Re: [GIT PULL] kbuild changes for v4.9-rc1

[Nicholas Piggin <npiggin@gmail.com>]

On Sat, 15 Oct 2016 17:22:05 -0700
Omar Sandoval <osandov@osandov.com> wrote:

> On Fri, Oct 14, 2016 at 10:12:46PM +0200, Michal Marek wrote:
> > Hi Linus,
> > 
> > please pull these kbuild changes for v4.9-rc1:
> > 
> > - EXPORT_SYMBOL for asm source by Al Viro. This does bring a regression,
> >   because genksyms no longer generates checksums for these symbols
> >   (CONFIG_MODVERSIONS). Nick Piggin is working on a patch to fix this.
> >   Plus, we are talking about functions like strcpy(), which rarely
> >   change prototypes.  
> 
> So this has broken all module loading for me. I get the following dmesg
> spew:
> 
> ...
> [    4.586914] scsi_mod: no symbol version for memset
> [    4.587920] scsi_mod: Unknown symbol memset (err -22)
> [    4.588443] scsi_mod: no symbol version for ___preempt_schedule
> [    4.589026] scsi_mod: Unknown symbol ___preempt_schedule (err -22)
> ...
> 
> Reverting 784d5699eddc ("x86: move exports to actual definitions") fixes
> it for me. This is with GCC 6.2.1, binutils 2.27, attached config.
> 

Thanks for the report. Could you try this patch and see if it helps?


Allow architectures to create asm/asm-prototypes.h file that
provides C prototypes for exported asm functions, which enables
proper CRC versions to be generated for them.

It's done by creating a trivial C program that includes that file
and the EXPORT_SYMBOL()s from the .S file, and preprocesses that
then sends the result to genksyms.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 scripts/Makefile.build | 71 +++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 65 insertions(+), 6 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index de46ab0..edcf876 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -159,7 +159,8 @@ cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 $(obj)/%.i: $(src)/%.c FORCE
 	$(call if_changed_dep,cpp_i_c)
 
-cmd_gensymtypes =                                                           \
+# These mirror gensymtypes_S and co below, keep them in synch.
+cmd_gensymtypes_c =                                                         \
     $(CPP) -D__GENKSYMS__ $(c_flags) $< |                                   \
     $(GENKSYMS) $(if $(1), -T $(2))                                         \
      $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
@@ -169,7 +170,7 @@ cmd_gensymtypes =                                                           \
 quiet_cmd_cc_symtypes_c = SYM $(quiet_modtag) $@
 cmd_cc_symtypes_c =                                                         \
     set -e;                                                                 \
-    $(call cmd_gensymtypes,true,$@) >/dev/null;                             \
+    $(call cmd_gensymtypes_c,true,$@) >/dev/null;                           \
     test -s $@ || rm -f $@
 
 $(obj)/%.symtypes : $(src)/%.c FORCE
@@ -198,9 +199,10 @@ else
 #   the actual value of the checksum generated by genksyms
 
 cmd_cc_o_c = $(CC) $(c_flags) -c -o $(@D)/.tmp_$(@F) $<
-cmd_modversions =								\
+
+cmd_modversions_c =								\
 	if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then		\
-		$(call cmd_gensymtypes,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
+		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
 		    > $(@D)/.tmp_$(@F:.o=.ver);					\
 										\
 		$(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) 			\
@@ -268,13 +270,14 @@ endif # CONFIG_STACK_VALIDATION
 define rule_cc_o_c
 	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
 	$(call cmd_and_fixdep,cc_o_c)					  \
-	$(cmd_modversions)						  \
+	$(cmd_modversions_c)						  \
 	$(cmd_objtool)						          \
 	$(call echo-cmd,record_mcount) $(cmd_record_mcount)
 endef
 
 define rule_as_o_S
 	$(call cmd_and_fixdep,as_o_S)					  \
+	$(cmd_modversions_S)						  \
 	$(cmd_objtool)
 endef
 
@@ -314,6 +317,32 @@ modkern_aflags := $(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL)
 $(real-objs-m)      : modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 $(real-objs-m:.o=.s): modkern_aflags := $(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE)
 
+# .S file exports must have their C prototypes defined in asm/asm-prototypes.h
+# or a file that it includes, in order to get versioned symbols. We build a
+# dummy C file that includes asm-prototypes and the EXPORT_SYMBOL lines from
+# the .S file (with trailing ';'), and run genksyms on that, to extract vers.
+#
+# 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>" ;                              \
+     grep EXPORT_SYMBOL $< | sed 's/$$/;/' ) |                              \
+    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - |                                \
+    $(GENKSYMS) $(if $(1), -T $(2))                                         \
+     $(patsubst y,-s _,$(CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX))             \
+     $(if $(KBUILD_PRESERVE),-p)                                            \
+     -r $(firstword $(wildcard $(2:.symtypes=.symref) /dev/null))
+
+quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
+cmd_cc_symtypes_S =                                                         \
+    set -e;                                                                 \
+    $(call cmd_gensymtypes_S,true,$@) >/dev/null;                           \
+    test -s $@ || rm -f $@
+
+$(obj)/%.symtypes : $(src)/%.S FORCE
+	$(call cmd,cc_symtypes_S)
+
+
 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
 
@@ -321,7 +350,37 @@ $(obj)/%.s: $(src)/%.S FORCE
 	$(call if_changed_dep,cpp_s_S)
 
 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
-cmd_as_o_S       = $(CC) $(a_flags) -c -o $@ $<
+
+ifndef CONFIG_MODVERSIONS
+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.
+
+cmd_as_o_S = $(CC) $(a_flags) -c -o $(@D)/.tmp_$(@F) $<
+
+cmd_modversions_S =								\
+	if $(OBJDUMP) -h $(@D)/.tmp_$(@F) | grep -q __ksymtab; then		\
+		$(call cmd_gensymtypes_S,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
+		    > $(@D)/.tmp_$(@F:.o=.ver);					\
+										\
+		$(LD) $(LDFLAGS) -r -o $@ $(@D)/.tmp_$(@F) 			\
+			-T $(@D)/.tmp_$(@F:.o=.ver);				\
+		rm -f $(@D)/.tmp_$(@F) $(@D)/.tmp_$(@F:.o=.ver);		\
+	else									\
+		mv -f $(@D)/.tmp_$(@F) $@;					\
+	fi;
+endif
+endif
 
 $(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
 	$(call if_changed_rule,as_o_S)
-- 
2.9.3