378 lines
15 KiB
Go
378 lines
15 KiB
Go
// 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 platform provides a Platform abstraction.
|
|
//
|
|
// See Platform for more information.
|
|
package platform
|
|
|
|
import (
|
|
"fmt"
|
|
"os"
|
|
|
|
"gvisor.dev/gvisor/pkg/abi/linux"
|
|
"gvisor.dev/gvisor/pkg/seccomp"
|
|
"gvisor.dev/gvisor/pkg/sentry/arch"
|
|
"gvisor.dev/gvisor/pkg/sentry/safemem"
|
|
"gvisor.dev/gvisor/pkg/sentry/usermem"
|
|
)
|
|
|
|
// Platform provides abstractions for execution contexts (Context,
|
|
// AddressSpace).
|
|
type Platform interface {
|
|
// SupportsAddressSpaceIO returns true if AddressSpaces returned by this
|
|
// Platform support AddressSpaceIO methods.
|
|
//
|
|
// The value returned by SupportsAddressSpaceIO is guaranteed to remain
|
|
// unchanged over the lifetime of the Platform.
|
|
SupportsAddressSpaceIO() bool
|
|
|
|
// CooperativelySchedulesAddressSpace returns true if the Platform has a
|
|
// limited number of AddressSpaces, such that mm.MemoryManager.Deactivate
|
|
// should call AddressSpace.Release when there are no goroutines that
|
|
// require the mm.MemoryManager to have an active AddressSpace.
|
|
//
|
|
// The value returned by CooperativelySchedulesAddressSpace is guaranteed
|
|
// to remain unchanged over the lifetime of the Platform.
|
|
CooperativelySchedulesAddressSpace() bool
|
|
|
|
// DetectsCPUPreemption returns true if Contexts returned by the Platform
|
|
// can reliably return ErrContextCPUPreempted.
|
|
DetectsCPUPreemption() bool
|
|
|
|
// MapUnit returns the alignment used for optional mappings into this
|
|
// platform's AddressSpaces. Higher values indicate lower per-page costs
|
|
// for AddressSpace.MapFile. As a special case, a MapUnit of 0 indicates
|
|
// that the cost of AddressSpace.MapFile is effectively independent of the
|
|
// number of pages mapped. If MapUnit is non-zero, it must be a power-of-2
|
|
// multiple of usermem.PageSize.
|
|
MapUnit() uint64
|
|
|
|
// MinUserAddress returns the minimum mappable address on this
|
|
// platform.
|
|
MinUserAddress() usermem.Addr
|
|
|
|
// MaxUserAddress returns the maximum mappable address on this
|
|
// platform.
|
|
MaxUserAddress() usermem.Addr
|
|
|
|
// NewAddressSpace returns a new memory context for this platform.
|
|
//
|
|
// If mappingsID is not nil, the platform may assume that (1) all calls
|
|
// to NewAddressSpace with the same mappingsID represent the same
|
|
// (mutable) set of mappings, and (2) the set of mappings has not
|
|
// changed since the last time AddressSpace.Release was called on an
|
|
// AddressSpace returned by a call to NewAddressSpace with the same
|
|
// mappingsID.
|
|
//
|
|
// If a new AddressSpace cannot be created immediately, a nil
|
|
// AddressSpace is returned, along with channel that is closed when
|
|
// the caller should retry a call to NewAddressSpace.
|
|
//
|
|
// In general, this blocking behavior only occurs when
|
|
// CooperativelySchedulesAddressSpace (above) returns false.
|
|
NewAddressSpace(mappingsID interface{}) (AddressSpace, <-chan struct{}, error)
|
|
|
|
// NewContext returns a new execution context.
|
|
NewContext() Context
|
|
|
|
// PreemptAllCPUs causes all concurrent calls to Context.Switch(), as well
|
|
// as the first following call to Context.Switch() for each Context, to
|
|
// return ErrContextCPUPreempted.
|
|
//
|
|
// PreemptAllCPUs is only supported if DetectsCPUPremption() == true.
|
|
// Platforms for which this does not hold may panic if PreemptAllCPUs is
|
|
// called.
|
|
PreemptAllCPUs() error
|
|
|
|
// SyscallFilters returns syscalls made exclusively by this platform.
