diff options
| -rwxr-xr-x | pkg/sentry/vfs/file_description_impl_util.go | 76 |
1 files changed, 61 insertions, 15 deletions
diff --git a/pkg/sentry/vfs/file_description_impl_util.go b/pkg/sentry/vfs/file_description_impl_util.go index fb9b87fdc..a4900c170 100755 --- a/pkg/sentry/vfs/file_description_impl_util.go +++ b/pkg/sentry/vfs/file_description_impl_util.go @@ -192,21 +192,6 @@ func (DentryMetadataFileDescriptionImpl) SetStat(ctx context.Context, opts SetSt panic("illegal call to DentryMetadataFileDescriptionImpl.SetStat") } -// DynamicBytesFileDescriptionImpl may be embedded by implementations of -// FileDescriptionImpl that represent read-only regular files whose contents -// are backed by a bytes.Buffer that is regenerated when necessary, consistent -// with Linux's fs/seq_file.c:single_open(). -// -// DynamicBytesFileDescriptionImpl.SetDataSource() must be called before first -// use. -type DynamicBytesFileDescriptionImpl struct { - data DynamicBytesSource // immutable - mu sync.Mutex // protects the following fields - buf bytes.Buffer - off int64 - lastRead int64 // offset at which the last Read, PRead, or Seek ended -} - // DynamicBytesSource represents a data source for a // DynamicBytesFileDescriptionImpl. type DynamicBytesSource interface { @@ -225,6 +210,30 @@ func (s *StaticData) Generate(ctx context.Context, buf *bytes.Buffer) error { return nil } +// WritableDynamicBytesSource extends DynamicBytesSource to allow writes to the +// underlying source. +type WritableDynamicBytesSource interface { + DynamicBytesSource + + // Write sends writes to the source. + Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) +} + +// DynamicBytesFileDescriptionImpl may be embedded by implementations of +// FileDescriptionImpl that represent read-only regular files whose contents +// are backed by a bytes.Buffer that is regenerated when necessary, consistent +// with Linux's fs/seq_file.c:single_open(). +// +// DynamicBytesFileDescriptionImpl.SetDataSource() must be called before first +// use. +type DynamicBytesFileDescriptionImpl struct { + data DynamicBytesSource // immutable + mu sync.Mutex // protects the following fields + buf bytes.Buffer + off int64 + lastRead int64 // offset at which the last Read, PRead, or Seek ended +} + // SetDataSource must be called exactly once on fd before first use. func (fd *DynamicBytesFileDescriptionImpl) SetDataSource(data DynamicBytesSource) { fd.data = data @@ -304,6 +313,43 @@ func (fd *DynamicBytesFileDescriptionImpl) Seek(ctx context.Context, offset int6 return offset, nil } +// Preconditions: fd.mu must be locked. +func (fd *DynamicBytesFileDescriptionImpl) pwriteLocked(ctx context.Context, src usermem.IOSequence, offset int64, opts WriteOptions) (int64, error) { + if opts.Flags&^(linux.RWF_HIPRI|linux.RWF_DSYNC|linux.RWF_SYNC) != 0 { + return 0, syserror.EOPNOTSUPP + } + + writable, ok := fd.data.(WritableDynamicBytesSource) + if !ok { + return 0, syserror.EINVAL + } + n, err := writable.Write(ctx, src, offset) + if err != nil { + return 0, err + } + + // Invalidate cached data that might exist prior to this call. + fd.buf.Reset() + return n, nil +} + +// PWrite implements FileDescriptionImpl.PWrite. +func (fd *DynamicBytesFileDescriptionImpl) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts WriteOptions) (int64, error) { + fd.mu.Lock() + n, err := fd.pwriteLocked(ctx, src, offset, opts) + fd.mu.Unlock() + return n, err +} + +// Write implements FileDescriptionImpl.Write. +func (fd *DynamicBytesFileDescriptionImpl) Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) { + fd.mu.Lock() + n, err := fd.pwriteLocked(ctx, src, fd.off, opts) + fd.off += n + fd.mu.Unlock() + return n, err +} + // GenericConfigureMMap may be used by most implementations of // FileDescriptionImpl.ConfigureMMap. func GenericConfigureMMap(fd *FileDescription, m memmap.Mappable, opts *memmap.MMapOpts) error { |