From d624007eb12b7707bf360346160b27fdd84785aa Mon Sep 17 00:00:00 2001
From: Will McVicker <willmcvicker@google.com>
Date: Fri, 14 Oct 2022 22:35:15 -0700
Subject: [PATCH] ANDROID: kbuild: re-add vmlinux.symvers for mixed building

The modpost build phase was refactored upstream in commit f73edc8951b2
("kbuild: unify two modpost invocations"). The new implementation does
not generate a vmlinux.symvers which our existing mixed build
implementation depends upon to match the KMI between the modules and GKI
kernel (via depmod). Since the Module.symvers is equal to the
vmlinux.symvers + modules-only.symvers, this patch adds support to
generate the vmlinux.symvers in order to continue using the existing
mixed build implementation.

Just a couple of notes:
  1) This allows us to use the same mixed build implementation for
     android14-6.1 and android14-5.15 without making any build tooling
     changes.
  2) This implementation won't catch build-time vendor changes to GKI
     Module CRCs during modpost. This is due to the fact that we are
     only using the vmlinux.symvers from the GKI kernel pass and not
     including the CRCs for the GKI modules.

Bug: 253726452
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I4b964434d02abbcdb694d3e03bfa4dc2d5a81f85
---
 Makefile                 |  2 +-
 scripts/Makefile.modpost | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index d708bfa0c004..8e42be0655cc 100644
--- a/Makefile
+++ b/Makefile
@@ -1975,7 +1975,7 @@ KBUILD_MODULES :=
 endif # CONFIG_MODULES
 
 PHONY += modpost
-modpost: $(if $(single-build),, $(if $(KBUILD_BUILTIN), vmlinux.o)) \
+modpost: $(if $(single-build),, $(if $(KBUILD_MIXED_TREE),,$(if $(KBUILD_BUILTIN), vmlinux.o))) \
 	 $(if $(KBUILD_MODULES), modules_check)
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index b315a410d729..1e11f6f582c3 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -60,8 +60,10 @@ ifeq ($(KBUILD_EXTMOD),)
 
 # This is used to retrieve symbol versions generated by genksyms.
 ifdef CONFIG_MODVERSIONS
+ifndef KBUILD_MIXED_TREE
 vmlinux.symvers Module.symvers: .vmlinux.objs
 endif
+endif
 
 # Ignore libgcc.a
 # Some architectures do '$(CC) --print-libgcc-file-name' to borrow libgcc.a
@@ -76,9 +78,17 @@ quiet_cmd_vmlinux_objs = GEN     $@
 		esac			\
 	done > $@
 
+quiet_cmd_vmlinux_symvers = GEN     $@
+      cmd_vmlinux_symvers = grep "\<vmlinux\s\+EXPORT" $< > $@
+
+quiet_cmd_cat_symvers = GEN     $@
+      cmd_cat_symvers = cat $(real-prereqs) > $@
+
+ifndef KBUILD_MIXED_TREE
 targets += .vmlinux.objs
 .vmlinux.objs: vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
 	$(call if_changed,vmlinux_objs)
+endif
 
 vmlinux.o-if-present := $(wildcard vmlinux.o)
 output-symdump := vmlinux.symvers
@@ -86,6 +96,27 @@ output-symdump := vmlinux.symvers
 ifdef KBUILD_MODULES
 output-symdump := $(if $(vmlinux.o-if-present), Module.symvers, modules-only.symvers)
 missing-input := $(filter-out $(vmlinux.o-if-present),vmlinux.o)
+
+targets += vmlinux.symvers
+vmlinux.symvers: Module.symvers FORCE
+	$(call if_changed,vmlinux_symvers)
+
+__modpost: $(if $(vmlinux.o-if-present),vmlinux.symvers,)
+endif
+
+# Overwrite values for mixed building (overwritting makes merges easier)
+ifdef KBUILD_MIXED_TREE
+targets += Module.symvers
+Module.symvers: $(mixed-build-prefix)vmlinux.symvers modules-only.symvers FORCE
+	$(call if_changed,cat_symvers)
+
+__modpost: Module.symvers
+
+vmlinux.o-if-present :=
+vmlinux.symvers-if-present := $(wildcard $(mixed-build-prefix)vmlinux.symvers)
+modpost-args += $(addprefix -i ,$(vmlinux.symvers-if-present))
+output-symdump := modules-only.symvers
+missing-input := $(filter-out $(vmlinux.symvers-if-present),$(mixed-build-prefix)vmlinux.symvers)
 endif
 
 else