[cc_toolchains] Cleanup libc versions.

Summary: libc_version was being used for both the libc version and the abi. This defines abi separately from libc version.

Test Plan: Shouldn't be any functional changes. Relying on existing tests.

Reviewers: zasgar, vihang, michelle

Reviewed By: vihang

Signed-off-by: James Bartlett <jamesbartlett@pixielabs.ai>

Differential Revision: https://phab.corp.pixielabs.ai/D12848

GitOrigin-RevId: 11e3b3f5882a9435aaaf6f6741a3e79daf5de667

.bazelrc

@@ -68,7 +68,6 @@ build:linux --action_env=BAZEL_DO_NOT_DETECT_CPP_TOOLCHAIN=1
 
 # Build for Clang:
 build:clang --//bazel/cc_toolchains:compiler=clang
-build:clang --//bazel/cc_toolchains:libc_version=gnu
 
 # Build for Clang using Libc++.
 build:libc++ --define use_libcpp=1
@@ -77,7 +76,6 @@ build:libc++ --copt -D_LIBCPP_NO_EXPERIMENTAL_DEPRECATION_WARNING_FILESYSTEM
 build:libc++ --build_tag_filters=-no_libcpp
 build:libc++ --test_tag_filters=-no_libcpp,-requires_root,-requires_bpf,-disabled
 build:libc++ --//bazel/cc_toolchains:compiler=clang
-build:libc++ --//bazel/cc_toolchains:libc_version=gnu
 build:libc++ --features=libc++ --features=-libstdc++
 
 # Build for GCC.
@@ -90,7 +88,6 @@ build:gcc --copt -Wno-error=maybe-uninitialized
 build:gcc --build_tag_filters=-no_gcc
 build:gcc --test_tag_filters=-no_gcc,-requires_root,-requires_bpf,-disabled
 build:gcc --//bazel/cc_toolchains:compiler=gcc
-build:gcc --//bazel/cc_toolchains:libc_version=gnu
 
 
 # bazel build --config asan ...

bazel/cc_toolchains/clang.bzl

@@ -15,6 +15,8 @@
 # SPDX-License-Identifier: Apache-2.0
 
 load("//bazel:repository_locations.bzl", "REPOSITORY_LOCATIONS")
+load("//bazel/cc_toolchains:settings.bzl", "HOST_GLIBC_VERSION")
+load("//bazel/cc_toolchains:utils.bzl", "abi")
 
 def _download_repo(rctx, repo_name, output):
     loc = REPOSITORY_LOCATIONS[repo_name]
@@ -52,10 +54,11 @@ def _clang_toolchain_impl(rctx):
         substitutions = {
             "{clang_major_version}": rctx.attr.clang_version.split(".")[0],
             "{clang_version}": rctx.attr.clang_version,
+            "{host_abi}": abi(rctx.attr.host_arch, rctx.attr.host_libc_version),
             "{host_arch}": rctx.attr.host_arch,
-            "{host_libc_version}": rctx.attr.host_libc_version,
             "{libc_version}": rctx.attr.libc_version,
             "{libcxx_path}": libcxx_path,
+            "{target_abi}": abi(rctx.attr.target_arch, rctx.attr.libc_version),
             "{target_arch}": rctx.attr.target_arch,
             "{this_repo}": rctx.attr.name,
             "{toolchain_path}": toolchain_path,
@@ -83,9 +86,9 @@ def _clang_register_toolchain(
         libcxx_repo,
         target_arch,
         clang_version,
-        libc_version = "gnu",
+        libc_version = HOST_GLIBC_VERSION,
         host_arch = "x86_64",
-        host_libc_version = "gnu",
+        host_libc_version = HOST_GLIBC_VERSION,
         use_for_host_tools = False):
     clang_toolchain(
         name = name,

bazel/cc_toolchains/clang/toolchain.BUILD

@@ -49,21 +49,13 @@ includes = [
     "{libcxx_path}/include/c++/v1",
 ]
 
-_LIBC_VERSION_TO_LONG_NAME = {
-    "gnu": "glibc_unknown",
-}
-
 _PLATFORMS = {
     "x86_64": "@platforms//cpu:x86_64",
 }
 
