Remove linux.EpollEvent.Fd.

glibc defines struct epoll_event in such a way that epoll_event.data.fd exists.
However, the kernel's definition of struct epoll_event makes epoll_event.data
an opaque uint64, so naming half of it "fd" just introduces confusion. Remove
the Fd field, and make Data a [2]int32 to compensate.

Also add required padding to linux.EpollEvent on ARM64.

PiperOrigin-RevId: 295250424

2 files changed, 10 insertions, 12 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_epoll.go b/pkg/sentry/syscalls/linux/sys_epoll.go
index 5f11b496c..fbef5b376 100644
--- a/pkg/sentry/syscalls/linux/sys_epoll.go
+++ b/pkg/sentry/syscalls/linux/sys_epoll.go
@@ -83,8 +83,7 @@ func EpollCtl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 		}
 
 		mask = waiter.EventMaskFromLinux(e.Events)
-		data[0] = e.Fd
-		data[1] = e.Data
+		data = e.Data
 	}
 
 	// Perform the requested operations.
diff --git a/pkg/sentry/vfs/epoll.go b/pkg/sentry/vfs/epoll.go
index 7c83f9a5a..eed41139b 100644
--- a/pkg/sentry/vfs/epoll.go
+++ b/pkg/sentry/vfs/epoll.go
@@ -85,8 +85,8 @@ type epollInterest struct {
 	ready bool
 	epollInterestEntry
 
-	// userData is the epoll_data_t associated with this epollInterest.
-	// userData is protected by epoll.mu.
+	// userData is the struct epoll_event::data associated with this
+	// epollInterest. userData is protected by epoll.mu.
 	userData [2]int32
 }
 
@@ -157,7 +157,7 @@ func (ep *EpollInstance) Seek(ctx context.Context, offset int64, whence int32) (
 // AddInterest implements the semantics of EPOLL_CTL_ADD.
 //
 // Preconditions: A reference must be held on file.
-func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, mask uint32, userData [2]int32) error {
+func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, event linux.EpollEvent) error {
 	// Check for cyclic polling if necessary.
 	subep, _ := file.impl.(*EpollInstance)
 	if subep != nil {
@@ -183,12 +183,12 @@ func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, mask uint
 	}
 
 	// Register interest in file.
-	mask |= linux.EPOLLERR | linux.EPOLLRDHUP
+	mask := event.Events | linux.EPOLLERR | linux.EPOLLRDHUP
 	epi := &epollInterest{
 		epoll:    ep,
 		key:      key,
 		mask:     mask,
-		userData: userData,
+		userData: event.Data,
 	}
 	ep.interest[key] = epi
 	wmask := waiter.EventMaskFromLinux(mask)
@@ -236,7 +236,7 @@ func (ep *EpollInstance) mightPollRecursive(ep2 *EpollInstance, remainingRecursi
 // ModifyInterest implements the semantics of EPOLL_CTL_MOD.
 //
 // Preconditions: A reference must be held on file.
-func (ep *EpollInstance) ModifyInterest(file *FileDescription, num int32, mask uint32, userData [2]int32) error {
+func (ep *EpollInstance) ModifyInterest(file *FileDescription, num int32, event linux.EpollEvent) error {
 	ep.interestMu.Lock()
 	defer ep.interestMu.Unlock()
 
@@ -250,13 +250,13 @@ func (ep *EpollInstance) ModifyInterest(file *FileDescription, num int32, mask u
 	}
 
 	// Update epi for the next call to ep.ReadEvents().
+	mask := event.Events | linux.EPOLLERR | linux.EPOLLRDHUP
 	ep.mu.Lock()
 	epi.mask = mask
-	epi.userData = userData
+	epi.userData = event.Data
 	ep.mu.Unlock()
 
 	// Re-register with the new mask.
-	mask |= linux.EPOLLERR | linux.EPOLLRDHUP
 	file.EventUnregister(&epi.waiter)
 	wmask := waiter.EventMaskFromLinux(mask)
 	file.EventRegister(&epi.waiter, wmask)
@@ -363,8 +363,7 @@ func (ep *EpollInstance) ReadEvents(events []linux.EpollEvent) int {
 		// Report ievents.
 		events[i] = linux.EpollEvent{
 			Events: ievents.ToLinux(),
-			Fd:     epi.userData[0],
-			Data:   epi.userData[1],
+			Data:   epi.userData,
 		}
 		i++
 		if i == len(events) {