[PATCH v8 17/18] kbuild: Add gendwarfksyms as an alternative to genksyms

[Sami Tolvanen <samitolvanen@google.com>]

When MODVERSIONS is enabled, allow selecting gendwarfksyms as the
implementation, but default to genksyms.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/module/Kconfig  | 22 ++++++++++++++++++++++
 scripts/Makefile       |  2 +-
 scripts/Makefile.build | 35 +++++++++++++++++++++++++++++------
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 4637f063d0fc..d443fc504ffc 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -169,6 +169,22 @@ config MODVERSIONS
 	  make them incompatible with the kernel you are running.  If
 	  unsure, say N.
 
+choice
+	prompt "Module versioning implementation"
+	depends on MODVERSIONS
+	help
+	  Select the tool used to calculate symbol versions for modules.
+
+	  If unsure, select GENKSYMS.
+
+config GENKSYMS
+	bool "genksyms (from source code)"
+	help
+	  Calculate symbol versions from pre-processed source code using
+	  genksyms.
+
+	  If unsure, say Y.
+
 config GENDWARFKSYMS
 	bool "gendwarfksyms (from debugging information)"
 	depends on DEBUG_INFO
@@ -176,6 +192,12 @@ config GENDWARFKSYMS
 	depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT
 	# Requires ELF object files.
 	depends on !LTO
+	help
+	  Calculate symbol versions from DWARF debugging information using
+	  gendwarfksyms. Requires DEBUG_INFO to be enabled.
+
+	  If unsure, say N.
+endchoice
 
 config ASM_MODVERSIONS
 	bool
diff --git a/scripts/Makefile b/scripts/Makefile
index d7fec46d38c0..8533f4498885 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -53,7 +53,7 @@ hostprogs += unifdef
 targets += module.lds
 
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
-subdir-$(CONFIG_MODVERSIONS) += genksyms
+subdir-$(CONFIG_GENKSYMS) += genksyms
 subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_SECURITY_IPE) += ipe
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index c16e4cf54d77..81d9dacad03c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -107,13 +107,24 @@ cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 $(obj)/%.i: $(obj)/%.c FORCE
 	$(call if_changed_dep,cpp_i_c)
 
+getexportsymbols = $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/$(1)/p'
+
+gendwarfksyms = $(objtree)/scripts/gendwarfksyms/gendwarfksyms	\
+	$(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes))	\
+	$(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable)
+
 genksyms = $(objtree)/scripts/genksyms/genksyms		\
 	$(if $(KBUILD_SYMTYPES), -T $(@:.o=.symtypes))	\
 	$(if $(KBUILD_PRESERVE), -p)			\
 	$(addprefix -r , $(wildcard $(@:.o=.symref)))
 
 # These mirror gensymtypes_S and co below, keep them in synch.
+ifdef CONFIG_GENDWARFKSYMS
+cmd_gensymtypes_c = $(if $(skip_gendwarfksyms),,	\
+	$(call getexportsymbols,\1) | $(gendwarfksyms) $@)
+else
 cmd_gensymtypes_c = $(CPP) -D__GENKSYMS__ $(c_flags) $< | $(genksyms)
+endif # CONFIG_GENDWARFKSYMS
 
 # LLVM assembly
 # Generate .ll files from .c
@@ -286,14 +297,26 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
 # This is convoluted. The .S file must first be preprocessed to run guards and
 # expand names, then the resulting exports must be constructed into plain
 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
-# to make the genksyms input.
+# to make the genksyms input or compiled into an object for gendwarfksyms.
 #
 # These mirror gensymtypes_c and co above, keep them in synch.
-cmd_gensymtypes_S =                                                         \
-   { echo "\#include <linux/kernel.h>" ;                                    \
-     echo "\#include <asm/asm-prototypes.h>" ;                              \
-     $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/EXPORT_SYMBOL(\1);/p' ; } | \
-    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+getasmexports =								\
+   { echo "\#include <linux/kernel.h>" ;				\
+     echo "\#include <linux/string.h>" ;				\
+     echo "\#include <asm/asm-prototypes.h>" ;				\
+     $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
+
+ifdef CONFIG_GENDWARFKSYMS
+cmd_gensymtypes_S =							\
+	$(getasmexports) |						\
+	$(CC) $(c_flags) -c -o $(@:.o=.gendwarfksyms.o) -xc -;		\
+	$(call getexportsymbols,\1) |					\
+	$(gendwarfksyms) $(@:.o=.gendwarfksyms.o)
+else
+cmd_gensymtypes_S =							\
+	$(getasmexports) |						\
+	$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+endif # CONFIG_GENDWARFKSYMS
 
 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
-- 
2.47.1.613.gc27f4b7a9f-goog