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2020-10-23Support VFS2 save/restore.Jamie Liu
Inode number consistency checks are now skipped in save/restore tests for reasons described in greatest detail in StatTest.StateDoesntChangeAfterRename. They pass in VFS1 due to the bug described in new test case SimpleStatTest.DifferentFilesHaveDifferentDeviceInodeNumberPairs. Fixes #1663 PiperOrigin-RevId: 338776148
2020-10-23Rewrite reference leak checker without finalizers.Dean Deng
Our current reference leak checker uses finalizers to verify whether an object has reached zero references before it is garbage collected. There are multiple problems with this mechanism, so a rewrite is in order. With finalizers, there is no way to guarantee that a finalizer will run before the program exits. When an unreachable object with a finalizer is garbage collected, its finalizer will be added to a queue and run asynchronously. The best we can do is run garbage collection upon sandbox exit to make sure that all finalizers are enqueued. Furthermore, if there is a chain of finalized objects, e.g. A points to B points to C, garbage collection needs to run multiple times before all of the finalizers are enqueued. The first GC run will register the finalizer for A but not free it. It takes another GC run to free A, at which point B's finalizer can be registered. As a result, we need to run GC as many times as the length of the longest such chain to have a somewhat reliable leak checker. Finally, a cyclical chain of structs pointing to one another will never be garbage collected if a finalizer is set. This is a well-known issue with Go finalizers (https://github.com/golang/go/issues/7358). Using leak checking on filesystem objects that produce cycles will not work and even result in memory leaks. The new leak checker stores reference counted objects in a global map when leak check is enabled and removes them once they are destroyed. At sandbox exit, any remaining objects in the map are considered as leaked. This provides a deterministic way of detecting leaks without relying on the complexities of finalizers and garbage collection. This approach has several benefits over the former, including: - Always detects leaks of objects that should be destroyed very close to sandbox exit. The old checker very rarely detected these leaks, because it relied on garbage collection to be run in a short window of time. - Panics if we forgot to enable leak check on a ref-counted object (we will try to remove it from the map when it is destroyed, but it will never have been added). - Can store extra logging information in the map values without adding to the size of the ref count struct itself. With the size of just an int64, the ref count object remains compact, meaning frequent operations like IncRef/DecRef are more cache-efficient. - Can aggregate leak results in a single report after the sandbox exits. Instead of having warnings littered in the log, which were non-deterministically triggered by garbage collection, we can print all warning messages at once. Note that this could also be a limitation--the sandbox must exit properly for leaks to be detected. Some basic benchmarking indicates that this change does not significantly affect performance when leak checking is enabled, which is understandable since registering/unregistering is only done once for each filesystem object. Updates #1486. PiperOrigin-RevId: 338685972
2020-10-02Convert uses of the binary package in kernel to go-marshal.Rahat Mahmood
PiperOrigin-RevId: 335077195
2020-08-25Use new reference count utility throughout gvisor.Dean Deng
This uses the refs_vfs2 template in vfs2 as well as objects common to vfs1 and vfs2. Note that vfs1-only refcounts are not replaced, since vfs1 will be deleted soon anyway. The following structs now use the new tool, with leak check enabled: devpts:rootInode fuse:inode kernfs:Dentry kernfs:dir kernfs:readonlyDir kernfs:StaticDirectory proc:fdDirInode proc:fdInfoDirInode proc:subtasksInode proc:taskInode proc:tasksInode vfs:FileDescription vfs:MountNamespace vfs:Filesystem sys:dir kernel:FSContext kernel:ProcessGroup kernel:Session shm:Shm mm:aioMappable mm:SpecialMappable transport:queue And the following use the template, but because they currently are not leak checked, a TODO is left instead of enabling leak check in this patch: kernel:FDTable tun:tunEndpoint Updates #1486. PiperOrigin-RevId: 328460377
