Implement sysv shm.

PiperOrigin-RevId: 197058289
Change-Id: I3946c25028b7e032be4894d61acb48ac0c24d574

1 files changed, 20 insertions, 0 deletions

diff --git a/pkg/sentry/context/context.go b/pkg/sentry/context/context.go
index e0dffafba..598c5b4ff 100644
--- a/pkg/sentry/context/context.go
+++ b/pkg/sentry/context/context.go
@@ -20,6 +20,26 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/log"
 )
 
+type contextID int
+
+// Globally accessible values from a context. These keys are defined in the
+// context package to resolve dependency cycles by not requiring the caller to
+// import packages usually required to get these information.
+const (
+	// CtxThreadGroupID is the current thread group ID when a context represents
+	// a task context. The value is represented as an int32.
+	CtxThreadGroupID contextID = iota
+)
+
+// ThreadGroupIDFromContext returns the current thread group ID when ctx
+// represents a task context.
+func ThreadGroupIDFromContext(ctx Context) (tgid int32, ok bool) {
+	if tgid := ctx.Value(CtxThreadGroupID); tgid != nil {
+		return tgid.(int32), true
+	}
+	return 0, false
+}
+
 // A Context represents a thread of execution (hereafter "goroutine" to reflect
 // Go idiosyncrasy). It carries state associated with the goroutine across API
 // boundaries.