diff --git a/.buckconfig.oss b/.buckconfig.oss
index 097106924613..a289ddd82a14 100644
--- a/.buckconfig.oss
+++ b/.buckconfig.oss
@@ -1,5 +1,8 @@
+[pt]
+  is_oss=1
+
 [buildfile]
-name = BUCK.oss
+  name = BUCK.oss
 
 [repositories]
   bazel_skylib = third_party/bazel-skylib/
diff --git a/BUCK.oss b/BUCK.oss
index 1a1c21e51a50..3e275b4bd5cd 100644
--- a/BUCK.oss
+++ b/BUCK.oss
@@ -23,6 +23,11 @@ load(
     "aten_ufunc_generated_all_cpu_sources",
     "TEMPLATE_SOURCE_LIST",
 )
+load(":buckbuild.bzl",
+    "define_buck_targets",
+)
+
+define_buck_targets()
 
 cxx_library(
     name = "pthreadpool",
@@ -85,67 +90,23 @@ cxx_library(
     visibility = ['PUBLIC'],
 )
 
-cxx_library(
-    name = "aten_header",
-    header_namespace = "",
-    exported_headers = subdir_glob([
-        # ATen Core
-        ("aten/src", "ATen/core/**/*.h"),
-        ("aten/src", "ATen/ops/*.h"),
-        # ATen Base
-        ("aten/src", "ATen/*.h"),
-        ("aten/src", "ATen/cpu/**/*.h"),
-        ("aten/src", "ATen/detail/*.h"),
-        ("aten/src", "ATen/quantized/*.h"),
-        ("aten/src", "ATen/vulkan/*.h"),
-        ("aten/src", "ATen/metal/*.h"),
-        ("aten/src", "ATen/mps/*.h"),
-        ("aten/src", "ATen/nnapi/*.h"),
-        # ATen Native
-        ("aten/src", "ATen/native/*.h"),
-        ("aten/src", "ATen/native/ao_sparse/quantized/cpu/*.h"),
-        ("aten/src", "ATen/native/cpu/**/*.h"),
-        ("aten/src", "ATen/native/sparse/*.h"),
-        ("aten/src", "ATen/native/mps/*.h"),
-        ("aten/src", "ATen/native/nested/*.h"),
-        ("aten/src", "ATen/native/quantized/*.h"),
-        ("aten/src", "ATen/native/quantized/cpu/*.h"),
-        ("aten/src", "ATen/native/transformers/*.h"),
-        ("aten/src", "ATen/native/ufunc/*.h"),
-        ("aten/src", "ATen/native/utils/*.h"),
-        ("aten/src", "ATen/native/vulkan/ops/*.h"),
-        ("aten/src", "ATen/native/xnnpack/*.h"),
-        # Remove the following after modifying codegen for mobile.
-        ("aten/src", "ATen/mkl/*.h"),
-        ("aten/src", "ATen/native/mkl/*.h"),
-        ("aten/src", "ATen/native/mkldnn/*.h"),
-    ], exclude = ["aten/src/ATen/Config.h"]),
-    visibility = ["PUBLIC"],
-)
-
-cxx_library(
-    name = "jit_core_headers",
-    header_namespace = "",
-    exported_headers = subdir_glob([("", x) for x in jit_core_headers]),
-)
-
-cxx_library(
-    name = "generated_aten_config_header",
-    header_namespace = "ATen",
-    exported_headers = {
-        "Config.h": ":generate_aten_config[Config.h]",
-    },
-)
-
-cxx_library(
-    name = "torch_mobile_headers",
-    header_namespace = "",
-    exported_headers = subdir_glob(
-        [
-            ("", "torch/csrc/jit/mobile/*.h"),
-        ],
-    ),
-    visibility = ["PUBLIC"],
+build_aten_cpu(
+    name = "aten_cpu",
+    srcs = jit_core_sources +
+           aten_cpu_source_list + [
+        # Generated
+        ":gen_aten[Functions.cpp]",
+        ":gen_aten[Operators_0.cpp]",
+        ":gen_aten[Operators_1.cpp]",
+        ":gen_aten[Operators_2.cpp]",
+        ":gen_aten[Operators_3.cpp]",
+        ":gen_aten[Operators_4.cpp]",
+        ":gen_aten[core/ATenOpList.cpp]",
+        ":gen_aten[core/TensorMethods.cpp]",
+    ] + [
+        # Needed by ATen/native/EmbeddingBag.cpp
+        "caffe2/perfkernels/embedding_lookup_idx.cc",
+    ],
 )
 
 fb_xplat_genrule(
