The TPU userspace driver needs access to specific PCI device information
located in Linux sysfs. We mirror the sysfs paths the driver reads on the host
in the Sentry sysfs. This way we can ensure we only expose the host device
information that's strictly necessary for TPU to run.
PiperOrigin-RevId: 550005271
These inodes can never be part of a filesystem tree. They are nameless and
never have a parent.
This allows us to avoid taking a lock in kernfs.InotifyWithParent for such
anonymous inodes.
PiperOrigin-RevId: 538823227
This catches up the interface to the `EmitUnimplementedEvent` method signature
on `kernel.Kernel`.
Also add build-time test to verify that `kernel.Kernel` implements this
interface, in order to catch such breakages at build time in the future.
PiperOrigin-RevId: 519000411
Some implementations handle more flags than others, so it doesn't
make sense to have one set of rules for all.
This change should functionally be a no-op.
PiperOrigin-RevId: 502712415
This is consistent with Linux. Some applications recursively add
files to inotify FD. They fail if they run into kernfs files
because inotify_add_watch(2) returns EPERM in that case.
PiperOrigin-RevId: 462642204
Since refsvfs2 are used in netstack, we should use atomicbitops to avoid
breaking 32-bit builds.
On 64-bit builds there is no performance difference.
PiperOrigin-RevId: 439687980
Some applications use product_name to find out if they are running inside
cloud providers and behave differently, like changing network settings or
expecting services to be available to the VM.
More details here: https://docs.google.com/document/d/1xQXE27x9wTvwPsgiX9Hn0o8mcq5z3SKi-1jwscQsCAk
This is also needed for: go/auth-library-noping
PiperOrigin-RevId: 435454155
Create the /sys/fs/cgroup directory when cgroups are available. This
creates the empty directory to serve as the mountpoint, actually
mounting cgroups is left to the launcher/userspace. This is consistent
with Linux behaviour.
Without this mountpoint, getdents(2) on /sys/fs indicates an empty
directory even if the launcher mounts cgroupfs at /sys/fs/cgroup. The
launcher can't create the mountpoint directory since sysfs doesn't
support mkdir.
PiperOrigin-RevId: 398596698
Removes package syserror and moves still relevant code to either linuxerr
or to syserr (to be later removed).
Internal errors are converted from random types to *errors.Error types used
in linuxerr. Internal errors are in linuxerr/internal.go.
PiperOrigin-RevId: 390724202
Update all instances of the above errors to the faster linuxerr implementation.
With the temporary linuxerr.Equals(), no logical changes are made.
PiperOrigin-RevId: 382306655
Remove three syserror entries duplicated in linuxerr. Because of the
linuxerr.Equals method, this is a mere change of return values from
syserror to linuxerr definitions.
Done with only these three errnos as CLs removing all grow to a significantly
large size.
PiperOrigin-RevId: 382173835
Add a coverage-report flag that will cause the sandbox to generate a coverage
report (with suffix .cov) in the debug log directory upon exiting. For the
report to be generated, runsc must have been built with the following Bazel
flags: `--collect_code_coverage --instrumentation_filter=...`.
With coverage reports, we should be able to aggregate results across all tests
to surface code coverage statistics for the project as a whole.
The report is simply a text file with each line representing a covered block
as `file:start_line.start_col,end_line.end_col`. Note that this is similar to
the format of coverage reports generated with `go test -coverprofile`,
although we omit the count and number of statements, which are not useful for
us.
Some simple ways of getting coverage reports:
bazel test <some_test> --collect_code_coverage \
--instrumentation_filter=//pkg/...
bazel build //runsc --collect_code_coverage \
--instrumentation_filter=//pkg/...
runsc -coverage-report=dir/ <other_flags> do ...
PiperOrigin-RevId: 368952911
This lets us avoid treating a value of 0 as one reference. All references
using the refsvfs2 template must call InitRefs() before the reference is
incremented/decremented, or else a panic will occur. Therefore, it should be
pretty easy to identify missing InitRef calls during testing.
Updates #1486.
PiperOrigin-RevId: 341411151
Much like the VFS2 gofer client, kernfs too now caches dentries. The size of the
LRU cache is configurable via mount options.
Have adopted the same reference semantics from gofer client dentry.
Only sysfs and procfs use this LRU cache. The rest of the kernfs users (devpts,
fusefs, host, pipefs, sockfs) still use the no cache approach.
PiperOrigin-RevId: 339139835
Added the following fields in kernfs.InodeAttr:
- blockSize
- atime
- mtime
- ctime
Also resolved all TODOs for #1193.
