = [summaryLevels]uint{ 47 heapAddrBits - summaryL0Bits, 48 heapAddrBits - summaryL0Bits - 1*summaryLevelBits, 49 heapAddrBits - summaryL0Bits - 2*summaryLevelBits, 50 heapAddrBits - summaryL0Bits - 3*summaryLevelBits, 51 heapAddrBits - summaryL0Bits - 4*summaryLevelBits, 52 } 53 54 // levelLogPages is log2 the maximum number of runtime pages in the address space 55 // a summary in the given level represents. 56 // 57 // The leaf level always represents exactly log2 of 1 chunk's worth of pages. 58 var levelLogPages = [summaryLevels]uint{ 59 logPallocChunkPages + 4*summaryLevelBits, 60 logPallocChunkPages + 3*summaryLevelBits, 61 logPallocChunkPages + 2*summaryLevelBits, 62 logPallocChunkPages + 1*summaryLevelBits, 63 logPallocChunkPages, 64 } 65 66 // sysInit performs architecture-dependent initialization of fields 67 // in pageAlloc. pageAlloc should be uninitialized except for sysStat 68 // if any runtime statistic should be updated. 69 func (p *pageAlloc) sysInit() { 70 // Reserve memory for each level. This will get mapped in 71 // as R/W by setArenas. 72 for l, shift := range levelShift { 73 entries := 1 << (heapAddrBits - shift) 74 75 // Reserve b bytes of memory anywhere in the address space. 76 b := alignUp(uintptr(entries)*pallocSumBytes, physPageSize) 77 r := sysReserve(nil, b) 78 if r == nil { 79 throw("failed to reserve page summary memory") 80 } 81 82 // Put this reservation into a slice. 83 sl := notInHeapSlice{(*notInHeap)(r), 0, entries} 84 p.summary[l] = *(*[]pallocSum)(unsafe.Pointer(&sl)) 85 } 86 } 87 88 // sysGrow performs architecture-dependent operations on heap 89 // growth for the page allocator, such as mapping in new memory 90 // for summaries. It also updates the length of the slices in 91 // [.summary. 92 // 93 // base is the base of the newly-added heap memory and limit is 94 // the first address past the end of the newly-added heap memory. 95 // Both must be aligned to pallocChunkBytes. 96 // 97 // The caller must update p.start and p.end after calling sysGrow. 98 func (p *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 // addrRangeToSummaryRange converts a range of addresses into a range 105 // of summary indices which must be mapped to support those addresses 106 // in the summary range. 107 addrRangeToSummaryRange := func(level int, r addrRange) (int, int) { 108 sumIdxBase, sumIdxLimit := addrsToSummaryRange(level, r.base.addr(), r.limit.addr()) 109 return blockAlignSummaryRange(level, sumIdxBase, sumIdxLimit) 110 } 111 112 // summaryRangeToSumAddrRange converts a range of indices in any 113 // level of p.summary into page-aligned addresses which cover that 114 // range of indices. 115 summaryRangeToSumAddrRange := func(level, sumIdxBase, sumIdxLimit int) addrRange { 116 baseOffset := alignDown(uintptr(sumIdxBase)*pallocSumBytes, physPageSize) 117 limitOffset := alignUp(uintptr(sumIdxLimit)*pallocSumBytes, physPageSize) 118 base := unsafe.Pointer(&p.summary[level][0]) 119 return addrRange{ 120 offAddr{uintptr(add(base, baseOffset))}, 121 offAddr{uintptr(add(base, limitOffset))}, 122 } 123 } 124 125 // addrRangeToSumAddrRange is a convienience function that converts 126 // an address range r to the address range of the given summary level 127 // that stores the summaries for r. 128 addrRangeToSumAddrRange := func(level int, r addrRange) addrRange { 129 sumIdxBase, sumIdxLimit := addrRangeToSummaryRange(level, r) 130 return summaryRangeToSumAddrRange(level, sumIdxBase, sumIdxLimit) 131 } 132 133 // Find the first inUse index which is strictly greater than base. 134 // 135 // Because this function will never be asked remap the same memory 136 // twice, this index is effectively the index at which we would insert 137 // this new growth, and base will never overlap/be contained within 138 // any existing range. 139 // 140 // This will be used to look at what memory in the summary array is already 141 // mapped before and after this new range. 142 inUseIndex := p.inUse.findSucc(base) 143 144 // Walk up the radix tree and map summaries in as needed. 145 for l := range p.summary { 146 // Figure out what part of the summary array this new address space needs. 147 needIdxBase, needIdxLimit := addrRangeToSummaryRange(l, makeAddrRange(base, limit)) 148 149 // Update the summary slices with a new upper-bound. This ensures 150 // we get tight bounds checks on at least the top bound. 151 // 152 // We must do this regardless of whether we map new memory. 153 if needIdxLimit > len(p.summary[l]) { 154 p.summary[l] = p.summary[l][:needIdxLimit] 155 } 156 157 // Compute the needed address range in the summary array for level l. 158 need := summaryRangeToSumAddrRange(l, needIdxBase, needIdxLimit) 159 160 // Prune need down to what needs to be newly mapped. Some parts of it may 161 // already be mapped by what inUse describes due to page alignment requirements 162 // for mapping. prune's invariants are guaranteed by the fact that this 163 // function will never be asked to remap the same memory twice. 164 if inUseIndex > 0 { 165 need = need.subtract(addrRangeToSumAddrRange(l, p.inUse.ranges[inUseIndex-1])) 166 } 167 if inUseIndex < len(p.inUse.ranges) { 168 need = need.subtract(addrRangeToSumAddrRange(l, p.inUse.ranges[inUseIndex])) 169 } 170 // It's possible that after our pruning above, there's nothing new to map. 171 if need.size() == 0 { 172 continue 173 } 174 175 // Map and commit need. 176 sysMap(unsafe.Pointer(need.base.addr()), need.size(), p.sysStat) 177 sysUsed(unsafe.Pointer(need.base.addr()), need.size()) 178 } 179 } 180