@@ -169,7 +130,7 @@ fb_xplat_genrule(
         "-e 's/@AT_BUILD_WITH_LAPACK@/USE_LAPACK_FBXPLAT/g'",
         "-e 's/@AT_BLAS_F2C@/AT_BLAS_F2C_FBXPLAT/g'",
         "-e 's/@AT_BLAS_USE_CBLAS_DOT@/AT_BLAS_USE_CBLAS_DOT_FBXPLAT/g'",
-        "aten/src/ATen/Config.h.in > $OUT/Config.h"
+        "aten/src/ATen/Config.h.in > $OUT/Config.h",
     ]),
     outs = {
         "Config.h": ["Config.h"],
@@ -206,56 +167,8 @@ cxx_library(
     header_namespace = "ATen",
     exported_headers = ATEN_EXPORTED_HEADERS,
 )
-
-filegroup(
-    name = "aten_src_path",
-    srcs = [
-        "aten/src/ATen/native/native_functions.yaml",
-        "aten/src/ATen/native/tags.yaml",
-    ] + glob(["aten/src/ATen/templates/*"]),
-    visibility = [
-        "PUBLIC",
-    ],
-)
-
-build_aten_cpu(
-    name = "aten_cpu",
-    srcs = jit_core_sources +
-           aten_cpu_source_list + [
-        # Generated
-        ":gen_aten[Functions.cpp]",
-        ":gen_aten[Operators_0.cpp]",
-        ":gen_aten[Operators_1.cpp]",
-        ":gen_aten[Operators_2.cpp]",
-        ":gen_aten[Operators_3.cpp]",
-        ":gen_aten[Operators_4.cpp]",
-        ":gen_aten[core/ATenOpList.cpp]",
-        ":gen_aten[core/TensorMethods.cpp]",
-    ] + [
-        # Needed by ATen/native/EmbeddingBag.cpp
-        "caffe2/perfkernels/embedding_lookup_idx.cc",
-    ],
-)
-
 gen_aten_libtorch_files(name = "gen_aten_libtorch")
 
-
-GENERATED_AUTOGRAD_H = {
-    "Functions.h": ":gen_aten_libtorch[autograd/generated/Functions.h]",
-    "VariableType.h": ":gen_aten_libtorch[autograd/generated/VariableType.h]",
-    "variable_factories.h": ":gen_aten_libtorch[autograd/generated/variable_factories.h]",
-
-    # Don't build python bindings on mobile.
-    #"python_functions.h",
-}
-
-cxx_library(
-    name = "generated-autograd-headers",
-    header_namespace = "torch/csrc/autograd/generated",
-    exported_headers = GENERATED_AUTOGRAD_H,
-    visibility = ["PUBLIC"],
-)
-
 cxx_library(
     name = "torch_mobile_observer",
     srcs = [
@@ -276,63 +189,13 @@ cxx_library(
     ],
 )
 
-fb_xplat_genrule(
-    name = "generate-version-header",
-    srcs = [
-        "torch/csrc/api/include/torch/version.h.in",
-        "version.txt",
-    ],
-    cmd = "$(exe //tools/setup_helpers:gen-version-header) " + " ".join([
-        "--template-path",
-        "torch/csrc/api/include/torch/version.h.in",
-        "--version-path",
-        "version.txt",
-        "--output-path",
-        "$OUT/version.h",
+python_library(
+    name = "aten_code_template",
+    srcs = subdir_glob([
+        ("aten", "src/ATen/code_template.py"),
     ]),
-    outs = {
-        "version.h": ["version.h"],
-    },
-    default_outs = ["."],
-)
-
-cxx_library(
-    name = "generated-version-header",
-    header_namespace = "torch",
-    exported_headers = {
-        "version.h": ":generate-version-header[version.h]",
-    },
-)
-
-cxx_library(
-    name = "torch_headers",
-    header_namespace = "",
-    exported_headers = subdir_glob(
-        [
-            ("torch/csrc/api/include", "torch/**/*.h"),
-            ("", "torch/csrc/**/*.h"),
-            ("", "torch/csrc/generic/*.cpp"),
-            ("", "torch/script.h"),
-            ("", "torch/library.h"),
-            ("", "torch/custom_class.h"),
-            ("", "torch/custom_class_detail.h"),
-            # Add again due to namespace difference from aten_header.
