platform

package
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 Go to latest Published: May 9, 2021 License: Apache-2.0, MIT Imports: 13 Imported by: 0

Documentation

Overview

Package platform provides a Platform abstraction.

See Platform for more information.

Index

Constants

View Source 
const (
	// CtxPlatform is a Context.Value key for a Platform.
	CtxPlatform contextID = iota
)
View Source 
const SignalInterrupt = linux.SIGCHLD

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.

Variables

View Source 
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")
)

Functions

func Register 

func Register(name string, platform Constructor)

Register registers a new platform type.

func SystemMMapMinAddr 

func SystemMMapMinAddr() hostarch.Addr

SystemMMapMinAddr returns the minimum system address.

Types

type AddressSpace 

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 hostarch.Addr, f memmap.File, fr memmap.FileRange, at hostarch.AccessType, precommit bool) error

	// Unmap unmaps the given range.
	//
	// Preconditions:
	// * addr is page-aligned.
	// * length > 0.
	Unmap(addr hostarch.Addr, length uint64)

	// Release releases this address space. After releasing, a new AddressSpace
	// must be acquired via platform.NewAddressSpace().
	Release()

	// PreFork() is called before creating a copy of AddressSpace. This
	// guarantees that this address space will be in a consistent state.
	PreFork()

	// PostFork() is called after creating a copy of AddressSpace.
	PostFork()

	// 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
}

AddressSpace represents a virtual address space in which a Context can execute.

type AddressSpaceIO 

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 hostarch.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 hostarch.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 hostarch.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 hostarch.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 hostarch.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 hostarch.Addr) (uint32, error)
}

AddressSpaceIO supports IO through the memory mappings installed in an AddressSpace.

AddressSpaceIO implementors are responsible for ensuring that address ranges are application-mappable.

type Constructor 

type Constructor interface {
	// New returns a new platform instance.
	//
	// Arguments:
	//
	// * deviceFile - the device file (e.g. /dev/kvm for the KVM platform).
	New(deviceFile *os.File) (Platform, error)
	OpenDevice() (*os.File, error)

	// Requirements returns platform specific requirements.
	Requirements() Requirements
}

Constructor represents a platform type.

func Lookup 

func Lookup(name string) (Constructor, error)

Lookup looks up the platform constructor by name.

type Context 

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 hostarch.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(ctx context.Context, mm MemoryManager, ac arch.Context, cpu int32) (*arch.SignalInfo, hostarch.AccessType, error)

	// PullFullState() pulls a full state of the application thread.
	//
	// A platform can support lazy loading/restoring of a thread state
	// which includes registers and a floating point state.
	//
	// For example, when the Sentry handles a system call, it may have only
	// syscall arguments without other registers and a floating point
	// state. And in this case, if the Sentry will need to construct a
	// signal frame to call a signal handler, it will need to call
	// PullFullState() to load all registers and FPU state.
	//
	// Preconditions: The caller must be running on the task goroutine.
	PullFullState(as AddressSpace, ac arch.Context)

	// FullStateChanged() indicates that a thread state has been changed by
	// the Sentry. This happens in case of the rt_sigreturn, execve, etc.
	//
	// First, it indicates that the Sentry has the full state of the thread
	// and PullFullState() has to do nothing if it is called after
	// FullStateChanged().
	//
	// Second, it forces restoring the full state of the application
	// thread. A platform can support lazy loading/restoring of a thread
	// state. This means that if the Sentry has not changed a thread state,
	// the platform may not restore it.
	//
	// Preconditions: The caller must be running on the task goroutine.
	FullStateChanged()

	// Interrupt interrupts a concurrent call to Switch(), causing it to return
	// ErrContextInterrupt.
	Interrupt()

	// Release() releases any resources associated with this context.
	Release()
}

Context represents the execution context for a single thread.

type MMapMinAddr 

type MMapMinAddr struct {
}

MMapMinAddr is a size zero struct that implements MinUserAddress based on the system minimum address. It is suitable for embedding in platforms that rely on the system mmap, and thus require the system minimum.

func (*MMapMinAddr) MinUserAddress 

func (*MMapMinAddr) MinUserAddress() hostarch.Addr

MinUserAddress implements platform.MinUserAddresss.

type MemoryManager 

type MemoryManager interface {
	//usermem.IO provides access to the contents of a virtual memory space.
	usermem.IO
	// MMap establishes a memory mapping.
	MMap(ctx context.Context, opts memmap.MMapOpts) (hostarch.Addr, error)
	// AddressSpace returns the AddressSpace bound to mm.
	AddressSpace() AddressSpace
}

MemoryManager represents an abstraction above the platform address space which manages memory mappings and their contents.

type NoAddressSpaceIO 

type NoAddressSpaceIO struct{}

NoAddressSpaceIO implements AddressSpaceIO methods by panicking.

func (NoAddressSpaceIO) CompareAndSwapUint32 

func (NoAddressSpaceIO) CompareAndSwapUint32(addr hostarch.Addr, old, new uint32) (uint32, error)

CompareAndSwapUint32 implements AddressSpaceIO.CompareAndSwapUint32.

func (NoAddressSpaceIO) CopyIn 

func (NoAddressSpaceIO) CopyIn(addr hostarch.Addr, dst []byte) (int, error)

CopyIn implements AddressSpaceIO.CopyIn.

func (NoAddressSpaceIO) CopyOut 

func (NoAddressSpaceIO) CopyOut(addr hostarch.Addr, src []byte) (int, error)

