Remove map from fd_map, change to fd_table.

This renames FDMap to FDTable and drops the kernel.FD type, which had an entire
package to itself and didn't serve much use (it was freely cast between types,
and served as more of an annoyance than providing any protection.)

Based on BenchmarkFDLookupAndDecRef-12, we can expect 5-10 ns per lookup
operation, and 10-15 ns per concurrent lookup operation of savings.

This also fixes two tangential usage issues with the FDMap. Namely, non-atomic
use of NewFDFrom and associated calls to Remove (that are both racy and fail to
drop the reference on the underlying file.)

PiperOrigin-RevId: 256285890

1 files changed, 41 insertions, 49 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index ccdb079bb..d1165a57a 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -23,7 +23,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/kdefs"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
 	"gvisor.dev/gvisor/pkg/sentry/socket/control"
@@ -200,9 +199,9 @@ func Socket(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	})
 	defer s.DecRef()
 
-	fd, err := t.FDMap().NewFDFrom(0, s, kernel.FDFlags{
+	fd, err := t.NewFDFrom(0, s, kernel.FDFlags{
 		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
-	}, t.ThreadGroup().Limits())
+	})
 	if err != nil {
 		return 0, nil, err
 	}
@@ -225,9 +224,6 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	fileFlags := fs.SettableFileFlags{
 		NonBlocking: stype&linux.SOCK_NONBLOCK != 0,
 	}
-	fdFlags := kernel.FDFlags{
-		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
-	}
 
 	// Create the socket pair.
 	s1, s2, e := socket.Pair(t, domain, linux.SockType(stype&0xf), protocol)
@@ -240,20 +236,16 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	defer s2.DecRef()
 
 	// Create the FDs for the sockets.
-	fd1, err := t.FDMap().NewFDFrom(0, s1, fdFlags, t.ThreadGroup().Limits())
-	if err != nil {
-		return 0, nil, err
-	}
-	fd2, err := t.FDMap().NewFDFrom(0, s2, fdFlags, t.ThreadGroup().Limits())
+	fds, err := t.NewFDs(0, []*fs.File{s1, s2}, kernel.FDFlags{
+		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
+	})
 	if err != nil {
-		t.FDMap().Remove(fd1)
 		return 0, nil, err
 	}
 
 	// Copy the file descriptors out.
-	if _, err := t.CopyOut(socks, []int32{int32(fd1), int32(fd2)}); err != nil {
-		t.FDMap().Remove(fd1)
-		t.FDMap().Remove(fd2)
+	if _, err := t.CopyOut(socks, fds); err != nil {
+		// Note that we don't close files here; see pipe(2) also.
 		return 0, nil, err
 	}
 
@@ -262,12 +254,12 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // Connect implements the linux syscall connect(2).
 func Connect(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Uint()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -291,14 +283,14 @@ func Connect(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // accept is the implementation of the accept syscall. It is called by accept
 // and accept4 syscall handlers.
-func accept(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, addrLen usermem.Addr, flags int) (uintptr, error) {
+func accept(t *kernel.Task, fd int32, addr usermem.Addr, addrLen usermem.Addr, flags int) (uintptr, error) {
 	// Check that no unsupported flags are passed in.
 	if flags & ^(linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
 		return 0, syscall.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, syscall.EBADF
 	}
@@ -331,7 +323,7 @@ func accept(t *kernel.Task, fd kdefs.FD, addr usermem.Addr, addrLen usermem.Addr
 
 // Accept4 implements the linux syscall accept4(2).
 func Accept4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 	flags := int(args[3].Int())
@@ -342,7 +334,7 @@ func Accept4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // Accept implements the linux syscall accept(2).
 func Accept(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
@@ -352,12 +344,12 @@ func Accept(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Bind implements the linux syscall bind(2).
 func Bind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Uint()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -380,11 +372,11 @@ func Bind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallC
 
