3 files changed, 104 insertions, 2 deletions
diff --git a/pkg/sentry/syscalls/linux/vfs2/BUILD b/pkg/sentry/syscalls/linux/vfs2/BUILD
index 4c7b8f819..14838aa2c 100644
--- a/pkg/sentry/syscalls/linux/vfs2/BUILD
+++ b/pkg/sentry/syscalls/linux/vfs2/BUILD
@@ -19,6 +19,7 @@ go_library(
         "poll.go",
         "read_write.go",
         "setstat.go",
+        "signal.go",
         "socket.go",
         "stat.go",
         "stat_amd64.go",
@@ -39,6 +40,7 @@ go_library(
         "//pkg/sentry/arch",
         "//pkg/sentry/fsbridge",
         "//pkg/sentry/fsimpl/pipefs",
+        "//pkg/sentry/fsimpl/signalfd",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/pipe",
diff --git a/pkg/sentry/syscalls/linux/vfs2/signal.go b/pkg/sentry/syscalls/linux/vfs2/signal.go
new file mode 100644
index 000000000..623992f6f
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/signal.go
@@ -0,0 +1,100 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs2
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/signalfd"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// sharedSignalfd is shared between the two calls.
+func sharedSignalfd(t *kernel.Task, fd int32, sigset usermem.Addr, sigsetsize uint, flags int32) (uintptr, *kernel.SyscallControl, error) {
+	// Copy in the signal mask.
+	mask, err := slinux.CopyInSigSet(t, sigset, sigsetsize)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Always check for valid flags, even if not creating.
+	if flags&^(linux.SFD_NONBLOCK|linux.SFD_CLOEXEC) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Is this a change to an existing signalfd?
+	//
+	// The spec indicates that this should adjust the mask.
+	if fd != -1 {
+		file := t.GetFileVFS2(fd)
+		if file == nil {
+			return 0, nil, syserror.EBADF
+		}
+		defer file.DecRef()
+
+		// Is this a signalfd?
+		if sfd, ok := file.Impl().(*signalfd.SignalFileDescription); ok {
+			sfd.SetMask(mask)
+			return 0, nil, nil
+		}
+
+		// Not a signalfd.
+		return 0, nil, syserror.EINVAL
+	}
+
+	fileFlags := uint32(linux.O_RDWR)
+	if flags&linux.SFD_NONBLOCK != 0 {
+		fileFlags |= linux.O_NONBLOCK
+	}
+
+	// Create a new file.
+	vfsObj := t.Kernel().VFS()
+	file, err := signalfd.New(vfsObj, t, mask, fileFlags)
+	if err != nil {
+		return 0, nil, err
+	}
+	defer file.DecRef()
+
+	// Create a new descriptor.
+	fd, err = t.NewFDFromVFS2(0, file, kernel.FDFlags{
+		CloseOnExec: flags&linux.SFD_CLOEXEC != 0,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Done.
+	return uintptr(fd), nil, nil
+}
+
+// Signalfd implements the linux syscall signalfd(2).
+func Signalfd(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	sigset := args[1].Pointer()
+	sigsetsize := args[2].SizeT()
+	return sharedSignalfd(t, fd, sigset, sigsetsize, 0)
+}
+
+// Signalfd4 implements the linux syscall signalfd4(2).
+func Signalfd4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	sigset := args[1].Pointer()
+	sigsetsize := args[2].SizeT()
+	flags := args[3].Int()
+	return sharedSignalfd(t, fd, sigset, sigsetsize, flags)
+}
diff --git a/pkg/sentry/syscalls/linux/vfs2/vfs2.go b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
index f1b697844..9c04677f1 100644
--- a/pkg/sentry/syscalls/linux/vfs2/vfs2.go
+++ b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
@@ -139,14 +139,14 @@ func Override() {
 	s.Table[277] = syscalls.Supported("sync_file_range", SyncFileRange)
 	s.Table[280] = syscalls.Supported("utimensat", Utimensat)
 	s.Table[281] = syscalls.Supported("epoll_pwait", EpollPwait)
-	delete(s.Table, 282) // signalfd
+	s.Table[282] = syscalls.Supported("signalfd", Signalfd)
 	s.Table[283] = syscalls.Supported("timerfd_create", TimerfdCreate)
 	s.Table[284] = syscalls.Supported("eventfd", Eventfd)
 	delete(s.Table, 285) // fallocate
 	s.Table[286] = syscalls.Supported("timerfd_settime", TimerfdSettime)
 	s.Table[287] = syscalls.Supported("timerfd_gettime", TimerfdGettime)
 	s.Table[288] = syscalls.Supported("accept4", Accept4)
-	delete(s.Table, 289) // signalfd4
+	s.Table[289] = syscalls.Supported("signalfd4", Signalfd4)
 	s.Table[290] = syscalls.Supported("eventfd2", Eventfd2)
 	s.Table[291] = syscalls.Supported("epoll_create1", EpollCreate1)
 	s.Table[292] = syscalls.Supported("dup3", Dup3)