checklinkname: rudimentary type-checking of linkname directives

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

9 files changed, 49 insertions, 21 deletions

diff --git a/pkg/gohacks/gohacks_unsafe.go b/pkg/gohacks/gohacks_unsafe.go
index 09fc14787..bd8ceba19 100644
--- a/pkg/gohacks/gohacks_unsafe.go
+++ b/pkg/gohacks/gohacks_unsafe.go
@@ -15,7 +15,13 @@
 //go:build go1.13 && !go1.18
 // +build go1.13,!go1.18
 
-// Check type signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
+
+// Check type signatures and Noescape when updating Go version.
+//
+// TODO(b/165820485): add these checks to checklinkname.
 
 // Package gohacks contains utilities for subverting the Go compiler.
 package gohacks
diff --git a/pkg/procid/procid_amd64.s b/pkg/procid/procid_amd64.s
index b5bbfff90..74a8de42c 100644
--- a/pkg/procid/procid_amd64.s
+++ b/pkg/procid/procid_amd64.s
@@ -15,6 +15,10 @@
 //go:build amd64 && go1.8 && !go1.18 && go1.1
 // +build amd64,go1.8,!go1.18,go1.1
 
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
+
 #include "textflag.h"
 
 TEXT ·Current(SB),NOSPLIT,$0-8
diff --git a/pkg/procid/procid_arm64.s b/pkg/procid/procid_arm64.s
index 772d96289..48182c4a9 100644
--- a/pkg/procid/procid_arm64.s
+++ b/pkg/procid/procid_arm64.s
@@ -15,6 +15,10 @@
 //go:build arm64 && go1.8 && !go1.18 && go1.1
 // +build arm64,go1.8,!go1.18,go1.1
 
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
+
 #include "textflag.h"
 
 TEXT ·Current(SB),NOSPLIT,$0-8
diff --git a/pkg/sentry/platform/kvm/bluepill_unsafe.go b/pkg/sentry/platform/kvm/bluepill_unsafe.go
index f63ab6aba..0f0c1e73b 100644
--- a/pkg/sentry/platform/kvm/bluepill_unsafe.go
+++ b/pkg/sentry/platform/kvm/bluepill_unsafe.go
@@ -12,10 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.12 && !go1.18
-// +build go1.12,!go1.18
+//go:build go1.12
+// +build go1.12
 
-// Check go:linkname function signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
 
 package kvm
 
@@ -28,7 +30,7 @@ import (
 )
 
 //go:linkname throw runtime.throw
-func throw(string)
+func throw(s string)
 
 // vCPUPtr returns a CPU for the given address.
 //
diff --git a/pkg/sentry/platform/kvm/machine_unsafe.go b/pkg/sentry/platform/kvm/machine_unsafe.go
index 35660e827..cc3a1253b 100644
--- a/pkg/sentry/platform/kvm/machine_unsafe.go
+++ b/pkg/sentry/platform/kvm/machine_unsafe.go
@@ -12,10 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.12 && !go1.18
-// +build go1.12,!go1.18
+//go:build go1.12
+// +build go1.12
 
-// Check go:linkname function signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
 
 package kvm
 
diff --git a/pkg/sentry/platform/ptrace/subprocess_unsafe.go b/pkg/sentry/platform/ptrace/subprocess_unsafe.go
index ffd4665f4..304722200 100644
--- a/pkg/sentry/platform/ptrace/subprocess_unsafe.go
+++ b/pkg/sentry/platform/ptrace/subprocess_unsafe.go
@@ -12,10 +12,12 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build go1.12 && !go1.18
-// +build go1.12,!go1.18
+//go:build go1.12
+// +build go1.12
 
-// Check go:linkname function signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
 
 package ptrace
 
diff --git a/pkg/sync/goyield_unsafe.go b/pkg/sync/goyield_unsafe.go
index 8639bb64e..757edbaba 100644
--- a/pkg/sync/goyield_unsafe.go
+++ b/pkg/sync/goyield_unsafe.go
@@ -3,10 +3,12 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.14 && !go1.18
-// +build go1.14,!go1.18
+//go:build go1.14
+// +build go1.14
 
-// Check go:linkname function signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
 
 package sync
 
diff --git a/pkg/sync/runtime_unsafe.go b/pkg/sync/runtime_unsafe.go
index 1d9cf304e..49d4109a9 100644
--- a/pkg/sync/runtime_unsafe.go
+++ b/pkg/sync/runtime_unsafe.go
@@ -6,8 +6,13 @@
 //go:build go1.13 && !go1.18
 // +build go1.13,!go1.18
 
-// Check go:linkname function signatures, type definitions, and constants when
-// updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
+
+// Check type definitions and constants when updating Go version.
+//
+// TODO(b/165820485): add these checks to checklinkname.
 
 package sync
 
@@ -109,10 +114,10 @@ type maptype struct {
 // These functions are only used within the sync package.
 
 //go:linkname semacquire sync.runtime_Semacquire
-func semacquire(s *uint32)
+func semacquire(addr *uint32)
 
 //go:linkname semrelease sync.runtime_Semrelease
-func semrelease(s *uint32, handoff bool, skipframes int)
+func semrelease(addr *uint32, handoff bool, skipframes int)
 
 //go:linkname canSpin sync.runtime_canSpin
 func canSpin(i int) bool
diff --git a/pkg/tcpip/link/rawfile/blockingpoll_yield_unsafe.go b/pkg/tcpip/link/rawfile/blockingpoll_yield_unsafe.go
index da900c24b..0b7b9e3de 100644
--- a/pkg/tcpip/link/rawfile/blockingpoll_yield_unsafe.go
+++ b/pkg/tcpip/link/rawfile/blockingpoll_yield_unsafe.go
@@ -12,12 +12,13 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-//go:build ((linux && amd64) || (linux && arm64)) && go1.12 && !go1.18
+//go:build ((linux && amd64) || (linux && arm64)) && go1.12
 // +build linux,amd64 linux,arm64
 // +build go1.12
-// +build !go1.18
 
-// Check go:linkname function signatures when updating Go version.
+// //go:linkname directives type-checked by checklinkname. Any other
+// non-linkname assumptions outside the Go 1 compatibility guarantee should
+// have an accompanied vet check or version guard build tag.
 
 package rawfile