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Date:   Sat, 20 Jan 2018 23:21:08 +0100 (CET)
From:   Jiri Kosina <jikos@kernel.org>
To:     "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
cc:     "Woodhouse, David" <dwmw@amazon.co.uk>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
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        "peterz@infradead.org" <peterz@infradead.org>,
        "arjan@linux.intel.com" <arjan@linux.intel.com>,
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Subject: Re: [PATCH 4.9 85/96] x86/retpoline: Add initial retpoline support
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References: <20180115123404.270241256@linuxfoundation.org> <20180115123411.215283265@linuxfoundation.org> <cf155f1d-4eea-5d57-7639-63437b10c373@suse.cz> <1516099115.4937.40.camel@amazon.co.uk> <20180117135144.GB3957@kroah.com>
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On Wed, 17 Jan 2018, gregkh@linuxfoundation.org wrote:

> > http://git.infradead.org/retpoline-stable.git/shortlog/refs/heads/linux-4.4.y
> 
> And I've now queued up all of these patches, thanks very much for doing
> this work!

The patch below is needed on top of it, otherwise if CONFIG_MODVERSIONS is 
enabled, all the _thunk symbols end up with 0x0 checksum and fail to load 
due to mismatch.

	0x00000000      __x86_indirect_thunk_rcx        vmlinux EXPORT_SYMBOL

so please consider queuing it on top; I am queuing it in SLE12 codestreams 
now.


From: Nicholas Piggin <npiggin@gmail.com>
Date: Tue, 1 Nov 2016 12:46:19 +1100
Subject: [PATCH] kbuild: modversions for EXPORT_SYMBOL() for asm
Git-commit: 4efca4ed05cbdfd13ec3e8cb623fb77d6e4ab187
Patch-mainline: 4.9-rc6

[jkosina@suse.cz: folded cc6acc11cad1 fixup in as well ]

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.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
---
 scripts/Makefile.build |   87 +++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 80 insertions(+), 7 deletions(-)

--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -158,7 +158,8 @@ cmd_cc_i_c       = $(CPP) $(c_flags)   -
 $(obj)/%.i: $(src)/%.c FORCE
 	$(call if_changed_dep,cc_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) 			\
@@ -245,7 +247,7 @@ endif
 define rule_cc_o_c
 	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
 	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);				  \
-	$(cmd_modversions)						  \
+	$(cmd_modversions_c)						  \
 	$(call echo-cmd,record_mcount)					  \
 	$(cmd_record_mcount)						  \
 	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
@@ -254,6 +256,15 @@ define rule_cc_o_c
 	mv -f $(dot-target).tmp $(dot-target).cmd
 endef
 
+define rule_as_o_S
+       $(call echo-cmd,as_o_S) $(cmd_as_o_S);                            \
+       scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,as_o_S)' >    \
+                                                     $(dot-target).tmp;  \
+       $(cmd_modversions_S)						 \
+       rm -f $(depfile);                                                 \
+       mv -f $(dot-target).tmp $(dot-target).cmd
+endef
+
 # Built-in and composite module parts
 $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
 	$(call cmd,force_checksrc)
@@ -282,6 +293,38 @@ modkern_aflags := $(KBUILD_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.
+#
+# 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.
+#
+# 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);/' ) | \
+    $(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_as_s_S = CPP $(quiet_modtag) $@
 cmd_as_s_S       = $(CPP) $(a_flags)   -o $@ $<
 
@@ -289,10 +332,40 @@ $(obj)/%.s: $(src)/%.S FORCE
 	$(call if_changed_dep,as_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 FORCE
-	$(call if_changed_dep,as_o_S)
+	$(call if_changed_rule,as_o_S)
 
 targets += $(real-objs-y) $(real-objs-m) $(lib-y)
 targets += $(extra-y) $(MAKECMDGOALS) $(always)

-- 
Jiri Kosina
SUSE Labs