CopyOut implements AddressSpaceIO.CopyOut.

func (NoAddressSpaceIO) LoadUint32 

func (NoAddressSpaceIO) LoadUint32(addr hostarch.Addr) (uint32, error)

LoadUint32 implements AddressSpaceIO.LoadUint32.

func (NoAddressSpaceIO) SwapUint32 

func (NoAddressSpaceIO) SwapUint32(addr hostarch.Addr, new uint32) (uint32, error)

SwapUint32 implements AddressSpaceIO.SwapUint32.

func (NoAddressSpaceIO) ZeroOut 

func (NoAddressSpaceIO) ZeroOut(addr hostarch.Addr, toZero uintptr) (uintptr, error)

ZeroOut implements AddressSpaceIO.ZeroOut.

type NoCPUPreemptionDetection 

type NoCPUPreemptionDetection struct{}

NoCPUPreemptionDetection implements Platform.DetectsCPUPreemption and dependent methods for Platforms that do not support this feature.

func (NoCPUPreemptionDetection) DetectsCPUPreemption 

func (NoCPUPreemptionDetection) DetectsCPUPreemption() bool

DetectsCPUPreemption implements Platform.DetectsCPUPreemption.

func (NoCPUPreemptionDetection) PreemptAllCPUs 

func (NoCPUPreemptionDetection) PreemptAllCPUs() error

PreemptAllCPUs implements Platform.PreemptAllCPUs.

type Platform 

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

	// HaveGlobalMemoryBarrier returns true if the GlobalMemoryBarrier method
	// is supported.
	HaveGlobalMemoryBarrier() 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 hostarch.PageSize.
	MapUnit() uint64

	// MinUserAddress returns the minimum mappable address on this
	// platform.
	MinUserAddress() hostarch.Addr

	// MaxUserAddress returns the maximum mappable address on this
	// platform.
	MaxUserAddress() hostarch.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

	// GlobalMemoryBarrier blocks until all threads running application code
	// (via Context.Switch) and all task goroutines "have passed through a
	// state where all memory accesses to user-space addresses match program
	// order between entry to and return from [GlobalMemoryBarrier]", as for
	// membarrier(2).
	//
	// Preconditions: HaveGlobalMemoryBarrier() == true.
	GlobalMemoryBarrier() error

	// SyscallFilters returns syscalls made exclusively by this platform.
	SyscallFilters() seccomp.SyscallRules
}

Platform provides abstractions for execution contexts (Context, AddressSpace).

func FromContext 

func FromContext(ctx context.Context) Platform

FromContext returns the Platform that is used to execute ctx's application code, or nil if no such Platform exists.

type Requirements 

type Requirements struct {
	// RequiresCurrentPIDNS indicates that the sandbox has to be started in the
	// current pid namespace.
	RequiresCurrentPIDNS bool
	// RequiresCapSysPtrace indicates that the sandbox has to be started with
	// the CAP_SYS_PTRACE capability.
	RequiresCapSysPtrace bool
}

Requirements is used to specify platform specific requirements.

type SegmentationFault 

type SegmentationFault struct {
	// Addr is the address at which the fault occurred.
	Addr hostarch.Addr
}

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.

func (SegmentationFault) Error 

func (f SegmentationFault) Error() string

Error implements error.Error.

type UseHostGlobalMemoryBarrier 

type UseHostGlobalMemoryBarrier struct{}

UseHostGlobalMemoryBarrier implements Platform.HaveGlobalMemoryBarrier and Platform.GlobalMemoryBarrier by invoking equivalent functionality on the host.

func (UseHostGlobalMemoryBarrier) GlobalMemoryBarrier 

func (UseHostGlobalMemoryBarrier) GlobalMemoryBarrier() error

GlobalMemoryBarrier implements Platform.GlobalMemoryBarrier.

func (UseHostGlobalMemoryBarrier) HaveGlobalMemoryBarrier 

func (UseHostGlobalMemoryBarrier) HaveGlobalMemoryBarrier() bool

HaveGlobalMemoryBarrier implements Platform.HaveGlobalMemoryBarrier.

type UseHostProcessMemoryBarrier 

type UseHostProcessMemoryBarrier struct{}

UseHostProcessMemoryBarrier implements Platform.HaveGlobalMemoryBarrier and Platform.GlobalMemoryBarrier by invoking a process-local memory barrier. This is faster than UseHostGlobalMemoryBarrier, but is only appropriate for platforms for which application code executes while using the sentry's mm_struct.

func (UseHostProcessMemoryBarrier) GlobalMemoryBarrier 

func (UseHostProcessMemoryBarrier) GlobalMemoryBarrier() error

GlobalMemoryBarrier implements Platform.GlobalMemoryBarrier.

func (UseHostProcessMemoryBarrier) HaveGlobalMemoryBarrier 

func (UseHostProcessMemoryBarrier) HaveGlobalMemoryBarrier() bool

HaveGlobalMemoryBarrier implements Platform.HaveGlobalMemoryBarrier.

Source Files

View all Source files

Directories

Path Synopsis
Package interrupt provides an interrupt helper.
 Package interrupt provides an interrupt helper.
Package kvm provides a kvm-based implementation of the platform interface.
 Package kvm provides a kvm-based implementation of the platform interface.
Package ptrace provides a ptrace-based implementation of the platform interface.
 Package ptrace provides a ptrace-based implementation of the platform interface.

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