linux-kernel - [PATCH 1/2] kbuild: improve EXPORT

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Date:   Wed,  7 Dec 2016 23:24:06 -0500
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Michal Marek <mmarek@...e.com>, Nicholas Piggin <npiggin@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>, viro@...iv.linux.org.uk,
        linux-arm-kernel@...ts.infradead.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] kbuild: improve EXPORT_SYMBOL() parsing from asm code

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@...aro.org>
---
 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