[PATCH v17 2/9] x86/objtool: Add CONFIG_STACK_VALIDATION option

[Josh Poimboeuf]

Add a CONFIG_STACK_VALIDATION option which will run "objtool check" for
each .o file to ensure the validity of its stack metadata.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 Makefile               |  5 ++++-
 arch/Kconfig           |  6 ++++++
 lib/Kconfig.debug      | 12 ++++++++++++
 scripts/Makefile.build | 39 +++++++++++++++++++++++++++++++++++----
 scripts/mod/Makefile   |  2 ++
 5 files changed, 59 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 701c360..866b215 100644
--- a/Makefile
+++ b/Makefile
@@ -993,7 +993,10 @@ prepare0: archprepare FORCE
 	$(Q)$(MAKE) $(build)=.
 
 # All the preparing..
-prepare: prepare0
+prepare: prepare0 prepare-objtool
+
+PHONY += prepare-objtool
+prepare-objtool: $(if $(CONFIG_STACK_VALIDATION), tools/objtool FORCE)
 
 # Generate some files
 # ---------------------------------------------------------------------------
diff --git a/arch/Kconfig b/arch/Kconfig
index f6b649d..81869a5 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -583,6 +583,12 @@ config HAVE_COPY_THREAD_TLS
 	  normal C parameter passing, rather than extracting the syscall
 	  argument from pt_regs.
 
+config HAVE_STACK_VALIDATION
+	bool
+	help
+	  Architecture supports the 'objtool check' host tool command, which
+	  performs compile-time stack metadata validation.
+
 #
 # ABI hall of shame
 #
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8bfd1ac..c130d3c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -342,6 +342,18 @@ config FRAME_POINTER
 	  larger and slower, but it gives very useful debugging information
 	  in case of kernel bugs. (precise oopses/stacktraces/warnings)
 
+config STACK_VALIDATION
+	bool "Compile-time stack metadata validation"
+	depends on HAVE_STACK_VALIDATION
+	default n
+	help
+	  Add compile-time checks to validate stack metadata including frame
+	  pointers (if CONFIG_FRAME_POINTER is enabled).  This helps ensure
+	  that runtime stack traces are more reliable.
+
+	  For more information, see
+	  tools/objtool/Documentation/stack-validation.txt.
+
 config DEBUG_FORCE_WEAK_PER_CPU
 	bool "Force weak per-cpu definitions"
 	depends on DEBUG_KERNEL
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 2c47f9c..130a452 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -241,10 +241,32 @@ cmd_record_mcount =						\
 	fi;
 endif
 
+ifdef CONFIG_STACK_VALIDATION
+
+__objtool_obj := $(objtree)/tools/objtool/objtool
+
+objtool_args = check
+ifndef CONFIG_FRAME_POINTER
+objtool_args += --no-fp
+endif
+
+# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
+# 'OBJECT_FILES_NON_STANDARD_foo.o := 'y': skip objtool checking for a file
+# 'OBJECT_FILES_NON_STANDARD_foo.o := 'n': override directory skip for a file
+cmd_objtool = $(if $(patsubst y%,, \
+	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
+	$(__objtool_obj) $(objtool_args) "$(@)";)
+objtool_obj = $(if $(patsubst y%,, \
+	$(OBJECT_FILES_NON_STANDARD_$(basetarget).o)$(OBJECT_FILES_NON_STANDARD)n), \
+	$(__objtool_obj))
+
+endif # CONFIG_STACK_VALIDATION
+
 define rule_cc_o_c
 	$(call echo-cmd,checksrc) $(cmd_checksrc)			  \
 	$(call echo-cmd,cc_o_c) $(cmd_cc_o_c);				  \
 	$(cmd_modversions)						  \
+	$(cmd_objtool)						  \
 	$(call echo-cmd,record_mcount)					  \
 	$(cmd_record_mcount)						  \
 	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,cc_o_c)' >    \
@@ -253,14 +275,23 @@ 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);				  \
+	$(cmd_objtool)						  \
+	scripts/basic/fixdep $(depfile) $@ '$(call make-cmd,as_o_S)' >    \
+	                                              $(dot-target).tmp;  \
+	rm -f $(depfile);						  \
+	mv -f $(dot-target).tmp $(dot-target).cmd
+endef
+
 # Built-in and composite module parts
-$(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
 	$(call cmd,force_checksrc)
 	$(call if_changed_rule,cc_o_c)
 
 # Single-part modules are special since we need to mark them in $(MODVERDIR)
 
-$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) FORCE
+$(single-used-m): $(obj)/%.o: $(src)/%.c $(recordmcount_source) $(objtool_obj) FORCE
 	$(call cmd,force_checksrc)
 	$(call if_changed_rule,cc_o_c)
 	@{ echo $(@:.o=.ko); echo $@; } > $(MODVERDIR)/$(@F:.o=.mod)
@@ -290,8 +321,8 @@ $(obj)/%.s: $(src)/%.S FORCE
 quiet_cmd_as_o_S = AS $(quiet_modtag)  $@
 cmd_as_o_S       = $(CC) $(a_flags) -c -o $@ $<
 
-$(obj)/%.o: $(src)/%.S FORCE
-	$(call if_changed_dep,as_o_S)
+$(obj)/%.o: $(src)/%.S $(objtool_obj) FORCE
+	$(call if_changed_rule,as_o_S)
 
 targets += $(real-objs-y) $(real-objs-m) $(lib-y)
 targets += $(extra-y) $(MAKECMDGOALS) $(always)
diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index c11212f..19d9bca 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -1,3 +1,5 @@
+OBJECT_FILES_NON_STANDARD := y
+
 hostprogs-y	:= modpost mk_elfconfig
 always		:= $(hostprogs-y) empty.o
 
-- 
2.4.3