Prepare for supporting cross compilation.

PiperOrigin-RevId: 346496532

pkg/flipcall/BUILD

@@ -11,7 +11,8 @@ go_library(
         "futex_linux.go",
         "io.go",
         "packet_window_allocator.go",
-        "packet_window_mmap.go",
+        "packet_window_mmap_amd64.go",
+        "packet_window_mmap_arm64.go",
     ],
     visibility = ["//visibility:public"],
     deps = [

pkg/flipcall/packet_window_mmap_arm64.go

@@ -0,0 +1,27 @@
+// 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.
+
+// +build arm64
+
+package flipcall
+
+import (
+	"syscall"
+)
+
+// Return a memory mapping of the pwd in memory that can be shared outside the sandbox.
+func packetWindowMmap(pwd PacketWindowDescriptor) (uintptr, syscall.Errno) {
+	m, _, err := syscall.RawSyscall6(syscall.SYS_MMAP, 0, uintptr(pwd.Length), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED, uintptr(pwd.FD), uintptr(pwd.Offset))
+	return m, err
+}

pkg/sentry/platform/ring0/BUILD

@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_library")
+load("//tools:defs.bzl", "arch_genrule", "go_library")
 load("//tools/go_generics:defs.bzl", "go_template", "go_template_instance")
 
 package(licenses = ["notice"])
@@ -39,19 +39,19 @@ go_template_instance(
     template = ":defs_arm64",
 )
 
-genrule(
+arch_genrule(
     name = "entry_impl_amd64",
     srcs = ["entry_amd64.s"],
     outs = ["entry_impl_amd64.s"],
-    cmd = "(echo -e '// build +amd64\\n' && $(location //pkg/sentry/platform/ring0/gen_offsets) && cat $(SRCS)) > $@",
+    cmd = "(echo -e '// build +amd64\\n' && QEMU $(location //pkg/sentry/platform/ring0/gen_offsets) && cat $(location entry_amd64.s)) > $@",
     tools = ["//pkg/sentry/platform/ring0/gen_offsets"],
 )
 
-genrule(
+arch_genrule(
     name = "entry_impl_arm64",
     srcs = ["entry_arm64.s"],
     outs = ["entry_impl_arm64.s"],
-    cmd = "(echo -e '// build +arm64\\n' && $(location //pkg/sentry/platform/ring0/gen_offsets) && cat $(SRCS)) > $@",
+    cmd = "(echo -e '// build +arm64\\n' && QEMU $(location //pkg/sentry/platform/ring0/gen_offsets) && cat $(location entry_arm64.s)) > $@",
     tools = ["//pkg/sentry/platform/ring0/gen_offsets"],
 )
 

pkg/sentry/platform/ring0/gen_offsets/BUILD

@@ -24,6 +24,9 @@ go_binary(
         "defs_impl_arm64.go",
         "main.go",
     ],
+    # Use the libc malloc to avoid any extra dependencies. This is required to
+    # pass the sentry deps test.
+    system_malloc = True,
     visibility = [
         "//pkg/sentry/platform/kvm:__pkg__",
         "//pkg/sentry/platform/ring0:__pkg__",

tools/bazeldefs/BUILD

@@ -58,3 +58,21 @@ bzl_library(
     srcs = ["defs.bzl"],
     visibility = ["//visibility:private"],
 )
+
+config_setting(
+    name = "linux_arm64_cross",
+    values = {
+        "cpu": "aarch64",
+        "host_cpu": "k8",
+    },
+    visibility = ["//visibility:private"],
+)
+
+config_setting(
+    name = "linux_amd64_cross",
+    values = {
+        "cpu": "k8",
+        "host_cpu": "aarch64",
+    },
+    visibility = ["//visibility:private"],
+)

tools/bazeldefs/defs.bzl

@@ -39,3 +39,44 @@ def default_net_util():
 
 def coreutil():
     return []  # Nothing needed.
+
+def select_native_vs_cross(native = [], amd64 = [], arm64 = [], cross = []):
+    values = {
+        "//tools/bazeldefs:linux_arm64_cross": arm64 + cross,
+        "//tools/bazeldefs:linux_amd64_cross": amd64 + cross,
+        "//conditions:default": native,
+    }
+    return select(values)
+
+def arch_genrule(name, srcs, outs, cmd, tools):
+    """Runs a gen command on the target architecture.
+
+    If the target architecture isn't match the host architecture, it will build
+    a command for the target architecture and run it via qemu.
+
+    The native genrule runs the command on the host architecture.
+
+    Args:
+     name: name of generated target.
+     srcs: A list of inputs for this rule.
+     cmd: The command to run. It has to contain " QEMU " before executed binaries.
+     outs: A list of files generated by this rule.
+     tools: A list of tool dependencies for this rule.
+    """
+    qemu_arm64 = "qemu-aarch64-static"
+    qemu_amd64 = "qemu-x86_64-static"
+    srcs = select_native_vs_cross(
+        cross = srcs + tools,
+        native = srcs,
+    )
+    tools = select_native_vs_cross(
+        cross = [],
+        native = tools,
+    )
+    cmd = select_native_vs_cross(
+        arm64 = cmd.replace("QEMU", qemu_arm64),
+        amd64 = cmd.replace("QEMU", qemu_amd64),
+        native = cmd.replace("QEMU", ""),
+        cross = "",
+    )
+    native.genrule(name = name, srcs = srcs, outs = outs, cmd = cmd, tools = tools)