-_LIBC_CONSTRAINTS = {
-    "gnu": "@px//bazel/cc_toolchains:libc_version_gnu",
-}
-
 cc_toolchain_config(
     name = "toolchain_config",
-    abi_libc_version = _LIBC_VERSION_TO_LONG_NAME["{libc_version}"],
+    abi_libc_version = "{libc_version}",
     abi_version = "clang",
     compile_flags = [
         "-fstack-protector",
@@ -85,7 +77,7 @@ cc_toolchain_config(
     ],
     dbg_compile_flags = ["-g"],
     enable_sanitizers = not {use_for_host_tools},
-    host_system_name = "{host_arch}-unknown-linux-{host_libc_version}",
+    host_system_name = "{host_arch}-unknown-linux-{host_abi}",
     libclang_rt_path = "external/{this_repo}/{toolchain_path}/lib/clang/{clang_version}/lib/linux",
     libcxx_path = "external/{this_repo}/{libcxx_path}",
     link_flags = [
@@ -106,8 +98,8 @@ cc_toolchain_config(
     ],
     opt_link_flags = ["-Wl,--gc-sections"],
     supports_start_end_lib = True,
-    target_libc = _LIBC_VERSION_TO_LONG_NAME["{libc_version}"],
-    target_system_name = "{target_arch}-unknown-linux-{libc_version}",
+    target_libc = "{libc_version}",
+    target_system_name = "{target_arch}-unknown-linux-{target_abi}",
     tool_paths = tool_paths,
     toolchain_identifier = toolchain_identifier,
     unfiltered_compile_flags = [
@@ -206,7 +198,7 @@ toolchain(
     ] + ["@px//bazel/cc_toolchains:is_exec_true"] if {use_for_host_tools} else ["@px//bazel/cc_toolchains:is_exec_false"],
     target_settings = [
         "@px//bazel/cc_toolchains:compiler_clang",
-        _LIBC_CONSTRAINTS["{libc_version}"],
+        "@px//bazel/cc_toolchains:libc_version_{libc_version}",
     ],
     toolchain = ":cc_toolchain",
     toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",

bazel/cc_toolchains/gcc.bzl

@@ -119,7 +119,7 @@ def _gcc_x86_64_gnu():
         ],
         target_settings = [
             ":compiler_gcc",
-            ":libc_version_gnu",
+            ":libc_version_glibc_host",
         ],
         toolchain = ":cc-compiler-gcc-x86_64-gnu",
         toolchain_type = "@bazel_tools//tools/cpp:toolchain_type",

bazel/cc_toolchains/settings.bzl

@@ -16,28 +16,27 @@
 
 load("@bazel_skylib//rules:common_settings.bzl", "string_flag")
 
+HOST_GLIBC_VERSION = "glibc_host"
+
 def _settings():
+    libc_versions = [
+        HOST_GLIBC_VERSION,
+        "static_musl",
+    ]
     string_flag(
         name = "libc_version",
-        build_setting_default = "gnu",
-        values = [
-            "gnu",
-            "static_musl",
-        ],
-    )
-    native.config_setting(
-        name = "libc_version_gnu",
-        flag_values = {
-            "//bazel/cc_toolchains:libc_version": "gnu",
-        },
-    )
-    native.config_setting(
-        name = "libc_version_static_musl",
-        flag_values = {
-            "//bazel/cc_toolchains:libc_version": "static_musl",
-        },
+        build_setting_default = HOST_GLIBC_VERSION,
+        values = libc_versions,
     )
 
+    for version in libc_versions:
+        native.config_setting(
+            name = "libc_version_" + version,
+            flag_values = {
+                "//bazel/cc_toolchains:libc_version": version,
+            },
+        )
+
     string_flag(
         name = "compiler",
         build_setting_default = "clang",

bazel/cc_toolchains/utils.bzl

@@ -0,0 +1,29 @@
+# Copyright 2018- The Pixie 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.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# abi returns the expected abi for the given arch libc_version pair.
+# Currently, doesn't support musl.
+def abi(arch, libc_version):
+    if arch == "aarch64":
+        return "eabi"
+    if libc_version.startswith("glibc"):
+        return "gnu"
+
+    # We should support musl in the future.
+    fail("Cannot determine abi from arch ({arch}) and libc version ({libc_version})".format(
+        arch = arch,
+        libc_version = libc_version,
+    ))