// Copyright 2010 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import (
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"unsafe"
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)
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const (
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_MEM_COMMIT = 0x1000
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_MEM_RESERVE = 0x2000
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_MEM_DECOMMIT = 0x4000
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_MEM_RELEASE = 0x8000
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_PAGE_READWRITE = 0x0004
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_PAGE_NOACCESS = 0x0001
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_ERROR_NOT_ENOUGH_MEMORY = 8
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_ERROR_COMMITMENT_LIMIT = 1455
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)
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// Don't split the stack as this function may be invoked without a valid G,
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// which prevents us from allocating more stack.
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//go:nosplit
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func sysAlloc(n uintptr, sysStat *uint64) unsafe.Pointer {
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mSysStatInc(sysStat, n)
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return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_COMMIT|_MEM_RESERVE, _PAGE_READWRITE))
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}
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func sysUnused(v unsafe.Pointer, n uintptr) {
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r := stdcall3(_VirtualFree, uintptr(v), n, _MEM_DECOMMIT)
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if r != 0 {
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return
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}
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// Decommit failed. Usual reason is that we've merged memory from two different
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// VirtualAlloc calls, and Windows will only let each VirtualFree handle pages from
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// a single VirtualAlloc. It is okay to specify a subset of the pages from a single alloc,
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// just not pages from multiple allocs. This is a rare case, arising only when we're
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// trying to give memory back to the operating system, which happens on a time
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// scale of minutes. It doesn't have to be terribly fast. Instead of extra bookkeeping
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// on all our VirtualAlloc calls, try freeing successively smaller pieces until
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// we manage to free something, and then repeat. This ends up being O(n log n)
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// in the worst case, but that's fast enough.
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for n > 0 {
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small := n
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for small >= 4096 && stdcall3(_VirtualFree, uintptr(v), small, _MEM_DECOMMIT) == 0 {
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small /= 2
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small &^= 4096 - 1
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}
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if small < 4096 {
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print("runtime: VirtualFree of ", small, " bytes failed with errno=", getlasterror(), "\n")
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throw("runtime: failed to decommit pages")
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}
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v = add(v, small)
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n -= small
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}
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}
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func sysUsed(v unsafe.Pointer, n uintptr) {
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r := stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_COMMIT, _PAGE_READWRITE)
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if r != 0 {
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return
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}
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// Commit failed. See SysUnused.
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for n > 0 {
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small := n
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for small >= 4096 && stdcall4(_VirtualAlloc, uintptr(v), small, _MEM_COMMIT, _PAGE_READWRITE) == 0 {
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small /= 2
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small &^= 4096 - 1
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}
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if small < 4096 {
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print("runtime: VirtualAlloc of ", small, " bytes failed with errno=", getlasterror(), "\n")
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throw("runtime: failed to commit pages")
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}
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v = add(v, small)
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n -= small
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}
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}
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// Don't split the stack as this function may be invoked without a valid G,
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// which prevents us from allocating more stack.
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//go:nosplit
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func sysFree(v unsafe.Pointer, n uintptr, sysStat *uint64) {
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mSysStatDec(sysStat, n)
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r := stdcall3(_VirtualFree, uintptr(v), 0, _MEM_RELEASE)
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if r == 0 {
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print("runtime: VirtualFree of ", n, " bytes failed with errno=", getlasterror(), "\n")
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throw("runtime: failed to release pages")
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}
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}
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func sysFault(v unsafe.Pointer, n uintptr) {
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// SysUnused makes the memory inaccessible and prevents its reuse
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sysUnused(v, n)
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}
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func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
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// v is just a hint.
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// First try at v.
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// This will fail if any of [v, v+n) is already reserved.
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v = unsafe.Pointer(stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_RESERVE, _PAGE_READWRITE))
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if v != nil {
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return v
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}
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// Next let the kernel choose the address.
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return unsafe.Pointer(stdcall4(_VirtualAlloc, 0, n, _MEM_RESERVE, _PAGE_READWRITE))
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}
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func sysMap(v unsafe.Pointer, n uintptr, sysStat *uint64) {
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mSysStatInc(sysStat, n)
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p := stdcall4(_VirtualAlloc, uintptr(v), n, _MEM_COMMIT, _PAGE_READWRITE)
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if p != uintptr(v) {
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errno := getlasterror()
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print("runtime: VirtualAlloc of ", n, " bytes failed with errno=", errno, "\n")
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switch errno {
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case _ERROR_NOT_ENOUGH_MEMORY, _ERROR_COMMITMENT_LIMIT:
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throw("out of memory")
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default:
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throw("runtime: cannot map pages in arena address space")
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}
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}
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}
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