From 1336af78d5dc2a6bc54d22ed45f4dd4793c2f964 Mon Sep 17 00:00:00 2001
From: Jamie Liu <jamieliu@google.com>
Date: Tue, 6 Oct 2020 13:53:26 -0700
Subject: Implement membarrier(2) commands other than *_SYNC_CORE.

Updates #267

PiperOrigin-RevId: 335713923
---
 pkg/sentry/syscalls/linux/BUILD             |  1 +
 pkg/sentry/syscalls/linux/linux64.go        |  4 +-
 pkg/sentry/syscalls/linux/sys_membarrier.go | 70 +++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 2 deletions(-)
 create mode 100644 pkg/sentry/syscalls/linux/sys_membarrier.go

(limited to 'pkg/sentry/syscalls')

diff --git a/pkg/sentry/syscalls/linux/BUILD b/pkg/sentry/syscalls/linux/BUILD
index 75752b2e6..a2e441448 100644
--- a/pkg/sentry/syscalls/linux/BUILD
+++ b/pkg/sentry/syscalls/linux/BUILD
@@ -21,6 +21,7 @@ go_library(
         "sys_identity.go",
         "sys_inotify.go",
         "sys_lseek.go",
+        "sys_membarrier.go",
         "sys_mempolicy.go",
         "sys_mmap.go",
         "sys_mount.go",
diff --git a/pkg/sentry/syscalls/linux/linux64.go b/pkg/sentry/syscalls/linux/linux64.go
index b293669de..9c9def7cd 100644
--- a/pkg/sentry/syscalls/linux/linux64.go
+++ b/pkg/sentry/syscalls/linux/linux64.go
@@ -376,7 +376,7 @@ var AMD64 = &kernel.SyscallTable{
 		321: syscalls.CapError("bpf", linux.CAP_SYS_ADMIN, "", nil),
 		322: syscalls.Supported("execveat", Execveat),
 		323: syscalls.ErrorWithEvent("userfaultfd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/266"}), // TODO(b/118906345)
-		324: syscalls.ErrorWithEvent("membarrier", syserror.ENOSYS, "", []string{"gvisor.dev/issue/267"}),  // TODO(gvisor.dev/issue/267)
+		324: syscalls.PartiallySupported("membarrier", Membarrier, "Not supported on all platforms.", nil),
 		325: syscalls.PartiallySupported("mlock2", Mlock2, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
 
 		// Syscalls implemented after 325 are "backports" from versions
@@ -695,7 +695,7 @@ var ARM64 = &kernel.SyscallTable{
 		280: syscalls.CapError("bpf", linux.CAP_SYS_ADMIN, "", nil),
 		281: syscalls.Supported("execveat", Execveat),
 		282: syscalls.ErrorWithEvent("userfaultfd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/266"}), // TODO(b/118906345)
-		283: syscalls.ErrorWithEvent("membarrier", syserror.ENOSYS, "", []string{"gvisor.dev/issue/267"}),  // TODO(gvisor.dev/issue/267)
+		283: syscalls.PartiallySupported("membarrier", Membarrier, "Not supported on all platforms.", nil),
 		284: syscalls.PartiallySupported("mlock2", Mlock2, "Stub implementation. The sandbox lacks appropriate permissions.", nil),
 
 		// Syscalls after 284 are "backports" from versions of Linux after 4.4.
diff --git a/pkg/sentry/syscalls/linux/sys_membarrier.go b/pkg/sentry/syscalls/linux/sys_membarrier.go
new file mode 100644
index 000000000..288cd8512
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_membarrier.go
@@ -0,0 +1,70 @@
+// Copyright 2020 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 linux
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// Membarrier implements syscall membarrier(2).
+func Membarrier(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	cmd := args[0].Int()
+	flags := args[1].Int()
+
+	p := t.Kernel().Platform
+	if !p.HaveGlobalMemoryBarrier() {
+		// Event for applications that want membarrier on a configuration that
+		// doesn't support them.
+		t.Kernel().EmitUnimplementedEvent(t)
+		return 0, nil, syserror.ENOSYS
+	}
+
+	if flags != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	switch cmd {
+	case linux.MEMBARRIER_CMD_QUERY:
+		const supportedCommands = linux.MEMBARRIER_CMD_GLOBAL |
+			linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED |
+			linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED |
+			linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED |
+			linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED
+		return supportedCommands, nil, nil
+	case linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED:
+		if !t.MemoryManager().IsMembarrierPrivateEnabled() {
+			return 0, nil, syserror.EPERM
+		}
+		fallthrough
+	case linux.MEMBARRIER_CMD_GLOBAL, linux.MEMBARRIER_CMD_GLOBAL_EXPEDITED:
+		return 0, nil, p.GlobalMemoryBarrier()
+	case linux.MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED:
+		// no-op
+		return 0, nil, nil
+	case linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
+		t.MemoryManager().EnableMembarrierPrivate()
+		return 0, nil, nil
+	case linux.MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE, linux.MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE:
+		// We're aware of these, but they aren't implemented since no platform
+		// supports them yet.
+		t.Kernel().EmitUnimplementedEvent(t)
+		fallthrough
+	default:
+		return 0, nil, syserror.EINVAL
+	}
+}
-- 
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