126 lines
3.8 KiB
Go
126 lines
3.8 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package usermem
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import (
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"fmt"
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)
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// Addr represents a generic virtual address.
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//
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// +stateify savable
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type Addr uintptr
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// AddLength adds the given length to start and returns the result. ok is true
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// iff adding the length did not overflow the range of Addr.
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//
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// Note: This function is usually used to get the end of an address range
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// defined by its start address and length. Since the resulting end is
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// exclusive, end == 0 is technically valid, and corresponds to a range that
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// extends to the end of the address space, but ok will be false. This isn't
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// expected to ever come up in practice.
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func (v Addr) AddLength(length uint64) (end Addr, ok bool) {
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end = v + Addr(length)
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// The second half of the following check is needed in case uintptr is
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// smaller than 64 bits.
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ok = end >= v && length <= uint64(^Addr(0))
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return
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}
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// RoundDown returns the address rounded down to the nearest page boundary.
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func (v Addr) RoundDown() Addr {
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return v & ^Addr(PageSize-1)
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}
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// RoundUp returns the address rounded up to the nearest page boundary. ok is
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// true iff rounding up did not wrap around.
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func (v Addr) RoundUp() (addr Addr, ok bool) {
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addr = Addr(v + PageSize - 1).RoundDown()
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ok = addr >= v
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return
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}
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// MustRoundUp is equivalent to RoundUp, but panics if rounding up wraps
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// around.
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func (v Addr) MustRoundUp() Addr {
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addr, ok := v.RoundUp()
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if !ok {
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panic(fmt.Sprintf("usermem.Addr(%d).RoundUp() wraps", v))
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}
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return addr
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}
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// HugeRoundDown returns the address rounded down to the nearest huge page
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// boundary.
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func (v Addr) HugeRoundDown() Addr {
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return v & ^Addr(HugePageSize-1)
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}
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// HugeRoundUp returns the address rounded up to the nearest huge page boundary.
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// ok is true iff rounding up did not wrap around.
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func (v Addr) HugeRoundUp() (addr Addr, ok bool) {
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addr = Addr(v + HugePageSize - 1).HugeRoundDown()
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ok = addr >= v
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return
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}
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// PageOffset returns the offset of v into the current page.
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func (v Addr) PageOffset() uint64 {
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return uint64(v & Addr(PageSize-1))
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}
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// IsPageAligned returns true if v.PageOffset() == 0.
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func (v Addr) IsPageAligned() bool {
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return v.PageOffset() == 0
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}
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// AddrRange is a range of Addrs.
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//
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// type AddrRange <generated by go_generics>
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// ToRange returns [v, v+length).
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func (v Addr) ToRange(length uint64) (AddrRange, bool) {
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end, ok := v.AddLength(length)
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return AddrRange{v, end}, ok
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}
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// IsPageAligned returns true if ar.Start.IsPageAligned() and
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// ar.End.IsPageAligned().
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func (ar AddrRange) IsPageAligned() bool {
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return ar.Start.IsPageAligned() && ar.End.IsPageAligned()
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}
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// String implements fmt.Stringer.String.
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func (ar AddrRange) String() string {
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return fmt.Sprintf("[%#x, %#x)", ar.Start, ar.End)
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}
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// PageRoundDown/Up are equivalent to Addr.RoundDown/Up, but without the
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// potentially truncating conversion from uint64 to Addr. This is necessary
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// because there is no way to define generic "PageRoundDown/Up" functions in Go.
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// PageRoundDown returns x rounded down to the nearest page boundary.
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func PageRoundDown(x uint64) uint64 {
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return x &^ (PageSize - 1)
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}
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// PageRoundUp returns x rounded up to the nearest page boundary.
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// ok is true iff rounding up did not wrap around.
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func PageRoundUp(x uint64) (addr uint64, ok bool) {
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addr = PageRoundDown(x + PageSize - 1)
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ok = addr >= x
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return
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}
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