2020-06-17Implement POSIX locksFabricio Voznika
- Change FileDescriptionImpl Lock/UnlockPOSIX signature to take {start,length,whence}, so the correct offset can be calculated in the implementations. - Create PosixLocker interface to make it possible to share the same locking code from different implementations. Closes #1480 PiperOrigin-RevId: 316910286
2020-06-09Implement flock(2) in VFS2Fabricio Voznika
LockFD is the generic implementation that can be embedded in FileDescriptionImpl implementations. Unique lock ID is maintained in vfs.FileDescription and is created on demand. Updates #1480 PiperOrigin-RevId: 315604825
2020-05-29Port inotify to vfs2, with support in tmpfs.Dean Deng
Support in other filesystem impls is still needed. Unlike in Linux and vfs1, we need to plumb inotify down to each filesystem implementation in order to keep track of links/inode structures properly. IN_EXCL_UNLINK still needs to be implemented, as well as a few inotify hooks that are not present in either vfs1 or vfs2. Those will be addressed in subsequent changes. Updates #1479. PiperOrigin-RevId: 313781995
2020-05-07Move pkg/sentry/vfs/{eventfd,timerfd} to new packages in pkg/sentry/fsimpl.Nicolas Lacasse
They don't depend on anything in VFS2, so they should be their own packages. PiperOrigin-RevId: 310416807
2020-05-07Port signalfd to vfs2.Nicolas Lacasse
PiperOrigin-RevId: 310404113
2020-05-04Port eventfd to VFS2.Nicolas Lacasse
And move sys_timerfd.go to just timerfd.go for consistency. Updates #1475. PiperOrigin-RevId: 309835029
2020-04-06Port timerfd to VFS2.Nicolas Lacasse
PiperOrigin-RevId: 305067208
2020-03-26Add BoundEndpointAt filesystem operation.Dean Deng
BoundEndpointAt() is needed to support Unix sockets bound at a file path, corresponding to BoundEndpoint() in VFS1. Updates #1476. PiperOrigin-RevId: 303258251
2020-03-16Enforce file size rlimits in VFS2Fabricio Voznika
Updates #1035 PiperOrigin-RevId: 301255357
2020-03-06Add plumbing for importing fds in VFS2, along with non-socket, non-TTY impl.Dean Deng
In VFS2, imported file descriptors are stored in a kernfs-based filesystem. Upon calling ImportFD, the host fd can be accessed in two ways: 1. a FileDescription that can be added to the FDTable, and 2. a Dentry in the host.filesystem mount, which we will want to access through magic symlinks in /proc/[pid]/fd/. An implementation of the kernfs.Inode interface stores a unique host fd. This inode can be inserted into file descriptions as well as dentries. This change also plumbs in three FileDescriptionImpls corresponding to fds for sockets, TTYs, and other files (only the latter is implemented here). These implementations will mostly make corresponding syscalls to the host. Where possible, the logic is ported over from pkg/sentry/fs/host. Updates #1672 PiperOrigin-RevId: 299417263
2020-02-25Port most syscalls to VFS2.Jamie Liu
pipe and pipe2 aren't ported, pending a slight rework of pipe FDs for VFS2. mount and umount2 aren't ported out of temporary laziness. access and faccessat need additional FSImpl methods to implement properly, but are stubbed to prevent googletest from CHECK-failing. Other syscalls require additional plumbing. Updates #1623 PiperOrigin-RevId: 297188448
2020-02-14Plumb VFS2 inside the SentrygVisor bot
- Added fsbridge package with interface that can be used to open and read from VFS1 and VFS2 files. - Converted ELF loader to use fsbridge - Added VFS2 types to FSContext - Added vfs.MountNamespace to ThreadGroup Updates #1623 PiperOrigin-RevId: 295183950
2020-01-29Add plumbing for file locks in VFS2.Dean Deng
Updates #1480 PiperOrigin-RevId: 292180192
2020-01-28Add VFS2 support for epoll.Jamie Liu
PiperOrigin-RevId: 291997879
2020-01-28Implement an anon_inode equivalent for VFS2.Jamie Liu
PiperOrigin-RevId: 291986033
2020-01-27Update package locations.Adin Scannell
Because the abi will depend on the core types for marshalling (usermem, context, safemem, safecopy), these need to be flattened from the sentry directory. These packages contain no sentry-specific details. PiperOrigin-RevId: 291811289
2020-01-27Standardize on tools directory.Adin Scannell
PiperOrigin-RevId: 291745021
2020-01-09New sync package.Ian Gudger