Fixes#1193
PiperOrigin-RevId: 338714527
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
Singleton filesystem like devpts and devtmpfs have a single filesystem shared
among all mounts, so they acquire a "self-reference" when initialized that
must be released when the entire virtual filesystem is released at sandbox
exit.
PiperOrigin-RevId: 336828852
This change aims to fix the memory leak issue reported in #3933.
Background:
VFS2 kernfs kept accumulating invalid dentries if those dentries were not
walked on. After substantial consideration of the problem by our team, we
decided to have an LRU cache solution. This change is the first part to that
solution, where we don't cache anything. The LRU cache can be added on top of
this.
What has changed:
- Introduced the concept of an inode tree in kernfs.OrderedChildren.
This is helpful is cases where the lifecycle of an inode is different from
that of a dentry.
- OrderedChildren now deals with initialized inodes instead of initialized
dentries. It now implements Lookup() where it constructs a new dentry
using the inode.
- OrderedChildren holds a ref on all its children inodes. With this change,
now an inode can "outlive" a dentry pointing to it. See comments in
kernfs.OrderedChildren.
- The kernfs dentry tree is solely maintained by kernfs only. Inode
implementations can not modify the dentry tree.
- Dentries that reach ref count 0 are removed from the dentry tree.
- revalidateChildLocked now defer-DecRefs the newly created dentry from
Inode.Lookup(), limiting its life to the current filesystem operation. If
refs are picked on the dentry during the FS op (via an FD or something),
then it will stick around and will be removed when the FD is closed. So there
is essentially _no caching_ for Look()ed up dentries.
- kernfs.DecRef does not have the precondition that fs.mu must be locked.
Fixes#3933
PiperOrigin-RevId: 336768576
- When the KCOV_ENABLE_TRACE ioctl is called with the trace kind KCOV_TRACE_PC,
the kcov mode should be set to KCOV_*MODE*_TRACE_PC.
- When the owning task of kcov exits, the memory mapping should not be cleared
so it can be used by other tasks.
- Add more tests (also tested on native Linux kcov).
PiperOrigin-RevId: 335202585
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
In Linux, a kernel configuration is set that compiles the kernel with a
custom function that is called at the beginning of every basic block, which
updates the memory-mapped coverage information. The Go coverage tool does not
allow us to inject arbitrary instructions into basic blocks, but it does
provide data that we can convert to a kcov-like format and transfer them to
userspace through a memory mapping.
Note that this is not a strict implementation of kcov, which is especially
tricky to do because we do not have the same coverage tools available in Go
that that are available for the actual Linux kernel. In Linux, a kernel
configuration is set that compiles the kernel with a custom function that is
called at the beginning of every basic block to write program counters to the
kcov memory mapping. In Go, however, coverage tools only give us a count of
basic blocks as they are executed. Every time we return to userspace, we
collect the coverage information and write out PCs for each block that was
executed, providing userspace with the illusion that the kcov data is always
up to date. For convenience, we also generate a unique synthetic PC for each
block instead of using actual PCs. Finally, we do not provide thread-specific
coverage data (each kcov instance only contains PCs executed by the thread
owning it); instead, we will supply data for any file specified by --
instrumentation_filter.
Also, fix issue in nogo that was causing pkg/coverage:coverage_nogo
compilation to fail.
PiperOrigin-RevId: 328426526
- Remove comment about GenericDirectoryFD not being compatible with
dynamic directories. It is currently being used to implement dynamic
directories.
- Try to handle SEEK_END better than setting the offset to
infinity. SEEK_END is poorly defined for dynamic directories
anyways, so at least try make it work correctly for the static
entries.
Updates #1193.
PiperOrigin-RevId: 327890128
- 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
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
- Return ENOENT for /proc/[pid]/task if task is zoombied or terminated
- Allow directory to be Seek() to the end
- Construct synthetic files for /proc/[pid]/ns/*
- Changed GenericDirectoryFD.Init to not register with FileDescription,
otherwise other implementation cannot change behavior.
Updates #1195,1193
PiperOrigin-RevId: 308294649
Both have analogues in Linux:
* struct file_system_type has a char *name field.
* struct super_block keeps a pointer to the file_system_type.
These fields are necessary to support the `filesystem type` field in
/proc/[pid]/mountinfo.
PiperOrigin-RevId: 303434063
Only gofer filesystem was calling vfs.CheckSetStat for
vfs.FilesystemImpl.SetStatAt and vfs.FileDescriptionImpl.SetStat.
Updates #1193, #1672, #1197
PiperOrigin-RevId: 301226522
