[PATCH 1/3] kbuild: improve EXPORT_SYMBOL() parsing from asm code

From: Nicolas Pitre
Date: Wed Nov 30 2016 - 03:50:52 EST


First, make the asm-prototypes.h presence optional. The next patch will
make it unneeded for modversion support.

Use the -D__GENKSYMS__ like we do for .c files but to expand the
EXPORT_SYMBOL macro using the preprocessor instead of a sed script.
The preprocessor output parsing is then limited to a simpler filtering
and made more robust against multiple assembly statements on a single
line.

Signed-off-by: Nicolas Pitre <nico@xxxxxxxxxx>
---
include/asm-generic/export.h | 9 +++++++++
scripts/Makefile.build | 20 ++++++--------------
2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 63554e9f6e..39a19dc366 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -28,6 +28,8 @@
#define KSYM(name) name
#endif

+#if defined(__KERNEL__) && !defined(__GENKSYMS__)
+
/*
* note on .section use: @progbits vs %progbits nastiness doesn't matter,
* since we immediately emit into those sections anyway.
@@ -82,6 +84,13 @@ KSYM(__kcrctab_\name):
#define __EXPORT_SYMBOL(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
#endif

+#else /* __GENKSYMS__ */
+
+/* create a preprocessor output suitable for cmd_gensymtypes_S */
+#define __EXPORT_SYMBOL(sym, val, sec) EXPORT_SYMBOL(sym)
+
+#endif /* __GENKSYMS__ */
+
#define EXPORT_SYMBOL(name) \
__EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)),)
#define EXPORT_SYMBOL_GPL(name) \
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 7675d11ee6..ebf6e08ae4 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -325,15 +325,15 @@ $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
# 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. See also include/asm-generic/export.h.
#
# 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>" ; \
- $(CPP) $(a_flags) $< | \
- grep "\<___EXPORT_SYMBOL\>" | \
- sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ) | \
+ ( echo "\#include <linux/kernel.h>" ; \
+ if [ -e $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h ]; \
+ then echo "\#include <asm/asm-prototypes.h>"; fi; \
+ $(CPP) -D__GENKSYMS__ $(a_flags) $< | tr ";" "\n" | \
+ sed -n -e '/EXPORT_SYMBOL(/s/$$/;/p' ) | \
$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | \
$(GENKSYMS) $(if $(1), -T $(2)) \
$(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX)) \
@@ -363,13 +363,6 @@ cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<

else

-ASM_PROTOTYPES := $(wildcard $(srctree)/arch/$(SRCARCH)/include/asm/asm-prototypes.h)
-
-ifeq ($(ASM_PROTOTYPES),)
-cmd_as_o_S = $(CC) $(a_flags) -c -o $@ $<
-
-else
-
# versioning matches the C process described above, with difference that
# we parse asm-prototypes.h C header to get function definitions.

@@ -387,7 +380,6 @@ cmd_modversions_S = \
mv -f $(@D)/.tmp_$(@F) $@; \
fi;
endif
-endif

$(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
$(call if_changed_rule,as_o_S)
--
2.7.4