-            ("", "aten/src/ATen/*.h"),
-            ("", "aten/src/ATen/quantized/*.h"),
-        ],
-        exclude = [
-            # Don't need on mobile.
-            "torch/csrc/Exceptions.h",
-            "torch/csrc/python_headers.h",
-            "torch/csrc/utils/auto_gil.h",
-            "torch/csrc/jit/serialization/mobile_bytecode_generated.h",
-            "torch/csrc/api/include/torch/version.h",
-        ],
-    ),
+    base_module = "",
     visibility = ["PUBLIC"],
-    deps = [
-        ":generated-version-header",
-    ],
 )
 
 
@@ -541,6 +404,17 @@ python_library(
     ],
 )
 
+python_binary(
+    name = "gen_aten_bin",
+    main_module = "torchgen.gen",
+    visibility = [
+        "PUBLIC",
+    ],
+    deps = [
+        "//torchgen:torchgen",
+    ],
+)
+
 python_binary(
     name = "gen_operators_yaml",
     main_module = "gen_operators_yaml",
diff --git a/buckbuild.bzl b/buckbuild.bzl
new file mode 100644
index 000000000000..9150061912c8
--- /dev/null
+++ b/buckbuild.bzl
@@ -0,0 +1,242 @@
+load("//tools/build_defs:expect.bzl", "expect")
+
+# NOTE: This file is shared by internal and OSS BUCK build.
+# These load paths point to different files in internal and OSS environment
+load("//tools/build_defs:fb_native_wrapper.bzl", "fb_native")
+load("//tools/build_defs:fb_xplat_cxx_library.bzl", "fb_xplat_cxx_library")
+load("//tools/build_defs:glob_defs.bzl", "subdir_glob")
+load(
+    ":build_variables.bzl",
+    "jit_core_headers",
+)
+
+def read_bool(section, field, default):
+    # @lint-ignore BUCKRESTRICTEDSYNTAX
+    value = read_config(section, field)
+    if value == None:
+        return default
+    expect(
+        value == "0" or value == "1",
+        "{}.{} == \"{}\", wanted \"0\" or \"1\".".format(section, field, value),
+    )
+    return bool(int(value))
+
+def is_oss_build():
+    return read_bool("pt", "is_oss", False)
+
+# for targets in caffe2 root path
+ROOT_NAME = "//" if is_oss_build() else "//xplat/caffe2"
+
+# for targets in subfolders
+ROOT_PATH = "//" if is_oss_build() else "//xplat/caffe2/"
+
+# these targets are shared by internal and OSS BUCK
+def define_buck_targets(
+        feature = None,
+        labels = []):
+    fb_xplat_cxx_library(
+        name = "th_header",
+        header_namespace = "",
+        exported_headers = subdir_glob([
+            # TH
+            ("aten/src", "TH/*.h"),
+            ("aten/src", "TH/*.hpp"),
+            ("aten/src", "TH/generic/*.h"),
+            ("aten/src", "TH/generic/*.hpp"),
+            ("aten/src", "TH/generic/simd/*.h"),
+            ("aten/src", "TH/vector/*.h"),
+            ("aten/src", "TH/generic/*.c"),
+            ("aten/src", "TH/generic/*.cpp"),
+            ("aten/src/TH", "*.h"),  # for #include <THGenerateFloatTypes.h>
+            # THNN
+            ("aten/src", "THNN/*.h"),
+            ("aten/src", "THNN/generic/*.h"),
+            ("aten/src", "THNN/generic/*.c"),
+        ]),
+        feature = feature,
+        labels = labels,
+    )
+
+    fb_xplat_cxx_library(
+        name = "aten_header",