|
|
SyscallFilters() seccomp.SyscallRules
|
|
}
|
|
|
|
// NoCPUPreemptionDetection implements Platform.DetectsCPUPreemption and
|
|
// dependent methods for Platforms that do not support this feature.
|
|
type NoCPUPreemptionDetection struct{}
|
|
|
|
// DetectsCPUPreemption implements Platform.DetectsCPUPreemption.
|
|
func (NoCPUPreemptionDetection) DetectsCPUPreemption() bool {
|
|
return false
|
|
}
|
|
|
|
// PreemptAllCPUs implements Platform.PreemptAllCPUs.
|
|
func (NoCPUPreemptionDetection) PreemptAllCPUs() error {
|
|
panic("This platform does not support CPU preemption detection")
|
|
}
|
|
|
|
// Context represents the execution context for a single thread.
|
|
type Context interface {
|
|
// Switch resumes execution of the thread specified by the arch.Context
|
|
// in the provided address space. This call will block while the thread
|
|
// is executing.
|
|
//
|
|
// If cpu is non-negative, and it is not the number of the CPU that the
|
|
// thread executes on, Context should return ErrContextCPUPreempted. cpu
|
|
// can only be non-negative if Platform.DetectsCPUPreemption() is true;
|
|
// Contexts from Platforms for which this does not hold may ignore cpu, or
|
|
// panic if cpu is non-negative.
|
|
//
|
|
// Switch may return one of the following special errors:
|
|
//
|
|
// - nil: The Context invoked a system call.
|
|
//
|
|
// - ErrContextSignal: The Context was interrupted by a signal. The
|
|
// returned *arch.SignalInfo contains information about the signal. If
|
|
// arch.SignalInfo.Signo == SIGSEGV, the returned usermem.AccessType
|
|
// contains the access type of the triggering fault. The caller owns
|
|
// the returned SignalInfo.
|
|
//
|
|
// - ErrContextInterrupt: The Context was interrupted by a call to
|
|
// Interrupt(). Switch() may return ErrContextInterrupt spuriously. In
|
|
// particular, most implementations of Interrupt() will cause the first
|
|
// following call to Switch() to return ErrContextInterrupt if there is no
|
|
// concurrent call to Switch().
|
|
//
|
|
// - ErrContextCPUPreempted: See the definition of that error for details.
|
|
Switch(as AddressSpace, ac arch.Context, cpu int32) (*arch.SignalInfo, usermem.AccessType, error)
|
|
|
|
// Interrupt interrupts a concurrent call to Switch(), causing it to return
|
|
// ErrContextInterrupt.
|
|
Interrupt()
|
|
}
|
|
|
|
var (
|
|
// ErrContextSignal is returned by Context.Switch() to indicate that the
|
|
// Context was interrupted by a signal.
|
|
ErrContextSignal = fmt.Errorf("interrupted by signal")
|
|
|
|
// ErrContextSignalCPUID is equivalent to ErrContextSignal, except that
|
|
// a check should be done for execution of the CPUID instruction. If
|
|
// the current instruction pointer is a CPUID instruction, then this
|
|
// should be emulated appropriately. If not, then the given signal
|
|
// should be handled per above.
|
|
ErrContextSignalCPUID = fmt.Errorf("interrupted by signal, possible CPUID")
|
|
|
|
// ErrContextInterrupt is returned by Context.Switch() to indicate that the
|
|
// Context was interrupted by a call to Context.Interrupt().
|
|
ErrContextInterrupt = fmt.Errorf("interrupted by platform.Context.Interrupt()")
|
|
|
|
// ErrContextCPUPreempted is returned by Context.Switch() to indicate that
|
|
// one of the following occurred:
|
|
//
|
|
// - The CPU executing the Context is not the CPU passed to
|
|
// Context.Switch().
|
|
//
|
|
// - The CPU executing the Context may have executed another Context since
|
|
// the last time it executed this one; or the CPU has previously executed
|
|
// another Context, and has never executed this one.
|
|
//
|
|
// - Platform.PreemptAllCPUs() was called since the last return from
|
|
// Context.Switch().
|
|
ErrContextCPUPreempted = fmt.Errorf("interrupted by CPU preemption")
|
|
)
|
|
|
|
// SignalInterrupt is a signal reserved for use by implementations of
|
|
// Context.Interrupt(). The sentry guarantees that it will ignore delivery of
|
|
// this signal both to Contexts and to the sentry itself, under the assumption
|
|
// that they originate from races with Context.Interrupt().
