[DTrace-devel] [PATCH v4] build: support kernel builds with or without object directory

[Kris Van Hees]

It should be possible to build DTrace against kernel headers provided in
a variety of ways.  They can be provided as installed kernel header
packages with combined or separated generated and standard headers, and
linked from /lib/modules/<kernelv-version> or simply available as
directory hierarchies elsewhere on the system.

It should also be possible to build DTrace against kernel headers that
are found in a locally built kernel, whether it is installed or not.

This patch provides a cleanup for the build system to accomplish this
with minimal configuration.

Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
Reviewed-by: Nick Alcock <nick.alcock at oracle.com>
---
 GNUmakefile     | 21 ++++++++++++++-------
 libdtrace/Build | 21 ++++++++++-----------
 2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/GNUmakefile b/GNUmakefile
index 54a3c48c..2ffd4c49 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -3,7 +3,7 @@
 # Build files in subdirectories are included by this file.
 #
 # Oracle Linux DTrace.
-# Copyright (c) 2011, 2022, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2011, 2023, Oracle and/or its affiliates. All rights reserved.
 # Licensed under the Universal Permissive License v 1.0 as shown at
 # http://oss.oracle.com/licenses/upl.
 
@@ -65,12 +65,19 @@ UNPRIV_HOME ?= /run/initramfs
 # pathnames), and about the pieces of the pathname before and after the kernel
 # version (so it can build include paths).
 
-KERNELS=$(shell uname -r)
-KERNELDIRPREFIX=/lib/modules
-KERNELODIR=
-# This allows you to build using a locally installed kernel built with O= by
-# just specifying KERNELODIR=relative/path/to/your/kernel/o/dir.
-KERNELDIRSUFFIX=$(if $(KERNELODIR),/source,/build)
+# Headers for installed kernels should be found automatically by the build
+# logic.  For local builds, one should specify KERNELSRCDIR as the source
+# location of the kernel tree, and KERNELOBJDIR as the location of the object
+# tree.  If the kernel was built within the source tree, KERNELOBJDIR need not
+# be specified.
+
+KERNELS = $(shell uname -r)
+KERNELMODDIR = /lib/modules
+
+ifdef KERNELSRCDIR
+KERNELOBJDIR ?= $(KERNELSRCDIR)
+endif
+
 KERNELARCH := $(subst sparc64,sparc,$(subst aarch64,arm64,$(subst x86_64,x86,$(ARCH))))
 
 # Paths.
diff --git a/libdtrace/Build b/libdtrace/Build
index 7dc2d5d6..35c0fd4a 100644
--- a/libdtrace/Build
+++ b/libdtrace/Build
@@ -166,6 +166,8 @@ $(objdir)/dlibs/.dir.stamp:
 define dlib-kernel-ver-template
 $(objdir)/dlibs/$(shell printf %s $(1) | sed -e 's/^\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*$$/\1.\2.\3/')/%.d: override SHORTKERNELVER := $(shell printf %s $(1) | sed -e 's/^\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*$$/\1.\2.\3/' | awk -F. '{ print $$1 * 1000 * 1000 + $$2 * 1000 + $$3 }')
 $(objdir)/dlibs/$(shell printf %s $(1) | sed -e 's/^\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*$$/\1.\2.\3/')/%.d: override KERNELVER := $(1)
+$(objdir)/dlibs/$(shell printf %s $(1) | sed -e 's/^\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*$$/\1.\2.\3/')/%.d: override KERNELSRCDIR ?= $(KERNELMODDIR)/$(1)/source
+$(objdir)/dlibs/$(shell printf %s $(1) | sed -e 's/^\([0-9]*\)\.\([0-9]*\)\.\([0-9]*\).*$$/\1.\2.\3/')/%.d: override KERNELOBJDIR ?= $(KERNELMODDIR)/$(1)/build
 endef
 
 $(foreach kernel,$(KERNELS),$(eval $(call dlib-kernel-ver-template,$(kernel))))
@@ -178,17 +180,14 @@ $(m4-dlib-targets): $(objdir)/dlibs/%.d: $$(foreach name,$$(notdir %.d.in), \
 			$(objdir)/dlibs/.dir.stamp
 	$(call describe-target,M4,$<)
 	$(PREPROCESS) -P -x c -Ilibdtrace/$(ARCHINC) \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/arch/$(KERNELARCH)/include \
-		      $(if $(KERNELODIR),-I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/arch/$(KERNELARCH)/include/generated/uapi) \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/arch/$(KERNELARCH)/include/generated/uapi \
-		      $(if $(KERNELODIR),-I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/arch/$(KERNELARCH)include/generated) \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/arch/$(KERNELARCH)/include/generated \
-		      $(if $(KERNELODIR),-I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/include) \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/include \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/arch/$(KERNELARCH)/include/uapi \
-		      $(if $(KERNELODIR),-I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/include/generated/uapi) \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/$(KERNELODIR)/include/generated/uapi \
-		      -I$(KERNELDIRPREFIX)/$(KERNELVER)$(KERNELDIRSUFFIX)/include/uapi \
+		      -I$(KERNELSRCDIR)/arch/$(KERNELARCH)/include \
+		      -I$(KERNELOBJDIR)/arch/$(KERNELARCH)/include/generated/uapi \
+		      -I$(KERNELOBJDIR)/arch/$(KERNELARCH)/include/generated \
+		      -I$(KERNELOBJDIR)/include \
+		      -I$(KERNELSRCDIR)/include \
+		      -I$(KERNELSRCDIR)/arch/$(KERNELARCH)/include/uapi \
+		      -I$(KERNELOBJDIR)/include/generated/uapi \
+		      -I$(KERNELSRCDIR)/include/uapi \
 		      -D_KERNEL -D__KERNEL__ $(basename $(basename $<)).m4 2>$@.h.err | grep -v '^# [0-9]' | tee $@.h | \
 	m4 --prefix-builtins -DSUBST_KERNEL=$(SHORTKERNELVER) -DSUBST_ARCH=$(KERNELARCH) $(libdtrace-build_DIR)def-start.m4 \
 		$(libdtrace-build_DIR)def-replace.m4 - $(libdtrace-build_DIR)/d-subst.m4 \
-- 
2.40.1