[bazel] Define rules-based CC lowRISC toolchain

.bazelrc

@@ -14,16 +14,6 @@ build --conlyopt='-std=gnu11'
 # disassemblies when compilation mode is fastbuild.
 build --strip='never'
 
-# Override default enablement of flags from @crt//common to control C compiler
-# warnings.
-build --features=-pedantic_warnings
-build --host_features=-pedantic_warnings
-
-# Enable toolchain hardening features.
-# `guards` adds `unimp` guard instructions after unconditional jumps.
-build --features=guards
-build --host_features=guards
-
 # Use --config=disable_hardening to disable hardening to measure the
 # impact of the hardened sequences on code size.
 build:disable_hardening --features=-guards --copt=-DOT_DISABLE_HARDENING=1

MODULE.bazel

@@ -114,6 +114,9 @@ use_repo(open_dice, "open-dice")
 hyperdebug = use_extension("//third_party/hyperdebug:extensions.bzl", "hyperdebug")
 use_repo(hyperdebug, "hyperdebug_firmware")
 
+lowrisc_rv32imcb_toolchain = use_extension("//third_party/lowrisc:extensions.bzl", "lowrisc_rv32imcb_toolchain")
+use_repo(lowrisc_rv32imcb_toolchain, "lowrisc_rv32imcb_toolchain")
+
 # Extension for linking in externally managed test and provisioning customizations
 # for both secure/non-secure manufacturer domains.
 hooks = use_extension("//rules:extensions.bzl", "hooks")
@@ -140,3 +143,5 @@ use_repo(
 )
 
 register_toolchains("//rules/opentitan:localtools")
+
+register_toolchains("//toolchain:cc_toolchain_opentitan")

SUMMARY.md

@@ -415,6 +415,7 @@
 
 - [Build Software](./sw/doc/build_software.md)
   - [External dependencies](./third_party/README.md)
+  - [RISC-V toolchain](./toolchain/README.md)
 
 - [Device Software](./sw/device/README.md)
   - [Build & Test Rules](./rules/opentitan/README.md)

WORKSPACE.bzlmod

@@ -6,14 +6,3 @@
 # //third_party/README.md first.
 
 workspace(name = "lowrisc_opentitan")
-
-# CRT is the Compiler Repository Toolkit.  It contains the configuration for
-# the windows compiler.
-load("//third_party/crt:repos.bzl", "crt_repos")
-crt_repos()
-load("@crt//:repos.bzl", "crt_repos")
-crt_repos()
-load("@crt//:deps.bzl", "crt_deps")
-crt_deps()
-load("@crt//config:registration.bzl", "crt_register_toolchains")
-crt_register_toolchains(riscv32 = True)

hw/ip/otbn/dv/uvm/get-toolchain-paths.sh

@@ -13,18 +13,18 @@ if [[ -n ${BAZEL_CACHE} ]]; then
   ${BAZEL_CMD} fetch \
     --distdir="${BAZEL_DISTDIR}" \
     --repository_cache="${BAZEL_CACHE}" \
-    @lowrisc_rv32imcb_files//...
+    @lowrisc_rv32imcb_toolchain//...
 else
   BAZEL_CMD="./bazelisk.sh"
-  ${BAZEL_CMD} fetch @lowrisc_rv32imcb_files//...
+  ${BAZEL_CMD} fetch @lowrisc_rv32imcb_toolchain//...
 fi
 
 # Set environment variables for the RV32 linker and assembler.
 RV32_TOOL_LD=$(${BAZEL_CMD} query \
-  'deps(@lowrisc_rv32imcb_files//:bin/riscv32-unknown-elf-ld)' \
+  'deps(@lowrisc_rv32imcb_toolchain//:bin/riscv32-unknown-elf-ld)' \
   --output location | cut -f1 -d:)
 RV32_TOOL_AS=$(${BAZEL_CMD} query \
-  'deps(@lowrisc_rv32imcb_files//:bin/riscv32-unknown-elf-as)' \
+  'deps(@lowrisc_rv32imcb_toolchain//:bin/riscv32-unknown-elf-as)' \
   --output location | cut -f1 -d:)
 export RV32_TOOL_LD
 export RV32_TOOL_AS

third_party/crt/BUILD.bazel → rules/actions.bzl

@@ -2,4 +2,4 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
-package(default_visibility = ["//visibility:public"])
+OT_ACTION_OBJDUMP = "objdump"

rules/certificates.bzl

@@ -71,7 +71,7 @@ certificate_codegen = rule(
     attrs = {
         "template": attr.label(allow_single_file = True, doc = "path to the hjson template file"),
         "clang_format": attr.label(
-            default = "@lowrisc_rv32imcb_files//:bin/clang-format",
+            default = "@lowrisc_rv32imcb_toolchain//:bin/clang-format",
             allow_single_file = True,
             cfg = "host",
             executable = True,

rules/opentitan/legacy.bzl

@@ -53,6 +53,7 @@ obj_transform = rv_rule(
         "format": attr.string(default = "binary"),
         "_cc_toolchain": attr.label(default = Label("@bazel_tools//tools/cpp:current_cc_toolchain")),
     },
+    fragments = ["cpp"],
     toolchains = ["@rules_cc//cc:toolchain_type"],
 )
 

rules/opentitan/static_library.bzl

@@ -7,6 +7,7 @@
 # Inspired by:
 # https://gist.github.com/shareefj/4e314b16148fded3a8ec874e71b07143
 