|
|
//
|
|
// NOTE(b/23420492): The Go runtime only guarantees that a small subset
|
|
// of signals will be always be unblocked on all threads, one of which
|
|
// is SIGCHLD.
|
|
const SignalInterrupt = linux.SIGCHLD
|
|
|
|
// AddressSpace represents a virtual address space in which a Context can
|
|
// execute.
|
|
type AddressSpace interface {
|
|
// MapFile creates a shared mapping of offsets fr from f at address addr.
|
|
// Any existing overlapping mappings are silently replaced.
|
|
//
|
|
// If precommit is true, the platform should eagerly commit resources (e.g.
|
|
// physical memory) to the mapping. The precommit flag is advisory and
|
|
// implementations may choose to ignore it.
|
|
//
|
|
// Preconditions: addr and fr must be page-aligned. fr.Length() > 0.
|
|
// at.Any() == true. At least one reference must be held on all pages in
|
|
// fr, and must continue to be held as long as pages are mapped.
|
|
MapFile(addr usermem.Addr, f File, fr FileRange, at usermem.AccessType, precommit bool) error
|
|
|
|
// Unmap unmaps the given range.
|
|
//
|
|
// Preconditions: addr is page-aligned. length > 0.
|
|
Unmap(addr usermem.Addr, length uint64)
|
|
|
|
// Release releases this address space. After releasing, a new AddressSpace
|
|
// must be acquired via platform.NewAddressSpace().
|
|
Release()
|
|
|
|
// AddressSpaceIO methods are supported iff the associated platform's
|
|
// Platform.SupportsAddressSpaceIO() == true. AddressSpaces for which this
|
|
// does not hold may panic if AddressSpaceIO methods are invoked.
|
|
AddressSpaceIO
|
|
}
|
|
|
|
// AddressSpaceIO supports IO through the memory mappings installed in an
|
|
// AddressSpace.
|
|
//
|
|
// AddressSpaceIO implementors are responsible for ensuring that address ranges
|
|
// are application-mappable.
|
|
type AddressSpaceIO interface {
|
|
// CopyOut copies len(src) bytes from src to the memory mapped at addr. It
|
|
// returns the number of bytes copied. If the number of bytes copied is <
|
|
// len(src), it returns a non-nil error explaining why.
|
|
CopyOut(addr usermem.Addr, src []byte) (int, error)
|
|
|
|
// CopyIn copies len(dst) bytes from the memory mapped at addr to dst.
|
|
// It returns the number of bytes copied. If the number of bytes copied is
|
|
// < len(dst), it returns a non-nil error explaining why.
|
|
CopyIn(addr usermem.Addr, dst []byte) (int, error)
|
|
|
|
// ZeroOut sets toZero bytes to 0, starting at addr. It returns the number
|
|
// of bytes zeroed. If the number of bytes zeroed is < toZero, it returns a
|
|
// non-nil error explaining why.
|
|
ZeroOut(addr usermem.Addr, toZero uintptr) (uintptr, error)
|
|
|
|
// SwapUint32 atomically sets the uint32 value at addr to new and returns
|
|
// the previous value.
|
|
//
|
|
// Preconditions: addr must be aligned to a 4-byte boundary.
|
|
SwapUint32(addr usermem.Addr, new uint32) (uint32, error)
|
|
|
|
// CompareAndSwapUint32 atomically compares the uint32 value at addr to
|
|
// old; if they are equal, the value in memory is replaced by new. In
|
|
// either case, the previous value stored in memory is returned.
|
|
//
|
|
// Preconditions: addr must be aligned to a 4-byte boundary.
|
|
CompareAndSwapUint32(addr usermem.Addr, old, new uint32) (uint32, error)
|
|
|
|
// LoadUint32 atomically loads the uint32 value at addr and returns it.
|
|
//
|
|
// Preconditions: addr must be aligned to a 4-byte boundary.
|
|
LoadUint32(addr usermem.Addr) (uint32, error)
|
|
}
|
|
|
|
// NoAddressSpaceIO implements AddressSpaceIO methods by panicking.
|
|
type NoAddressSpaceIO struct{}
|
|
|
|
// CopyOut implements AddressSpaceIO.CopyOut.
|
|
func (NoAddressSpaceIO) CopyOut(addr usermem.Addr, src []byte) (int, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// CopyIn implements AddressSpaceIO.CopyIn.