+        header_namespace = "",
+        exported_headers = subdir_glob([
+            # ATen Core
+            ("aten/src", "ATen/core/**/*.h"),
+            ("aten/src", "ATen/ops/*.h"),
+            # ATen Base
+            ("aten/src", "ATen/*.h"),
+            ("aten/src", "ATen/cpu/**/*.h"),
+            ("aten/src", "ATen/detail/*.h"),
+            ("aten/src", "ATen/quantized/*.h"),
+            ("aten/src", "ATen/vulkan/*.h"),
+            ("aten/src", "ATen/metal/*.h"),
+            ("aten/src", "ATen/nnapi/*.h"),
+            # ATen Native
+            ("aten/src", "ATen/native/*.h"),
+            ("aten/src", "ATen/native/ao_sparse/quantized/cpu/*.h"),
+            ("aten/src", "ATen/native/cpu/**/*.h"),
+            ("aten/src", "ATen/native/sparse/*.h"),
+            ("aten/src", "ATen/native/nested/*.h"),
+            ("aten/src", "ATen/native/quantized/*.h"),
+            ("aten/src", "ATen/native/quantized/cpu/*.h"),
+            ("aten/src", "ATen/native/transformers/*.h"),
+            ("aten/src", "ATen/native/ufunc/*.h"),
+            ("aten/src", "ATen/native/utils/*.h"),
+            ("aten/src", "ATen/native/vulkan/ops/*.h"),
+            ("aten/src", "ATen/native/xnnpack/*.h"),
+            ("aten/src", "ATen/mps/*.h"),
+            ("aten/src", "ATen/native/mps/*.h"),
+            # Remove the following after modifying codegen for mobile.
+            ("aten/src", "ATen/mkl/*.h"),
+            ("aten/src", "ATen/native/mkl/*.h"),
+            ("aten/src", "ATen/native/mkldnn/*.h"),
+        ]),
+        visibility = ["PUBLIC"],
+        feature = feature,
+        labels = labels,
+    )
+
+    fb_xplat_cxx_library(
+        name = "aten_vulkan_header",
+        header_namespace = "",
+        exported_headers = subdir_glob([
+            ("aten/src", "ATen/native/vulkan/*.h"),
+            ("aten/src", "ATen/native/vulkan/api/*.h"),
+            ("aten/src", "ATen/native/vulkan/ops/*.h"),
+            ("aten/src", "ATen/vulkan/*.h"),
+        ]),
+        feature = feature,
+        labels = labels,
+        visibility = ["PUBLIC"],
+    )
+
+    fb_xplat_cxx_library(
+        name = "jit_core_headers",
+        header_namespace = "",
+        exported_headers = subdir_glob([("", x) for x in jit_core_headers]),
+        feature = feature,
+        labels = labels,
+    )
+
+    fb_xplat_cxx_library(
+        name = "torch_headers",
+        header_namespace = "",
+        exported_headers = subdir_glob(
+            [
+                ("torch/csrc/api/include", "torch/**/*.h"),
+                ("", "torch/csrc/**/*.h"),
+                ("", "torch/csrc/generic/*.cpp"),
+                ("", "torch/script.h"),
+                ("", "torch/library.h"),
+                ("", "torch/custom_class.h"),
+                ("", "torch/custom_class_detail.h"),
+                # Add again due to namespace difference from aten_header.
+                ("", "aten/src/ATen/*.h"),
+                ("", "aten/src/ATen/quantized/*.h"),
+            ],
+            exclude = [
+                # Don't need on mobile.
