kleaf: --gcov implemented with defconfig_fragments

Add a conditional (select()) filegroup to
kernel_build.defconfig_fragments so that, when --gcov is
set, the gcov CONFIGs are added.

Remove gcov from kernel_config_settings now that it is
represented by defconfig_fragments already.

Bug: 295233214
Test: bazel build //common:kernel_aarch64 --gcov
Test: bazel build //common:kernel_x86_64 --gcov
Test: bazel build //common:kernel_riscv64 --gcov
Test: bazel test //build/kernel/kleaf/tests/kernel_config_test:kernel_defconfig_fragments_test
Change-Id: I2e674f0f4661c0fa4d912590e8f43377eb229c6e

7 files changed, 34 insertions, 32 deletions

diff --git a/kleaf/BUILD.bazel b/kleaf/BUILD.bazel
index a0f08ca..cd42d0b 100644
--- a/kleaf/BUILD.bazel
+++ b/kleaf/BUILD.bazel
@@ -255,6 +255,12 @@ bool_flag(
     visibility = ["//visibility:public"],
 )
 
+config_setting(
+    name = "gcov_is_true",
+    flag_values = {":gcov": "1"},
+    visibility = ["//build/kernel/kleaf/impl/defconfig:__pkg__"],
+)
+
 # If true, allow modules to be undeclared in kernel_build.
 bool_flag(
     name = "allow_undeclared_modules",
diff --git a/kleaf/docs/kernel_config.md b/kleaf/docs/kernel_config.md
index e796fb0..86e7bd1 100644
--- a/kleaf/docs/kernel_config.md
+++ b/kleaf/docs/kernel_config.md
@@ -88,18 +88,20 @@ Example:
 ```python
 # path/to/tuna/BUILD.bazel
 exports_files([
-    "gcov_defconfig",
+    "kasan_hw_tags_defconfig",
 ])
 kernel_build(name = "tuna", ...)
 ```
 ```shell
-# gcov_defconfig
-CONFIG_GCOV_KERNEL=y
-CONFIG_GCOV_PROFILE_ALL=y
+# kasan_hw_tags_defconfig
+CONFIG_KASAN=y
+CONFIG_KASAN_HW_TAGS=y
+# CONFIG_KASAN_SW_TAGS is not set
+# etc. Add your configs!
 ```
 ```shell
 $ tools/bazel build \
-    --defconfig_fragment=//path/to/tuna:gcov_defconfig \
+    --defconfig_fragment=//path/to/tuna:kasan_hw_tags_defconfig \
     //path/to/tuna:tuna
 ```
 
@@ -132,6 +134,7 @@ own defconfig fragments to avoid fragmentation in the ecosystem (pun intended).
 
 *   `--btf_debug_info`
 *   `--debug`
+*   `--gcov`
 *   `--kasan`
 *   `--kasan_sw_tags`
 *   `--kasan_generic`
@@ -188,8 +191,8 @@ To shorten `--defconfig_fragment` flags, you may use
 
 ```text
 # device.bazelrc
-build:gcov --defconfig_fragment=//path/to/tuna:gcov_defconfig
+build:kasan_hw_tags --defconfig_fragment=//path/to/tuna:kasan_hw_tags_defconfig
 ```
 ```shell
-$ tools/bazel build --config=gcov //path/to/tuna:tuna
+$ tools/bazel build --config=kasan_hw_tags //path/to/tuna:tuna
 ```
diff --git a/kleaf/impl/defconfig/BUILD.bazel b/kleaf/impl/defconfig/BUILD.bazel
index b30bbc9..ef212fb 100644
--- a/kleaf/impl/defconfig/BUILD.bazel
+++ b/kleaf/impl/defconfig/BUILD.bazel
@@ -172,3 +172,12 @@ filegroup(
     srcs = ["signing_modules_disabled_defconfig"],
     visibility = ["//visibility:public"],
 )
+
+filegroup(
+    name = "gcov",
+    srcs = select({
+        "//build/kernel/kleaf:gcov_is_true": ["gcov_defconfig"],
+        "//conditions:default": [],
+    }),
+    visibility = ["//visibility:public"],
+)
diff --git a/kleaf/impl/defconfig/gcov_defconfig b/kleaf/impl/defconfig/gcov_defconfig
new file mode 100644
index 0000000..9fce6cd
--- /dev/null
+++ b/kleaf/impl/defconfig/gcov_defconfig
@@ -0,0 +1,6 @@
+CONFIG_GCOV_KERNEL=y
+CONFIG_GCOV_PROFILE_ALL=y
+
+# TODO(b/291710318) Allow section mismatch when using GCOV_PROFILE_ALL
+#  modpost: vmlinux.o: section mismatch in reference: cpumask_andnot (section: .text) -> efi_systab_phys (section: .init.data)
+CONFIG_SECTION_MISMATCH_WARN_ONLY=y
diff --git a/kleaf/impl/kernel_build.bzl b/kleaf/impl/kernel_build.bzl
index 6ead741..5bf8278 100644
--- a/kleaf/impl/kernel_build.bzl
+++ b/kleaf/impl/kernel_build.bzl
@@ -756,6 +756,7 @@ def _get_defconfig_fragments(
     additional_fragments = [
         Label("//build/kernel/kleaf:defconfig_fragment"),
         Label("//build/kernel/kleaf/impl/defconfig:debug"),
+        Label("//build/kernel/kleaf/impl/defconfig:gcov"),
         Label("//build/kernel/kleaf/impl/defconfig:rust"),
         Label("//build/kernel/kleaf/impl/defconfig:zstd_dwarf_compression"),
     ]
@@ -2152,6 +2153,7 @@ _kernel_build = rule(
         "_warn_undeclared_modules": attr.label(default = "//build/kernel/kleaf:warn_undeclared_modules"),
         "_preserve_cmd": attr.label(default = "//build/kernel/kleaf/impl:preserve_cmd"),
         "_kmi_symbol_list_violations_check": attr.label(default = "//build/kernel/kleaf:kmi_symbol_list_violations_check"),
+        "_gcov": attr.label(default = "//build/kernel/kleaf:gcov"),
         # Though these rules are unrelated to the `_kernel_build` rule, they are added as fake
         # dependencies so KernelBuildExtModuleInfo and KernelBuildUapiInfo works.
         # There are no real dependencies. Bazel does not build these targets before building the
diff --git a/kleaf/impl/kernel_config.bzl b/kleaf/impl/kernel_config.bzl
index ebb9491..0b521a4 100644
--- a/kleaf/impl/kernel_config.bzl
+++ b/kleaf/impl/kernel_config.bzl
@@ -105,28 +105,6 @@ def _determine_system_trusted_key_path(ctx):
 
