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ANDROID: Kbuild: Add support for KBUILD_MIXED_TREE

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When KBUILD_MIXED_TREE points to the output folder of another kernel's
build output, Kbuild can compile a complete kernel tree's modules
against that other kernel tree's vmlinux. This is useful when two
kernel trees exist: a "Generic Kernel Image" tree and a "device kernel"
tree.  Both trees are complete kernel source trees, and the "Generic
Kernel Image" should provide the kernel Image and device kernel tree
provides device driver modules.

To accomplish this, references to vmlinux.symvers in the device kernel
should point to the generic kernel's vmlinux.symvers and the device
kernel should skip compilation of built-in files.

Bug: 178469391
Change-Id: I614f3e87519236c4e2c5da74937cb0ecd98a278a
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
Signed-off-by: Giuliano Procida <gprocida@google.com>
This commit is contained in:
Elliot Berman 2021-04-07 08:03:11 -07:00 committed by Giuliano Procida
parent e41d160482
commit 7d5e1de98e
3 changed files with 33 additions and 10 deletions
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30
Makefile
View File

@ -225,6 +225,20 @@ export KBUILD_CHECKSRC KBUILD_EXTMOD
extmod-prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
# ANDROID: set up mixed-build support. mixed-build allows device kernel modules
# to be compiled against a GKI kernel. This approach still uses the headers and
# Kbuild from device kernel, so care must be taken to ensure that those headers match.
ifdef KBUILD_MIXED_TREE
# Need vmlinux.symvers for modpost and System.map for depmod, check whether they exist in KBUILD_MIXED_TREE
required_mixed_files=vmlinux.symvers System.map
$(if $(filter-out $(words $(required_mixed_files)), \
$(words $(wildcard $(add-prefix $(KBUILD_MIXED_TREE)/,$(required_mixed_files))))),,\
$(error KBUILD_MIXED_TREE=$(KBUILD_MIXED_TREE) doesn't contain $(required_mixed_files)))
endif
mixed-build-prefix = $(if $(KBUILD_MIXED_TREE),$(KBUILD_MIXED_TREE)/)
export KBUILD_MIXED_TREE
ifeq ($(abs_srctree),$(abs_objtree))
# building in the source tree
srctree := .
@ -655,11 +669,13 @@ drivers-y += net/ virt/
libs-y := lib/
endif # KBUILD_EXTMOD
ifndef KBUILD_MIXED_TREE
# The all: target is the default when no target is given on the
# command line.
# This allow a user to issue only 'make' to build a kernel including modules
# Defaults to vmlinux, but the arch makefile usually adds further targets
all: vmlinux
endif
CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \
$(call cc-option,-fno-tree-loop-im) \
@ -1255,8 +1271,10 @@ cmd_link-vmlinux = \
$(CONFIG_SHELL) $< "$(LD)" "$(KBUILD_LDFLAGS)" "$(LDFLAGS_vmlinux)"; \
$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
ifndef KBUILD_MIXED_TREE
vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE
+$(call if_changed,link-vmlinux)
endif
targets := vmlinux
@ -1472,7 +1490,9 @@ endif
# using awk while concatenating to the final file.
PHONY += modules
modules: $(if $(KBUILD_BUILTIN),vmlinux) modules_check modules_prepare
# if KBUILD_BUILTIN && !KBUILD_MIXED_TREE, depend on vmlinux
modules: $(if $(KBUILD_BUILTIN), $(if $(KBUILD_MIXED_TREE),,vmlinux))
modules: modules_check modules_prepare
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
PHONY += modules_check
@ -1506,8 +1526,8 @@ _modinst_:
ln -s $(CURDIR) $(MODLIB)/build ; \
fi
@sed 's:^:kernel/:' modules.order > $(MODLIB)/modules.order
@cp -f modules.builtin $(MODLIB)/
@cp -f $(objtree)/modules.builtin.modinfo $(MODLIB)/
@cp -f $(mixed-build-prefix)modules.builtin $(MODLIB)/
@cp -f $(or $(mixed-build-prefix),$(objtree)/)modules.builtin.modinfo $(MODLIB)/
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modinst
# This depmod is only for convenience to give the initial
@ -1886,7 +1906,7 @@ descend: $(build-dirs)
$(build-dirs): prepare
$(Q)$(MAKE) $(build)=$@ \
single-build=$(if $(filter-out $@/, $(filter $@/%, $(KBUILD_SINGLE_TARGETS))),1) \
need-builtin=1 need-modorder=1
$(if $(KBUILD_MIXED_TREE),,need-builtin=1) need-modorder=1
clean-dirs := $(addprefix _clean_, $(clean-dirs))
PHONY += $(clean-dirs) clean
@ -2020,7 +2040,7 @@ quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN $(wildcard $(rm-files))
# Run depmod only if we have System.map and depmod is executable
quiet_cmd_depmod = DEPMOD $(KERNELRELEASE)
cmd_depmod = $(CONFIG_SHELL) $(srctree)/scripts/depmod.sh $(DEPMOD) \
$(KERNELRELEASE)
$(KERNELRELEASE) $(mixed-build-prefix)
# read saved command lines for existing targets
existing-targets := $(wildcard $(sort $(targets)))

4
scripts/Makefile.modpost
View File

@ -46,6 +46,8 @@ include scripts/Kbuild.include
# for ld_flags
include scripts/Makefile.lib
mixed-build-prefix = $(if $(KBUILD_MIXED_TREE),$(KBUILD_MIXED_TREE)/)
MODPOST = scripts/mod/modpost \
$(if $(CONFIG_MODVERSIONS),-m) \
$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \
@ -67,7 +69,7 @@ else
ifeq ($(KBUILD_EXTMOD),)
input-symdump := vmlinux.symvers
input-symdump := $(mixed-build-prefix)vmlinux.symvers
output-symdump := Module.symvers
module_srcpath := $(srctree)

9
scripts/depmod.sh
View File

@ -3,14 +3,15 @@
#
# A depmod wrapper used by the toplevel Makefile
if test $# -ne 2; then
echo "Usage: $0 /sbin/depmod <kernelrelease>" >&2
if test $# -ne 2 -a $# -ne 3; then
echo "Usage: $0 /sbin/depmod <kernelrelease> [System.map folder]" >&2
exit 1
fi
DEPMOD=$1
KERNELRELEASE=$2
KBUILD_MIXED_TREE=$3
if ! test -r System.map ; then
if ! test -r ${KBUILD_MIXED_TREE}System.map ; then
echo "Warning: modules_install: missing 'System.map' file. Skipping depmod." >&2
exit 0
fi
@ -41,7 +42,7 @@ if $depmod_hack_needed; then
KERNELRELEASE=99.98.$KERNELRELEASE
fi
set -- -ae -F System.map
set -- -ae -F ${KBUILD_MIXED_TREE}System.map
if test -n "$INSTALL_MOD_PATH"; then
set -- "$@" -b "$INSTALL_MOD_PATH"
fi