+                "torch/csrc/Exceptions.h",
+                "torch/csrc/python_headers.h",
+                "torch/csrc/utils/auto_gil.h",
+                "torch/csrc/jit/serialization/mobile_bytecode_generated.h",
+            ],
+        ),
+        feature = feature,
+        labels = labels,
+        visibility = ["PUBLIC"],
+        deps = [
+            ":generated-version-header",
+        ],
+    )
+
+    fb_xplat_cxx_library(
+        name = "aten_test_header",
+        header_namespace = "",
+        exported_headers = subdir_glob([
+            ("aten/src", "ATen/test/*.h"),
+        ]),
+    )
+
+    fb_xplat_cxx_library(
+        name = "torch_mobile_headers",
+        header_namespace = "",
+        exported_headers = subdir_glob(
+            [
+                ("", "torch/csrc/jit/mobile/*.h"),
+            ],
+        ),
+        feature = feature,
+        labels = labels,
+        visibility = ["PUBLIC"],
+    )
+
+    fb_xplat_cxx_library(
+        name = "generated_aten_config_header",
+        header_namespace = "ATen",
+        exported_headers = {
+            "Config.h": ":generate_aten_config[Config.h]",
+        },
+        feature = feature,
+        labels = labels,
+    )
+
+    fb_xplat_cxx_library(
+        name = "generated-autograd-headers",
+        header_namespace = "torch/csrc/autograd/generated",
+        exported_headers = {
+            "Functions.h": ":gen_aten_libtorch[autograd/generated/Functions.h]",
+            "VariableType.h": ":gen_aten_libtorch[autograd/generated/VariableType.h]",
+            "variable_factories.h": ":gen_aten_libtorch[autograd/generated/variable_factories.h]",
+            # Don't build python bindings on mobile.
+            #"python_functions.h",
+        },
+        feature = feature,
+        labels = labels,
+        visibility = ["PUBLIC"],
+    )
+
+    fb_xplat_cxx_library(
+        name = "generated-version-header",
+        header_namespace = "torch",
+        exported_headers = {
+            "version.h": ":generate-version-header[version.h]",
+        },
+        feature = feature,
+        labels = labels,
+    )
+
+    # @lint-ignore BUCKLINT
+    fb_native.genrule(
+        name = "generate-version-header",
+        srcs = [
+            "torch/csrc/api/include/torch/version.h.in",
+            "version.txt",
+        ],
+        cmd = "$(exe {}tools/setup_helpers:gen-version-header) ".format(ROOT_PATH) + " ".join([
+            "--template-path",
+            "torch/csrc/api/include/torch/version.h.in",
+            "--version-path",
+            "version.txt",
+            "--output-path",
+            "$OUT/version.h",
+        ]),
+        outs = {
+            "version.h": ["version.h"],
+        },
+        default_outs = ["."],
+    )
+
+    # @lint-ignore BUCKLINT
+    fb_native.filegroup(
+        name = "aten_src_path",
+        srcs = [
+            "aten/src/ATen/native/native_functions.yaml",
+            "aten/src/ATen/native/tags.yaml",
+            # @lint-ignore BUCKRESTRICTEDSYNTAX
+        ] + glob(["aten/src/ATen/templates/*"]),
+        visibility = [
+            "PUBLIC",
+        ],
+    )
diff --git a/tools/build_defs/buck_helpers.bzl b/tools/build_defs/buck_helpers.bzl
new file mode 100644
index 000000000000..c946f87eba06
--- /dev/null
+++ b/tools/build_defs/buck_helpers.bzl
@@ -0,0 +1,73 @@
+# Only used for PyTorch open source BUCK build
+
+IGNORED_ATTRIBUTE_PREFIX = [
+    "apple",
+    "fbobjc",
+    "windows",
+    "fbandroid",
+    "macosx",
+]
+
+IGNORED_ATTRIBUTES = [
+    "feature",
+    "platforms",
+]
+
+def filter_attributes(kwgs):
+    keys = list(kwgs.keys())