 // Listen implements the linux syscall listen(2).
 func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	backlog := args[1].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -409,11 +401,11 @@ func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 
 // Shutdown implements the linux syscall shutdown(2).
 func Shutdown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	how := args[1].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -437,14 +429,14 @@ func Shutdown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // GetSockOpt implements the linux syscall getsockopt(2).
 func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	level := args[1].Int()
 	name := args[2].Int()
 	optValAddr := args[3].Pointer()
 	optLenAddr := args[4].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -521,14 +513,14 @@ func getSockOpt(t *kernel.Task, s socket.Socket, level, name, len int) (interfac
 //
 // Note that unlike Linux, enabling SO_PASSCRED does not autobind the socket.
 func SetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	level := args[1].Int()
 	name := args[2].Int()
 	optValAddr := args[3].Pointer()
 	optLen := args[4].Int()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -561,12 +553,12 @@ func SetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // GetSockName implements the linux syscall getsockname(2).
 func GetSockName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -589,12 +581,12 @@ func GetSockName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // GetPeerName implements the linux syscall getpeername(2).
 func GetPeerName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	addr := args[1].Pointer()
 	addrlen := args[2].Pointer()
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -617,7 +609,7 @@ func GetPeerName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.S
 
 // RecvMsg implements the linux syscall recvmsg(2).
 func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	flags := args[2].Int()
 
@@ -627,7 +619,7 @@ func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -663,7 +655,7 @@ func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // RecvMMsg implements the linux syscall recvmmsg(2).
 func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	vlen := args[2].Uint()
 	flags := args[3].Int()
@@ -680,7 +672,7 @@ func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -842,7 +834,7 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 
 // recvFrom is the implementation of the recvfrom syscall. It is called by
 // recvfrom and recv syscall handlers.
-func recvFrom(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLenPtr usermem.Addr) (uintptr, error) {
+func recvFrom(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLenPtr usermem.Addr) (uintptr, error) {
 	if int(bufLen) < 0 {
 		return 0, syscall.EINVAL
 	}
@@ -853,7 +845,7 @@ func recvFrom(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, f
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, syscall.EBADF
 	}
@@ -903,7 +895,7 @@ func recvFrom(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, f
 
 // RecvFrom implements the linux syscall recvfrom(2).
 func RecvFrom(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	bufPtr := args[1].Pointer()
 	bufLen := args[2].Uint64()
 	flags := args[3].Int()
@@ -916,7 +908,7 @@ func RecvFrom(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 
 // SendMsg implements the linux syscall sendmsg(2).
 func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	flags := args[2].Int()
 
@@ -926,7 +918,7 @@ func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -953,7 +945,7 @@ func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 
 // SendMMsg implements the linux syscall sendmmsg(2).
 func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	msgPtr := args[1].Pointer()
 	vlen := args[2].Uint()
 	flags := args[3].Int()
@@ -964,7 +956,7 @@ func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, nil, syscall.EBADF
 	}
@@ -1079,14 +1071,14 @@ func sendSingleMsg(t *kernel.Task, s socket.Socket, file *fs.File, msgPtr userme
 
 // sendTo is the implementation of the sendto syscall. It is called by sendto
 // and send syscall handlers.
-func sendTo(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLen uint32) (uintptr, error) {
+func sendTo(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLen uint32) (uintptr, error) {
 	bl := int(bufLen)
 	if bl < 0 {
 		return 0, syscall.EINVAL
 	}
 
 	// Get socket from the file descriptor.
-	file := t.FDMap().GetFile(fd)
+	file := t.GetFile(fd)
 	if file == nil {
 		return 0, syscall.EBADF
 	}
@@ -1135,7 +1127,7 @@ func sendTo(t *kernel.Task, fd kdefs.FD, bufPtr usermem.Addr, bufLen uint64, fla
 
 // SendTo implements the linux syscall sendto(2).
 func SendTo(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	fd := kdefs.FD(args[0].Int())
+	fd := args[0].Int()
 	bufPtr := args[1].Pointer()
 	bufLen := args[2].Uint64()
 	flags := args[3].Int()