scripts: Add conftest.sh support

The script conftest.sh can be used at build time to determine which
kernel headers or versions of kernel functions/macros are present in the
kernel that drivers are being compiled against. This is useful for cases
where changes are backported from upstream Linux kernels that may change
kernel functions and so we can no longer rely on the kernel version to
indicate which version of the kernel function to use.

The conftest.h header file is a top-level header file that includes all
the header files that are generated by the conftest.sh script. This
header file can be included by drivers so that they can use the various
definitions that are generated by conftest.sh. This file is located
along with the conftest.sh script because this is copied to the output
directory where all the generated header files are placed.

Bug 4119327
Bug 4228080

Change-Id: I781884e359e9688640661548620e01a178debac9
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/2974065
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>

scripts/conftest/Makefile

@@ -0,0 +1,160 @@
+###########################################################################
+# Kbuild file for NVIDIA Linux GPU driver kernel modules
+###########################################################################
+
+#
+# The parent makefile is expected to define:
+#
+#  NV_KERNEL_SOURCES : The root of the kernel source tree.
+#  NV_KERNEL_OUTPUT  : The kernel's output tree.
+#  NV_KERNEL_MODULES : A whitespace-separated list of modules to build.
+#  ARCH              : The target CPU architecture: x86_64|arm64|powerpc
+#
+# Kbuild provides the variables:
+#
+# $(src) : The directory containing this Kbuild file.
+# $(obj) : The directory where the output from this build is written.
+#
+
+#
+# The conftest.sh script tests various aspects of the target kernel.
+# The per-module Kbuild files included above should:
+#
+# - Append to the NV_CONFTEST_*_COMPILE_TESTS variables to indicate
+#   which conftests they require.
+# - Append to the NV_OBJECTS_DEPEND_ON_CONFTEST variable any object files
+#   that depend on conftest.
+#
+# The conftest machinery below will run the requested tests and
+# generate the appropriate header files.
+#
+
+CC ?= cc
+LD ?= ld
+
+NV_CONFTEST_SCRIPT := $(src)/conftest.sh
+NV_CONFTEST_HEADER := $(obj)/conftest/headers.h
+
+NV_CONFTEST_CMD := /bin/sh $(NV_CONFTEST_SCRIPT) \
+  "$(CC)" $(ARCH) $(NV_KERNEL_SOURCES) $(NV_KERNEL_OUTPUT)
+
+NV_CFLAGS_FROM_CONFTEST := $(shell $(NV_CONFTEST_CMD) build_cflags)
+
+NV_CONFTEST_CFLAGS = $(NV_CFLAGS_FROM_CONFTEST) $(EXTRA_CFLAGS) -fno-pie
+
+NV_CONFTEST_COMPILE_TEST_HEADERS := $(obj)/conftest/macros.h
+NV_CONFTEST_COMPILE_TEST_HEADERS += $(obj)/conftest/functions.h
+NV_CONFTEST_COMPILE_TEST_HEADERS += $(obj)/conftest/symbols.h
+NV_CONFTEST_COMPILE_TEST_HEADERS += $(obj)/conftest/types.h
+NV_CONFTEST_COMPILE_TEST_HEADERS += $(obj)/conftest/generic.h
+
+NV_CONFTEST_HEADERS := $(obj)/conftest/patches.h
+NV_CONFTEST_HEADERS += $(obj)/conftest/headers.h
+NV_CONFTEST_HEADERS += $(NV_CONFTEST_COMPILE_TEST_HEADERS)
+
+all: $(NV_CONFTEST_HEADERS)
+
+#
+# Generate a header file for a single conftest compile test. Each compile test
+# header depends on conftest.sh, as well as the generated conftest/headers.h
+# file, which is included in the compile test preamble.
+#
+
+$(obj)/conftest/compile-tests/%.h: $(NV_CONFTEST_SCRIPT) $(NV_CONFTEST_HEADER)
+	@mkdir -p $(obj)/conftest/compile-tests
+	@echo "  CONFTEST: $(notdir $*)"
+	@$(NV_CONFTEST_CMD) compile_tests '$(NV_CONFTEST_CFLAGS)' \
+	  $(notdir $*) > $@
+
+#
+# Concatenate a conftest/*.h header from its constituent compile test headers
+#
