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From: Sami Tolvanen <samitolvanen@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
	Will Deacon <will@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Kees Cook <keescook@chromium.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	clang-built-linux@googlegroups.com,
	kernel-hardening@lists.openwall.com, linux-arch@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-pci@vger.kernel.org, x86@kernel.org,
	Sami Tolvanen <samitolvanen@google.com>
Subject: [PATCH v5 09/29] kbuild: lto: fix module versioning
Date: Fri,  9 Oct 2020 09:13:18 -0700
Message-ID: <20201009161338.657380-10-samitolvanen@google.com> (raw)
In-Reply-To: <20201009161338.657380-1-samitolvanen@google.com>

With CONFIG_MODVERSIONS, version information is linked into each
compilation unit that exports symbols. With LTO, we cannot use this
method as all C code is compiled into LLVM bitcode instead. This
change collects symbol versions into .symversions files and merges
them in link-vmlinux.sh where they are all linked into vmlinux.o at
the same time.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
 .gitignore               |  1 +
 Makefile                 |  3 ++-
 arch/Kconfig             |  1 -
 scripts/Makefile.build   | 33 +++++++++++++++++++++++++++++++--
 scripts/Makefile.modpost |  6 +++++-
 scripts/link-vmlinux.sh  | 23 ++++++++++++++++++++++-
 6 files changed, 61 insertions(+), 6 deletions(-)

diff --git a/.gitignore b/.gitignore
index 162bd2b67bdf..06e76dc39ffe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -41,6 +41,7 @@
 *.so.dbg
 *.su
 *.symtypes
+*.symversions
 *.tab.[ch]
 *.tar
 *.xz
diff --git a/Makefile b/Makefile
index a3baf8388163..6d31a78d79ce 100644
--- a/Makefile
+++ b/Makefile
@@ -1827,7 +1827,8 @@ clean: $(clean-dirs)
 		-o -name '.tmp_*.o.*' \
 		-o -name '*.c.[012]*.*' \
 		-o -name '*.ll' \
-		-o -name '*.gcno' \) -type f -print | xargs rm -f
+		-o -name '*.gcno' \
+		-o -name '*.*.symversions' \) -type f -print | xargs rm -f
 
 # Generate tags for editors
 # ---------------------------------------------------------------------------
diff --git a/arch/Kconfig b/arch/Kconfig
index 4ac5dda6d873..caeb6feb517e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -615,7 +615,6 @@ config LTO_CLANG
 	depends on !FTRACE_MCOUNT_RECORD
 	depends on !KASAN
 	depends on !GCOV_KERNEL
-	depends on !MODVERSIONS
 	select LTO
 	help
           This option enables Clang's Link Time Optimization (LTO), which
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index ed74b2f986f7..eae2f5386a03 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -166,6 +166,15 @@ ifdef CONFIG_MODVERSIONS
 #   the actual value of the checksum generated by genksyms
 # o remove .tmp_<file>.o to <file>.o
 
+ifdef CONFIG_LTO_CLANG
+# Generate .o.symversions files for each .o with exported symbols, and link these
+# to the kernel and/or modules at the end.
+cmd_modversions_c =								\
+	if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then			\
+		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
+		    > $@.symversions;						\
+	fi;
+else
 cmd_modversions_c =								\
 	if $(OBJDUMP) -h $@ | grep -q __ksymtab; then				\
 		$(call cmd_gensymtypes_c,$(KBUILD_SYMTYPES),$(@:.o=.symtypes))	\
@@ -177,6 +186,7 @@ cmd_modversions_c =								\
 		rm -f $(@D)/.tmp_$(@F:.o=.ver);					\
 	fi
 endif
+endif
 
 ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT
 # compiler will not generate __mcount_loc use recordmcount or recordmcount.pl
@@ -390,6 +400,18 @@ $(obj)/%.asn1.c $(obj)/%.asn1.h: $(src)/%.asn1 $(objtree)/scripts/asn1_compiler
 $(subdir-builtin): $(obj)/%/built-in.a: $(obj)/% ;
 $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 
+# combine symversions for later processing
+quiet_cmd_update_lto_symversions = SYMVER  $@
+ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
+      cmd_update_lto_symversions =					\
+	rm -f $@.symversions						\
+	$(foreach n, $(filter-out FORCE,$^),				\
+		$(if $(wildcard $(n).symversions),			\
+			; cat $(n).symversions >> $@.symversions))
+else
+      cmd_update_lto_symversions = echo >/dev/null
+endif
+
 #
 # Rule to compile a set of .o files into one .a file (without symbol table)
 #
@@ -397,8 +419,11 @@ $(subdir-modorder): $(obj)/%/modules.order: $(obj)/% ;
 quiet_cmd_ar_builtin = AR      $@
       cmd_ar_builtin = rm -f $@; $(AR) cDPrST $@ $(real-prereqs)
 
+quiet_cmd_ar_and_symver = AR      $@
+      cmd_ar_and_symver = $(cmd_update_lto_symversions); $(cmd_ar_builtin)
+
 $(obj)/built-in.a: $(real-obj-y) FORCE
-	$(call if_changed,ar_builtin)
+	$(call if_changed,ar_and_symver)
 
 #
 # Rule to create modules.order file
@@ -418,8 +443,11 @@ $(obj)/modules.order: $(obj-m) FORCE
 #
 # Rule to compile a set of .o files into one .a file (with symbol table)
 #
+quiet_cmd_ar_lib = AR      $@
+      cmd_ar_lib = $(cmd_update_lto_symversions); $(cmd_ar)
+
 $(obj)/lib.a: $(lib-y) FORCE
-	$(call if_changed,ar)
+	$(call if_changed,ar_lib)
 