     return _determine_local_path(ctx, "trusted_key.pem", ctx.file.system_trusted_key)
 
-def _config_gcov(ctx):
-    """Return configs for GCOV.
-
-    Args:
-        ctx: ctx
-    Returns:
-        A struct, where `configs` is a list of arguments to `scripts/config`,
-        and `deps` is a list of input files.
-    """
-    gcov = ctx.attr.gcov[BuildSettingInfo].value
-
-    if not gcov:
-        return struct(configs = [], deps = [])
-    configs = [
-        _config.enable("GCOV_KERNEL"),
-        _config.enable("GCOV_PROFILE_ALL"),
-        # TODO(b/291710318) Allow section mismatch when using GCOV_PROFILE_ALL
-        #  modpost: vmlinux.o: section mismatch in reference: cpumask_andnot (section: .text) -> efi_systab_phys (section: .init.data)
-        _config.enable("SECTION_MISMATCH_WARN_ONLY"),
-    ]
-    return struct(configs = configs, deps = [])
-
 def _config_lto(ctx):
     """Return configs for LTO.
 
@@ -340,7 +318,6 @@ def _reconfig(ctx):
         _config_kasan,
         _config_kasan_sw_tags,
         _config_kasan_generic,
-        _config_gcov,
         _config_keys,
         kgdb.get_scripts_config_args,
     ):
diff --git a/kleaf/impl/kernel_config_settings.bzl b/kleaf/impl/kernel_config_settings.bzl
index a23f813..894d6dc 100644
--- a/kleaf/impl/kernel_config_settings.bzl
+++ b/kleaf/impl/kernel_config_settings.bzl
@@ -33,6 +33,7 @@ mentioned here. In particular:
 - The following is not listed because it is already handled by defconfig_fragments. See
   kernel_env.bzl, _handle_config_tags:
   - btf_debug_info
+  - gcov
 """
 
 load("@bazel_skylib//lib:dicts.bzl", "dicts")
@@ -73,7 +74,6 @@ def _kernel_build_config_settings_raw():
         compile_commands_utils.config_settings_raw(),
         {
             "_use_kmi_symbol_list_strict_mode": "//build/kernel/kleaf:kmi_symbol_list_strict_mode",
-            "_gcov": "//build/kernel/kleaf:gcov",
             "_debug": "//build/kernel/kleaf:debug",
             "_kasan": "//build/kernel/kleaf:kasan",
             "_kasan_sw_tags": "//build/kernel/kleaf:kasan_sw_tags",
@@ -98,7 +98,6 @@ def _kernel_config_config_settings_raw():
             "kasan_sw_tags": "//build/kernel/kleaf:kasan_sw_tags",
             "kasan_generic": "//build/kernel/kleaf:kasan_generic",
             "kcsan": "//build/kernel/kleaf:kcsan",
-            "gcov": "//build/kernel/kleaf:gcov",
         },
     )