+
+    # drop unncessary attributes
+    for key in keys:
+        if key in IGNORED_ATTRIBUTES:
+            kwgs.pop(key)
+        else:
+            for invalid_prefix in IGNORED_ATTRIBUTE_PREFIX:
+                if key.startswith(invalid_prefix):
+                    kwgs.pop(key)
+    return kwgs
+
+# maps known fbsource deps to OSS deps
+DEPS_MAP = {
+    "//third-party/FP16:FP16": "//third_party:FP16",
+    "//third-party/FXdiv:FXdiv": "//third_party:FXdiv",
+    "//third-party/XNNPACK:XNNPACK": "//third_party:XNNPACK",
+    "//third-party/clog:clog": "//third_party:clog",
+    "//third-party/cpuinfo:cpuinfo": "//third_party:cpuinfo",
+    "//third-party/fmt:fmt": "//third_party:fmt",
+    "//third-party/glog:glog": "//third_party:glog",
+    "//third-party/psimd:psimd": "//third_party:psimd",
+    "//third-party/pthreadpool:pthreadpool": "//third_party:pthreadpool",
+    "//third-party/pthreadpool:pthreadpool_header": "//third_party:pthreadpool_header",
+    "//third-party/ruy:ruy_xplat_lib": "//third_party:ruy_lib",
+}
+
+# map fbsource deps to OSS deps
+def to_oss_deps(deps = []):
+    new_deps = []
+    for dep in deps:
+        new_deps += map_deps(dep)
+    return new_deps
+
+def map_deps(dep):
+    # remove @fbsource prefix
+    if dep.startswith("@fbsource"):
+        dep = dep[len("@fbsource"):]
+
+    # ignore all fbsource linker_lib targets
+    if dep.startswith("//xplat/third-party/linker_lib"):
+        return []
+
+    # map targets in caffe2 root folder. Just use relative path
+    if dep.startswith("//xplat/caffe2:"):
+        return [dep[len("//xplat/caffe2"):]]
+
+    # map targets in caffe2 subfolders
+    if dep.startswith("//xplat/caffe2/"):
+        return ["//" + dep[len("//xplat/caffe2/"):]]
+
+    # map other known targets
+    if dep in DEPS_MAP:
+        return DEPS_MAP[dep]
+
+    # drop other unknown deps
+    return []
diff --git a/tools/build_defs/default_platform_defs.bzl b/tools/build_defs/default_platform_defs.bzl
new file mode 100644
index 000000000000..643789e8d0b0
--- /dev/null
+++ b/tools/build_defs/default_platform_defs.bzl
@@ -0,0 +1,18 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+
+def compose_platform_setting_list(settings):
+    """Settings object:
+    os/cpu pair: should be valid key, or at most one part can be wildcard.
+    flags: the values added to the compiler flags
+    """
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
+    result = []
+    for setting in settings:
+        result.append([
+            "^{}-{}$".format(setting["os"], setting["cpu"]),
+            setting["flags"],
+        ])
+    return result
diff --git a/tools/build_defs/expect.bzl b/tools/build_defs/expect.bzl
new file mode 100644
index 000000000000..b298b40b7705
--- /dev/null
+++ b/tools/build_defs/expect.bzl
@@ -0,0 +1,5 @@
+# Only used for PyTorch open source BUCK build
+
+def expect(condition, message = None):
+    if not condition:
+        fail(message)
diff --git a/tools/build_defs/fb_native_wrapper.bzl b/tools/build_defs/fb_native_wrapper.bzl
new file mode 100644
index 000000000000..7d4ca06b2161
--- /dev/null
+++ b/tools/build_defs/fb_native_wrapper.bzl
@@ -0,0 +1,22 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+def _genrule(default_outs = ["."], **kwargs):
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
+    genrule(
+        # default_outs is only needed for internal BUCK
+        **kwargs
+    )
+
+def _read_config(**kwargs):
+    read_config(**kwargs)
+
+def _filegroup(**kwargs):
+    filegroup(**kwargs)
+
+fb_native = struct(
+    genrule = _genrule,
+    read_config = _read_config,
