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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 syserror contains syscall error codes exported as error interface
// instead of Errno. This allows for fast comparison and returns when the
// comparand or return value is of type error because there is no need to
// convert from Errno to an interface, i.e., runtime.convT2I isn't called.
package syserror
import (
"errors"
"golang.org/x/sys/unix"
)
// The following variables have the same meaning as their syscall equivalent.
var (
EEXIST = error(unix.EEXIST)
EFAULT = error(unix.EFAULT)
EIDRM = error(unix.EIDRM)
EINTR = error(unix.EINTR)
EIO = error(unix.EIO)
EISDIR = error(unix.EISDIR)
ENOENT = error(unix.ENOENT)
ENOEXEC = error(unix.ENOEXEC)
ENOMEM = error(unix.ENOMEM)
ENOTSOCK = error(unix.ENOTSOCK)
ENOSPC = error(unix.ENOSPC)
ENOSYS = error(unix.ENOSYS)
ENOTDIR = error(unix.ENOTDIR)
ENOTTY = error(unix.ENOTTY)
EOPNOTSUPP = error(unix.EOPNOTSUPP)
ERANGE = error(unix.ERANGE)
ESRCH = error(unix.ESRCH)
)
var (
// ErrWouldBlock is an internal error used to indicate that an operation
// cannot be satisfied immediately, and should be retried at a later
// time, possibly when the caller has received a notification that the
// operation may be able to complete. It is used by implementations of
// the kio.File interface.
ErrWouldBlock = errors.New("request would block")
// ErrInterrupted is returned if a request is interrupted before it can
// complete.
ErrInterrupted = errors.New("request was interrupted")
// ErrExceedsFileSizeLimit is returned if a request would exceed the
// file's size limit.
ErrExceedsFileSizeLimit = errors.New("exceeds file size limit")
)
// errorMap is the map used to convert generic errors into errnos.
var errorMap = map[error]unix.Errno{}
// errorUnwrappers is an array of unwrap functions to extract typed errors.
var errorUnwrappers = []func(error) (unix.Errno, bool){}
// AddErrorTranslation allows modules to populate the error map by adding their
// own translations during initialization. Returns if the error translation is
// accepted or not. A pre-existing translation will not be overwritten by the
// new translation.
func AddErrorTranslation(from error, to unix.Errno) bool {
if _, ok := errorMap[from]; ok {
return false
}
errorMap[from] = to
return true
}
// AddErrorUnwrapper registers an unwrap method that can extract a concrete error
// from a typed, but not initialized, error.
func AddErrorUnwrapper(unwrap func(e error) (unix.Errno, bool)) {
errorUnwrappers = append(errorUnwrappers, unwrap)
}
// TranslateError translates errors to errnos, it will return false if
// the error was not registered.
func TranslateError(from error) (unix.Errno, bool) {
if err, ok := errorMap[from]; ok {
return err, true
}
// Try to unwrap the error if we couldn't match an error
// exactly. This might mean that a package has its own
// error type.
for _, unwrap := range errorUnwrappers {
if err, ok := unwrap(from); ok {
return err, true
}
}
return 0, false
}
// ConvertIntr converts the provided error code (err) to another one (intr) if
// the first error corresponds to an interrupted operation.
func ConvertIntr(err, intr error) error {
if err == ErrInterrupted {
return intr
}
return err
}
// SyscallRestartErrno represents a ERESTART* errno defined in the Linux's kernel
// include/linux/errno.h. These errnos are never returned to userspace
// directly, but are used to communicate the expected behavior of an
// interrupted syscall from the syscall to signal handling.
type SyscallRestartErrno int
// These numeric values are significant because ptrace syscall exit tracing can
// observe them.
//
// For all of the following errnos, if the syscall is not interrupted by a
// signal delivered to a user handler, the syscall is restarted.
const (
// ERESTARTSYS is returned by an interrupted syscall to indicate that it
// should be converted to EINTR if interrupted by a signal delivered to a
// user handler without SA_RESTART set, and restarted otherwise.
ERESTARTSYS = SyscallRestartErrno(512)
// ERESTARTNOINTR is returned by an interrupted syscall to indicate that it
// should always be restarted.
ERESTARTNOINTR = SyscallRestartErrno(513)
// ERESTARTNOHAND is returned by an interrupted syscall to indicate that it
// should be converted to EINTR if interrupted by a signal delivered to a
// user handler, and restarted otherwise.
ERESTARTNOHAND = SyscallRestartErrno(514)
// ERESTART_RESTARTBLOCK is returned by an interrupted syscall to indicate
// that it should be restarted using a custom function. The interrupted
// syscall must register a custom restart function by calling
// Task.SetRestartSyscallFn.
ERESTART_RESTARTBLOCK = SyscallRestartErrno(516)
)
// Error implements error.Error.
func (e SyscallRestartErrno) Error() string {
// Descriptions are borrowed from strace.
switch e {
case ERESTARTSYS:
return "to be restarted if SA_RESTART is set"
case ERESTARTNOINTR:
return "to be restarted"
case ERESTARTNOHAND:
return "to be restarted if no handler"
case ERESTART_RESTARTBLOCK:
return "interrupted by signal"
default:
return "(unknown interrupt error)"
}
}
// SyscallRestartErrnoFromReturn returns the SyscallRestartErrno represented by
// rv, the value in a syscall return register.
func SyscallRestartErrnoFromReturn(rv uintptr) (SyscallRestartErrno, bool) {
switch int(rv) {
case -int(ERESTARTSYS):
return ERESTARTSYS, true
case -int(ERESTARTNOINTR):
return ERESTARTNOINTR, true
case -int(ERESTARTNOHAND):
return ERESTARTNOHAND, true
case -int(ERESTART_RESTARTBLOCK):
return ERESTART_RESTARTBLOCK, true
default:
return 0, false
}
}
func init() {
AddErrorTranslation(ErrWouldBlock, unix.EWOULDBLOCK)
AddErrorTranslation(ErrInterrupted, unix.EINTR)
AddErrorTranslation(ErrExceedsFileSizeLimit, unix.EFBIG)
}
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