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