+load("@rules_cc//cc:action_names.bzl", "CPP_LINK_STATIC_LIBRARY_ACTION_NAME")
 load("@rules_cc//cc:find_cc_toolchain.bzl", "find_cc_toolchain")
 load("@lowrisc_opentitan//rules:rv.bzl", "rv_rule")
 
@@ -15,6 +16,16 @@ def _ot_static_library_impl(ctx):
     output_flags = ctx.actions.declare_file("lib{}.link".format(ctx.attr.name))
 
     cc_toolchain = find_cc_toolchain(ctx)
+    feature_config = cc_common.configure_features(
+        ctx = ctx,
+        cc_toolchain = cc_toolchain,
+        requested_features = ctx.features,
+        unsupported_features = ctx.disabled_features,
+    )
+    archiver = cc_common.get_tool_for_action(
+        feature_configuration = feature_config,
+        action_name = CPP_LINK_STATIC_LIBRARY_ACTION_NAME,
+    )
 
     # Aggregate linker inputs of all dependencies
     lib_sets = []
@@ -42,11 +53,9 @@ def _ot_static_library_impl(ctx):
 
     lib_paths = [lib.path for lib in libs]
 
-    ar_path = cc_toolchain.ar_executable
-
     ctx.actions.run_shell(
         command = "\"{0}\" rcT {1} {2} && echo -e 'create {1}\naddlib {1}\nsave\nend' | \"{0}\" -M".format(
-            ar_path,
+            archiver,
             output_lib.path,
             " ".join(lib_paths),
         ),

rules/opentitan/transform.bzl

@@ -3,9 +3,11 @@
 # SPDX-License-Identifier: Apache-2.0
 
 load("@bazel_skylib//rules:common_settings.bzl", "BuildSettingInfo")
+load("@rules_cc//cc:action_names.bzl", "OBJ_COPY_ACTION_NAME")
 load("@rules_cc//cc:find_cc_toolchain.bzl", "find_cc_toolchain")
 load("@bazel_skylib//lib:paths.bzl", "paths")
 load("@lowrisc_opentitan//rules/opentitan:util.bzl", "get_override")
+load("//rules:actions.bzl", "OT_ACTION_OBJDUMP")
 
 def obj_transform(ctx, **kwargs):
     """Transform an object file via objcopy.
@@ -21,6 +23,17 @@ def obj_transform(ctx, **kwargs):
       The transformed File.
     """
     cc_toolchain = find_cc_toolchain(ctx)
+    feature_config = cc_common.configure_features(
+        ctx = ctx,
+        cc_toolchain = cc_toolchain,
+        requested_features = ctx.features,
+        unsupported_features = ctx.disabled_features,
+    )
+    objcopy = cc_common.get_tool_for_action(
+        feature_configuration = feature_config,
+        action_name = OBJ_COPY_ACTION_NAME,
+    )
+
     output = kwargs.get("output")
     if not output:
         name = get_override(ctx, "attr.name", kwargs)
@@ -40,7 +53,7 @@ def obj_transform(ctx, **kwargs):
             src.path,
             output.path,
         ],
-        executable = cc_toolchain.objcopy_executable,
+        executable = objcopy,
     )
     return output
 
@@ -57,6 +70,17 @@ def obj_disassemble(ctx, **kwargs):
       The disassembled File.
     """
     cc_toolchain = find_cc_toolchain(ctx)
+    feature_config = cc_common.configure_features(
+        ctx = ctx,
+        cc_toolchain = cc_toolchain,
+        requested_features = ctx.features,
+        unsupported_features = ctx.disabled_features,
+    )
+    objdump = cc_common.get_tool_for_action(
+        feature_configuration = feature_config,
+        action_name = OT_ACTION_OBJDUMP,
+    )
+
     output = kwargs.get("output")
     if not output:
         name = get_override(ctx, "attr.name", kwargs)
@@ -69,7 +93,7 @@ def obj_disassemble(ctx, **kwargs):
         outputs = [output],
         inputs = [src] + cc_toolchain.all_files.to_list(),
         arguments = [
-            cc_toolchain.objdump_executable,
+            objdump,
             src.path,
             output.path,
         ],