* Rename syncutil to sync. * Add aliases to sync types. * Replace existing usage of standard library sync package. This will make it easier to swap out synchronization primitives. For example, this will allow us to use primitives from github.com/sasha-s/go-deadlock to check for lock ordering violations. Updates #1472 PiperOrigin-RevId: 289033387
2019-12-30Add VFS2 support for device special files.Jamie Liu
- Add FileDescriptionOptions.UseDentryMetadata, which reduces the amount of boilerplate needed for device FDs and the like between filesystems. - Switch back to having FileDescription.Init() take references on the Mount and Dentry; otherwise managing refcounts around failed calls to OpenDeviceSpecialFile() / Device.Open() is tricky. PiperOrigin-RevId: 287575574
2019-12-11Add vfs.Pathname{WithDeleted,ForGetcwd}.Jamie Liu
The former is needed for vfs.FileDescription to implement memmap.MappingIdentity, and the latter is needed to implement getcwd(2). PiperOrigin-RevId: 285051855
2019-12-10Add most VFS methods for syscalls.Jamie Liu
PiperOrigin-RevId: 284892289
2019-11-21Import and structure cleanup.Adin Scannell
PiperOrigin-RevId: 281795269
2019-11-18Add vfs.GenericParseMountOptions().Jamie Liu
Equivalent to fs.GenericMountSourceOptions(). PiperOrigin-RevId: 281179287
2019-09-12Remove go_test from go_stateify and go_marshalMichael Pratt
They are no-ops, so the standard rule works fine. PiperOrigin-RevId: 268776264
2019-08-13Add vfs.DynamicBytesFileDescriptionImpl.Jamie Liu
This replaces fs/proc/seqfile for vfs2-based filesystems. PiperOrigin-RevId: 263254647
2019-07-18Sentry virtual filesystem, v2Jamie Liu
Major differences from the current ("v1") sentry VFS: - Path resolution is Filesystem-driven (FilesystemImpl methods call vfs.ResolvingPath methods) rather than VFS-driven (fs package owns a Dirent tree and calls fs.InodeOperations methods to populate it). This drastically improves performance, primarily by reducing overhead from inefficient synchronization and indirection. It also makes it possible to implement remote filesystem protocols that translate FS system calls into single RPCs, rather than having to make (at least) one RPC per path component, significantly reducing the latency of remote filesystems (especially during cold starts and for uncacheable shared filesystems). - Mounts are correctly represented as a separate check based on contextual state (current mount) rather than direct replacement in a fs.Dirent tree. This makes it possible to support (non-recursive) bind mounts and mount namespaces. Included in this CL is fsimpl/memfs, an incomplete in-memory filesystem that exists primarily to demonstrate intended filesystem implementation patterns and for benchmarking: BenchmarkVFS1TmpfsStat/1-6 3000000 497 ns/op BenchmarkVFS1TmpfsStat/2-6 2000000 676 ns/op BenchmarkVFS1TmpfsStat/3-6 2000000 904 ns/op BenchmarkVFS1TmpfsStat/8-6 1000000 1944 ns/op BenchmarkVFS1TmpfsStat/64-6 100000 14067 ns/op BenchmarkVFS1TmpfsStat/100-6 50000 21700 ns/op BenchmarkVFS2MemfsStat/1-6 10000000 197 ns/op BenchmarkVFS2MemfsStat/2-6 5000000 233 ns/op BenchmarkVFS2MemfsStat/3-6 5000000 268 ns/op BenchmarkVFS2MemfsStat/8-6 3000000 477 ns/op BenchmarkVFS2MemfsStat/64-6 500000 2592 ns/op BenchmarkVFS2MemfsStat/100-6 300000 4045 ns/op BenchmarkVFS1TmpfsMountStat/1-6 2000000 679 ns/op BenchmarkVFS1TmpfsMountStat/2-6 2000000 912 ns/op BenchmarkVFS1TmpfsMountStat/3-6 1000000 1113 ns/op BenchmarkVFS1TmpfsMountStat/8-6 1000000 2118 ns/op BenchmarkVFS1TmpfsMountStat/64-6 100000 14251 ns/op BenchmarkVFS1TmpfsMountStat/100-6 100000 22397 ns/op BenchmarkVFS2MemfsMountStat/1-6 5000000 317 ns/op BenchmarkVFS2MemfsMountStat/2-6 5000000 361 ns/op BenchmarkVFS2MemfsMountStat/3-6 5000000 387 ns/op BenchmarkVFS2MemfsMountStat/8-6 3000000 582 ns/op BenchmarkVFS2MemfsMountStat/64-6 500000 2699 ns/op BenchmarkVFS2MemfsMountStat/100-6 300000 4133 ns/op From this we can infer that, on this machine: - Constant cost for tmpfs stat() is ~160ns in VFS2 and ~280ns in VFS1. - Per-path-component cost is ~35ns in VFS2 and ~215ns in VFS1, a difference of about 6x. - The cost of crossing a mount boundary is about 80ns in VFS2 (MemfsMountStat/1 does approximately the same amount of work as MemfsStat/2, except that it also crosses a mount boundary). This is an inescapable cost of the separate mount lookup needed to support bind mounts and mount namespaces. PiperOrigin-RevId: 258853946
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