|
|
func (NoAddressSpaceIO) CopyIn(addr usermem.Addr, dst []byte) (int, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// ZeroOut implements AddressSpaceIO.ZeroOut.
|
|
func (NoAddressSpaceIO) ZeroOut(addr usermem.Addr, toZero uintptr) (uintptr, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// SwapUint32 implements AddressSpaceIO.SwapUint32.
|
|
func (NoAddressSpaceIO) SwapUint32(addr usermem.Addr, new uint32) (uint32, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// CompareAndSwapUint32 implements AddressSpaceIO.CompareAndSwapUint32.
|
|
func (NoAddressSpaceIO) CompareAndSwapUint32(addr usermem.Addr, old, new uint32) (uint32, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// LoadUint32 implements AddressSpaceIO.LoadUint32.
|
|
func (NoAddressSpaceIO) LoadUint32(addr usermem.Addr) (uint32, error) {
|
|
panic("This platform does not support AddressSpaceIO")
|
|
}
|
|
|
|
// SegmentationFault is an error returned by AddressSpaceIO methods when IO
|
|
// fails due to access of an unmapped page, or a mapped page with insufficient
|
|
// permissions.
|
|
type SegmentationFault struct {
|
|
// Addr is the address at which the fault occurred.
|
|
Addr usermem.Addr
|
|
}
|
|
|
|
// Error implements error.Error.
|
|
func (f SegmentationFault) Error() string {
|
|
return fmt.Sprintf("segmentation fault at %#x", f.Addr)
|
|
}
|
|
|
|
// File represents a host file that may be mapped into an AddressSpace.
|
|
type File interface {
|
|
// All pages in a File are reference-counted.
|
|
|
|
// IncRef increments the reference count on all pages in fr.
|
|
//
|
|
// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
|
|
// 0. At least one reference must be held on all pages in fr. (The File
|
|
// interface does not provide a way to acquire an initial reference;
|
|
// implementors may define mechanisms for doing so.)
|
|
IncRef(fr FileRange)
|
|
|
|
// DecRef decrements the reference count on all pages in fr.
|
|
//
|
|
// Preconditions: fr.Start and fr.End must be page-aligned. fr.Length() >
|
|
// 0. At least one reference must be held on all pages in fr.
|
|
DecRef(fr FileRange)
|
|
|
|
// MapInternal returns a mapping of the given file offsets in the invoking
|
|
// process' address space for reading and writing.
|
|
//
|
|
// Note that fr.Start and fr.End need not be page-aligned.
|
|
//
|
|
// Preconditions: fr.Length() > 0. At least one reference must be held on
|
|
// all pages in fr.
|
|
//
|
|
// Postconditions: The returned mapping is valid as long as at least one
|
|
// reference is held on the mapped pages.
|
|
MapInternal(fr FileRange, at usermem.AccessType) (safemem.BlockSeq, error)
|
|
|
|
// FD returns the file descriptor represented by the File.
|
|
//
|
|
// The only permitted operation on the returned file descriptor is to map
|
|
// pages from it consistent with the requirements of AddressSpace.MapFile.
|
|
FD() int
|
|
}
|
|
|
|
// FileRange represents a range of uint64 offsets into a File.
|
|
//
|
|
// type FileRange <generated using go_generics>
|
|
|
|
// String implements fmt.Stringer.String.
|
|
func (fr FileRange) String() string {
|
|
return fmt.Sprintf("[%#x, %#x)", fr.Start, fr.End)
|
|
}
|
|
|
|
// Constructor represents a platform type.
|
|
type Constructor interface {
|
|
New(deviceFile *os.File) (Platform, error)
|
|
OpenDevice() (*os.File, error)
|
|
}
|
|
|
|
// platforms contains all available platform types.
|
|
var platforms = map[string]Constructor{}
|
|
|
|
// Register registers a new platform type.
|
|
func Register(name string, platform Constructor) {
|
|
platforms[name] = platform
|
|
}
|
|
|
|
// Lookup looks up the platform constructor by name.
|
|
func Lookup(name string) (Constructor, error) {
|
|
p, ok := platforms[name]
|
|
if !ok {
|
|
return nil, fmt.Errorf("unknown platform: %v", name)
|
|
}
|
|
return p, nil
|
|
}
|