+    filegroup = _filegroup,
+)
diff --git a/tools/build_defs/fb_python_binary.bzl b/tools/build_defs/fb_python_binary.bzl
new file mode 100644
index 000000000000..f403b4bbbda6
--- /dev/null
+++ b/tools/build_defs/fb_python_binary.bzl
@@ -0,0 +1,10 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+
+load("@fbcode_macros//build_defs:python_binary.bzl", "python_binary")
+
+def fb_python_binary(**kwgs):
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
+    python_binary(**kwgs)
diff --git a/tools/build_defs/fb_xplat_cxx_library.bzl b/tools/build_defs/fb_xplat_cxx_library.bzl
new file mode 100644
index 000000000000..785983606213
--- /dev/null
+++ b/tools/build_defs/fb_xplat_cxx_library.bzl
@@ -0,0 +1,19 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+
+load(":buck_helpers.bzl", "filter_attributes", "to_oss_deps")
+
+def fb_xplat_cxx_library(
+        name,
+        deps = [],
+        exported_deps = [],
+        **kwgs):
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
+    cxx_library(
+        name = name,
+        deps = to_oss_deps(deps),
+        exported_deps = to_oss_deps(exported_deps),
+        **filter_attributes(kwgs)
+    )
diff --git a/tools/build_defs/fb_xplat_genrule.bzl b/tools/build_defs/fb_xplat_genrule.bzl
index ddc19b2373e9..8d61967cdb41 100644
--- a/tools/build_defs/fb_xplat_genrule.bzl
+++ b/tools/build_defs/fb_xplat_genrule.bzl
@@ -1,4 +1,10 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+
 def fb_xplat_genrule(default_outs = ["."], **kwargs):
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
     genrule(
         # default_outs=default_outs, # only needed for internal BUCK
         **kwargs
diff --git a/tools/build_defs/fbsource_utils.bzl b/tools/build_defs/fbsource_utils.bzl
new file mode 100644
index 000000000000..0cbfd63304d1
--- /dev/null
+++ b/tools/build_defs/fbsource_utils.bzl
@@ -0,0 +1,8 @@
+# Only used for PyTorch open source BUCK build
+# @lint-ignore-every BUCKRESTRICTEDSYNTAX
+
+def is_arvr_mode():
+    if read_config("pt", "is_oss", "0") == "0":
+        fail("This file is for open source pytorch build. Do not use it in fbsource!")
+
+    return False
diff --git a/tools/build_defs/glob_defs.bzl b/tools/build_defs/glob_defs.bzl
index a0eea247e839..2fad1bc518d2 100644
--- a/tools/build_defs/glob_defs.bzl
+++ b/tools/build_defs/glob_defs.bzl
@@ -1,3 +1,5 @@
+# Only used for PyTorch open source BUCK build
+
 """Provides utility macros for working with globs."""
 
 load("@bazel_skylib//lib:paths.bzl", "paths")
diff --git a/tools/build_defs/platform_defs.bzl b/tools/build_defs/platform_defs.bzl
new file mode 100644
index 000000000000..04d6c2dd4e33
--- /dev/null
+++ b/tools/build_defs/platform_defs.bzl
@@ -0,0 +1,38 @@
+# Only used for PyTorch open source BUCK build
+
+CXX = "Default"
+
+ANDROID = "Android"
+
+APPLE = "Apple"
+
+FBCODE = "Fbcode"
+
+WINDOWS = "Windows"
+
+UNIFIED = "Unified"
+
+# Apple SDK Definitions
+IOS = "ios"
+
+WATCHOS = "watchos"
+
+MACOSX = "macosx"
+
+APPLETVOS = "appletvos"
+
+xplat_platforms = struct(
+    ANDROID = ANDROID,
+    APPLE = APPLE,
+    CXX = CXX,
+    FBCODE = FBCODE,
+    WINDOWS = WINDOWS,
+    UNIFIED = UNIFIED,
+)
+
+apple_sdks = struct(
+    IOS = IOS,
+    WATCHOS = WATCHOS,
+    MACOSX = MACOSX,
+    APPLETVOS = APPLETVOS,
+)
diff --git a/tools/build_defs/type_defs.bzl b/tools/build_defs/type_defs.bzl
index afc02702e8ad..7a905e7d6cc0 100644
--- a/tools/build_defs/type_defs.bzl
+++ b/tools/build_defs/type_defs.bzl
@@ -1,3 +1,5 @@
+# Only used for PyTorch open source BUCK build
+
 """Provides macros for queries type information."""
 
 _SELECT_TYPE = type(select({"DEFAULT": []}))