Go's dev.typeparams branch already claims to be Go 1.18, so our !go1.18 build
tags breaking testing gVisor with that branch.
Normally I would not want to bump the build tags this early, but I plan to
extend checklinkname to check the assumptions in these files and remove the
build tags ASAP. So we just go ahead and bump the tags until then to unblock
testing.
PiperOrigin-RevId: 389037239
This CL introduces a 'checklinkname' analyzer, which provides rudimentary
type-checking that verifies that function signatures on the local and remote
sides of //go:linkname directives match expected values.
If the Go standard library changes the definitions of any of these function,
checklinkname will flag the change as a finding, providing an error informing
the gVisor team to adapt to the upstream changes. This allows us to eliminate
the majority of gVisor's forward-looking negative build tags, as we can catch
mismatches in testing [1].
The remaining forward-looking negative build tags are covering shared struct
definitions, which I hope to add to checklinkname in a future CL.
[1] Of course, semantics/requirements can change without the signature
changing, so we still must be careful, but this covers the common case.
PiperOrigin-RevId: 387873847
See https://github.com/golang/go/issues/19367 for rationale. Note that the
upstream decision arrived at in that thread, while useful for some of our use
cases, doesn't account for all of our SliceHeader use cases (we often use
SliceHeader to extract pointers from slices in a way that avoids bounds
checking and/or handles nil slices correctly) and also doesn't exist yet.
PiperOrigin-RevId: 358071574
Previously, it was not possible to encode/decode an object graph which
contained a pointer to a field within another type. This was because the
encoder was previously unable to disambiguate a pointer to an object and a
pointer within the object.
This CL remedies this by constructing an address map tracking the full memory
range object occupy. The encoded Refvalue message has been extended to allow
references to children objects within another object. Because the encoding
process may learn about object structure over time, we cannot encode any
objects under the entire graph has been generated.
This CL also updates the state package to use standard interfaces intead of
reflection-based dispatch in order to improve performance overall. This
includes a custom wire protocol to significantly reduce the number of
allocations and take advantage of structure packing.
As part of these changes, there are a small number of minor changes in other
places of the code base:
* The lists used during encoding are changed to use intrusive lists with the
objectEncodeState directly, which required that the ilist Len() method is
updated to work properly with the ElementMapper mechanism.
* A bug is fixed in the list code wherein Remove() called on an element that is
already removed can corrupt the list (removing the element if there's only a
single element). Now the behavior is correct.
* Standard error wrapping is introduced.
* Compressio was updated to implement the new wire.Reader and wire.Writer
inteface methods directly. The lack of a ReadByte and WriteByte caused issues
not due to interface dispatch, but because underlying slices for a Read or
Write call through an interface would always escape to the heap!
* Statify has been updated to support the new APIs.
See README.md for a description of how the new mechanism works.
PiperOrigin-RevId: 318010298
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
Michael Pratt
Jamie Liu
Zach Koopmans
Adin Scannell