 # NOTE:
 # Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
@@ -428,6 +456,7 @@ $(obj)/lib.a: $(lib-y) FORCE
 ifdef CONFIG_LTO_CLANG
 quiet_cmd_link_multi-m = AR [M]  $@
 cmd_link_multi-m =						\
+	$(cmd_update_lto_symversions);				\
 	rm -f $@; 						\
 	$(AR) cDPrsT $@ $(filter %.o,$^)
 else
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 9ff8bfdb574d..066beffca09a 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -111,7 +111,11 @@ ifdef CONFIG_LTO_CLANG
 prelink-ext := .lto
 
 quiet_cmd_cc_lto_link_modules = LTO [M] $@
-cmd_cc_lto_link_modules = $(LD) $(ld_flags) -r -o $@ --whole-archive $^
+cmd_cc_lto_link_modules =						\
+	$(LD) $(ld_flags) -r -o $@					\
+		$(shell [ -s $(@:.lto.o=.o.symversions) ] &&		\
+			echo -T $(@:.lto.o=.o.symversions))		\
+		--whole-archive $^
 
 %.lto.o: %.o
 	$(call if_changed,cc_lto_link_modules)
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index ebb9f912aab6..1a48ef525f46 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -43,11 +43,26 @@ info()
 	fi
 }
 
+# If CONFIG_LTO_CLANG is selected, collect generated symbol versions into
+# .tmp_symversions.lds
+gen_symversions()
+{
+	info GEN .tmp_symversions.lds
+	rm -f .tmp_symversions.lds
+
+	for o in ${KBUILD_VMLINUX_OBJS} ${KBUILD_VMLINUX_LIBS}; do
+		if [ -f ${o}.symversions ]; then
+			cat ${o}.symversions >> .tmp_symversions.lds
+		fi
+	done
+}
+
 # Link of vmlinux.o used for section mismatch analysis
 # ${1} output file
 modpost_link()
 {
 	local objects
+	local lds=""
 
 	objects="--whole-archive				\
 		${KBUILD_VMLINUX_OBJS}				\
@@ -57,6 +72,11 @@ modpost_link()
 		--end-group"
 
 	if [ -n "${CONFIG_LTO_CLANG}" ]; then
+		if [ -n "${CONFIG_MODVERSIONS}" ]; then
+			gen_symversions
+			lds="${lds} -T .tmp_symversions.lds"
+		fi
+
 		# This might take a while, so indicate that we're doing
 		# an LTO link
 		info LTO ${1}
@@ -64,7 +84,7 @@ modpost_link()
 		info LD ${1}
 	fi
 
-	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${objects}
+	${LD} ${KBUILD_LDFLAGS} -r -o ${1} ${lds} ${objects}
 }
 
 objtool_link()
@@ -242,6 +262,7 @@ cleanup()
 {
 	rm -f .btf.*
 	rm -f .tmp_System.map
+	rm -f .tmp_symversions.lds
 	rm -f .tmp_vmlinux*
 	rm -f System.map
 	rm -f vmlinux
-- 
2.28.0.1011.ga647a8990f-goog


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-09 16:13 [PATCH v5 00/29] Add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 01/29] kbuild: preprocess module linker script Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 02/29] objtool: Add a pass for generating __mcount_loc Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 03/29] objtool: Don't autodetect vmlinux.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 04/29] tracing: move function tracer options to Kconfig Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 05/29] tracing: add support for objtool mcount Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 06/29] x86, build: use " Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 07/29] treewide: remove DISABLE_LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 08/29] kbuild: add support for Clang LTO Sami Tolvanen
2020-10-09 16:13 ` Sami Tolvanen [this message]
2020-10-09 16:13 ` [PATCH v5 10/29] objtool: Split noinstr validation from --vmlinux Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 11/29] kbuild: lto: postpone objtool Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 12/29] kbuild: lto: limit inlining Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 13/29] kbuild: lto: merge module sections Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 14/29] kbuild: lto: remove duplicate dependencies from .mod files Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 15/29] init: lto: ensure initcall ordering Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 16/29] init: lto: fix PREL32 relocations Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 17/29] PCI: Fix PREL32 relocations for LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 18/29] modpost: lto: strip .lto from module names Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 19/29] scripts/mod: disable LTO for empty.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 20/29] efi/libstub: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 21/29] drivers/misc/lkdtm: disable LTO for rodata.o Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 22/29] arm64: vdso: disable LTO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 23/29] KVM: arm64: disable LTO for the nVHE directory Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 24/29] arm64: disable recordmcount with DYNAMIC_FTRACE_WITH_REGS Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 25/29] arm64: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-12  8:31   ` Will Deacon
2020-10-12 20:44     ` Kees Cook
2020-10-12 20:51       ` Will Deacon
2020-10-12 21:02         ` Kees Cook
2020-10-09 16:13 ` [PATCH v5 26/29] x86/asm: annotate indirect jumps Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 27/29] x86, vdso: disable LTO only for vDSO Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 28/29] x86, cpu: disable LTO for cpu.c Sami Tolvanen
2020-10-09 16:13 ` [PATCH v5 29/29] x86, build: allow LTO_CLANG and THINLTO to be selected Sami Tolvanen
2020-10-09 16:30 ` [PATCH v5 00/29] Add support for Clang LTO Sedat Dilek
2020-10-09 20:50   ` Sami Tolvanen
     [not found] ` <20201009153512.1546446a@gandalf.local.home>
2020-10-09 21:05   ` Sami Tolvanen
2020-10-09 23:38     ` Steven Rostedt
2020-10-10  0:00       ` Sami Tolvanen

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