tools/bazeldefs/go.bzl

@@ -28,7 +28,7 @@ def go_proto_library(name, **kwargs):
 def go_grpc_and_proto_libraries(name, **kwargs):
     _go_proto_or_grpc_library(_go_grpc_library, name, **kwargs)
 
-def go_binary(name, static = False, pure = False, x_defs = None, **kwargs):
+def go_binary(name, static = False, pure = False, x_defs = None, system_malloc = False, **kwargs):
     """Build a go binary.
 
     Args:
@@ -52,7 +52,7 @@ def go_importpath(target):
     """Returns the importpath for the target."""
     return target[GoLibrary].importpath
 
-def go_library(name, **kwargs):
+def go_library(name, arch_deps = [], **kwargs):
     _go_library(
         name = name,
         importpath = "gvisor.dev/gvisor/" + native.package_name(),

tools/defs.bzl

@@ -8,7 +8,7 @@ change for Google-internal and bazel-compatible rules.
 load("//tools/go_stateify:defs.bzl", "go_stateify")
 load("//tools/go_marshal:defs.bzl", "go_marshal", "marshal_deps", "marshal_test_deps")
 load("//tools/nogo:defs.bzl", "nogo_test")
-load("//tools/bazeldefs:defs.bzl", _build_test = "build_test", _bzl_library = "bzl_library", _coreutil = "coreutil", _default_installer = "default_installer", _default_net_util = "default_net_util", _more_shards = "more_shards", _most_shards = "most_shards", _proto_library = "proto_library", _rbe_platform = "rbe_platform", _rbe_toolchain = "rbe_toolchain", _select_arch = "select_arch", _select_system = "select_system", _short_path = "short_path")
+load("//tools/bazeldefs:defs.bzl", _arch_genrule = "arch_genrule", _build_test = "build_test", _bzl_library = "bzl_library", _coreutil = "coreutil", _default_installer = "default_installer", _default_net_util = "default_net_util", _more_shards = "more_shards", _most_shards = "most_shards", _proto_library = "proto_library", _rbe_platform = "rbe_platform", _rbe_toolchain = "rbe_toolchain", _select_arch = "select_arch", _select_system = "select_system", _short_path = "short_path")
 load("//tools/bazeldefs:cc.bzl", _cc_binary = "cc_binary", _cc_flags_supplier = "cc_flags_supplier", _cc_grpc_library = "cc_grpc_library", _cc_library = "cc_library", _cc_proto_library = "cc_proto_library", _cc_test = "cc_test", _cc_toolchain = "cc_toolchain", _gbenchmark = "gbenchmark", _grpcpp = "grpcpp", _gtest = "gtest", _vdso_linker_option = "vdso_linker_option")
 load("//tools/bazeldefs:go.bzl", _gazelle = "gazelle", _go_binary = "go_binary", _go_embed_data = "go_embed_data", _go_grpc_and_proto_libraries = "go_grpc_and_proto_libraries", _go_library = "go_library", _go_path = "go_path", _go_proto_library = "go_proto_library", _go_test = "go_test", _select_goarch = "select_goarch", _select_goos = "select_goos")
 load("//tools/bazeldefs:pkg.bzl", _pkg_deb = "pkg_deb", _pkg_tar = "pkg_tar")
@@ -16,6 +16,7 @@ load("//tools/bazeldefs:platforms.bzl", _default_platform = "default_platform",
 load("//tools/bazeldefs:tags.bzl", "go_suffixes")
 
 # Core rules.
+arch_genrule = _arch_genrule
 build_test = _build_test
 bzl_library = _bzl_library
 default_installer = _default_installer
@@ -184,6 +185,7 @@ def go_library(name, srcs, deps = [], imports = [], stateify = True, marshal = F
             name + suffix + "_state_autogen.go"
             for suffix in state_sets.keys()
         ]
+
         if "//pkg/state" not in all_deps:
             all_deps = all_deps + ["//pkg/state"]