platform

package
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 Go to latest Published: Dec 23, 2019 License: Apache-2.0 Imports: 11 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() usermem.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 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
}

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 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)
}

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(deviceFile *os.File) (Platform, error)
	OpenDevice() (*os.File, error)
}

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 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()
}

Context represents the execution context for a single thread.

type File 

type File interface {

	// 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
}

File represents a host file that may be mapped into an AddressSpace.

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() usermem.Addr

MinUserAddress implements platform.MinUserAddresss.

type NoAddressSpaceIO 

type NoAddressSpaceIO struct{}

NoAddressSpaceIO implements AddressSpaceIO methods by panicking.

func (NoAddressSpaceIO) CompareAndSwapUint32 

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

CompareAndSwapUint32 implements AddressSpaceIO.CompareAndSwapUint32.

func (NoAddressSpaceIO) CopyIn 

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

CopyIn implements AddressSpaceIO.CopyIn.

func (NoAddressSpaceIO) CopyOut 

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

CopyOut implements AddressSpaceIO.CopyOut.

func (NoAddressSpaceIO) LoadUint32 

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

LoadUint32 implements AddressSpaceIO.LoadUint32.

func (NoAddressSpaceIO) SwapUint32 

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

SwapUint32 implements AddressSpaceIO.SwapUint32.

func (NoAddressSpaceIO) ZeroOut 

func (NoAddressSpaceIO) ZeroOut(addr usermem.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

	// 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
}

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 SegmentationFault 

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

Source Files

View all Source files

Directories

Path Synopsis
Package interrupt provides an interrupt helper.
 Package interrupt provides an interrupt helper.
kvm
Package kvm provides a kvm-based implementation of the platform interface.
 Package kvm provides a kvm-based implementation of the platform interface.
testutil
Package testutil provides common assembly stubs for testing.
 Package testutil provides common assembly stubs for testing.
Package ptrace provides a ptrace-based implementation of the platform interface.
 Package ptrace provides a ptrace-based implementation of the platform interface.
Package ring0 provides basic operating system-level stubs.
 Package ring0 provides basic operating system-level stubs.
gen_offsets
Binary gen_offsets is a helper for generating offset headers.
 Binary gen_offsets is a helper for generating offset headers.
pagetables
Package pagetables provides a generic implementation of pagetables.
 Package pagetables provides a generic implementation of pagetables.
Package safecopy provides an efficient implementation of functions to access memory that may result in SIGSEGV or SIGBUS being sent to the accessor.
 Package safecopy provides an efficient implementation of functions to access memory that may result in SIGSEGV or SIGBUS being sent to the accessor.

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