+# $(1): The name of the concatenated header
+# $(2): The list of compile tests that make up the header
+#
+
+define NV_GENERATE_COMPILE_TEST_HEADER
+  $(obj)/conftest/$(1).h: $(addprefix $(obj)/conftest/compile-tests/,$(addsuffix .h,$(2)))
+	@mkdir -p $(obj)/conftest
+	@# concatenate /dev/null to prevent cat from hanging when $$^ is empty
+	@cat $$^ /dev/null > $$@
+endef
+
+#
+# Generate the conftest compile test headers from the lists of compile tests
+# provided by the module-specific Kbuild files.
+#
+
+NV_CONFTEST_FUNCTION_COMPILE_TESTS ?=
+NV_CONFTEST_GENERIC_COMPILE_TESTS ?=
+NV_CONFTEST_MACRO_COMPILE_TESTS ?=
+NV_CONFTEST_SYMBOL_COMPILE_TESTS ?=
+NV_CONFTEST_TYPE_COMPILE_TESTS ?=
+
+$(eval $(call NV_GENERATE_COMPILE_TEST_HEADER,functions,$(NV_CONFTEST_FUNCTION_COMPILE_TESTS)))
+$(eval $(call NV_GENERATE_COMPILE_TEST_HEADER,generic,$(NV_CONFTEST_GENERIC_COMPILE_TESTS)))
+$(eval $(call NV_GENERATE_COMPILE_TEST_HEADER,macros,$(NV_CONFTEST_MACRO_COMPILE_TESTS)))
+$(eval $(call NV_GENERATE_COMPILE_TEST_HEADER,symbols,$(NV_CONFTEST_SYMBOL_COMPILE_TESTS)))
+$(eval $(call NV_GENERATE_COMPILE_TEST_HEADER,types,$(NV_CONFTEST_TYPE_COMPILE_TESTS)))
+
+$(obj)/conftest/patches.h: $(NV_CONFTEST_SCRIPT)
+	@mkdir -p $(obj)/conftest
+	@$(NV_CONFTEST_CMD) patch_check > $@
+
+
+# Each of these headers is checked for presence with a test #include; a
+# corresponding #define will be generated in conftest/headers.h.
+NV_HEADER_PRESENCE_TESTS = \
+  generated/autoconf.h \
+  linux/kconfig.h
+
+# Filename to store the define for the header in $(1); this is only consumed by
+# the rule below that concatenates all of these together.
+NV_HEADER_PRESENCE_PART = $(addprefix $(obj)/conftest/header_presence/,$(addsuffix .part,$(1)))
+
+# Define a rule to check the header $(1).
+define NV_HEADER_PRESENCE_CHECK
+  $$(call NV_HEADER_PRESENCE_PART,$(1)): $$(NV_CONFTEST_SCRIPT) $(obj)/conftest/uts_release
+	@mkdir -p $$(dir $$@)
+	@$$(NV_CONFTEST_CMD) test_kernel_header '$$(NV_CONFTEST_CFLAGS)' '$(1)' > $$@
+endef
+
+# Evaluate the rule above for each header in the list.
+$(foreach header,$(NV_HEADER_PRESENCE_TESTS),$(eval $(call NV_HEADER_PRESENCE_CHECK,$(header))))
+
+# Concatenate all of the parts into headers.h.
+$(obj)/conftest/headers.h: $(call NV_HEADER_PRESENCE_PART,$(NV_HEADER_PRESENCE_TESTS))
+	@cat $^ > $@
+
+clean-dirs := $(obj)/conftest
+
+# For any object files that depend on conftest, declare the dependency here.
+$(addprefix $(obj)/,$(NV_OBJECTS_DEPEND_ON_CONFTEST)): | $(NV_CONFTEST_HEADERS)
+
+# Sanity checks of the build environment and target system/kernel
+
+BUILD_SANITY_CHECKS = \
+  cc_sanity_check \
+  cc_version_check \
+  module_symvers_sanity_check
+
+.PHONY: $(BUILD_SANITY_CHECKS)
+
+$(BUILD_SANITY_CHECKS):
+	@$(NV_CONFTEST_CMD) $@ full_output
+
+# Perform all sanity checks before generating the conftest headers
+
+$(NV_CONFTEST_HEADERS): | $(BUILD_SANITY_CHECKS)
+
+# Make the conftest headers depend on the kernel version string
+
+$(obj)/conftest/uts_release: NV_GENERATE_UTS_RELEASE
+	@mkdir -p $(dir $@)
+	@NV_UTS_RELEASE="// Kernel version: `$(NV_CONFTEST_CMD) compile_tests '$(NV_CONFTEST_CFLAGS)' uts_release`"; \
+	if ! [ -f "$@" ] || [ "$$NV_UTS_RELEASE" != "`cat $@`" ]; \
+	then echo "$$NV_UTS_RELEASE" > $@; fi
+
+.PHONY: NV_GENERATE_UTS_RELEASE
+
+$(NV_CONFTEST_HEADERS): $(obj)/conftest/uts_release

scripts/conftest/conftest.h

@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef _CONFTEST_H
+#define _CONFTEST_H
+
+#include "conftest/headers.h"
+#include "conftest/functions.h"
+#include "conftest/generic.h"
+#include "conftest/macros.h"
+#include "conftest/symbols.h"
+#include "conftest/types.h"
+
+#endif