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limits.go
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limits.go
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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 limits provides resource limits.
package limits
import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/sync"
)
// LimitType defines a type of resource limit.
type LimitType int
// Set of constants defining the different types of resource limits.
const (
CPU LimitType = iota
FileSize
Data
Stack
Core
Rss
ProcessCount
NumberOfFiles
MemoryLocked
AS
Locks
SignalsPending
MessageQueueBytes
Nice
RealTimePriority
Rttime
)
// AllLimitTypes contains all types in the order how they are presented in
// /proc/pid/limits.
var AllLimitTypes = []LimitType{
CPU,
FileSize,
Data,
Stack,
Core,
Rss,
ProcessCount,
NumberOfFiles,
MemoryLocked,
AS,
Locks,
SignalsPending,
MessageQueueBytes,
Nice,
RealTimePriority,
Rttime,
}
// Name returns the kernel name of the limit
func (lt LimitType) Name() string {
switch lt {
case CPU:
return "Max cpu time"
case FileSize:
return "Max file size"
case Data:
return "Max data size"
case Stack:
return "Max stack size"
case Core:
return "Max core file size"
case Rss:
return "Max resident set"
case ProcessCount:
return "Max processes"
case NumberOfFiles:
return "Max open files"
case MemoryLocked:
return "Max locked memory"
case AS:
return "Max address space"
case Locks:
return "Max file locks"
case SignalsPending:
return "Max pending signals"
case MessageQueueBytes:
return "Max msgqueue size"
case Nice:
return "Max nice priority"
case RealTimePriority:
return "Max realtime priority"
case Rttime:
return "Max realtime timeout"
}
return "unknown"
}
// Unit returns the unit string for a limit
func (lt LimitType) Unit() string {
switch lt {
case CPU:
return "seconds"
case FileSize:
return "bytes"
case Data:
return "bytes"
case Stack:
return "bytes"
case Core:
return "bytes"
case Rss:
return "bytes"
case ProcessCount:
return "processes"
case NumberOfFiles:
return "files"
case MemoryLocked:
return "bytes"
case AS:
return "bytes"
case Locks:
return "locks"
case SignalsPending:
return "signals"
case MessageQueueBytes:
return "bytes"
case Nice:
return ""
case RealTimePriority:
return ""
case Rttime:
return "us"
}
return ""
}
// Infinity is a constant representing a resource with no limit.
const Infinity = ^uint64(0)
// Limit specifies a system limit.
//
// +stateify savable
type Limit struct {
// Cur specifies the current limit.
Cur uint64 `json:"cur,omitempty"`
// Max specifies the maximum settable limit.
Max uint64 `json:"max,omitempty"`
}
// LimitSet represents the Limits that correspond to each LimitType.
//
// +stateify savable
type LimitSet struct {
mu sync.Mutex `state:"nosave"`
data map[LimitType]Limit
}
// NewLimitSet creates a new, empty LimitSet.
func NewLimitSet() *LimitSet {
return &LimitSet{
data: make(map[LimitType]Limit),
}
}
// GetCopy returns a clone of the LimitSet.
func (l *LimitSet) GetCopy() *LimitSet {
l.mu.Lock()
defer l.mu.Unlock()
copyData := make(map[LimitType]Limit)
for k, v := range l.data {
copyData[k] = v
}
return &LimitSet{
data: copyData,
}
}
// Get returns the resource limit associated with LimitType t.
// If no limit is provided, it defaults to an infinite limit.Infinity.
func (l *LimitSet) Get(t LimitType) Limit {
l.mu.Lock()
defer l.mu.Unlock()
s, ok := l.data[t]
if !ok {
return Limit{Cur: Infinity, Max: Infinity}
}
return s
}
// GetCapped returns the current value for the limit, capped as specified.
func (l *LimitSet) GetCapped(t LimitType, max uint64) uint64 {
s := l.Get(t)
if s.Cur == Infinity || s.Cur > max {
return max
}
return s.Cur
}
// SetUnchecked assigns value v to resource of LimitType t.
func (l *LimitSet) SetUnchecked(t LimitType, v Limit) {
l.mu.Lock()
defer l.mu.Unlock()
l.data[t] = v
}
// Set assigns value v to resource of LimitType t and returns the old value.
// privileged should be true only when either the caller has CAP_SYS_RESOURCE
// or when creating limits for a new kernel.
func (l *LimitSet) Set(t LimitType, v Limit, privileged bool) (Limit, error) {
l.mu.Lock()
defer l.mu.Unlock()
// If a limit is already set, make sure the new limit doesn't
// exceed the previous max limit.
if _, ok := l.data[t]; ok {
// Unprivileged users can only lower their hard limits.
if l.data[t].Max < v.Max && !privileged {
return Limit{}, unix.EPERM
}
if v.Cur > v.Max {
return Limit{}, unix.EINVAL
}
}
old := l.data[t]
l.data[t] = v
return old, nil
}