1 // Copyright 2010 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 package runtime 6 7 import ( 8 "unsafe" 9 ) 10 11 const ( 12 _MEM_COMMIT = 0x1000 13 _MEM_RESERVE = 0x2000 14 _MEM_DECOMMIT = 0x4000 15 _MEM_RELEASE = 0x8000 16 17 _PAGE_READWRITE = 0x0004 18 _PAGE_NOACCESS = 0x0001 19 20 _ERROR_NOT_ENOUGH_MEMORY = 8 21 _ERROR_COMMITMENT_LIMIT = 1455 22 ) 23 24 // Don't split the stack as this function may be invoked without a valid G, 25 // which prevents us from allocating more stack. 26 //go:nosplit 27 func sysAlloc(n uintptr, sysStat *uint64) unsafe.Pointer { 28 mSysStatInc(sysStat, n) 29 return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_COMMIT|_MEM_RESERVE, _PAGE_READWRITE)) 30 } 31 32 func sysUnused(v unsafe.Pointer, n uintptr) { 33 r := stdcall3(_VirtualFree, uintptr(v), n, _MEM_DECOMMIT) 34 if r != 0 { 35 return 36 } 37 38 // Decommit failed. Usual reason is that we've merged memory from two different 39 // VirtualAlloc calls, and Windows will only let each VirtualFree handle pages from 40 // a single VirtualAlloc. It is okay to specify a subset of the pages from a single alloc, 41 // just not pages from multiple allocs. This is a rare case, arising only when we're 42 // trying to give memory back to the operating system, which happens on a time 43 // scale of minutes. It doesn't have to be terribly fast. Instead of extra bookkeeping 44 // on all our VirtualAlloc calls, try freeing successively smaller pieces until 45 // we manage to free something, and then repeat. This ends up being O(n log n) 46 // in the worst case, but that's fast enough. 47 for n > 0 { 48 small := n 49 for small >= 4096 && stdcall3(_VirtualFree, uintptr(v), small, _MEM_DECOMMIT) == 0 { 50 small /= 2 51 small &^= 4096 - 1 52 } 53 if small < 4096 { 54 print("runtime: VirtualFree of ", small, " bytes failed with errno=", getlasterror(), "\n") 55 throw("runtime: failed to decommit pages") 56 } 57 v = add(v, small) 58 n -= small 59 } 60 } 61 62 func sysUsed(v unsafe.Pointer, n uintptr) { 63 r := stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_COMMIT, _PAGE_READWRITE) 64 if r == uintptr(v) { 65 return 66 } 67 68 // Commit failed. See SysUnused. 69 for n > 0 { 70 small := n 71 for small >= 4096 && stdcall4(_VirtualAlloc, uintptr(v), small, _MEM_COMMIT, _PAGE_READWRITE) == 0 { 72 small /= 2 73 small &^= 4096 - 1 74 } 75 if small < 4096 { 76 print("runtime: VirtualAlloc of ", small, " bytes failed with errno=", getlasterror(), "\n") 77 throw("runtime: failed to commit pages") 78 } 79 v = add(v, small) 80 n -= small 81 } 82 } 83 84 // Don't split the stack as this function may be invoked without a valid G, 85 // which prevents us from allocating more stack. 86 //go:nosplit 87 func sysFree(v unsafe.Pointer, n uintptr, sysStat *uint64) { 88 mSysStatDec(sysStat, n) 89 r := stdcall3(_VirtualFree, uintptr(v), 0, _MEM_RELEASE) 90 if r == 0 { 91 print("runtime: VirtualFree of ", n, " bytes failed with errno=", getlasterror(), "\n") 92 throw("runtime: failed to release pages") 93 } 94 } 95 96 func sysFault(v unsafe.Pointer, n uintptr) { 97 // SysUnused makes the memory inaccessible and prevents its reuse 98 sysUnused(v, n) 99 } 100 101 func sysReserve(v unsafe.Pointer, n uintptr, reserved *bool) unsafe.Pointer { 102 *reserved = true 103 // v is just a hint. 104 // First try at v. 105 v = unsafe.Pointer(stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_RESERVE, _PAGE_READWRITE)) 106 if v != nil { 107 return v 108 } 109 110 // Next let the kernel choose the address. 111 return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_RESERVE, _PAGE_READWRITE)) 112 } 113 114 func sysMap(v unsafe.Pointer, n uintptr, reserved bool, sysStat *uint64) { 115 mSysStatInc(sysStat, n) 116 p := stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_COMMIT, _PAGE_READWRITE) 117 if p != uintptr(v) { 118 errno := getlasterror() 119 print("runtime: VirtualAlloc of ", n, " bytes failed with errno=", errno, "\n") 120 switch errno { 121 case _ERROR_NOT_ENOUGH_MEMORY, _ERROR_COMMITMENT_LIMIT: 122 throw("out of memory") 123 default: 124 throw("runtime: cannot map pages in arena address space") 125 } 126 } 127 } 128
